Ring Contraction of 3-Carboxamide or 3-Carboxylate of 4-Hydroxy-2-methyl-2H-1,2-benzothiazine-1,1-dioxide and Analogous 1(2H)-Isoquinolinone-3-carboxylate
摘要:
A novel ring transformation of 3-carboxylate or 3-carboxamide of 4-hydroxy-2-methyl-2H-1,2-benzothiazine-1,1-dioxide and analogous 1(2H)-isoquinolinone-3-carboxylate to the 5-membered rings upon the reaction with carbonyl compounds in the presence of primary or secondary amines is described.
An improved method for the synthesis of 4-hydroxy-2-methyl-l-oxo-1,2-dihydroisoquinoline-3-carboxylic acid derivatives is described. The synthetic route involves initial phthalic anhydride aminolysis with alkylaminoacetic acid derivatives, further esterification with diazomethane and final heterocyclization of the phthalamic ester intermediates by alkoxide-induced Dieckmann condensation. The best yields