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International Symposium on the Chemistry of Small Rings.

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Bis(trimethylsily1)diimine and
Tetrakis(trimethylsily1)hydrazine [I1
By N . Wiberg, W.-Ch. Joo, and W. Uhlenbrock [*I
Whereas bisalkyldiimines (azoalkanes) which contain the
characteristic atomic grouping ( I ) have long been known,
attempts to synthesize bissilyldiimines (azosilanes) [2,31,
which contain the atomic grouping (2) have hitherto remained unsuccessful [41.
In reaction of p-toluenesulfonyl azide [51 with tris(trimethy1sily1)hydrazide we have obtained access to the class of bissilyldiimines:
The product is light blue [Amax = 786 nm (ether)], volatile in
a high vacuum at -4OoC, and sensitive to hydrolysis.
That it is bis(trimethylsily1)diimine (hexamethylazosilane)
follows from elemental analysis, the mass spectrum (base
peak for the molecular ion at mje = 174), the 1H-NMR
spectrum (one signal at 6 = -12.5 Hz referred to TMS as
internal standard; determined in ether at -40 "C), and thermolysis. The azo compound (3) decomposes quantitatively
above about -35 "C according to the scheme:
This affords molecular nitrogen and the sterically hindered
tetrakis(trimethylsily1)hydrazine (4) which was previously
unknown. The structure of (4). m.p. 271 "C, was proved by
analyses, mass spectrum, IH-NMR spectrum (only one
proton signal, namely, at 6 = -13.0 Hz referred to TMS as
internal standard, recorded in benzene), and by independent
synthesis as follows:
+ R3SiCI
-+ LiCl+
R = CH3
Preparation of (3): Suspensions of p-toluenesulfonyl azide
(12.0 mmoles) and lithium tris(trimethylsi1yl)hydrazide
(12.0 mmoles) each in ether (25 ml) were mixed at -78 "C
with exclusion of moisture and oxygen. After reaction for 2 h
at -78 O C , during which 12.2 mmoles of nitrogen was evolved,
first the ether was condensed off from the reaction mixture in
a high vacuum at -55 "C, and then pure ( 3 ) at -5 "C (yield 50
to 60 %). N-Lithio-N-(trimethylsilyl)-p-toluenesulfonamide,
containing (4) as an impurity, remained as a solid residue.
Preparation of (4): Equimolar amounts of N-lithium tris(trimethylsily1)hydrazide and trimethylchlorosilane in benzene are heated in a Carius tube at 120'C for 48 h. After
separating off the lithium chloride which has been formed,
the benzene is distilled from the reaction solution and the
residue (4) remaining is purified by several sublimations in
high vacuum at 65 "C.
Received: April 5th, 1968
IZ 824 IE]
German version: Angew. Chem. 80, 661 (1968)
Publication delayed at the authors' request.
[*I Priv.-Doz. Dr. N. Wiberg, Dr. W.-Ch. Joo, and
W. Uhlenbrock
Institut fur Anorganische Chemie der Universitat
8 Munchen 2, Meiserstr. 1 (Germany)
[I] Part 7 of "Silicon Compounds". - Part 6: N. Wiberg,
F. Raschig, and K . H . Schmid, J. organometallic Chem. 10, 29
[ZJ H. Bock, Z. Naturforsch. 176, 423 (1962).
[31 U . Wannugut and C. Kriiger, Z . anorg. allg. Chem. 326, 288
[4] Azo compounds containing the grouping -C-N=N-Siare known [3].
[5] Or p-toluenesulfonyl chloride.
International Symposium on the Chemistry of Small Rings
The Sociitd Chimique de Belgique held a symposium on the
chemistry of small rings at Louvain (Belgium) from September 12 to 15. 1967.
afford the cyclopropane derivatives ( 5 ) and ( 6 ) . 93 % of ( 5 )
and 1% of ( 6 ) are obtained independently of whether one
starts from the cis- or the trans-ester.
F r o m the lectures:
cis- or trans-(I) and the alkylidenephosphorane ( 3 ) give the
sterically homogeneous cyclopropane derivative (7). The
benzylidenephosphorane ( 4 ) and the ester ( I ) afford the
derivatives (8) (11%). (9) (33%). and (10) (56%).
Syntheses of Cyclopropanes and Azirines by Means of
By H . J. Bestmann[*l
In the reaction of alkylidenephosphoranes with compounds
containing "electron-deficient" double bonds, cyclopropane
derivatives and triphenylphosphine are formed
by way of
an intermediate betaine that is formed in a reversible reaction.
The stereochemistry of this cyclopropane formation has been
studied in detail. The ylide (2) and methyl 2-butenoate ( I )
Reaction of the diylide (11) with 1,2-diketones (12) gives
sterically homogeneous dibenzonorcaradiene derivatives
(13) [21, whose structure was determined by nuclear resonance and in particular the solvent-dependence of the chemical shift [31 of the cyclopropane protons.
When heated above the melting point, the phosphonium salt
(14) loses COz and gives cyclopropyltriphenylphosphonium
bromide (IS) 141, which can be converted into cyclopropylidenetriphenylphosphorane (16) by phenyllithium. This
product (16) reacts as nucleophile with many compounds,
Angew. Chem. infernat. Edit. / Vol. 7 (1968) / No. 8
Reactivity of Cyclopropanone and Some of its Adducts
Von Th. J . de Boer[*]
Reaction of diazomethane with an excess of ketene in liquid
propane at -78 OC yields cyclopropanone ( I ) , which is obtainable as a practically pure liquid after removal of ketene
and propane. Cyclopropanone can be stored for a few days
at the temperature of liquid nitrogen. At higher temperatures
and with traces of water it polymerizes - without ringfissionlike formaldehyde. All common nucleophiles, e.g. water,
alcohols, thiols, acetic acid, hydrocyanic acid, and amines,
react with cyclopropanone to form 1: 1 adducts. The adducts
(2) and (3) can easily be obtained from ( I ) and amines.
