Michalik D, Jiao H, Langer P. NMR spectroscopic and theoretical study on the isomerism of dimethyl benzodiazepine(diylidene)diacetates.
MAGNETIC RESONANCE IN CHEMISTRY : MRC 2022;
60:845-856. [PMID:
35373394 DOI:
10.1002/mrc.5272]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/15/2022] [Accepted: 03/29/2022] [Indexed: 06/14/2023]
Abstract
The isomerism of dimethyl 2,2'-(7,8-dichloro-1H-benzo[b][1,4]diazepine-2,4-(3H,5H)diylidene)diacetate (1a) and dimethyl 2,2'-(7,8-dichloro-3-methyl-1H-benzo[b][1,4]diazepine-2,4-(3H,5H)diylidene)diacetate (1b) was investigated by 1 H, 13 C and 15 N nuclear magnetic resonance (NMR) spectroscopy. In CDCl3 solution, inversion of the diazepine ring was observed, whereas in (D6 )DMSO and (D7 )DMF solution, besides the ring inversion, a partial cleavage of one chelate ring appeared connected with (E/Z) isomerization about one of the exocyclic C=C bonds. Gibbs free energies (ΔG) and free activation energies (ΔG≠ ) were calculated based on B3PW91-SCRF/ZVP DFT computations. Agreement between NMR data and density functional theory (DFT) computations was found.
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