[1,4]Thiazino[2,3,4-ij]quinoline derivatives and related heterocycles

Abstract

Reaction of 2H-1,4-benzothiazin-3(4H)-one, 2H-1,4-benzoxazin-3(4H)-one, 2,3-dihydro-1,5-benzothiazepin-4(6H)-one, and 2,3-dihydro-1,6-benzoxazepin-4(5H)-one with propiolactone gave rise to the corresponding 3-propionic acids (1) and (4) in good yields. Cyclization of 3-(3-0~0-3,4-dihydr0-2H-1,4-benzothiazin-4-yl)-propionic acid with polyphosphoric acid gave 3,7-dioxo-2,3,6,7-tetrahydro-5H [1,4]thiazino[2,3,4-ij]quinoline (2a). The 1,4-oxazino analogue (2b) (oxajulolidine) and 3,8-dioxo-2,3,7,8-tetrahydro-4H,6H-[1,5]oxazepino[2,3,4-.ij]quinoline (5b; R = H) were prepared by a similar route. Some reactions of these compounds are described.