Transition metal catalyzed C-O bond functionalization: enantioselective arylation of oxocarbenium ion intermediates and enantiospecific borylation of allylic carboxylates
Date
2016
Authors
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Publisher
University of Delaware
Abstract
During the last half century, transition metal-catalyzed cross-coupling reactions have come to play an important role as a powerful tool in organic chemistry. Traditionally, halides and triflates are chosen as electrophiles for these reactions. However, alcohol-based substrates show advantages in both availability and environmental friendly. ☐ Chapter 1 discussed an enantioselective arylation of chromene acetals. We have found a copper(I)-catalyzed condition for this reaction. In this case, chromene acetals have been successfully coupled with arylboronic esters to afford a mixture of two regioisomers with mild enantioselectivity for the 1,4-addition product. Under our current study, a 1,2,4-triazolium N-heterocyclic carbene was identified as the most effective ligand. ☐ Chapter 2 describes a stereospecific Miyaura coupling of allylic pivalates with organodiboron reagents to afford highly enantioenriched α-chiral γ-alkyl/aryl allylic boronates. Notably, a significant solvent effect was observed. By the choice of solvent, either inversion or retention of stereochemistry can be obtained. Under optimized conditions, either enantiomer was obtained from a single enantiomer of starting material. ☐ Overall, this thesis describes my progress towards extend the methodology of transition metal catalyzed cross-coupling reactions using alcohol-based substrates as electrophiles.