Metal ions oxidize simple adducts like cyclopropanonehydrate or -hemiacetal ( 4 ) to adipic acid or its esters (6)
(R = CH3).
yielding cyclopropane derivatives 151, e.g. with alkylidenefluorenes it gives the spiro compounds ( I 7 ) and with fumaric
or maleic ester gives the di(cyclopropy1)maleic ester (18).
On reaction of nitrile oxides with alkylidenephosphoranes
loss of triphenylphosphine oxide may be accompanied by
formation either of a ketene imine with concomitant rearrangement or of an azirine [61. The mechanism of these reactions was discussed, as was its dependence upon the substituents present on the alkylidenephosphorane and on the
nitrile oxide.
[*I Prof. Dr. H. J. Bestmann
Institut fur Organische Chemie der Universitat
852 Erlangen, Henkestr. 42 (Germany)
[l] H. J. Bestmann and F. Seng, Angew. Chem. 74, 154 (1962);
Angew. Chem. internat. Edit. 1, 116 (1962).
[2] H. J. Bestmann and H. Morper, Angew. Chem. 79,578 (1967);
Angew. Chem. internat. Edit. 6, 561 (1967).
[3] 0. W. Boykin, A . B. Turner, and R. E. Lurz, Tetrahedron
Letters 1967, 817.
141 H. J. Bestmann, H. Hartung, and I. Pils, Angew. Chem. 77,
1011 (1965); Angew. Chem. internat. Edit. 4. 957 (1965).
[5] H. J . Bestmann and Th. Denzel, Tetrahedron Letters 1966,
3591 ;H. J. Bestmann, Th. Wenzel, R . Kunstmann, and I. Lengyel,
ibid. 1968, 2895.
[6] H . J . Bestmann and R. Kunstmann, Angew. Chem. 78, 1059
(1966); Angew. Chem. internat. Edit. 5, 1039 (1966); R. Huisgen
and J . Wulff; Tetrahedron Letters 1967, 917.
Angew. Chem. internat. Edit. 1 Vol. 7 (1968) No. 8
The intermediary radical ( 5 ) was detected by ESR spectroscopy. Dimerization of ( 5 ) yields the ester ( 6 ) . but only to
the extent of 20%; the rest of ( 6 ) is formed from ( 5 ) and
methyl acrylate via the intermediates ( 7 ) and (8), as was
shown when the reaction was carried out in D20.
( 7 ) can also be added to other olefinic compounds such as
methyl vinyl ketone, cyclopentenone, butadiene, or furan.
In the case of methyl- and gem-dimethyl-substituted cyclopropanones the ring opening (and thus the product distribution) depends strongly on the nature of the oxidizing metal
[*IProf. Dr. Th. J. de Boer
Universiteit van Amsterdam
Laboratorium voor organische Scheikunde
Nieuwe Achtergracht 129
Amsterdam (Netherlands)
Triplet Trimethylene Species
By R . J. Crawford and R . Moore[*1
The benzophenone photosensitized decomposition of both
cis- and trans-3,4-dimethyl-l-pyrazoline( I ) gives rise to a
70: 30 mixture of trans- and cis-1.2-dimethyicyclopropane
(2). No 3-methyl-1-butene is produced. It is believed that the
triplet pyrazoline decomposes to nitrogen and triplet trimethylene. The latter species is the same as that produced
when triplet methylene is added to cis- or trans-2-butene.
Stereochemistry is lost by rotation and both isomers give
64 1
This reaction also occurs with inversion of configuration.
Assignment of configuration of ( 6 ) was based upon close
[*I Prof. C. H. DePuy, W. C. Arneyjr., and Dr. D. H. Gibson
University of Colorado
Boulder, Colo. 80302 (USA)
rise to the same product ratio. This supports the contention
of Doering and Skell that triplet methylene forms an intermediate that is able to undergo rotation prior to ring closure.
Induced Paramagnetic Ring-current in the Four-membered R i n g of Biphenylene and Related Hydrocarbons
Using cis- or trans-3.5-dimethyl-1-pyrazoline( 3 ) a ratio of
40: 60 cis- to trans-dimethylcyclopropane was produced.
This ratio implies that the triplet formed from ( 1 ) is not
readily interconverted to the triplet species produced from
( 3 ) . The absence of olefins here suggests that in the reactions
of triplet methylene with the butenes the olefins are not
being formed via a 1,4-hydrogen-atom shift.
By H. P. Figeys 1*I
[*I Prof. R. J. Crawford and
R. Moore
University of Alberta
Edmonton, Alberta (Canada)
Electrophilic Cleavage of Cyclopropanols b y
Halogenating Agents
By C. H . DePuy, W. C. Arney jr., and D. H . Gibson[*]
Electrophilic ring-opening of cyclopropanols by protons in
acid solution has been shown previously to occur with retention of configuration at the carbon to which the hydrogen
becomes attached. Many cyclopropanols react readily with
sources of positive halogen (tert-butylhypohalite, halogen,
N-halosuccinimide) in a variety of solvents (tert-butyl alcohol, CC14, acetic acid). cis,trans- and trans,trans-2,3-dimethyl1 -phenylcyclopropanol ( ( 1 ) and (2). resp.) and their corresponding acetates react stereospecifically with brominating
c i s ~ r a n s( I )
e ythro
trans,trans (2)
cis (3)
trans (4)
Several authors have noted that the signals of the biphenylene
protons appear in the NMR-spectrum at a higher field than
those of the benzene protons [ I , 21. We have found that the
same is true for certain protons of the benzobiphenylenes.
