Special Seminar on Oct. 23rd, 2015 (10:00, E104)---Prof.Choon-Hong Tan (Nanyang

Author:scbb    Time:2015-10-09 16:02:46    Hits:


Speaker    Choon-Hong Tan (School of Physical & Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University)

Title          Chiral Pentanidiums as Phase Transfer Catalysts

Time         Oct. 23rd, 10:00-11:30

Venue       E-104

Host          Prof. Yong Huang   

Web of the speaker:http://www3.ntu.edu.sg/home/choonhong/cv.html



A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. Several highly enantioselective reactions will be described. 1) The enantioselective Michael addition reactions of tert-butylglycinate Schiff base and various unsaturated acceptors will be discussed. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. 2) Direct a-hydroxylation of 3-substituted-2-oxindoles using molecular oxygen has also been developed. This reaction does not require an additional reductant such as triethyl phosphite, which was typically added to reduce the peroxide intermediate. 3) Enantioselective alkylation of sulfenate anions to provide highly enantiopure chiral sulfoxides. It was found that halogen bonding is an important non-covalent interaction in the transition state.