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] ...