This behavior can have two different causes: either the occurrence of very low deshielding ring-currents in the various
rings, or the presence of an induced paramagnetic shielding
ring-current in the four-membered ring of this series of compounds. Such “reversed” ring-currents have indeed been
observed in the monocyclic annulenes and dehydroannulenes
having 4n x-electrons [3J.
We have obtained experimental evidence for this second
hypothesis by analyzing the NMR-spectrum (solvent CDC13;
standard TMS, internal) of benzo[b]biphenylene ( I ) ;the spectrum contains a broad singlet at 6.90 ppm which is attributed,
by comparison with several substituted derivatives [21, to
protons 1 to 5 and 10. Protons 6 to 9 give an A2B2 multiplet
centered at about 7.30 ppm. However, in the hypothesis of
deshielding ring-currents, 8H1 should appear at a lower field
than 8H2, whatever the relative values of the individual ringcurrents, owing to the closer proximity of rings 11,111, and IV.
The only way to explain the experimental observations is to
postulate a shielding ring-current in the four-membered
ring, whose difference in shielding effect o n protons 1 and 2
is almost completely compensated by the difference in
deshielding effect of rings 111 and IV.
Calculation of the ring-currents in biphenylene and in benzobiphenylenes by Mc Weeny’s method [41 showed that a n
induced paramagnetic ring-current occurs in the four-membered ring of each of these compounds. Condensation of a
benzene ring onto biphenylene (2) along the long axis of the
molecule results in a diminution of the shielding ring-current,
while condensation in a non-linear way has the opposite influence. Another interesting feature is the very low ringcurrent in the benzene rings adjacent to the four-membered
ring. These two effects are thus responsible for the position
of the high-field multiplet in the spectrum of these molecules.
The occurrence of a shielding ring-current in the four-membered ring in biphenylene raised another interesting problem,
namely the attributions of the individual resonance frequencies of protons 1 and 2 in (2). The contributions ~ R . c .of the
different rings to the calculated chemical shifts are given in
the Table.
The calculated chemical shifts are in good agreement with
experimental values: 6.598 and 6.702 ppm in CDC13 [61, 6.47
and 6.60 ppm in C C 4 solution [I]. Theoretical considerations
indicate that proton 2 is more deshielded than proton 1.
These assignments were confirmed by the analysis of the
N M R spectra of [I-D]- and [2-D]biphenylene prepared by
unambiguous syntheses [**I. The spectra of the deuterated
compounds were in excellent agreement with the calculated
7 H spectra obtained by S . Castellano and A. A . Bothner-By’s
LAOCOON computer program [71.
Optically active trans-2-phenyl-1-methylcyclopropanol(5)
reacts with chlorinating agents and brominating agents to
give 4-halo-4-phenyl-2-butanone (6) as the sole product.
Finally, in the series of molecules investigated, it appeared
that the shielding ring-current decreases when the structure
of the four-membered ring changes progressively from the
“cyclobutadiene-like” to the “tetramethylenecyclobutanelike” structure.
agents exclusively with inversion to give erythro- and threo-(3bromo-ketones respectively. These compounds are stereospecifically converted into (3) and ( 4 ) on treatment with
weak bases.
I c H ~ - C0 - c H~
Angew. Chem. internat. Edir. J Vol. 7 (1968) 1 No. 8
Our present findings can be summarized as follows:
Table. Contributions of the different rings to the calculated chemica
shifts of protons 1 and 2 in biphenylene ( 2 ) .
1 / 1 1
+ 0.648
+ 0.648
- 0.165
- 0.040
+ 0.050
+ 0.019
[a] Obtained by assuming SR.C. = 1.15 ppm for the benzene molecule [51.
[*] Dr. H. P. Figeys
Universite Libre de Bruxelles, Faculte des Sciences,
Service de Chimie Organique
50, Av. F. D. Roosevelt
Bruxelles 5 (Belgium)
[**I This work was carried out in collaboration with Prof. J . F.
W . McOmie, Bristol University.
[l] A . R. Karritzky and R. E. Reavill, Recueil Trav. chim. PaysBas 83, 1230 (1964).
[2] R. H. Martin, J . P. Van Trappen, N. Defay, and J . F. W .
McOmie, Tetrahedron 20, 2373 (1964).
[3] J. A. Pople and K. G . Untch, J. Amer. chem. SOC.88, 4811
(1966); C. Schroder and J. F. M. Oth, Tetrahedron Letters 1966,
4043; F. Sondheimer, I. C . Calder, J . A. Elix, Y . Gaoni, P. J. Garraft, K. Grohmann, G . di Maio, J. Mayer, M. V. Sargent, and R.
Wolovsky, Special Publ. No. 21 (chem. SOC.,London), 1967,
p. 75; I. C. Calder and F. Sondheimer, Chem. Commun. 1966,904.
[4] R . C. M c Weeny, Molecular Physics I, 311 (1958); A. Veillard,
J. Chim. physique 59, 1056 (1962); J. D. Memory, J. chem.
Physics 38, 1341 (1963).
151 H. P . Figeys, Tetrahedron Letters 1966, 4625.
I61 G. Fraenkel, Y. Asahi, M . J . Mitchell, and M. P. Cava, Tetrahedron 20, 1179 (1964).
[7] S. Castellano and A. A. Bothner-By, J. chem. Physics 41, 3863
1. Substituting chlorine for hydrogen on a system of cumulative double bonds appears to increase considerably its
reactivity (e.g. dichloroketene vs. ketene; tetrachloroallene
vs. allene).
2. The orientation of the cycloaddition is uniform and compatible with a nucleophilic attack of the olefin o n the central
carbon atom of the ketene molecule.
3. No 1,4 cycloadducts are formed even with cisoid dienes
such as cyclopentadiene o r cyclohexadiene. Furthermore, in
121 or tetracontrast to 1.l-dichloro-2,2-difluoroethylene
cyanoethylene [31, dichloroketene does not add across the
homodiene system of norbornadiene.
