4+2 Cycloaddition of a,b-Unsaturated Acid Anhydrides to 2-Furylpiperidin-4-ones: The Short Route to Annulated 8,10a-Epoxypyrido2,1-aisoindoles

摘要

A one-step preparation procedure of 8,10a-epoxypyrido2,1-aisoindoles and their 7-carboxylic derivativesis 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 levelof regio- and stereoselectivity. The same strategy has been successfully used for the synthesis of 9,11aepoxyimidazo40,50:3,4pyrido2,1-aisoindole-8-carboxylic acid from maleic anhydride and the spinacinederivatives – 4-(2-furyl)-4,5,6,7-tetrahydro-3H-imidazo4,5-cpyridines.