Condensed heterotricycles: Pyrido(1,2,3- de )(1,4)benzoxazines, pyrido(1,2,3- ef )(1,5)benzoxazepines and pyrido(1,2,3- fg )(1,6) benzoxazocines

Cyclization of N-(2-haloacyl)-8-hydroxy-l,2,3,4-tetrahydroqumolines4–7 and9 with alkali affords pyridobenzoxazinones21–24 and26 respectively and of the 4-chlorobutyramide13 with NaH, the benzoxazocinone31. Exposure of 3-chloropropionamide12 to NaH affords acrylamide15, benzoxazepinone28 or methyl benzoxazinone22 or mixtures thereof under various conditions.28 undergoes rapid base-catalysed ring contraction to22. NaH-catalysed ring closure of acrylamide15 affords mixtures of22 and28, while from the crotonamides16 and17, the methylbenzoxazepinones29 and30 are obtained preponderantly, the former amide yielding only traces of the ethyl benzoxazinone23.29 shows no propensity for ring contraction to give23. The cinnamoyl derivatives18,19 and20 are cyclized to benzyl benzoxazinones24,27 and25, respectively. The intermediacy of the phenyl benzoxazepinone39 in the formation of24 has been established by deuteration studies. Benzylidene benzoxazinone41 is obtained from dibromocinnamamide14 and propiolamide40. Dichloracetamides8 and10 undergo interesting ring closure to compounds45–54 upon treatment with amines. The course of electrophilic reactions of the lactams depends upon the ring size. Contribution No. 18 from Searle R & D Centre Presented at a symposium to felicitate Prof N S Narasimhan at the University of Poona, November 18–19, 1988