The 1,3,5,7-Tetraazadecalins:  Structure, Conformation, and Stereoelectronics. Theory vs Experiment¹

cis- and trans-1,3,5,7-tetraazadecalin (TAD) (2 and 4) and several N-Me (7−9) and N-acyl (10−12) substituted derivatives in the cis and trans series were prepared and characterized. The X-ray structures of 4 and 12 were analyzed and the conformational equilibria of 2 and 11 were evaluated by VT-NMR. A QM (ab initio) and MM computational study was carried out, to provide relative stabilities and geometrical parameters, which were compared with experiment. The MM2-AE (modified for the anomeric effect in N−C−N containing molecules) and MM3 force fields are useful tools for these systems. The results were interpreted in the light of stereoelectronic effects in such fused 1,3-diazane systems.