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Intermediate Occurrence of 1 2-Dehydrocyclooctatetraene.

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Reactions of the kind described above may perhaps be models
for protein synthesis in the living cell.
slowly eliminates H2S with the formation of polycrystalline
oligomers containing Ti-S-Ti bonds.
Received: September 3rd. 1965 [Z 57/883 I€]
German version: Angew. Chem. 77, 965 (1965)
.
-~
L
L
J"
(2a), n = 1
(2b), n = 2
(la). n = 1
(lb), n = 2
[I] G . Wi[kinson and J. M . Birmingham, J. Amer. chem. SOC.76,
4281 (1954).
[2] By vapor-pressure osmometry (Mechrolab 301 A).
[3] Saturated solution, tetramethylsilane as external standard
(Varian A 60).
[4] S. A . Giddings, U.S.-Patent 3030395 (April 17th, 1962);
Chem. Abstr. 57, 9881 (1962).
Intermediate Occurrence of
1,2-Dehydrocyclooctatetraene
By Dr. A. Krebs
Institut fur Organische Chemie
der Universitat Heidel berg (Germany)
7
( H3 C ) zC - C Hz - C H -C Hz - H - f:( C H3 ) 2
HOOA
I
HOOC
HOOC
The ring strain and reactivity of 1,2-dehydrocyclooctatetraene
( I ) should lie between those of 1,2-dehydrobenzene, a confirmed but non-isolable intermediate, and of cyclooctyne [ I ]
which can be isolated.
(4)
COOH
[Z 591886 IE]
Received: August 27th, 1965
German version: Angew. Chem. 77, 965 (1965)
[I] Synthesis: H . Kammerer, W . Rauseh, and H. Schweikert,
Makromolekulare Chem. 56, 123 (1962).
Di-x-cydopentadienyltitanium
Bis(hydrogen sulfide)
After treatment of bromocyclooctatetraene [2] with a n ethereal
suspension of potassium t-butoxide and subsequent hydrolysis
potassium bromide was found in the aqueous phase in
a yield of 95 %. Separation of the reaction mixture gave,
apart from a high-melting, brown powder insoluble in
ether and benzene, t-butoxycyclooctatetraene(2) by distillation, b. p. 37-38 "C/0.05 mm, yield 16 %, and naphtho-2,3cyclooctatetraene (3), m.p. 113-1 14'C, yield 9 %, by
chromatography of the distillation residue o n silica gel with
cc14.
By Dr. H. Kopf and Prof. Dr. Max Schmidt
lnstitut fur Anorganische Chemie
der Universitat Marburg (Germany)
Di-n-cyclopentadienyltitaniumbis(hydrogen sulfide) (2) was
prepared in almost quantitative yield by the reaction of di-rcyclopentadienyltitanium dichloride ( I ) [ l ] with hydrogen
sulfide and the stoichiometric amount of triethylamine in
anhydrous ether (1 h at 2OoC):
(CsH&TiC12
(1)
+ 2 H2S + 2 N(C?H&
+ (CSH&Ti(SH)2 + 2 (CzH&N.HCI
(2)
Compound (2), which is surprisingly stable towards oxidation by air and toward hydrolysis, is freed from the accompanying amine hydrochloride by extraction of the mixture with water and is recrystallized from chloroform. The
brown-black, malodorous crystals decompose at 150-160 "C.
I n chloroform solution (2) is monomeric [2]. The 1H-NMR
spectrum in CHCI3 [3] contains two sharp signals, at 6.34
(C5H5) and at 3.44 (SH) ppm, with a n intensity ratio of 5 : 1.
As expected, the proton signal at 3.44 pprn is missing in the
spectrum (in CDC13) of the compound (CsH5)2Ti(SD)2
prepared analogously from D2S.
