Reactions of 1-Arylbuta-1,3-dienes Generated from 3-Allyl-1,3-dihydro-2,1-benzisothiazole 2,2-Dioxides

Thermal (215_C) extrusion of sulfur dioxide from 3-allyl-1,3-dihydro-2,1-benzisothiazole 2,2-dioxides (3-allylbenzosultams) leads to aza-ortho-xylylenes, which by [1,5] sigmatropic hydrogen shift transform into 1-(2-aminophenyl)buta-1,3-dienes. In the presence of dienophiles, N-phenylmaleimide (NPMI) or dimethyl fumarate, these dienes enter Diels-Alder reaction and the formed adducts transform into 6a,7,8,10a-tetrahydro-5H-phenanthridin-6-one derivatives. Aza-ortho-xylylene 16 generated from 3,3-diallylbenzosultam 15 transforms into arylcyclohexadiene 19, which finally adds NPMI to form bicyclo[2.2.2]octene derivative 20.