Ring opening at N1–C2 bond of azetidin-2-ones by a molybdenum hydroxo-carbonyl complex: evidence from a computational study

Abstract

Computations on the reaction of azetidin-2-one, N-sulfonate azetidin-2-one, and 3-formylamine-N-sulfonate azetidin-2-one with [Mo(OH)(η³-C₃H₅)(CO)₂(N₂C₂H₄)] were performed at the B3LYP/6-31 + G(d,p) (LANL2DZ for Mo augmented by f polarization functions with exponents 1.043) taking into account solvent effects by means of the PCM-UAHF model. According to our calculations, the rate-determining energy barrier for the azetidin-2-one case, 38.0 kcal mol⁻¹, becomes 28.8 and 26.1 kcal mol⁻¹ for the N-sulfonate azetidin-2-one and 3-formylamine-N-sulfonate azetidin-2-one ones, respectively. The presence of the sulfonate group is crucial to cleave the β-lactam N1–C2 bond by the Mo complex thanks to the interaction of the sulfonate group with the hydroxyl and bidentate ligands of the complex. This could be of interest for the synthesis of β-amino acids and their derivatives from β-lactams in mild conditions and low polarity solvents promoted by organometallic complexes.