GENERATION AND REACTIONS OF HETEROANALOGUES OF AZA-ORTHO-XYLYLENES

Intramolecular nucleophilic substitution of chlorine in 2-chloro-3-(al kanesulfonylamino)pyridines furnishes N-alkyl-1,3-dihydroisothiazolo[4 ,3-b]pyridine 2,2-dioxides (pyridosultams, 8), which undergo thermal e xtrusion of SO2 giving heteroanalogues of aza-ortho-xylylenes 9. These reactive 1-azadienes enter [4+2] cycloaddition with dienophiles leadi ng to tetrahydro[1,5]naphthyridines 11. With an excess of dienophile ( N-phenylmaleimide) pyridoazocine derivatives 12 and 13 being 2:1 adduc ts are formed. (C) 1997 Elsevier Science Ltd.