A facile synthesis and structure determination from 13c-nmr spectroscopy of a novel heterocycle 1,1′-ethylenebis[2,3,8,8a-tetrahydro-5,8a-dimethyl-1H-imidazo[2,1-c][1,4]thiazine], a case of transannular stabilization

The condensation of 4-thiaheptane-2,6-dione with triethylenetetramine does not produce the macrocycle 1-thia-3,14-dimethyl-4,7,10-13-tetrazacyclopentadeca-3,13-diene; instead two molecules of the dione condense with one of the amine to give the title compound.