Crystal and Molecular Structure of 2,3,5,6- Bis（ortho-1,10-decylidene）dihydropyrazine

1 INTRODUCTION The 1,4-dihydropyrazine ring system has attrac- ted much interest as a structural unit: 1) the possi- bility of cyclic 8π-electron conjugation gives rise to “antiaromatic” character; 2) these ring systems are thus electron rich and readily lose a single electron (namely single electron transfer reaction, SET) to give stable radical cations which are stabilized by captodative effect and/or other factors. Calculations for planar 1,4-dihydropyrazine have predicted the occup…

Crystal and Molecular Structure of 2,3,5,6- Bis(ortho-1,10-decylidene)dihydropyrazine

The SnCl2 reduction of 2-nitrocyclododecanone or 2-bromo-12-nitrocyclododecanone gave a colorless compound 2,3,5,6-bis(ortho-1,10-decylidene)dihydropyrazine 1a characterized by IR, NMR and X-ray diffraction analysis. Crystal data for 1a: Mr = 358.60,monoclinic, space group P21/n, a = 0.48028(3), b = 2.8646(4), c = 0.77097(6) nm, β =98.432(12)°, V = 1.04924(19) nm3, Dc = 1.135 g/cm3, Z = 2, F(000) = 400 andμ(MoKα) =0.065 mm-1. All 1H- and 13C-NMR resonance lines of 1a were assigned by DEPT, COSY,HMQC and HMBC technology. In the crystal, the dihydropyrazine ring has a planar structure,two twelve-membered rings adopt [1ene2333] conformation, their double bonds have cis-configuration, and the whole molecule has a center of symmetry. In solution, the symmetric 1Hand 13C-NMR signals suggest that two twelve-membered rings of 1a may adopt enantiomorphous [ lene2333] conformation existing in a dynamic equilibrium.