Crystal structure and spectra of 6,7-dimethoxy-3,3-dimethyl-3,4-dihydroisocarbostyril azine

Crystal and molecular structures of 6,7-dimethoxy-3,4-dimethyl-3,4-dihydroi socarbostyril azine (I) were determined using X-ray diffraction analysis an d IR and electronic absorption spectroscopy. Compound I was found to exist in the form of an azine isomer, in which the N=C double bonds are located o utside the tetrahydroisoquinoline fragments, while the H atoms migrate towa rd the N(1) atoms of these moieties. Model quantum-chemical calculations we re performed.