The presence of two S H groups was confirmed by iodometric
determination of the hydrogen sulfide quantitatively liberated by hydrogen chloride according t o
and by methylation with dimethyl sulfate t o di-x-cyclopentydienyltitanium bis(methy1 sulfide) 141. Compound (2)
does not react with diazomethane. I n boiling benzene it
Angew. Chem. internat. Edit. / Vol. 4 (1965)
/ No.
I1
The structure (2) was proved by elemental analysis,theNMR
spectrum, acid hydrolysis to cycloocta-l,3,5-trien-7-one
(isolated as the 2,4-dinitrophenylhydrazone[3]), and hydrogenation t o t-butoxycyclooctane, which was synthesized
independently from cyclooctanol. T h e structure (3) was
proved by elementary analysis, spectra (particularly NMR),
oxidation (by 0 3 and CH3C03H) to 1,2,4,5-benzenetetracarboxylic acid, and independent synthesis of 2,3-cyclooctenonaphthalene, which is obtained o n hydrogenation of
13).
The probable intermediacy of 1,2-dehydrocyclooctatrienein
this reaction of bromocyclooctatetraene was shown by trapping reactions: if the HBr elimination is carried out e.g. in the
presence of tetraphenylcyclopentadienone o r phenyl azide,
the adducts (4),m.p. 241-242OC, yield 1 2 %, and (5), m.p.
67.5-68 O C , yield 38 %, respectively, are obtained. The con-
953
stitutional proof for the compounds (4) and (5) was obtained
from elementary analysis, spectra, and hydrogenation to the
corresponding known cyclooctyne adducts 141.
Received: September 6th, 1965 [ Z 5S/SS4 IE]
German version: Angew. Chem. 77, 966 (1965)
[ I ] '4.T. Blomquist and L. H . Liu. J. Amer. chem. SOC.75, 2153
(1953).
[2] Preparation: A. C. Cope and M . Burg, J. Amer. chem. SOC.
74, 168 (1952); G. Schroder, personal communication.
[3] A , S. Cope, S. F. Schaeren, and E. R.Trumbull, J. Amer.
chern. SOC.76, 1096 (1954).
141 G. Wittig and R. Pohlke, Chem. Ber. 94, 3276 (1961).
Selective Protolysis of Unsaturated
Organoaluminum Compounds
By Dr. B. BogdanoviC
Max-Planck-Institut fur Kohlenforschung,
Mulheim/Ruhr (Germany)
Vinyl groups can be removed preferentially from alkylvinyltin compounds by electrophilic reagents [l]. Similarly
vinylboranes are cleaved by acids more easily than alkylboranes [2]. We have found also that organoaluminum
compounds of type ( I ) , obtainable by addition of hydridodialkytaluminums to acetylenes, are susceptible to selective
protolysis. From compound ( I ) and acetylacetone one
obtains exclusively the olefin and acetylacetonatodialkylaluminum (2) although Al-alkyl bonds are easily cleaved
protolytically.
the H' ions attack the x-electron pair of the double bond
and not the electron pair of the nitrogen atom. The same is
true for compounds ( I ) .
Acetylacetonatodialkylaluminums, which have not been
described before [ 5 ] ,are liquids, sensitive to air, monomeric,
and almost colorless, and can be distilled in vacuum; their
compositions and infrared and HI-NMR spectra accord
with structure (2). Acetylacetonatodiethylaluminum has b. p.
55-56 'C/1-2 mm, and the diisobutyl analogue 40-45 "C/
10-4 mm.
Received: September 9th, 1965
[ Z 67/893 IE]
German version: Angew. Chem. 77, 1010 (1965)
[I] D . Seyferth, Progr. inorg. Chem. 3, 129 (1962).
[2] H. C. Brown and G. Zweifel, J. Amer. chem. SOC.81, 1512
(1959).
[2a] G. Wilke and H . Muller, Chem. Ber. 89, 444 (1956); Liebigs
Ann. Chem. 618,267 (1958); 629,222 (1960).
[3] L . .
I
Zakharkin
.
and J. M . Khorlina, Proc. Acad. Sci. USSR,
chem. Sect. (engl. Transl.) 116, 422 (1957).
