Recyclization of 2-oxotetrahydro-1,3-oxazines accompanied by decarboxylation: A convenient synthesis of tetrahydropyridine, quinolizidine, and indolizidine skeletons.

Abstract

Ethyl 6-vinyl-2-oxotetrahydro-1, 3-oxazine-5-carboxylate derivatives were converted with decarboxylation into ethyl 2-substituted 1, 2, 5, 6-tetrahydropyridine-5-carboxylates by heating with 1, 8-diazabicyclo[5.4.0.]undec-7-ene in dimethylsulfoxide at 120°C. This convenient method was used to synthesize quinolizidine, indolizidine skeletons and the alkaloid, (±)-lupinine.