Effect of a bulky alicyclic substituent in position 3 on the structure and spectral characteristics of 1-(4′,4′-dimethylcyclohexa-2′,6′-dion-1′-ylidene)- 1,2,3,4-tetrahydroisoquinoline

The synthesis of spiro{cyclohexane-1′3-[1-(4′4′-dimethylcyclohexa-2′, 6′-dion-1′-ylidene)-1,2,3,4-tetrahydroisoquinoline]) (I) is performed. X-ray diffraction analysis and IR and electronic absorption spectroscopies have revealed that compound I, similar to 3,3-dimethyl (II) and 3,3-dimethyl-6,7-dimethoxy (III) derivatives of 1-(4′,4′-dimethylcyclohexa-2′,6′-dion-1′-ylidene)- 1,2,3,4-tetrahydroisoquinoline, exists as a enamine-diketone tautomer in both the crystal state and solutions. It is shown that the substitution of cyclohexyl for two methyl groups in position 3 of molecule II weakly affects its three-dimensional and electronic structure.