Reduction of inner sulfonium salts, thioethers, and sulfones derived from closo-[B12H12]2- by lithium in methylamine: a new route to mercaptododecaborates.
Anions [Me2SB12H11]- (2) and [MeSB12H11]2- (3) can be reduced by excess lithium in methylamine at -15 degrees C to yield [HSB12H11]2- (1) after workup. Such behavior toward this reducing system is similar to that of alkyl aryl sulfides. The sulfone [MeSO2B12H11]2- (12) also yields 1 as a major boron product upon reduction, while alkyl aryl sulfones produce the corresponding arenes under the same conditions. Similarly, isomers of (Me2S)2B12H10 (4-6) are reduced by lithium in methylamine yielding dithiols [(HS)2B12H10]2- (7-9). The tetrabutylammonium salts of 1 and 7-9 are obtained in 80-90% yields and characterized by multinuclear NMR and mass spectrometry, the latter three compounds being isolated and characterized for the first time. The reduction reaction provides access to dithiols 7-9 for biological evaluation and use in synthesis. Thus, 2 and 4-6 can be easily converted to [R2SB12H11]- and (R2S)2B12H10 in a two-step reduction-alkylation procedure. 1,2-(Bn2S)2B12H10 (13) obtained by alkylation of the reduction product of 4 by benzyl chloride was characterized by single-crystal X-ray diffraction analysis. Crystal data for 1,2-(Bn2S)2B12H10.CD3CN: C2/c (No. 15), a = 13.666(1) A, b = 16.978(1) A, c = 14.667(1) A, beta = 91.08(1) degrees, Z = 4.
Kultyshev
R G
RG
Department of Chemistry, Ohio State University, Columbus, Ohio 43210, USA.
Liu
S
S
Shore
S G
SG