N-Heterocyclic carbene-catalyzed activation of esters for asymmetric reactions

Abstract

The work incorporated in this Ph.D. thesis was performed in the division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, under the supervision of Professor Yonggui Robin Chi. My study is mainly focused on the NHC organocatalytic activation of stable carboxylic acid esters to generate enolate equivalent intermediates for asymmetric reactions. The thesis is divided into five chapters:

 Chapter I contains a brief introduction on organocatalytic generation of enolate equivalents using enamine catalysis, chiral DMAP derivative/cinchona alkaloids and N-heterocyclic carbene catalysis.

 Chapter II describes the first example of Lewis base catalyzed α-activation of stable carboxylic esters, wherein DMAP efficiently catalyzed the formal [4+2] Diels- Alder reaction of carboxylic acid esters with 1,3-azadienes.

 Chapter III contains the first example of enantioselective activation of stable α-aryl carboxylic esters as enolate precursors via N-heterocyclic carbene cat-alysts.

 Chapter IV describes the first example of enantioselective activation of simple α-alkyl carboxylic esters as enolate precursors via N-heterocyclic carbene cat-alysts.

 Chapter V contains the first example of the activation of acetic esters as enolate precursors, which undergo highly enantioselective transformation via N-heterocyclic carbene catalysis.