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Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene
Author(s) -
Fordham James M.,
Grayson Matthew N.,
Aggarwal Varinder K.
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201907617
Subject(s) - chemistry , reagent , organic synthesis , stereoselectivity , silane , organic chemistry , boronic acid , combinatorial chemistry , catalysis
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.