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New Olefin Reactions.

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free anions (X = K in DMSO), these chelate complexes do
not possess magnetic anisotropy typical of aromatic compounds and consequently are not aromatic in character.
Dulrrozzo came to the same conclusion via a different approach 191. Use of the term “quasiaromatic” [3,101 in connection with such systems is best avoided, since “non-aromatic”
is not generally understood to be included under this heading.
It would appear attractive to study, in this way, the bonding character of further metal complexes and other five- and
six-membered chelates and heterocycles (e.g. [11-131), since
the method used here is obviously less susceptible to polar
and other effects than the position of the signals of protons
in the plane of the ring 161.
According t o their N M R spectra, compounds (6) and (7)
(X = H) are present almost completely in the enolized form.
These compounds were obtained from iodomesitylene and 9bromoanthracene and from the chromium complex of 3bromo-2,4-pentanedione respectively, by heating in the presence of copper powder (4 h, 240OC) followed by acid hydrolysis: (61, X = H , m.p. 83 “C, yield 40%; ( 7 ) , X = H, m.p.
182 “C, yield 7 %. Although the Ullmann reaction is a well
known classical method for the coupling of aromatic rings,
it has been used here to provide evidence against the aromatic character of the metal complexes of (6) and (7).
Received: November 14, 1968
[Z 923 IE]
German version: Angew. Chem. 8 1 , 150 (1969)
[*I Dip].-Chem. M. Kuhr and Prof. Dr. H. Musso
Abteilung fur Chemie der Universitat Bochum und
Institut fur Organische Chemie der Universitat Marburg
355 Marburg, Bahnhofstrasse 7 (Germany)
[I] Part VI of Organometai Complexes - Part V: H. Junge and
H . Musso, Spectrochim. Acta A 24. 1219 (1968).
[21 y.Calvin and K. W. Wilson, J . Amer. chem. SOC.67, 2003
(1945); R. E. Martell and M . Calvin: Die Chemie der Metallchelatverbindungen. Verlag Chemle, Weinheim 1958, pp. 149,
157, 160
[3] J . P. Collmon. R. A. Moss, S. D. Goldby, and W. S. fiahanovsky, Chem. and Ind. 1960, 1213; J. P. Coliman and M. Yumada, J. org. Chemistry 28, 3017 (1963); J. P. Collman, Angew.
Chem. 77, 154 (1965); Angew. Chem. internat. Edit. 4, 132
(1965).
[4] J. P. Fackler, Progr. inorg. Chem. 7, 374 (1966).
[5] In favor of aromatic character: J . P. Callman, R. L. Marshall,
and W. L. Young, Chem. and Ind. 1962, 1380; R. E. Hester, ibid.
IY63, 1397; W. L . Young, Dissertation Abstr. 268, 1358 (1967).
[6] Against the aromatic character: R. H . Holm and F. A. Cofton, J . Amer. chem. SOC.80, 5658 (1958); J . A . S . Smith and E. J .
Wilkins, J. chem. SOC.(London) A 1966, 1749; R. C. Fay and
N. Serpone, J. Amer. chem. SOC.90,5701 (1968).
[7] H. Muss0 and H . Junge, Chem. Ber. IOI, 801 (1968).
[8] J. A. Pople, J. chem. Physics 24, 1111 (1956); C. E. Johnson
and F. A. Bovey, ibid. 29, 1012 (1958).
[9] E. Daltrozzo and K. Feldmann, Angew. Chem. 79, 153 (1967);
Angew. Chem. internat. Edit. 6, 182 (1967); E . Daltrozzo, private
communication.
1101 D. M . G. Lloyd and D. R. Marshall, Chem. and Ind. 1964,
1760.
[ l l ] H. C. Smitherman and L. N. Ferguson, Tetrahedron 24, 923
(1968).
1121 A. Trestian, H . Niculesco-Majiwska, I. Bully, A. Barabas,
and A . T. Balaban, Tetrahedron 24, 2499 (1968).
[13] E. Bayer, E. Breifmaier, and V . Schurig, Chem. Ber. 101,
1594 (1968).
CONFERENCE REPORTS
New Olefin Reactions
A Symposium was held at the University of Manchester
Institute of Science and Technology, June 25 and 26, 1968,
that dealt with some of the more important recent advances
and trends in olefin reactions.
