An intramolecular journey of a carboxyl group around 1,2-dihydropyridines: multisite δ- versus γ-lactonization reactions

In contrast to substituted 4-acetic acid 1,4-dihydropyridines, giving only δ-lactones upon intramolecular reactions, 2-substituted 1,2-dihydropyridines led, besides to δ-lactones, also to new, structurally interesting γ-lactones as the result of a bromine-induced carbon-carbon double bond ‘Umpolung’.

Whereas alkylacetic acid-substituted 1,4-dihydropyridines gave upon electrophile-induced lactonization reactions, regio- and stereoselectively δ-lactones, the corresponding 1,2-dihydropyridines led, depending on the reaction conditions, to multisite lactonization products, γ- and δ-lactones.Figure optionsDownload as PowerPoint slide