Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene

Abstract

Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with lithiated epoxysilanes. Aliphatic and electron‐rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron‐deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the C−Si and C−B bond breaking transition states. This vinylidene homologation was used in a short six‐step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.

Eliminating Transition State Calculations for Faster and More Accurate Reactivity Prediction in Sulfa-Michael Additions Relevant to Human Health and the Environment

“…DFT calculations were performed with Gaussian 16 (Rev. A.03) at the M06-2X/def2-TZVPP level of theory under the IEFPCM implicit solvation model (water), which has been used extensively for modeling organic reactions. − Implicit solvation in water was chosen to simulate the experimental conditions used in the kinetic glutathione chemoassay. In line with previous studies, and to ensure computational feasibility, methanethiolate was used as a model nucleophile in all calculations. , All regression models were developed via the Scikit-learn Python package .…”