Addition reactions of heterocyclic compounds. Part LXII. A new rearrangement in the quinazoline series

Abstract

Dimethyl acetylenedicarboxylate with 4-ethoxyquinazoline and its 6-methyl derivative give tetramethyl 6-ethoxy-4aH-pyrido[1,2-a]quinazoline-1,2,3,4-tetracarboxylates, which by an acid catalysed ring-opening–ring-closure process isomerise to the corresponding 2,3,4,4a-tetracarboxylates. The structures of these compounds have been deduced from ¹H and ¹³C n.m.r. spectra, and their interactions with lanthanide shift reagents have been examined.