Chemistry Weekly Seminar - Hemkalyan Ballav, PhD Candidate

Title

NHC-Catalyzed Cross-Benzoin Reactions of a-Alkoxy Aldehydes and Synthesis of Novel Chiral Thiazolium Salts for Organocatalysis

Abstract

N-Hetereocyclic Carbenes (NHCs) are prominent organocatalysts due to their unique ability to reverse the polarity (i.e., umpolung) of aldehydes which gives access to acyl anion equivalents. The benzoin reaction is a potentially powerful C-C bond forming reaction in organic synthesis that uses the umpolung technique to couple two aldehydes and produce a-hydroxy ketone products. But chemo- and stereoselectivity in cross-benzoin reactions involving two different aldehydes remains a significant challenge. Recently, our group has established that a-amino aldehydes are useful acceptors in chemo- and diastereoselective cross-benzoin reactions with heteroaromatic or aliphatic aldehydes. To expand the scope of this reaction, a-alkoxy aldehydes were employed in NHC-catalyzed cross-benzoin reactions and were shown to give promising results with triazolium, thiazolium as well as recently developed new chiral thiazolium salts.

Moreover, the novel chiral thiazolium salts have shown promising results in initial studies with enantioselective intermolecular Stetter reactions. The synthesis of these new catalysts and their organocatalytic applications will be presented.

Date:    Friday, March 10

Time:    1:30 pm

Place:    HLTH GB06