THE MECHANISMS OF DILITHIATION REACTIONS IN ORGANIC SYNTHESES - A CASE-STUDY BASED ON THE SYNTHESES OF KETENE DITHIOACETALS

An investigation of the lithiation and CS2-insertion reactions of R(1) R(2)CH(2) precursors (reactions used in the syntheses of ketene dithio acetals) leads to the crystal structure determination of the monolithi ated complexes R(1)R(2)CHCS(2)Li . TMEDA, 3 (R(1) = Ph, R(2) = pyridyl ) and 4 (R(1) = H, R(2) = 2-methylpyrazine); attempted second lithiati on of 3 fails to give the R(1)R(2)C=CS2Li2 species anticipated in the mechanism of reactions of this type, but synthetic and H-1 NMR spectro scopic evidence indicates that 4 can be lithiated further.