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Borate Complexes Derived from Lithium Carbenoids Ч Mechanism of the УInverse Stevens RearrangementФ.

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Borate Complexes Derived from Lithium
Carbencids - Mechanism of the “Inverse Stevens
Rearrangement” [11
By G . Kobrich and H . R . Merkle[*I
Juger and Hesse 121 have contrasted the nitrogen ylides and
their ability to undergo the cationotropic Stevens rearrangement, with the boron ylides (3) because several anionotropic rearrangements of boron ate-complexes can he ascribed
to the fact that the arrangement of their charges is the reverse
of that in ( I ) . It has been an open question whether this
“inverse Stevens rearrangement” is really to be ascribed to a
boron ylide intermediate stage.
lated o n (12)l on rearrangement and acid hydrolysis. The
cis-isomer of compound (12) gives 98 % p u e trans-oc-methylstilbene (yield 71 %). These findings exclude a boron ylide
intermediate common to the two isomers. The steps (12) +
(13) + (14) and (16) + (17) are electrophilic reactions at
the unsaturated carbon atom with retention of configuration.
It then follows that the rearrangement step (14) + (16) occurs with inversion by rear attack (15) of the phenyl group
o n the carbon atom carrying the chlorine substituent.
(12ja R = H
(13); R = Li
(14), R = %(C6Hs)s Li@
c =c,
( I 6 ) , R = B(C6Hs)z
(17), R = H
Received: November 4th, 1966
[ Z 368 IE]
German version: Angew. Chem. 79, 50 (1967)
We observed inverse Stevens rearrangements when we treated
stable lithium carbenoids (5) [31 with triphenylboron. ateComplexes (6) were slowly formed which rearranged to boranes (7) with elimination of lithium chloride when the mixture was warmed to room temperature or boiled in tetrahydrofuran.
(aj, R = H
(b). R = C1
(c), R = CH3
Use of dichloromethyl-lithium (8) gives the corresponding
(chlorobenzy1)diphenylborane(9) The ate-complex (10) formed from trans-dichlorovinyl-lithium decomposes at -100 “C
into pure cis-styryl chloride and phenylacetylene (molar ratio
about 1: 3); presumably the borane (11) is first formed.
[*I Doz. Dr. G. Kobrich and Dip1.-Chem. H. R. Merkle
Organisch-ChernischesInstitut der Universitat
69 Heidelberg (Germany)
[l] Part XXII of Stable Carbenoids. - Part XXI: G. Kobrich,
H. Heinemann, and W. Ziindorf; Tetrahedron, in press. - We
thank the Deutsche Forschungsgemeinschaft, the Wirtschaftsministerium of Baden-Wiirtternberg, and the Fonds der Chemischen Industrie for financial support.
[2] H. Juger and G. Hesse, Chem. Ber. 95, 345 (1962).
[3] For a review, see G. Kobrich et al., Angew. Chern. 79, I5
(1967); Angew. Chern. internat. Edit. 6,41 (1967). Cf. G.Kobrich
and W. Drischel, Tetrahedron, 22, 2621 (1966).
[4] K. Flory, unpublished experiments (1963) ; F. Ansari, Dissertation, Universitat Heidelberg 1966.
Ethyl Diazoiodoacetate and its Decomposition to
By F. Gerhart, U. Schollkopf, and H . Schumacher[*I
Halogenodiazomethanes are of interest as precursors of
halogenocarbenes and as preparative reagents 111. We obtained ethyl diazoiodoacetate (2),the first characterized halogenodiazoalkane[zl, in about 80% yield when we treated diethyl mercuribisdiazoacetate ( I ) 131 in ether with rather less
than 2 equivalents of iodine. The filtrate was concentrated
(water-pump, room temperature, rotary evaporator) and the
residue was digested with petroleum ether (b.p. 4OoC) to
remove the last traces of mercuric iodide. Compound (2) is a
red oil, stable for days at 0-5 OC, giving IR bands at 2080 and
1680 cm-1. Triphenylphosphazine derivative: m.p. 109 to
112 O C (decomp. ; precipitated from benzene by petroleum
The ate-complex (14) formed from trans-methylstyryl
chloride (12) v i a the trans-carbenoid compound ( I S ) 141 affords 99% pure cis-a-methylstilbene (17) [yield 65 %, calcu-
Angew. Chem. internat. Edit.
Yol. 6 (1967) No. I
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уinverse, rearrangements, mechanism, borate, carbenoids, complexes, derived, stevens, lithium
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