1-Aminocyclohexene-2,4-dicarbonitrile derivatives. Syntheses and structural study

Abstract

Substituted 1-aminocyclohexene-2,4-dicarbonitriles were obtained by reaction of α,β-unsaturated nitriles (two equivalents) with benzyl cyanide. By recrystallization from ethanol one diastereomeric racemate was isolated in each case. The cyclohexene structures were established from spectroscopic data (IR, MS, and one- and two-dimensional NMR). Relative stereochemical configurations and conformational preferences in the solid state of cyclohexenes 2 and 3 and propanedicarbonitrile 1 were established from X-ray crystallography. Crystals of 1 (C17H14N2) belong to the orthorhombic space group Pbca. Cell dimensions are a = 17.168(7), b = 21.612(5), c = 7.508(2) Å, V = 2785(7) Å3. Final R = 0.078 and Rw = 0.091; 1363 reflections were observed. The compound 2 (C26H21N3) crystallizes in the monoclinic space group P21/n with Z = 4. The crystal data for 2 are a = 7.743(1), b = 24.420(1), c = 11.164(1) Å, β = 102.65(1)°, V = 2059.7(3) Å3. Final R = 0.046 and Rw = 0.059; 2701 reflections were observed. Crystals of 3 (C16H17N3) belong to the triclinic space group [Formula: see text] Cell dimensions are a = 14.582(1), b = 7.283(1), c = 7.116(1) Å, α = 110.84(0)°, β = 85.92(0)°, γ = 97.81(1)°, V = 696.9(2) Å3. Final R = 0.047 and Rw = 0.052; 2227 reflections were observed. The cyclohexene ring in 2 and 3 exists as a sofa rather then as a half-chair conformation. Keywords: 1-aminocyclohexenes, α,β-unsaturated nitriles, benzyl cyanide.