[*I Prof. Dr. L. Ghosez, Lic. R. Montaigne
Techn. Chem. H. Vanlierde,
and Lic. F. Dumay
Laboratoire de Chimie Organique Biologique
Universite de Louvain
Naamsestraat 96
Louvain (Belgium)
[l] H. C . Stevens, D. A. Reich, D. R. Brandt, K. R. Fountain, and
E. J . Caughan, J. Amer. chem. SOC.87, 5257 (1965); L. Ghosez,
R. Montaigne, and P . Mollet, Tetrahedron Letters 1966, 135.
[2] P . D. Bartlett, G. E. H. Wallbillich, and L. K . Montgomery,
J. org. Chemistry 32, 1290 (1967).
[3] A. T . Blomquist and Y . C. Meinwald, J. Amer. chem. SOC. 81,
667 (1959).
Synthesis and Chemistry of 1-Azirines
By A . Hassner [*I
Azirines (azacyclopropenes) (3) represent a difficulty accessible ring system. We now describe a general synthesis of
azirines from olefins. The sequence involves stereospecific
addition of IN3 to olefins followed by elimination of HI to
give vinyl azides (2). The latter are photolyzed to l-azirines ( 3 ) . In this manner highly strained azirines such as ( 4 )
are also accessible as components of bicyclic ring systems.
Cycloadditions of Dichloroketene
By L. Ghosez, R . Montaigne, H . Vanlierde, and F. Dumay[*l
Dichloroketene, generated in situ from dichloroacetyl chloride and triethylamine in refluxing pentane, reacts readily
with cyclopentadiene and cyclopentene
according to the
cycloaddition scheme 2 + 2 = 4.
The reaction can be extended to other olefins; for example
the 1,2-cycloadducts ( I ) to ( 4 ) , X = C1, have been obtained
in satisfactory yields (40-75 %) from cyclohexadiene, cyclohexene, dihydropyran, and indene.
The exo-adducts (5) and (61, X = CI, have been obtained
in 25% and 10% yield respectively from the reaction of dichloroketene with norbornadiene and norbornene. All adducts could be dehalogenated in high yield to the parent
cyclobutanones ( I ) to ( 6 ) . X = H, by refluxing in cyclohexane containing two equivalents of tributyltin hydride.
Angew. Chem. internat. Edit.
/ VoI. 7 (1968) 1 No.8
Azirines are only weakly basic compounds, insoluble in cold
dilute acid, and do not react with alkyl halides. On the other
hand, reaction occurs readily with acid chlorides to yield
oxazoles ( 6 ) , N-acyl-2-chloroaziridines( 5 ) being formed as
Reduction of 2,3-substituted azirines with LiAIH4 occurs
stereospecifically from the less hindered side to give cisaziridines. In this way, cis-aziridines can be synthesized from
either cis o r trans olefins or a mixture of both. The IN3 adduct of bromophenylacetylene pyrolyzes under mild conditions to diphenyldicyanoethylene, presumably via an azirinium ion or radical.
["I Prof. A. Hassner
University of Colorado
Boulder, Colo. 80302 (USA)
The exo-Tricyclo[*~4]octaneSystem
By C. W. Jefford[*I
produced on photosensitization but does not rearrange to
the triplet ketene, adding instead to the acceptor olefin to
give the spiroketones observed.
The addition reactions of monochlorocarbenoid to bi[*I Prof. M. Jones jr., and Dr. W. Ando
Princeton University
cyclo[2.2.2]oct-2-ene, to norbornene, and to 1-methyl- and
Princeton, N.J. 08540 (USA)
2-methylnorbornene have been studied. In the case of the
last three compounds the exo addition took place exclusively.
Quite strikingly, for all four olefins the addition occurred
with pronounced anti stereoselectivity, the syn-anti ratios
being 1:5 , 1:6 , 1:1.5, and 1:9.8 respectively. A typical synRearrangements of Highly Unsaturated Cyclopropyl
anti ratio for a monocyclic olefin is 3: 1. It should be pointed
out that these ratios apply to the generation of the carbene
from equimolar quantities of CHzCl2 and CH3Li (from
By M. Jones jr., S. D.Reich, L. T. Scott, and L. E. Sullivan [*I
CH3CI) in the presence of a 25 % excess of olefin. The synanti ratios have been rationalized in terms of dispersion
Generation of unsaturated cyclopropyl carbenes of the type
( I ) , (S), or (12) yields besides the normal ring-expanded
All the anti products, e.g. anti-3-chlorotricyclo[]- product, other rearrangement compounds [1,21. Thus ( I )
gives trans-9,lO-dihydronaphthalene(3), a product derived (31
octane ( I ) , were quite stable to heat and to Ag+ in aqueous
from the cyclobutene (2) and bicyclo[4.2.2.]deca-2,4,7,9solution. Clearly, ionization of the cyclopropyl chloride
portion is prevented by the geometric restriction of the
tetraene (4). A priori ( 4 ) could result from rearrangement of
appropriate disrotatory mode.
In the case of the norbornene derivatives, the syn-adducts
were not observed, only their rearrangement products, the
exo-4-chlorobicyclo[3.2.l]oct-2-enes, e.g. (2). Although the
syn adduct from bicyclo[2.2.2]oct-2-ene could be observed
below 60°C,it rearranged readily o n warming to 4-chlorobicyclo[3.2.2]non-2-ene. The geometry of the syn adducts
permits ionization to the allylic system.
The addition of chlorocarbenoid to 2-methylnorbornene
gave the stable exo-anti adduct and 2-methylenebicyclo[3.2.l]oct-3-ene which is derived from the exo-syn adduct.
It can be seen, therefore, that the elimination of hydrogen
chloride from the exo-syn adduct depends upon prior rearrangement or ionization to the allylic system.
