Reaction of 2,5-dimethyl-3,4-dinitrothiophen with secondary amines. Formation and crystal structure analysis of 2,5-dimethyl-trans-2,3- dimorpholino-4-nitro-2,3-dihydrothiophen

Abstract

2,5-Dimethyl-3,4-dinitrothiophen (2) reacts with both morpholine and piperidine, in neat amine, to yield 2,5-dimethyl-trans-2,3-dimorpholino-(5a) and 2,5-dimethyl-trans-2,3-dipiperidino-4-nitro-2,3-dihydrothiophen (5b). The structure of (5a) has been unambiguously determined by X-ray analysis. In the crystal (monoclinic space group P2₁/n, a= 14.126, b= 11.103, c= 10.821 Å, β= 96.66°, Z= 4; R= 0.041 over 1 898 observed reflections) the dihydrothiophen ring is puckered. The two C–S bond lengths are significantly different (1.89 and 1.73 Å, respectively). Steric hindrance is reflected by some short intra- and inter-molecular contacts. A reaction scheme is proposed.