Add time:07/12/2019         Source:sciencedirect.com

The synthesis of new N,N-dimethyl carbamoyl 5-aryloxytetrazoles have been reported. Their dynamic 1H-NMR via rotation about CN bonds in moiety of urea group [a; CO-NMe2 and b; (2-tetrazolyl)N-CO rotations] in the solvents CDCl3 (223–333 K) and DMSO (298–363 K) is studied. Accordingly, the free energies of activation, obtained 16.5 and 16.9 kcal mol−1 respectively, attributed to the conformational isomerization about the Me2NCO bond (a rotation). Moreover, a and b barrier to rotations in 5-((4-methylphenoxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide (P) also were computed at level of B3LYP using 6-311++G** basis set. The optimized geometry parameters are in good agreement with X-ray structure data. The computation of energy barrier for a and b was determined 16.9 and 2.5 kcal mol−1, respectively. The former is completely in agreement with the result obtained via dynamic NMR. X-ray structure analysis data demonstrate that just 2-acylated tetrazole was formed in the case of 5-(p-tolyloxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide. X-ray data also revealed a planar trigonal orientation of the Me2N group which is coplanar to carbonyl group with the partial double-bond CN character. It also demonstrates the synperiplanar position of CO group with tetrazolyl ring. On average, in solution the plane containing carbonyl bond is almost perpendicular to the plane of the tetrazolyl ring (because of steric effects as confirmed by B3LYP/6-311++G**) while the plane containing Me2N group is coplanar with carbonyl bond which is in contrast with similar urea derivatives and it demonstrates the unusually high rotational energy barrier of these compounds.

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