1,3-Oxazines and related compounds. XIII. Reaction of acyl Meldrum's acids with Schiff bases giving 2,3-disubstituted 5-acyl-3,4,5,6-tetrahydro-2H-1,3-oxazine-4,6-diones and 2,3,6-trisubstituted 2,3-dihydro-1,3-oxazin-4-ones.

Abstract

The reactions of Sehiff bases {2) with various acyl Me]drum's acids (1} were invcstigateci. Refiuxing of 1 and 2 in benzene caused an exchange te'actian of the Ltcetone nioiety of t with the SehilT base moiety through the intermediate acylketenes 11 formed in sittt t'rom 1 to give 2.3- disubstituted 5-aeyl-3.4.5,6-tetrahydro-2N-l.3-Qxazine-4,6-diones (3), The oxazindiones 3 undev- went therrnal conversion te alTorcl 2,3.6-trisubstituted 2.3-dihydro-t,3-oxaz[n-4-enes C4) ln geod yield. The intermediates 11 were found ta be forrned by thermal cieavage o{' both l ttnd 3,