The 1,3,5,7-Tetraazadecalins:  Structure, Conformation, and Stereoelectronics. Theory vs Experiment<sup>1</sup>

<i>cis</i>- and <i>trans</i>-1,3,5,7-tetraazadecalin (TAD) (<b>2 </b>and <b>4</b>) and several <i>N</i>-Me (<b>7</b>−<b>9</b>) and <i>N</i>-acyl (<b>10</b>−<b>12</b>) substituted derivatives in the <i>cis</i> and <i>trans</i> series were prepared and characterized. The X-ray structures of <b>4</b> and <b>12</b> were analyzed and the conformational equilibria of <b>2</b> and <b>11</b> 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.