Some reactions of 10-substituted-10H-pyrido[3,2-b][1,4]benzothiazine-n-butyllithium adducts with acyl and sulfonyl chlorides

Abstract

Reaction of 10H-pyrido[3,2-b][1,4]benzothiazines 1 possessing a 10-methyl 1f, 10-(3-dimethylaminopropyl) 1b, or 10-(2-dimethylaminopropyl) 1c substituent, with n-butyllithium and methyl chloroformate or diethyl chlorophosphate affords predominantly 1,2-dihydropyridines 11 and the 4-substituted derivatives 12. The 1,7-disubstituted product 15b was obtained from reaction of the 10-methyl compound 1f with p-fluorobenzoyl chloride. On the other hand, treatment of the 10-methyl analog 1f with trifluoromethanesulfonyl chloride gave the unexpected 4-chloro derivative 12c and 13c which probably arises from the 1-trifluoromethanesulfonyl-1,2-dihydropyridine 11c via elimination of trifluoromethanesulfonic (sulfinic) acid. The N-10 dealkylated product 1a was obtained from reaction of the 10-(1-methyl-2-dimethylaminoethyl) analog 1g with n-butyllithium and methyl chloroformate, whereas a similar reaction employing the 10-(2-dimethylaminoethyl) derivative 1h gave rise to the N-methoxycarbonyl derivative 18. On the other hand, reaction of 1h with n-butyllithium alone gave the N-10 n-hexyl product 19. Mechanisms for the formation of 1a, 11, 12, 13, 15, 16, and 19 are described.