Lithiated sulfoxides: α-sulfinyl functionalized carbanions.

Reactions of alkyl aryl sulfoxides H-CRR'S(O)Ar with n-BuLi-TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine) afforded α-sulfinyl functionalized alkyl aryl lithium compounds of the type [Li2{CRR'S(O)Ar}2(TMEDA)2] (1, R/R' = H/H, Ar = Ph; 2, R/R' = H/H, Ar = p-Tol; 3, R/R' = Me/Me, Ar = Ph; 4, R/R' = H/Ph, Ar = Ph; 5, R/R' = Me/Ph, Ar = Ph). The compounds were characterized by (1)H, (13)C and (7)Li NMR spectroscopy and, except for 5, by single-crystal X-ray diffraction analyses. In crystals of 1, 2, 3 and 4 ·Et2O dinuclear molecules with four-membered Li2O2 rings were found. There are no LiCα contacts, thus, "free" carbanions are the main structural feature. Reactions of 1-6 (6, R/R' = H/Me, Ar = Ph) with benzaldehyde and benzophenone afforded the corresponding sulfoxides of the type ArS(O)CRR'CHPhOH (1a-6a) and ArS(O)CRR'CPh2OH (1b-6b), respectively. The reactions yielding / and / proceeded with high diastereoselectivities. By X-ray diffractometry it has been shown that in the case of and the diastereomers consisting of the two enantiomers SSRC and RSSC were formed.