G. Wilke (Mulheim, Germany) reviewed the factors which
influence the reactions of olefins with transition metals. Metalolefin complexes are in general stabilized by the presence of
basic ligands in the molecule, and by partial decoupling of
the olefin --orbitals, usually achieved by ring strain in the
case of cyclic olefins, or in mono-olefin complexes by rotation
of the olefin so that it is at an angle to the plane of the molecule. The point was also made that complexes of chelating
diolefins are more stable than the analogous mono-olefin
complexes.
Several factors influence the reactivity of the complexed
olefin, for example, charge transfer can occur from metal to
ligand or from ligand t o metal, and evidence was presented
that in the compound bis(bipyridy1)cyclooctadienenickel the
cyclooctadiene exists as a dianion. Hydrogen transfer reactions are also known in metal-olefin complexes, for example,
the compound bis(cyc1ooctadiene)cobalt hydride exists as an
equilibrium mixture of a a-enyl and x-ally1 structure.
R. P e f t i f (Austin, Texas, USA) reviewed the chemistry of
cyclobutadiene complexes of transition metals and demonstrated how these complexes may be used as a convenient
source of cyclobutadiene in the synthesis of organic compounds. The synthesis was reported of several para-bonded
benzene derivatives by oxidative cleavage of (CqH4)Fe(CO)3
in the presence of acetylenes. The preparation of pentacyclo[4.3.0.02S.O3.~.04~7]nonan-9-ol
( I ) from 5,5-diethoxycyclopentadiene and (C4H4)Fe(C0)3 was also described.
148
HG
m
/v?\
HO
(1)
(2)
Oxidative cleavage of (benzocyc1abutadiene)iron tricarbonyl
in the presence of Agf gives 4b,Sb.8~,8e-tetrahydrodibenzo[h,e]cyclopropa[g,h]pentalene (2). by a normally forbidden
(Woodward-Hoffmann rules) disrotatory ring opening of the
Diels-Alder adduct, which becomes allowed when the adduct
is complexed t o silver.
The lecture concluded with some observations on the structure of free cyclobutadiene. A study of some Diels-Alder
reactions of cyclobutadiene with dimethylmaleate and fumarate tentatively suggests that cyclobutadiene reacts in the
singlet state (as a rectangular diolefin).
J . K. Hutnblin (Sunbury-on-Thames, England) reported the
dimerization of propene to methylpentenes (mainly 4methyl-1-pentene) at 150 OC and about 100 atm with sodium
or potassium on pure graphite or potassium carbonate. This
reaction can be carried out o n a pilot-plant scale and under
the best conditions a yield of 92% of 4-methyl-1-pentene has
been achieved.
Allylic anions from propene or butenes will react with ethylene. In a typical reaction a 1:1 molar ratio of ethylene and
propene gives a 92% yield of n-pentenes with small amounts
of hexenes and heptenes. Similarly, reaction of ethylene with
1-butene gives 3-methyl-1-pentene and 2-hexene. The reactivity of the allylic anions towards ethylene decreases in the
order C3H5- > n-CdH7- > iso-CqH7-.
Angew. Chem. internat. Edit. Vol. 8 (1969) 1 No. 2
R. D.Crotner (Wilniington, Delaware, USA) dealt with olefin
complexes of RhI and RhIII. Ethylene can be dimerized to
butenes (mainly I-butene) in up to 95% conversion by
RhC13.3 .&O, [(C2H&RhCI]2, or (d~ac)~Rh(CzH4)2in the
presence of hydrogen chloride in ethanol. The mechanism of
the reaction has been elucidated by a combination of kinetic
and spectroscopic techniques and involves the insertion of a
coordinated ethylene into the ethyl-rhodium bond in the
complex [ C * H S R ~ I I I C ~ ~ ( C ~ H(where
~ ) S ] - S = solvent molecule) as the rate determining step. The codimerization of
ethylene and butadiene to give 1,4- and 2,4-hexadiene, 3ethyl-l,4-hexadiene, and 3-methyl-l,4-heptadiene was described. This reaction differs from the ethylene dimerization
in that the reactive intermediates are x-allylrhodium c o n plexes.
