Multistep microwave-assisted solvent-free organic reactions: Synthesis of 4-oxo-tetrahydro-pyridine

Preparation and ring-closure of 2-dimethylaminomethylene-5-substituted-3-oxo-pent-4-enoic acid benzyl esters to dihydropyridine rings are efficiently and quickly carried out under solvent-free conditions in an open-vessel microwave system. The syntheses of 1,6-disubstituted-4-oxo-1,4,5,6-tetrahydro-pyridine-3-carboxylic acid benzyl esters are reported.