Unequivocal synthesis of 2,3,6‐triazaphenothiazine and two new tetraazaphenothiazine heterocycles

Abstract

This paper describes the unequivocal synthesis of three new heterocycles: 2, 3, 6‐triazaphenothiazine ( 7 ) and 2, 3, 6, 9‐tetraazaphenothiazine ( 18 ), both parents of the respective ring systems and the 6, 8‐dihydro‐7, 9‐di‐oxo derivative of 2, 3, 6, 8‐tetrahydrophenothiazine ( 12 ). These compounds were obtained by base‐catalysed condensation of 4, 5‐dichloropyridazine ( 8 ) with the appropriate o ‐amino‐heterocyclic thiols 9, 11, 16 . In contrast, reaction of 2, 3, 5‐trichloropyrazine ( 20 ) with 4, 6‐diaminopyrimidine‐5‐thiol ( 21 ) and 2‐amino‐6‐picoline‐3‐thiol ( 28 ) gave 5‐chloro‐2, 3‐bis(diaminopyrimidinyl‐5‐thio)pyrazine ( 33 ) and 5‐chloro‐2, 3‐bis(2‐amino‐6‐picolinyl‐3‐thio)pyrazine ( 29 ), respectively. Chloropyrazine ( 34 ) and 3‐aminopyridine‐2(1 H )‐thione ( 9 ) followed the latter reaction path to 2‐(3‐amino‐2‐pyridyl) pyrazinyl sulfide ( 35 ) in good yields. Structural assignments were based on their infrared, ultraviolet, nmr and mass spectra.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96349/1/5570200441_ftp.pd