RÉACTION DU SULFURE DE BORE AVEC QUELQUES GROUPES CARBONYLES

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Abstract
The reactions of boron sulphide with some types of carbonyls have been studied. The reaction of boron sulphide with aromatic aldehydes and aliphatic aldehydes which have been deprived of active hydrogen in the α position gives a good yield of the corresponding trithioaldehydes. This reaction is examined for four aldehydes, namely, benzaldehyde, 3-methylbenzaldehyde, 3-nitrobenzaldehyde, and 2,2′-dimethylpropionaldehyde. Through this study the authors have brought out a method which enables either the α-trithiobenzaldehyde, m.p. 166–167 °C, or the β-trithiobenzaldehyde, m.p. 225–226 °C, to be obtained selectively. The reaction of 3-methylbenzaldehyde with boron sulphide yields only one β stereoisomer, but nitrobenzaldehyde remains completely inert. The aldehydes having one active hydrogen in the α position undergo a dehydrogenation at the same time as the oxygen is being replaced by one atom of sulphur. 2,2′-Dimethylthiopropanal exists in a trimeric state at normal temperatures and becomes monomeric at higher temperatures, whereas the trithiobenzaldehydes do not depolymerize. Methyl benzoate reacts with boron sulphide to give tetraphenyldioxadiene. The structure of this extremely inert substance has been established mainly by physical means: infrared, ultraviolet, and n.m.r. spectra. The reaction of benzophenone and acetophenone with boron sulphide has been investigated. The former has been found inert to the action of the sulphide, and the latter reacts quite readily to give 2,4-diphenylthiophene. The structure of this thiophene is established by desulphuration over nickel. The role of boron sulphide as dehydrogenating and deoxygenating agent is discussed, and a laboratory preparation of boron sulphide is described.

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