Organic sulfur compounds. VII. Some reactions of benzothiazine hydroxamic acids

Abstract

Treatment of (3,4-dihydro-4-hydroxy-3-oxo-2H-l,4-benzothiazin-2-yl)acetic acid ( l a ) with sodium hydroxide yields the corresponding lactam, i.e. (3,4-dihydro-3-oxo-2H-l,4-benzothiazin-2-yl)acetic acid, together with the a,D-unsaturated acid, 3,4-d1hydro-3-oxo-2H-1,4-benzoth1az1ne-A~~~-acetic acid. The 6-methyl-and 6-bronio-derivatives of In behaved similarly when reacted with sodium hydroxide but when 3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzoth1azine was so treated a more complex reaction occurred.Methyl (6-bromo-3,4-dihydro-4-hydroxy-3-oxo-2H-I ,4-benzothiazin-2-yl)acetate was also treated with hydrochloric acid. The two products isolated were (6-bromo-3,4-d1hydro-3-oxo-2H-1,4-benzothiazin-2-yl)acetic acid and (6-bromo-7-chloro-3,4-dihydro-3-oxo-2H-1,4-benzoth1azin-2-yl)acet1c acid.The action of hydrochloric acid on 3,4-dihydro-4-hydroxy-7-methyl-3-oxo-2H-1,4-benzoth1azine also gave two products. One was the corresponding lactam; the other was unexpected and has been tentatively identified as bis[2-(3,4-dihydro-7-n1ethyl-3-0~0-2H-1,4-benzothiazine].