G . Wilkinson (London, England) reported that the compounds HRh(C0)[P(C6H5)& and HRhCI[P(C&)3]3
are
effective catalysts for the hydrogenation of terminal olefins at
ambient temperature. The reaction with HRh(CO)[P(C6H&]3
has been shown to involve the coordinatively unsaturated
Rhr complex Irans-HRh(CO)[P(C6H~)3]~,and the high
specificity towards I-alkenes and the lack of olefin isomerization in this reaction was explained by a combination of the
influence of the phosphine ligand on the direction of addition
of the metal hydride to the olefin, and the steric effect of the
bulky trans phosphine ligands in preventing formation of the
branched-chain alkyl derivative.
resulting from their hydrogenation are potential intermcdiates for high temperature lubricants. am'-Bis(ary1oxy)isobutenes readily undergo Claisen condensation to give phenols.
The rhodium complex HRh(CO)[P(C6HS)3]3 catalyzes the
hydroformylation of olefins to aldehydes (norma1:branched
chain ratio ca. 20:l) in 95 % yield at room temperature and
1 atm CO pressure. The efective catalyst in this reaction is
thought to be HRh(C0)2[P(C6H5)3]2 formed by the rapid
equilibria:
This reaction gives high yields and is of general applicability
for alkyl, allyl, benzyl, aryl, and vinyl halides and geminal
dihalides.
fast
HRh(CO)[P(C6H5)313
.\%\
E. J . Core,? (Cambridge, Mass., USA) reported that Ni(.CO),
catalyzes allylic dimerization at SO "C in polar solvents, this
reaction having been utilized i n the synthesis of C12. c 1 4 , and
cyclic dienes from the compounds (7) (where n = 6, 8, o r
BrCHz -CH
=
CH(CHdnCH
=
CH-CH?Rr
(7)
12 respectively); o n l y poor yields of smaller ring compounds
(CS or C ~ Oare
) obtained by this method. Ally1 bromide is dimerized to 1,4-hexadiene at 0 ° C in ether or dimethylfornianiide using (;r-C3HSNiBr)2, but as fast ligdnd exchange
occurs this reaction cannot be extended to prepare mixed
allyl dimers. Substituted methylallyl derivatives can be obtained in 70-90% yields from (x-C3HsNiBr)z and alkyl or
aryl halides in dimethylformamide, and this reaction is a
particularly effective means of introducing an allyl group
into an organic molecule.
Selective cross coupling of alkyl groups can be achieved
alkyl).
using copper salts of the type RzCu-Li+ (R
2
P. S. Skell (University Park, Pennsylvania, USA) described
the generation of C1, Cz, C3, and C4 molecules by a carbon
arc at low temperatures in high vacuum. These molecules
have been caused to react with a variety of substrates when
slow
condensed on to neopentane o n the surface of the reaction
CO
\
HRh(CO)z[P(C6H5)& i ~ ;
vessel at liquid nitrogen temperature.
[ P ( C ~ H ~ ) ~ ~ Z C O R ~ ( C O ) ~ R ~ C O [ The
P ( C C1
~ H molecule
~ ) ~ ~ ~ exists in three forms, a IS (singlet state;
:C:), a ID (singlet state: :C:),and a 3p (triplet state; :C) with
stabilities increasing in the order IS < 1D < 3p: The i p and
The iridium complex H I ~ ( C O ) ~ [ P ( C ~ H S ) &
has been
ID species add stereospecifically to olefins and conjugated
prepared, and has been shown to exist as an equilibrium
dienes to give dicyclopropane derivatives. The high energy
mixture of two unidentified species in solution. Neither this
1s species gives allene derivatives with olefins by an apparent
iridium compound nor the compound HRhCI[P(C6H5)313
insertion into the olefinic double bond.
are effective hydroformylation catalysts at room temperature.
F. Weiss (Lyon, France) reviewed the methods of synthesis
and the chemistry of ma'-substituted isobutenes of type (3)
(where X = halogen, OH, H, C02R, or CN) and the related
compound 2-methyleneoxetane ( 4 ) .
(4)
(3)
The epoxide of compound (3) (X = CI) is reported to polymerize to a high molecular weight polyether of the 'PENTON'
type with triethylaluminum.
The compounds of type ( 3 ) (X = halogen) behave normally
in substitution reactions to give, in the main, disubstituted
products, although monosubstitution can be achieved under
controlled conditions. Substituted isobutene derivatives
undergo some interesting molecular rearrangement reactions.
