DIELS-ALDER REACTIONS OF N-SULFONYL SUBSTITUTED AZA-ORTHO-XYLYLENES GENERATED FROM THE CORRESPONDING 1,4-DIHYDRO-2H-3,1-BENZOXAZIN-2-ONE DERIVATIVES

N-Tosyl- and N-alkylidene-sulfonyl substituted 1,4-dihydro-2N-3,1-benz oxazin-2-ones 2c-g easily undergo thermal carbon dioxide extrusion lea ding to the aza-ortho-xylylenes 3c-g, The intermediates 3c,d can be tr apped by electron-poor ethylenic and acetylenic dienophiles, giving te trahydroquinoline and quinoline derivatives, The reactions of 2c with non-symmetrical dienophiles are completely regioselective, N-Alkyliden esulfonyl substituted aza-ortho-xylylenes 3f-g undergo intramolecular Diels-Alder reactions leading to the tricyclic compounds 10 and 11, wh ile the aza-ortho-xylylene generated from ylsulfonyl)-1,4-tetrahydro-2 N-3,1-benzoxazin-2-one undergoes a [1,5] hydrogen shift leading to a-1 ,6-dien-1-ylphenyl]-4-methylbenzenesulfonamide.