Synthesis, NMR analysis and X-ray crystal structure of 3,9-bis(4-(trifluoromethyl)phenyl)-3,9-diazatetraasterane

Abstract Novel 3,9-bis(4-(trifluoromethyl)phenyl)-3,9-diazatetraasterane (3, Tetraethyl 3,9-bis(4-(trifluoromethyl)phenyl)-3,9-diazahexacyclo[6.4.0.02,7.04,11.05,10]dodecane-1,5,7,11-tetracarboxylate) was obtained by [2 + 2] photocycloaddition of diethyl 1-(4-(trifluoromethyl)phenyl)-1,4-dihydropyridine-3,5-dicarboxylate (1). The intermediate syn-dimer 2 was isolated and assisted to investigate the complexity of NMR spectra. The dimers’ structures of 2 & 3 were unequivocally confirmed by NMR, HRMS and XRD analysis. To discuss the steric symmetry effects on the NMR of the two dimers, NMR spectra analysis of 2 & 3 (1D-NMR and 2D-NMR) was conducted in details by the chemical shifts, couplings and correlations. XRD analysis aids to clarify the molecular symmetry of 2 & 3 and explicates that the steric effect and the special long-range coupling of CH2 lead to much more complicated NMR spectra of 2 than that of 3.