- [o]
either ( I ) or (2). Rearrangement of ( 5 ) leads to ( 6 ) and (7).
which are both possible rearrangement products of (8). and
( 8 ) itself. Compound ( 8 ) .however, rearranges to (9) and not
[*I Dr. C. W. Jefford
Chemistry Department, Temple University
Philadelphia, Pa. 19122 (USA)
The Photosensitized Decomposition of Diazoketones
By M . Jones jr. and W. Andor*]
Whereas diazoketone ( I ) undergoes the photochemical Wolff
rearrangement to ( 2 ) ,even in the presence of carbene acceptors, spiroketones are produced in 20-50% yield when the
decomposition is photosensitized with benzophenone. The
same mixture of the adducts (3) and ( 4 ) is formed from both
cis- and trans-2-butene. Presumably the triplet carbene is
to either ( 6 ) or (7). It seems likely, therefore, that the carbenes ( 1 ) and ( 5 ) are involved in the production of the rearranged products. A mechanism involving the opened species
1. hv, (C6H&C0,L=/
a. CH,OH
Angew. Chem. internat. Edit. J Vol. 7 (1968) No. 8
(10) and (11) is proposed. Similar rearrangements take place
in smaller systems. For example ( I 2 ) yields (131, (141, and
[*] Prof. M. Jones jr., S. D. Reich, L. T. Scott, and
Miss L. E. Sullivan
Princeton University
Princeton, N.J. 08540 (USA)
[l] M. Jones jr. and L. T . Scotr, J. Amer. chem. SOC.89, 150
[Z] M . Jones j r , and S. D . Reich, J. Amer. chem. SOC.89, 3935
[3] S. Masamune, C. G. Chin, K. Hojo, and R. T. Seidner,J. Amer.
chem. SOC.89,4804 (1967).
Compounds of type (3bj are particularly useful because they
can be converted into acetates in virtually quantitative yield
by the reagent acetic anhydride/BF3-ether. Cyclopropyl
esters (3a) are reductively cleaved to cyclopropanols by
methyllithium or LiAlH4; thus, the conversion of halide to
alcohol is possible.
[*] Prof. Dr. D. T. Longone
University of Michigan
Ann Arbor, Michigan 48104 (USA)
Bicyclo[6.2.0]deca-2,4,6,9-tetraene [ * *I
By S . Musamune 1 *I
The Synthesis and Chemistry of BicycIo[x.2.0] Systems
By A. P. Krapcho and J. H . Lesser[*]
A solution of bicyclo[6.1 .O]nona-2,4,6-triene-trans-9-carboxaldehyde tosylhydrazone ( I ) in dry tetrahydrofuran containing a n equivalent amount of sodium methoxide was
irradiated at -3OOC with a Hanovia mercury lamp (Pyrex
The I .2-cycloaddition of dimethylketene to cycloolefins has
been shown to be a general method for the preparation of
fused bicyclo[x.2.0]alkanones where x = 6 o r 7. Product
structures were determined by infrared, ultraviolet, and N M R
spectroscopy in conjunction with deuterium exchange experiments and elemental analysis.
Several of the bicyclo[x.2.0]alkanones were subjected to isomerization conditions. In these experiments, particular attention was focused o n the stability of the cis-ring fusion. The
N M R spectra of the isomerization products, especially the
geminal dimethyl region, facilitated product identification.
It was found that the truns-bicyclo[6.2.0]decane and -[7.2.0]undecane ring systems were more stable than their cisanalogs for the compounds studied.
Using a model system, the preliminary steps of a synthesis of
the sesquiterpene isocaryophylIene were investigated.
filter). Workup, at temperatures below 0 ° C of the reaction
products yielded two new compounds, A (45 % yield) and B
(21 %). in addition to bicyclo[4.2.2]deca-2,4,7,9-tetraene (2)
(7 %) and cyclooctatetraene (27 %).
NMR-, UV-, and mass-spectrometric data and chemical
evidence proved that compound A was bicyclo[6.2.0]deca2,4,6,9-tetraene ( 3 ) . The two structures ( 4 ) and (5) were
suggested for compound B.
[*I Prof. A. P. Krapcho und Dr. J. H. Lesser
Department of Chemistry, University of Vermont
Burlington, Vermont 05401 (USA)
The Direct Conversion of Cyclopropyl Bromides into
Cyclopropyloxy Derivatives
Compound (3) readily and quantitatively isomerizes to
trans-9.10-dihydronaphthalene. The isomerization is first
order and is characterized by the following kinetic data.
By D . T. Longonec*l
Cyclopropyl alcohols and esters are key intermediates in a
variety of current mechanistic investigations. Detailed studies
of these compounds have been limited only by their synthetic
availability. Cyclopropyl halides, despite their ease of preparation via halocarbene reactions, have not been useful as
precursors of cyclopropyloxy compounds (esters, ethers, and
alcohols). The halides are virtually inert in s N 2 displacements
and react via the SN1 path only with assisted ring-opening.
We wish to report the first synthetically useful conversion of
cyclopropyl halides into the corresponding cyclopropyloxy
derivatives. The method developed utilizes cyclopropyl carbanions as agents for nucleophiIic attack on the oxygen atom
of a n appropriate substrate. For example, the reaction of a
cyclopropyl Grignard reagent (I) with benzoyl peroxide
(2u) or tert-butyl perbenzoate (26) affords a cyclopropyl
benzoate (3a) or a tert-butyl cyclopropyl ether (36) in good
k46.y"' = (6.9
k74.8-c = (1.72
10-5 SeC-'
L 0.05) x 10-3 sec-1
A H * = 24.9 kcal/mole,
AS*= -0.4 cal-deg-1,mole-1
Upon irradiation with a low pressure mercury lamp at -80 "C
for one minute, (3) isomerjzed to trans-9.10-dihydronaphthalene (20-30 % yield), cis-9,lO-dihydronaphthalene(10 to
15%), ( 2 ) (50%), and bullvalene (3-10%).
