[4+2] Cycloaddition of a,b-Unsaturated Acid Anhydrides to 2-Furylpiperidin-4-ones: The Short Route to Annulated 8,10a-Epoxypyrido[2,1-a]isoindoles

摘要

A one-step preparation procedure of 8,10a-epoxypyrido[2,1-a]isoindoles and their 7-carboxylic derivatives is reported. The key synthetic step includes the intramolecular exo-Diels–Alder reaction (IMDAF) of N-furfurylacrylamide, produced in situ from 2-furylpiperidin-4-ones and a,b-unsaturated acid anhydrides. The synthesis of the title compounds can be performed under mild conditions with a high level of regio- and stereoselectivity. The same strategy has been successfully used for the synthesis of 9,11aepoxyimidazo[ 40,50:3,4]pyrido[2,1-a]isoindole-8-carboxylic acid from maleic anhydride and the spinacine derivatives – 4-(2-furyl)-4,5,6,7-tetrahydro-3H-imidazo[4,5-c]pyridines.