Treatment of α-formyl amides with RAlCl2 or PhAlCl2 provided threo-α-alkyl-substituted β-hydroxy amides under high stereocontrol. The method was successfully applied to the selective addition of alkyl group to α-methyl-substituted β-keto amides or esters. Treatment of α-methyl-β-keto amides or α-methyl-β-keto esters with trialkylaluminium or alkylmanganese halide afforded the corresponding erythro (or threo) α-methyl-substituted β-hydroxy amides or α-methyl-substituted β-hydroxy esters with high stereoselectivity.
Organometallic compounds derived from thioamides RCH2CSN(R3)2 condense normally with aldehydes and saturated ketones. Condensation with 4-t-butyl-cyclohexanone leads predominantly to equatorial attack by the organometallic compound. These results suggest that the organometallic structure as RCHC(SM)N(R3)2.