Effects of 3-substituents upon orientation in the 1,3-dipolar cyclo-addition reaction between 3-substituted pyridine N-imides and ethyl propiolate: syntheses of ethyl 4- and 6-substituted pyrazolo[1,5-a]-pyridine-3-carboxylates

Abstract

Quantitative data are presented relating to the effects of a series of 3-substituents upon orientation in the formation of ethyl pyrazolo[1,5-a]pyridine-3-carboxylates by a 1,3-dipolar cycloaddition reaction between 3-substituted pyridine N-imides and ethyl propiolate. The observed regioselectivity is discussed in terms of electronic and steric factors as well as hydrogen-bond formation.