In this paper, we describe a facile and efficient method to prepare compound 2, which had been previously obtained by a Vilsmeier reaction using DMF/POCl3 [1]. We found that employment of dimethylformamide-dimethylacetal (DMF-DMA) affords the title compound in better purity and higher yield.
A mixture of 0.47 g (1.98 mmol) of 4-phenyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one 1 [2,3] in 4.5 ml of dimethylformamide-dimethylacetal (DMF-DMA) was stirred at 100 °C for 4 hours and then cooled to room temperature. Filtration and washing with a little cold diethyl ether gave 0.46 g (75%) of 3-dimethylaminomethylene-4-phenyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one 2. The product obtained was recrystallized from diethyl ether.
Melting point: 224-225 °C (Diethyl ether).
MS (m/z, %): 292 ([M+H]+, 100%).
1H NMR (CDCl3, 400 MHz), δ(ppm): 2.55 (s, 6H, (CH3)2N), 2.80 (s, 1H, NH), 7.40 (s, 1H, C=CH-N(CH3)2), 6.80-7.90 (m, 9H, H-Ar).
13C NMR (CDCl3, 100 MHz), δ(ppm): 43.50 (N(CH3)2), 98.02 (C-3), 121.47, 124.59, 127.34, 128.13, 128.67, 128.89, 130.65, 131.78, 141.86 (C-Ar), 151.18 (C=CH-N(CH3)2), 167.40 (C-4), 178.57 (C=O).
Supplementary materials
Supplementary File 1Supplementary File 2Supplementary File 3References
- Solomko, Z.F.; Proshkina, V.N.; Bozhanova, N.Ya.; Loban, S.V.; Babichenko, L.N. Vilsmeier reaction with 4-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-2-one. Khim. Geterosikl. Soedin. 1984, 223. [Google Scholar] [CrossRef]
- Ried, W.; Stahlhofen, P. Über heterocyclische siebenringsysteme, vii der reaktionsverlauf zwischen o-phenylendiamin und alkyliden-brenztraubensäuren. Chem. Ber. 1957, 90, 828. [Google Scholar] [CrossRef]
- Nardi, D.; Tajana, A.; Rossi, S. J. Heterocyclic compounds from 3,3-dimercapto-1-aryl-2-propen-1-ones. Note 1. 4-aryl-1,3-dihydro-2H-1,5-benzodiazepine-2-thiones. Heterocyc. Chem. 1973, 10, 815. [Google Scholar] [CrossRef]
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