Synthesis and some chemical transformations of novel 1-oxo-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-8-carboxylic acids and their benzoannelated analogues

A preparatively convenient method is proposed for the synthesis of new 1-oxo-3,4-dihydro-1H-pyrrolo[2,1-с][1,4]oxazine-8- 4a-e and 4-oxo-4H-pyrrolo[2,1-c][1,4]benzoxazine-3-carboxylic acids 5a-f that is based on the interaction of methyl (2-oxomorpholin-3-ylidene)ethanoates 1a-e and methyl (2-oxo-2H-1,4-benzoxazine-3(4H)-ylidene)ethanoates 2a-f with 2-bromo-1,1-diethoxyethane. Obtained acids were transformed into the corresponding tert-butyl carbamates 6a-e, 7a-f and N-alkyl(aryl)carboxamides 11a-i, 12a-d. By treating tert-butyl carbamates 6a-e, 7a-f with hydrogen chloride, 8-amino-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazin-1-ones 8a-e and 3-amino-4H-pyrrolo[2,1-c][1,4]benzoxazin-4-ones 9a-f were obtained. By acylation of amines 8a-e, 9a-f with acetic anhydride, benzoyl chloride, methanesulfonyl chloride, and p-toluenesulfonyl chloride, corresponding N-acetamides 13a,b, 14, N-benzamides 15, 16, N-methanesulfonamides 17, 18, and N-p-toluenesulfonamides 19, 20 were synthesized. In total, 30 new derivatives of 1-oxo-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazinones and 27 new 4-oxo-4H-pyrrolo[2,1-c][1,4]benzoxazinones were obtained.