Addition reactions of heterocyclic compounds. Part LI. Cyclobuta-[b]pyridines from reactions of dimethyl acetylenedicarboxylate with 1-alkyl-1,4-dihydropyridines and the cycloelimination of amide and carboxy-groups

Abstract

Several 1,3-disubstituted 1,4-dihydropyridines with dimethyl acetylenedicarboxylate in acetonitrile at room temperature gave 1,4,4a,6a-tetrahydrocyclobuta[b]pyridines and where a 3-carboxy- or a 3-carbamoyl group was present, a novel cycloelimination of this group occurred to give the corresponding 3-(cis-1,2-dimethoxycarbonylvinyl) derivative. 1-Benzyl-1,4-dihydroquinoline-4-carbonitrile gave the 3-(cis-1,2-dimethoxycarbonylvinyl) derivative quantitatively, and 2-benzyl-1,2-dihydroisoquinoline-1-carbonitrile formed a phenanthridine.