Speaker: Professor Yoshitaka Hamashima

Institution: School of Pharmaceutical Sciences, University of Shizuoka

Hosted by: Professor Rongbiao TONG

Abstract

Selective functionalization with heteroatoms is extremely important, because incorporation of such functional groups can enhance the value of compounds considerably. We are particularly interested in difunctionalization of alkenes via asymmetric bromination and fluorination reactions. Considering the intrinsic nature of each halogen atom, we have been working on the development of novel organocatalysts for halogenation.

Thus, we found that chiral bisphosphines such as BINAPs are effective catalysts for enantioselective bromocyclization of allylic amide derivatives. Careful examination of the reaction mechanism revealed a unique role of BINAP derivative, which is distinct from regular Lewis basic action and provide a new guide for further study.

For fluorination reaction, we have created two anionic phase transfer catalysts to make fluorination reactions with cationic Selectfluor enantioselective. Probably due to mismatched hard/soft character between fluorine and p-bonds, stereoselective fluorination of alkenes has been difficult to achieve. Using our designer catalysts, unprecedented asymmetric fluorination reactions of alkenes became feasible.

In this presentation, the details of these studies and further applications will be discussed. Additionally, our recent work on C(sp3)-H fluorofunctionalization is briefly presented as a related study.