ON THE TENDENCY OF 1,2,3,6-TETRAHYDROBENZOCYCLOBUTENE-3,6-DIONES FOR UNDERGOING SITE-SELECTIVE DIELS-ALDER REACTIONS AT THE INTERNAL DOUBLE BOND

摘要

Diels-Alder reactions of cyclobutene-3,6-diones, 5 and 6 with dienes 7 - 10 gave predominantly adducts arising from attack of the diene at the internal double bond of the diones. Ab initio MO calculations suggest that the observed site selectivity of cyclobutene-3,6-diones is due to strain effects rather than to frontier orbital effects. [References: 13]