Direct vinylogous Mannich-type reactions via ring opening and rearrangement of vinyloxiranes

The first synthetic application of 2-methyl-2-vinyloxirane as a masked dienolate has been successfully demonstrated in the direct vinylogous Mannich-type reaction with an alpha-imino ester as an electrophile. The Mannich adduct was a useful intermediate en route to cis-5-substituted pipecolinic acid ethyl ester under simple hydrogenation conditions.