The sodium salt of cis-(I) provided the pyrazoline (6) in
excellent yield. Therrnolysis of (6j at 110-115 O C afforded
an approximately 1:l mixture of bullvalene and (2). Examination of a n N M R spectrum (-100 "C) of the photolyzate
of VI (photolysis was performed at 77 "K) revealed that the
product mixture consisted of ( 2 ) (65 % yield), bullvalene
(27 %), and compound B (8 %). These reactions were compared with the formation of tetracyclo[,10]deca3'8-diene.
[*I Prof. S. Masamune
University o f Alberta
Edmonton, Alberta (Canada)
[**I Investigation carried out in collaboration with C . G. Chin,
H. Zenda, K . Hojo, and R. T. Seidner.
Angew. Chem. internat. Edit. 1 Vol. 7 (1968)
No. 8
Preparation of Small Rings b y Cycloaddition of Polar
By G. Opitr[*l
Methanesulfonyl chloride and triethylamine in acetonitrile
at -40 "C afford mesylsulfene, SO~=CH-SOZ-CH~.In the
presence of vinyl ethers 3-alkoxy-2-mesylthietane 1,I-dioxides are formed in good yields by 2+2 cycloadditions.
Cycloaddition to cis- and trans-butenyl butyl ether is stereospecific with respect to olefin configuration. The cis-olefin
gives 86% of cis,trans-2-ethyl-3-propoxy-4-mesylthietane
1,l-dioxide, the trans-olefin gives a n 80% yield of a liquid
mixture o f 91 parts of trans,trans- and 9 parts of the trans,cisisomer.
However, cycloaddition of sulfene (from methanesulfonyl
chloride and triethylamine) to 4-(cis-propenyl)rnorpholine i s
not stereospecific. The cis-enamine in ether at -10 OC affords
60-70% yields of a mixture of 51 parts of cis-2-methyl-3morpholinothietane 1,l-dioxide and 49 parts of the transisomer. As expected, only the trans-product was obtained
from the trans-enamine.
The curve recorded with the calorimeter, together with
kinetic experiments carried out at different temperatures and
followed by N MR spectroscopy, showed that this rearrangement ( 3 ) +(2) proceeds via two parallel kinetic paths: In one
hexamethyl(Dewar benzene) ( I ) is formed as intermediate
and accumulates appreciably in the course of the reaction;
in the second, the rearrangement proceeds via the hexamethyltricycl0[]hex-2-ene(hexamethylbenzvalene)
( 4 ) . the stationary concentration of which remains always
very small [NMR signals at T = 8.375 (2 olefinic CH3), T =
9.05 (2 aliphatic CH3) and T = 9.17 (2 aliphatic CH,)].
The scheme of the thermal rearrangement of ( 3 ) is thus the
Prof. Dr. G. Opitz
Chernisches Institut der Universitat
74 Tubingen, Wilhelrnstr. 33 (Germany)
The Kinetics and Thermochemistry of the Thermal
Rearrangement of HexamethyKDewar benzene) and of
H e x a m ethylprismane
By J. F. M. Oth[*l
Hexamethylbicyclo[2.2.O]hexa-2,5-diene [hexamethyl(Dewar
benzene)] ( I ) rearranges thermally into hexamethylbenzene
(2) above 80 "C.
with the implications that kl > k2 and k4
The kinetic parameters for the steps characterized by the
rates kl, kz. and k3 are given in Table 1.
The overall heat of isomerization for the reaction (3) +(Z)
was found to be:
AHisom ( 3 ) 4 2 ) = H(z)-H(3)
= -91.2
From this value, the heat of combustion of (2). and thermochemical data we calculated the strain energy in ( 3 ) to be
116 kcal/mole. This quantity is essentially the strain energy
of the prismane skeleton but comprises also the non-bonding
interactions between the methyl groups.
This exothermal reaction was followed in a temperatureprogrammed calorimeter. From the curve recorded, the
kinetic parameters and the heat of the reaction could be
deduced (see Table 1).
Table 1. Kinetic data. All reactions being of first order.
k l s o " c (sec-1)
X 10-3
k3 = 6.32 X 10-4
k4> 6.32 X 10-4
ki = 1.06
ki =
+ k , = 1.69 X
1r: 1
Union Carbide European Research Associates
95, rue Gatti de Gamond
Bruxelles 18 (Belgium)
1 37.2
[*I Dr. J. F. M. 0 t h
:::;: I ;::: I 2;
I? I?
-31.7 [a]
[a] Value obtained by difference (91.2-59.5).
From the heat of isomerization (1) +(2) (AHisom. [i)+(z)
= -59.5 kcal/mole), the heat of combustion of (2), and
thermochemical data, we have computed the strain energy in
( I ) to be 44.5 kcal/mole. This quantity is essentially the strain
energy as accumulated in the bicyclic system, but it also
includes the non-bonding interactions between the methyl
~6.0305lhexane (hexamethylprismane) (3) rearranges thermally into hexamethylbenzene
(2) above 60 OC.
Reactions of Cyclopropyl Carbenes
By I. D. R . Stevens, H. M . Frey, and C . L. Bird[*]
The reaction of cyclopropyl carbene to give cyclobutene and
of cyclopropyl methyl carbene to give 1-methylcyclobutene,
discovered by Friedman and Shechter 111, has been shown to
be a general reaction of cyclopropyl-substituted carbenes
(see Table 1).
The reaction has great synthetic utility for the preparation of
cyclobutanes and gives yields in the range of 50-70 % (based
Angew. Chem. internat. Edit. / Vol. 7 (1968) 1 No. 8
[4] H. M. Frey and R. M . SoNy, personal communication.
