SITE-SELECTIVE DIELS-ALDER REACTIONS OF 7-(METHOXYIMINO)-4-METHYLCHROMENE-2,8-DIONE WITH ALKENES

Regio- and site-selective Diels−Alder reactions of o-quinone monooxime 1 are reported. The electron rich dienophiles 2, 4, 6, 8, and 10 react with the exocyclic diene system of monooxime 1 leading to the coumarin derivatives 3, 5, 7, 9, 11, and 12. The electron deficient dienophiles 13a,b and 18 react with the quinoid and the pyrone diene systems of compound 1 affording the cycloadducts 14a,b, 17a,b, and 19.