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Ring Expansion Tetrahydropyrimidin-2-ones into Tetrahydro-1H-1,3-diazepin-2-ones: a Theoretical Study
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1  N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Ave., 119991 Moscow, Russian Federation


A plausible mechanism for the nucleophile-mediated ring expansion of 4-chloromethyl-1,2,3,4-tetrahydropyrimidin-2-ones into 2,3,6,7-tetrahydro-1H-1,3-diazepin-2-ones based on DFT calculations at B3LYP/6-31+G(d,p) level is discussed. This mechanism involves the following subsequent steps: N(1)H deprotonation under the action of nucleophile, intramolecular nucleophilic substitution of the chlorine atom to give cyclopropane bicyclic intermediate, nucleophile-promoted cyclopropane ring opening leading to 2,5-dihydro-1H-1,3-diazepin-2-one, and addition of nucleophiles to the C=N bond to afford the final diazepinones.

Keywords: Tetrahydropyrimidin-2-ones; Tetrahydro-1H-1,3-diazepin-2-ones; Ring expansion; Nucleophiles; DFT calculations; Reaction mechanism