[ 5 ] C. F. Bradley and I. D . R. Sfevens, unpublished.
[6] C. L. Bird, H. M . Frey, and I. D.R. Sfevens, Chem. Commun.
Table 1. Rearrangement of symmetrically substituted
cyclopropyl carbenes.
1967, 707.
171 C . L. Bird and I. D. R. Slevens, unpublished.
I R3
Aminomethyl Cyclopropyl Ketones from
By G . Sturtz [ *I
Molecules containing cyclopropyl or amino-ketonic groups
have interesting pharmacological properties. We therefore
tried t o include both such groups in one molecule. Diethyl
2,3-dibromoallylphosphonate ( I ) and a n amine afford
readily the N,N-disubstituted 3-aminoacetonylphosphonate
(2) 111, which serves as our intermediate.
(C2H50)zP-CH2-CBr=CBrH + HNR2
on starting aldehyde or ketone). For those cases in which the
cyclopropane ring is not symmetrically substituted (Table 2).
a rationalization of the major product is proposed in terms
of the steric effects dominant in the intermediate carbene ( I ) .
H O@
(CzH50)zP-C Hz- C-CHz- NRz
We have shown previously
that carbanions from 2-0x0alkylphosphonates react with epoxides to yield alkyl cyclopropyJ ketones. The carbanion from (2) yields the desired
aminomethyl cyclopropyl ketones ( 3 ) in one step.
(C zH50)zP-C H- C - C H2- N R z + R’
Conversion t o cyclobutene necessarily involves rotation of
the “carbene” carbon into the plane of the ring and route (a)
or route (b) is followed depending o n whether the interaction
between R1, R2, and the “carbene” carbon is respectively
larger or smaller than the interaction between R1, Rz, and R3.
Thus in ( l a ) - ( I c ) (Table 2) this leads t o preferential migration by route (a) viz: the less substituted bond migrates and
in ( I d ) these are nearly equal leading t o reaction by both
routes in equal amounts.
Table 2. Rearrangement of unsymmetrically substituted cyclopropyl
carbenes ( I ) .
T07 -
For interpretation of the results of the reaction of (2) with
epoxides (see Table 1) the yields of ( 3 ) were compared with
the differences in the mobility of the protons o n each side of
the carbonyl group. To a first approximation the difference
in mobility can be determined from the chemical shift A8 =
~ H ( P ) - ~ H ( N ) [cf. (3c) and (3d)l. The substitution o n nitroTable 1.
A 6 = 8 ~ ( p ) - 8 ~ of
( ~(2)
) and yields of ( 3 ) .
H. M. Frey, and C. L. Bird
University of Southampton
[I] L. Friedman and H . Shechfer, J. Amer. chem. SOC.82, 1002
121 W . Kirmse and K.-H. Pook, Chern. Ber. 98, 4022 (1965).
[3] H . M . Frey and I . D. R. Stevens, unpublished.
[ * ] Dr. 1. D. R. Stevens,
Angew. Chem. internat. Edit. / Vol. 7 (1968) / No. 8
gen appears also t o play a part [cf. (3b) and (3c)l. From gas
chromatography it can be seen that preponderatingly (95 %)
one of the two stereoisomers of (3) is formed. The change in
the chemical shift by a factor of 2 on going from benzene t o
CDC13 indicates a truns-configuration 131.
Compounds (3) react with methyl iodide, yielding salts ( 4 ) i n
which R1 = H, R = R2 = CH3; R RI = ~2 = CH 3 ,. RI =
In recent workczl on the formation of aryl cycloaIkyl sulfones from aryl o-bromoalkyl sulfones under basic conditions (Table 1, reaction 5 ) , closure of a three-membered ring
occurred much more rapidly than that of a five-membered
ring. Measurement of isotope effects showed131 that the
cyclopropyl sulfone was formed in a stepwise process.
We postulate that, in a transition state which leads to the
formation of a three-membered ring, attachment of a conjugative substituent in such a way as to allow resonant interaction between the ring being formed and the substituent
reduces the unfavorable enthalpy term for this process. Such
interactions are well known for both ground and excited
states of cyclopropanes 141.
CH,, R2 -(CH&-O-(CH2)2-;
R1 = Rz = C H3,
RZ = -(CHZ)S-. These products have a laming action
similar to that of decamethonium [41.
[*] Dr. G.Sturtz
Laboratoire de Synthese Organique
1, rue Victor Cousin, Paris
Present address: Faculte des Sciences de Brest,
Plateau du Bouguen.
Brest (29 N) (France)
[I] Bull. SOC.chim. France 1967,1345.
121 G. Sturtr, Bull. SOC.chim. France 1964, 2349.
131 J. Seyden, P. Arnaud, J. L. Pierre, and M . Plat, Tetrahedron
Letters 1967, 3719.
141 We are grateful to the Institute Pasteur, Paris, where the
pharmacological tests were carried out.
The data collected in Table 1, which contains the results of
some of our own investigations, support our postulate for
systems in which (cf. reactions 1-6 versux 10-13) carbocyclic
rings are produced. Formation of a five-membered ring,
however, is preferred when the nucleophilic atom is that of a
first row element other than carbon even when a conjugative
substituent is attached to it (cf. reactions 8 and 9).
F o r m a t i o n of Small Rings by Intramolecular
Nucleophilic Substitution
By .C. J . M. Stirling [*I
This behavior is in accord with other experimental evidence
on poor conjugation via a heteroatom in a three-membered
ring 151 and is supported by theoretical considerations [61.
Systems in which the heteroatom is a second-row element
appear to obey the generalization (cf. reactions 7 and 13).
