Formation of β-Lactones through Lewis Acid-Promoted [2 + 2] Cycloaddition Reaction. A Theoretical Study

Abstract

The formation of β-lactone through Lewis acid-promoted [2 + 2] cycloaddition is studied using semiempirical (AM1/RHF and AM1/CI) and ab initio (HF/6-31G* and MP2/6-31G*) calculations. After a preliminary semiempirical study of the BF3-catalyzed parent reaction through two distinct reaction paths, ab initio and/or semiempirical studies on solvent and Lewis acid (BH3 and BF3) effects concentrate on the mechanism involving the prior formation of the C−C bond. At the HF/6-31G* level of theory the introduction of BF3 induces a reduction of the activation energy from 40.8 to 11.9 kcal/mol, and calculations performed with AM1/COSMO showed that the introduction of a solvent results in the formation of an earlier transition state. The case of BH3 is somehow more complicated since the studied system induces, both at the semiempirical and ab initio levels, a hydride transfer leading to a very stable product.

Influence of Polarity on the Scalability and Reproducibility of Solvent-Free Microwave-Assisted Reactions

“…All reaction paths were determined by the fullchn process [30]. All Transition Structures (TS) of full reaction paths were located by the chain method [32] and characterized by one and only one negative eigenvalue of the Hessian matrix. Furthermore, the corresponding vibration was found to be associated with nuclear motions along the reaction coordinate.…”

Aluminium(III) Trifluoromethanesulfonate as an Efficient Catalyst for the Intramolecular Hydroalkoxylation of Unactivated Olefins: Experimental and Theoretical Approaches

“…Finally, the transitions states found were shown to belong to the studied reaction by intrinsic reaction coordinate (IRC). The AM1 method was chosen mainly for three reasons: 1) its reliability compared to ab initio calculations for reactions involving Lewis acids and our experience in the field, [20] 2) the reasonably short calculation times, which enabled us to perform IRC on each transition state, and 3) the possibility to tackle the real molecules and therefore compare calculations to experiments.…”

The Formation of Silylated β‐Lactams from Silylketenes through Lewis Acid Promoted [2+2] Cycloaddition: A Combined Theoretical and Experimental Study

“…This conclusion, based on experimental [9] and theoretical work, [10] and the above-mentioned reactivity of silylketenes towards imines [6,7] led us to study, both experimentally and theoretically, the formation of β-lactams from silylketenes and imines under Lewis acid catalysis conditions. The publication of a study of a catalysed Staudinger reaction [11] prompted us to publish our results.…”