Table 4.

Calculated NBO parameters (ωB97X-D/aug-cc-pVTZ) for the most stable conformers of the compounds 1 and 2. Relative energy of the steric (E_rel,Lewis) and hyperconjugative (E_rel,Hyper) interactions are given in kcal mol⁻¹. The sum of E_rel,Lewis and E_rel,Hyper is the total energy of the system.

conformer	CHCl3		DMSO		nO→σ*N–H a
	Erel,Lewis	Erel,Hyper	Erel,Lewis	Erel,Hyper
1-Ib	0.89	1.66	1.76	2.27	0.72
1-IIa	1.84	2.44	1.92	2.51	−
1-IIIb	2.02	2.63	2.32	3.03	−
1-IVa	4.04	4.42	4.02	4.51	−
1-Vc	0.00	0.22	0.00	0.21	−
1-VIc	1.23	1.14	0.91	0.96	−
1-VIIb	0.18	0.00	0.25	0.00	0.94
1-VIIIb	0.54	0.38	0.38	0.31	0.86
2-Ib	0.00	0.00	1.74	2.76	−
2-IIa	2.05	2.11	4.76	5.98	−
2-IIIa	4.31	4.33	6.26	7.48	−
2-IVa	6.38	5.97	5.84	6.69	1.32
2-Va	3.59	2.95	7.62	8.03	−
2-VIb	2.14	1.26	0.00	0.00	−
2-VIIa	3.73	2.95	6.22	6.43	−
2-VIIIa	4.44	3.73	7.30	7.70	−

^aNBO calculations were realized with an energy threshold of 0.5 kcal mol⁻¹.