Spectral properties and isomerism of nitroenamines. Part 1. 3-Amino-2-nitro-acrylic esters

Abstract

3-Amino-2-nitroacrylic esters (1) with primary and secondary amino group crystallize either in the s-cis,Z(1A), the s-trans,Z(1B), or the s-cis,E(1C) isomeric forms, and in solution they exist as equilibrium mixtures of the three forms, in ratios strongly dependent on the polarity of the solvent. Each isomeric form has easily distinguishable i.r. absorptions. On the other hand, their ¹H and ¹³C n.m.r. spectra show signals due to the s-cis,E from (1C), and a second set of signals attributed to the two rapidly interconverting conformations (1A and B) of the Z isomer.