[4] Ketimines can be similarly obtained by addition of Grignard
compounds to nitriles, followed by protolysis: P. L. Pickard and
T. L. Tolbert, J. org. Chemistry 26, 4886 (1961).
151 Acetylacetonatodialkylboroncompounds have been described
recently: M. F. Hawthorne and M . Reintjes, J. Amer. chem. SOC.
86, 5016 (1964).
Divinylogous Methylenephosphoranes from
Conjugated Diynes, Trialkylphosphines, and
Active Methylene Compounds
By Dr. H.-E. Sprenger and Dr. W. Ziegenbein
Forschungslaboratorien der Chemischen Werke Hiils AG,.
Marl (Germany)
R' = H , Alkyl
RZ = Alkyl: A r y l
A solution of acetylacetone in a hydrocarbon, e.g. toluene,
is dropped slowly at O o to -3OOC into a solution of the
organoaluminum component (molar ratio 1 : 1). Disappearance of a yellow coloration due to interaction of the compounds ( I ) and (2) indicates the end of the reaction. The
olefin is separated from the organometallic component by
distillation. If this method of cleavage is used in the stereospecific reduction of acetylenes to cis-olefins with dialkylaluminum hydrides [2a], the usual hydrolytic cleavage of all
metal-carbon bonds can be avoided.
Aluminum imides (3), obtainable by addition of hydridodialkylaluminums to nitriles [3], can also be cleaved selectively
a t the AI-N linkage by means of acetylacetone, whereby
also compound (2) and aldimines result. This reaction is
significant for the synthesis of aldimines [4],since it can be
conducted at very low temperature (-80 "C) where aldimines
d o not polymerize.
a
?
R ~ A ~ - N = C H +R ~
H,C-C-CH~-C-CH, + (2)
+
HN=CHR~
(3)
R'
=
Alkyl
Compounds of the type RzAI-NRz (R = alkyl) are not
selectively cleaved at the AI-N linkage, which shows that
954
Direct preparation of divinylogous methylenephosphoranes
can be effected by simultaneous reaction of active methylene
compounds and trialkylphosphines with conjugated diynes.
For instance, equimolar amounts of diphenyl- or bismorpholinomethyl-l,3-butadiynewith tri-n-butylphosphine and
malononitrile, fluorene, or anthrone in ether, tetrahydrofuran, or benzonitrile under reflux afford the methylenephosphoranes ( l a ) - ( I d ) , which are isolated as follows:
After evaporation of the solvent or after mixing the benzonitrile solution with ether [for (Ic)] the reaction products are
washed with ether or quickly recrystallized from methanol,
ethanol,dioxane, and benzene [for ( I d ) , ( l a ) , (ic), and (2),
respectively].
(n - C4H9)3P=C - CH = CH -
B
R
= C R' RZ
(1)
( l a ) , R = Phenyl, R1= R2 = CN, m.p. 150 "C
( l b ) , R = Phenyl, CRlR2 = anthromylidene, m.p. 210 "C
( l c ) , R = Phenyl, CRlRZ = fluorenylidene,
m.p. 215 "C (decomp.)
( I d ) , R = Morpholinomethyl, R1 = R2 = CN,
m.p. 200 "C (decomp.)
(n - C,H,),P= C - CH=C H- C = N- C EN
I
C6H5
I
C6H5
(2), M.p. = 136°C
With NH-acidic compounds, e . g . , cyanamide, products of
type (2) are-formed.
Structures of the products were proved by elemental analysis
and by ultraviolet, infrared, and N M R spectroscopy.
Of the compounds indicated, only ( I c ) reacts with carbonyl
compounds and p-quinone to give colored, easily crystallizable olefination products of structures (3) and ( 4 ) . Reaction
conditions: (lc) is heated with e x e s carbonyl compound o r
in a solution of a n equimolecular amount of carbonyl comAngew. Chem. internat. Edit. / Voi.4 (1965)
1No. 1I
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