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Condensed 1,3‐benzothiazinones. 2 . Synthesis of 2‐substituted 1,2,4‐triazolo[5,1‐ b ][1,3]benzothiazin‐9‐ones
Author(s) -
Liu KangChien,
Shih BiJane,
Chern JiWang
Publication year - 1989
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570260237
Subject(s) - chemistry , chloroacetyl chloride , acetic anhydride , triethyl orthoformate , benzoyl chloride , formic acid , derivative (finance) , medicinal chemistry , chloride , acetic acid , organic chemistry , catalysis , financial economics , economics
Heating 3‐amino‐2‐imino‐3,4‐dihydro‐2 H ‐1,3‐benzothiazin‐4‐one (1) with formic acid neat or with trimethyl orthoformate ( 2a ) in xylene gave 1,2,4‐triazolo[5,1‐ b ][1,3]benzothiazin‐9‐one ( 3a ) in 49 and 81% yields, respectively. An analogous reaction of 1 with triethyl orthoacetate ( 2b ) and orthopropionate ( 2c ), trifluoro‐acetic and trichloroacetic anhydride ( 2d,e ), trichloroacetonitrile, dichloroacetyl, chloroacetyl, 2‐chloro‐propionyl, 3‐chloropropionyl, ethoxyoxalyl chloride ( 2f‐j ) and benzoyl chloride ( 2k ) under suitable conditions afforded a series of 2‐substituted 1,2,4‐triazolo[5,1‐ b ][1,3]benzothiazin‐9‐ones (3b‐k) in 59‐98% yields. Facile procedures for the preparation of 2‐hydroxy and 2‐mercapto derivative 31,m were developed by treating 1 with N,N ′‐carbonyl‐ and thiocarbonyldiimidazole (21,m) . The structures of all products were assigned on the bases of spectral and elemental analyses. Compound 3m was found to exist predominantly in the 2‐thioxo form.