Comparative kinetic information o n the ease of ring closure
by intramolecular nucleophilic substitution is scarce. Data
available[1] show that rates of ring formation are in the
following order of ring size: 5 > 6 > 4. Rates of closure of
three-membered rings are always greater than for four-membered rings and sometimes even faster than for five- and sixmembered rings (see Table). These variations are to be considered in terms of the balance between the enthalpy and
entropy of activation for ring closure; the former is unfavorable and latter is favorable for three-membered rings and
vice versa for five- and six-memberedArings.
[*I Dr. C. J. M. Stirling
Department of Chemistry
King's College, University of London
Strand, London W.C. 2 (England)
[I] B. Capon, Quart. Rev. (chem. SOC.,London) 18, 45 (1964).
121 A . C. Knipe and J. C. M . Stirling, J. chem. SOC.(London)
B 1967, 808.
Table 1. Relative rates (kreI) of ring closure versus number of ring members.
Starting material
9.1x 10-4
CHa-COcyclopropane [a]
12 N NaOH
Tosyl-CH (CH2)n-j
1 x 10-4
I X 10-4
- _ _ _~
0.25 [b]
0.25 [bl
CaH5-CHz-SOzcyclopropane Ia1
O ~ C H , ) .
OLCHz)n+ 1
5~ 10-3
[a] Sole product.
[b] Max. value
[c] K ferr-butoxide in terl-butdnol.
[dl Min. value.
Angew. Chem. internat. Edit. f Vol. 7 (1968)
/ No. 8
[3] R. Birdand J . C. M . Stirling, J. chem. SOC.(London) B 1968,
[4] R . Hoflmann, Tetrahedron Letters 1965, 3819.
[5] A . T . Botfini and C. P. Nash, J. Amer. chem. SOC.84, 734
[61 M . P . Melrose, private communication.
Diels-Alder Reactions of Tetrahalocyclopropenes
By S . W . Tobey and D . C . F. Law[*l
All tetrahalocyclopropenes of type ( I ) "1 undergo 1,4 addition to butadiene at 80 'C in CC14 to give stable Diels-Alder
adducts of type (2) in high yield. These same cyclopropenes
react with furan t o provide structures ( 3 ) and/or ( 4 ) (see
Table 1). Cyclopentadiene reacts with compounds of type
( I ) to provide analogous products.
Derivatives of the Trichlorocyclopropenylium Ion
By R . West[*J
Trichlorocyclopropenylium tetrachloraluminate,C3Cl~AICl~,
reacts with aromatic hydrocarbons with replacement of one,
two, or three chlorines by aromatic groups. When one of the
aromatic rings bears a hydroxyl group, proton elimination
takes place and quinocyclopropene is formed readily.
When C3Clf is allowed to react with three equivalents of a
2,6-dialkyl-substituted phenol, the initially formed triarylcyclopropenylium is converted into a bis(hydroxyary1)quinocyclopropane ( f ) . Oxidation of ( I ) leads to the formation of a triquinocyclopropane ( 2 ) .
All six compounds of type (2) that have been prepared so
far are dark violet solids which exhibit a strong absorption
band at 770 nm. Compounds (2) can be regarded as unusu-
ally stable derivatives of [3]-radialene; when R = tert-butyl
these compounds can be heated to 28OOC without decomposition.
The reaction ( I ) 4 2 ) proceeds via intermediary monoradicals.',The:ESR spectra of the radical anions of (2) show that
the unpaired electron is fully delocalized over the three sixmembered rings.
In accord with the predictions of the Woodward-Hoffmann
rules, ring opening of (3) to ( 4 ) occurs only via ionization of
the halide situated syn to the double bond. When R3 = F [as
in ( I c ) , ( l e ) , and ( I f ) ] , the original adduct ( 3 ) is stable; if
R3 = C1 or Br, ring opening to ( 4 ) occurs so readily that (3)
is not isolated.
The observed order of dienophilic character of cyclopropene
(1) towards furan suggests that in 3,3-difluorinated cyclopropenes [ ( I e ) and ( I f ) ] ring bonding is stabilized and the
energy of the ground state is lowered, thus increasing the
activation energy for Diels-Alder adduct formation. The
high thermal stabilities of (2a) and (2b) relative to (3a) and
(36) reflect the strain built into structures of type (3) by the
oxygen and methylene bridges. These bridges distort the
Diels-Alder adducts in precisely the direction required to
initiate disrotatory cyclopropane-ring opening 121.
[*I Dr. S. W. Tobey and Dr. D. C. F. Law
The Dow Chemical Company
Eastern Research Laboratory
Wayland, Mass. 01778 (USA)
111 S . W. Tohey and R . West, J. Amer. chem. SOC.88,2481 (1966).
For a complete account of this work, see D . C. F. Law and S .
W . Tobey, J. Amer. chem. SOC.90, 2376 (1968).
Angew. Chem. internat. Edit.1 Vol. 7 (1968) / No. 8
Reaction of 2,6-disubstituted phenols with C3CLa at 0 OC
leads to bis(hydroxyary1)cyclopropenones (3). which on
irradiation lose carbon monoxide and are converted into diarylacetylenes ( 4 ) . Compounds ( 3 ) undergo reversible oxidation to compounds (51, which lose carbon monoxide spontaneously to yield diquinoethylenes ( 6 ) . Compounds ( 6 ) are
also obtained from (4)by oxidation.
[VB 159 IEI
German version: Angew. Chem. 80, 628 (1968)
[*I Prof. R. West
Department of Chemistry, University of Wisconsin
Madison, Wisc. 53706 (USA)
Structure of Glutamate Dehydrogenase from
Ox Liver
By H. Sund[*l
Measurement of light scattering as a function of protein concentration (in the concentration range 25 pg/ml-8 mg/ml)
afforded results, which, o n comparison with the calculated
iiterdependence of apparent molecular weight and protein
concentration, indicate that the association-dissociation
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