Preparation of α, β-Unsaturated Carbonyl Compounds Using Dianion of N-Phenyl-2-[(pheneylsulfonyl)methyl] propenamide

Abstract

The dianions of heteroatom-substituted 2-methylpropenamides were generated at -78°C. Among the dianions studied, the reagent formed from N-phenyl-2-[(phenylsulfonyl)methyl] propenamide exhibited a high regioselectivity toward a wide variety of electrophiles in tetrahydrofuran (THF).
The α-adducts prepared from the dianion and alkyl halides gave stereoselectively (E)-2methyl-2-alkenamides on brief treatment with sodium borohydride in ethanol. The corresponding sequence using aldehydes and epoxidesa fforded( E)-4-hydroxy-2-methyl-2-alk. enamides and (E)-5-hydroxy-2-methyl-2-alkenamides, respectivelyu nder similar reaction, c onditions.5, 6-Dihydro-2 H-pyrans were prepared by treatment of α-adducts, obtained from the dianion of N-phenyl-2-[(phenylsulfonyl)methyl]propenamide and epoxides, with potassium t-butoxide in THF.