Thus esters such as ( 5 ) rearrange with sodium hydride to
pimelic acids (6). These pimelic acid derivatives and the diols
: C : ('S)
+
H3C-CH
11
3
CH,-CH=C=CH-CH,
H,C-CH
Evidence was presented that two forms of the C2 molecule
exist, a singlet species (:C=C:) which reacts with hydrocarbons to give ethylene, and a triplet species ( . C G C . )
which gives acetylene with the same substrate. The C3 molecule can exist in three forms: two singlet species (:C=C-C:)
and a triplet species (:C=C=C). The latter has been shown to
add stereospecifically to olefins, whereas one of the singlet
species exhibits non-stereospecific addition to olefins and
gives allene and propyne with hydrocarbon substrates. The
other singlet species, generated by a hot carbon filament,
gives allene exclusively with hydrocarbons.
A number of short papers read at the Symposium should
also be mentioned. D . H . Johnson (Blackley, England) reported the oxychlorination of n-butenes at 350°C with yalumina/cupric oxide/potassium chloride catalyst to give
1.4-dichlorobutadiene isomers.
A . J. Shuttleworth (Runcorn, England) described the pyrolysis
of trans-1 ,2-dichloroethylene to give mixed isomers of trichlorobenzene, small amounts of dichlorobenzenes, and
four isomers of trichlorobutadiene.
HO,C-CRR~-CH~-C-CH,-CRR'-CO,H
FHz
(6)
Angew. Chem. internat. Edit. / Vol. 8 (1969) No. 2
R . W. Humnzel (Wantage, England) reported the isomerization of cis-2-butene to trans-2-butene upon y-irradiation in
the presence of 1 "/: sulfur hexafluoride at 30 "C in an argon
atmosphere.
149
0. Onsager (Oslo, Norway) reported the dimerization of
propene to a mixture of cis-2-hexene, 2,3-dimethyl-l-butene.
2-methyl-1 -pentme, and 4-methyl-1-pentene with a catalyst
composed of tetramethylcyclobutadienenickel dichloride,
ethylaluminum dichloride, and tri-n-butylphosphine.
C. F. Kohl1 (Amsterdam, Netherlands) described the synthesis
of vinyl esters by the PdClz-catalyzed reaction of ethylene
and sodium acetate in glacial acetic acid.
J . M . Locke (Southampton, England) described the hydrogenation of unsaturated polymers, n-dodecene, styrene, or
diphenylacetylene using a catalyst prepared by the addition
of bis(isopropylsa1icylato)nickel to n-butyllithium in tetrahydrofuran or diglyme.
J . D . Littlehailes (Runcorn, England) reported the hydrodimerization of acrylonitrile to give an almost quantitative
yield of adiponitrile with sodium amalgam and water in the
presence of quaternary ammonium salts.
D. R. Taylor (Manchester, England) described the thermal
cycloaddition of allene t o fluoroolefins at 130 t o 160°C to
give high yields of cyclobutane derivatives. Tetramethylunder similar conditions
allene (2,4-dimethyl-2,3-pentadiene)
gives 1:l adducts arising by a preliminary isomerization of
[VB 177 IE]
the allene t o 2,4-dimethyl-l,3-pentadiene.
German version: Angew. Chem. 81, 155 (1969)
The Specific Trypsin Inhibitor from Pig Pancreas
By H . Tschesche
The trypsin inhibitors of low molecular weight are plant or
animal polypeptides with molecular weights of 6000-20000
(serum inhibitors: mol. wt. 75000). They may act either
specifically or polyvalently and inhibit other endopeptidases
as well as trypsin. The polyvalent inhibitors include, besides
plant inhibitors (mol. wt. 20000), the callicrein inactivator
from bovine organs which is identical with Kunitz’s trypsin
inhibitor from bovine pancreas. Bovine pancreas contains,
besides the intracellular Kunitz inhibitor, an inhibitor that is
specific against trypsin - Kazal’s inhibitor - which is secreted
in the fluid from the gland. Only the trypsin-specific inhibitor
of the Kazal type is found in other species of mammals, e.g.,
the pig “1.
