Nuclear magnetic resonance conformational studies of C-substituted pyrrolecarbaldehydes. Part I. Substituent effects on aldehyde conformations as shown by long range coupling constants

Abstract

The conformations of the formyl group of the two pyrrolecarbaldehydes and the mono-iodo, -nitro,-ethoxycarbonyl, and -formyl derivatives have been determined by a study of the ⁵J and ⁴J long range coupling constants. The results show the influence of the nature and position of the substituent on the relative proportions of the two conformers. The influence of solvent on the value of ⁵J and ⁴J is considered for certain cases.