Synthesis and Intramolecular Cycloaddition Reactions of Some 3-Substituted 6-Azidohexa-2,4-dienoate Esters

Article abstract of DOI:10.1021/jo00343a025

Several 3-substituted (methyl, n-butyl, phenyl) 6-azidohexa-2,4-dienoate esters were synthesized by conjugate addition of <(Z)-3-<(tetrahydropyranyl)oxy>-1-propenyl>copper to the appropriate acetylenic ester, followed by conversion to the azide by depyranylation , mesylation, and azide substitution.In the methyl and butyl cases, the addition was nonstereoselective under the conditions used, while the phenyl case gave nearly completely the product of anti addition.The azides all undergo intramolecular cycloaddition to form 3a,6-dihydro-3H-pyrrolo<1,2-c><1,2,3>triazolesat rates which depend upon the stereochemistry and substitution of the 6-azidohexa-2,4-dienoate.All of these adducts are unstable with respect to decomposition to a 2-substituted pyrrole, again at rates which are both substituent and solvent dependent.Under certain circumstances, the 3a,6-dihydro-3H-pyrrolo<1,2-c><1,2,3>triazoles are converted to the open chain valence tautomers which are α-diazo-2,5-dihydropyrrole-2-acetate esters.Possible factors contributing to the observed substituent and stereochemical effects are considered.