CHEMOSELECTIVITY OF [4+2] CYCLOADDITION IN <i>N</i>-MALEYL- AND <i>N</i>-ALLYL-2,6-DIFURYLPIPERIDIN-4-ONES

Abstract

On the basis of a transition state conformation analysis, an attempt was made to explain the high chemoselectivity of intramolecular [4+2] cycloaddition in 3-alkyl-2,6-difuryl-N-maleylpiperidin-4-ones. It was shown that the thermal Diels–Alder reaction in these piperidine derivatives takes place through the "boat" conformation and leads to the formation of hydrogenated 1-alkyl-4-(2-furyl)-2H-8,10a-epoxy-pyrido[2,1-a]isoindol-2-ones. The alternative regioisomers, 3-alkyl-4-(2-furyl)-2H-8,10a-epoxy-pyrido[2,1-a]isoindol-2-ones, are hardly formed at all. At the same time, the intramolecular Diels–Alder reaction in the isostructural 3-alkyl-N-allyl-2,6-difurylpiperidin-4-ones, takes place non-regioselectively from the "chair" conformation.

Authors: F. I. Zubkov, E. V. Nikitina, V. P. Zaytsev, V. N. Khrustalev, R. A. Novikov, R. S. Borisov, and A. V. Varlamov.

English Translation in Chemistry of Heterocyclic Compounds, 2012, 48 (5), pp 785-794

http://link.springer.com/article/10.1007/s10593-012-1057-4