Enantiospecific, Regioselective Suzuki-Miyaura Cross-Couplings of Secondary, Allylic Boronic Esters
Loading...
Authors
LaBine, Emily
Date
2013-11-14
Type
thesis
Language
eng
Keyword
Suzuki-Miyaura , Regioselective , Catalysis , Enantiospecific , Cross-Coupling
Alternative Title
Abstract
The stereochemical course of the Pd–catalyzed Suzuki-Miyaura cross-coupling of α-substituted, enantioenriched allylic boronic esters with phenyl iodide has been examined. The secondary boronic esters were prepared in both racemic and enantioenriched forms via borylationof a lithiated carbenoid with a geometrically defined vinyl boronic ester. The geometric purities were determined to be >99% and the enantiomeric excesses of stereodefined secondary boronic esters were found to exceed 98:2. In total, 8 allylic boronic esters were successfully cross-coupled, providing arylated products with high regioselectivities (>90:10) and complete enantiospecificities (>99%). The cross-coupling of a sterically and electronically unbiased, deuterated substrate confirmed that fully equilibrated π-allylic intermediates are not involved. Additionally, correlating the absolute configurations of the allylic boronic ester and the cross-coupling product allowed us to confirm that the transmetalation step of the reaction proceeded through a closed transition state via a syn-SE’ mechanism, which further suggests the importance of the distinct Pd-O-B bond linkage.
Further, the cross-coupling of vinyl iodides to secondary boronic esters was investigated.
Description
Thesis (Master, Chemistry) -- Queen's University, 2013-11-12 19:05:19.488
Citation
Publisher
License
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.