The inhibitors inhibit proteases by complex formation, in
that they mask the active center, usually in the ratio I: 1, as is
found from the inhibition curve also for the inhibitor from
pig pancreas. The reaction is competitive with this inhibitor. The dissociation constant can be estimated from the
inhibition curve and is certainly less than 10-11 M. Whereas
polyvalent inhibitors have permanent inhibition against
trypsin, the specific trypsin inhibitors become inactive during
the action; their inhibitory effect is only temporary [21.
This inactivation begins with selective hydrolysis of only one
lysine bond in the native polypeptide chain of the inhibitor
from pig pancreas (mol. wt. = 6000), which contains four
lysine and two arginine units. This lysine unit lies between
two disulfide bridges (loop) 131. Its hydrolysis gives a modified
inhibitor that is inactivated faster than the native molecule
under physiological conditions. Its dissociation constant,
which can be determined from the inhibition curve, is increased (KD = 1 0 - 9 ~ )and thus permits powerful interactions during tryptic inactivation.
The selective tryptic hydrolysis (modification) is responsible
for the appearance of electrophoretically and chromatographically separable active inhibitors such as were isolated
by Kazal and by Fritz and Werle from mammals of various
kinds by way of water-insoluble trypsin resin.
The modification occurs at a lysine bond in the inhibitor
from the pig and the dog, but at the arginine bond in the
inhibitor from the ox. These bonds probabiy lie in the active
center of the inhibitors[3*41. Modification of this type is
typical of all specific trypsin inhibitors of Kazal type; it
150
occurs at the p H region of 2 to 10 with soluble trypsin and
water-insoluble trypsin resin. The maximum of the tryptic
modification occurs at p H 3.4 for the inhibitor (I) from pig
pancreas. This is therefore a special substrate for trypsin
is bound to it as a complex owing to its high affinity for
trypsin even in strongly acid solution, and, unlike other
natural and synthetic substrates, is maximally hydrolyzed in
this p H range because of the increasing dissociation of the
complex [51. From the selective hydrolysis, from experiments
with insoluble trypsin resin, from the kinetics, and from the
maximal modification at lower p H values it must beconcluded
that the inhibitor is being modified within the complex TI
and not within a Michaelis-Menten complex TIT after further
addition of excess trypsin.
n),
Lecturc at Dortmund on October 14, 1968
German version: Angew. Chem. 81, 122 (1969) [VB 1761
[*I Dr. H. Tschesche
Organisch-Chemisches Institut der Technischen Hochschule
8 Miinchen 2, Arcisstr. 21 (Germany)
[I] H. Fritz, F. Woitinas, and E. Werfe, Hoppe-Seylers Z . physiol. Chem. 345, 168 (1966); L. J. Greene, J . J. DiCarZo, A . J .
Sussman, D . C. Barrelr, and D . E. Roark, J. biol. Chemistry 243,
1804 (1968).
[2] M. Luskowski and F. C. Wu, J. biol. Chemistry 204, 797
(1953).
[3] H. Tschesche, Hoppe-Seylers Z . physiol. Chem. 348, 1216,
1635 (1967).
141 K . Ozawu and M. Laskowskijr., J. biol. Chemistry 241, 3955
(1966).
[S] H . Tschesche and H. Klein, Hoppe-Seylers Z . physiol. Chemistry, 349, 1645 (1968).
Thermally Unstable Allenes and Related
Compounds
By A. Roedig[*]
The rate of thermal dimerization of allenes t o 1,2-dimethylcyclobutane derivatives is greatly influenced by substituents.
The accumulation of electron-acceptor groups destabilizes
the allene system. Several dehydrohalogenations and fragmentations give rise to intermediates consisting of allenes that
are thermally unstable, i.e., can be preserved only below
-60 “C and in some cases deflagrate in the undiluted state.
They can be isolated by treating HCI-rich or HBr-rich
precursors with NaNHz in liquid NH3/propane or with a
rert-butoxide of potassium or lithium in liquid propane or
light petroleum at -75 OC.
On dimerization of trichloroallenes C12C=C=CCIR (R = CN,
COOC2H5, or C&s) the electronically most active and the
largest substituents appear in the exocyclic methylene groups.
Kinetic measurements show that the rate of dimerization deS
creases in the order R = C N > COOC2H5 > CI > C ~ H =
Br > H. The activation entropy of dimerization of allenes is
-
I
t
Angew. Chem. internat. Edit. f Vol. 8 (1969) 1 No. 2
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