Synthesis of Some New Fused and Spiro 1,4-Benzoxazine Derivatives

Abstract

4-Methyl-3,4-dihydro-2H-1,4-benzoxazin-3-one 1 reacted with CS 2 and halo compounds to give thieno-1,4-benzoxazines 2a , b and 2-(1,3-dithiol-2-yliden)-1,4-benzoxazines 3a , b , respectively. Reaction of compound 1 with cyanoketene S,S diacetal afforded pyrano-1,4-benzoxazine derivatives 4 , 5 . Treatment of compound 1 with bromine in 1:2 molar ratio afforded 2,2-dibromo derivative 6 . Compound 6 reacted with bidentates, or with CS 2 and reactive methylenes to give the corresponding spiro compounds 7a–f and 8a–d , respectively. 2-(2-Bromo-4-methyl-3,4-dihydro-2H-1,4-benzoxazin-3-yliden)malononitrile 10 was allowed to react with ethyl thioglycolate, aniline or benzylamine to yield thiopyrano-1,4-benzoxazine 11 or pyrrolo-1,4-benzoxazines 12a , b , respectively. 2-(1-Ethoxy-methyliden)-4-methyl-3,4-dihydro-2H-1,4-benzoxazin-3-one 13 reacted with CS 2 and reactive methylenes or malononitrile to give spiro dithiolane 14a–c and 2-(4-methyl-3-oxo–3,4-dihydro-2H-1,4-benzoxazin-2-ylidenmethyl)malononitrile 15 , respectively. Reaction of compound 15 with some reactive methylene compounds gave the corresponding spiro cyclopentenes 16a–c .