Karen Thai

• University of Saskatchewan

Morpholinone and piperidinone-derived triazolium salts are shown to catalyze highly chemoselective cross-benzoin reactions between aliphatic and aromatic aldehydes. The reaction scope includes ortho, meta, and para substituted benzaldehyde derivatives with a range of electron donating and withdrawing groups, as well as branched and unbranched aliph...

An electron-deficient, valine-derived triazolium salt is shown to catalyze a highly chemo- and enantioselective cross-benzoin reaction between aliphatic aldehydes and α-ketoesters. This methodology represents the first high yielding and highly enantioselective intermolecular cross-benzoin reaction using an organocatalyst (up to 94% ee). Further dia...

The use of β,γ-unsaturated-α-ketoesters in the intermolecular Stetter reaction furnishes 1,2,5-tricarbonyl compounds in high yield and excellent enantioselectivity. The α,δ-diketoesters generated using this methodology serve as useful synthetic building blocks via chemo- and diastereoselective transformations.

The first chiral electron-poor guanidine organocatalysts were synthesized. The presence of a tunable electron-withdrawing group on the guanidine moiety allows for the modulation of the catalysts’ activity. The application of this new class of organocatalysts to the Michael reaction is demonstrated.

A very efficient NHC-catalyzed lactamization reaction is reported. For most cases, the ring expansion reaction proceeds to cleanly furnish five- and six-membered N-Ts and N-Bn lactams, without the need for further purification. Evidence is presented suggesting a dual role for the stoichiometric base: (1) deprotonation of the triazolium precatalyst...

Unsymmetrical di- and trisubstituted triflyl guanidines are accessed through a simple, one-pot protocol from the corresponding isothiocyanate and amine. Furthermore, in the presence of base, trisubstituted triflyl guanidines are alkylated to obtain tetrasubstituted triflyl guanidines in high yields and complete regioselectivity.

Imidazolinium-derived carbenes catalyze the ring-expansion lactonization of oxacycloalkane-2-carboxaldehydes. A variety of functionalized five-, six-, and seven-membered lactones can be formed efficiently under mild reaction conditions. The success of this new method for the construction of lactones is highly influenced by the electronic nature of...