Applications of planar-chiral heterocycles in asymmetric catalysis

The development of planar-chiral heterocycles for asymmetric catalysis and their applications to enantioselective processes were investigated. Reactions including the kinetic resolution of propargylic alcohols, the enantioselective ring opening of meso epoxides, and the asymmetric hydrosilylation of ketones were studied. ... During the past few years, our group has developed lb as one of the most effective and versatile nonenzymatic acylation catalysts for the kinetic resolution of arylalkylcarbinols. Surprisingly, however, when the optimized reaction conditions were applied to the kinetic resolution of secondary propargylic alcohols, only low to moderate selectivity factors were obtained. Detailed investigations revealed that triethylamine serves as a competitive general base catalyst in the acylation reaction of propargylic alcohols, thereby suppressing the intrinsic selectivity factor. When base is omitted, the selectivity factor for propargylic alcohol 2 (R1 = Ph, R2= Me) increases from 6 to 20. Using this new protocol, we can effect the kinetic resolution of a number of propargylic alcohols with selectivity factors of 10 or above. ... Catalysts in which oxygen is the nucleophilic site effect a number of useful transformations. In view of the utility of planar-chiral pyridine derivatives such as 1, it occurred to us that pyridine N-oxides 3 might also prove to be effective asymmetric catalysts. We synthesized complexes 3a-c and were gratified to discover that 3a efficiently catalyzes the ring opening of cis-stilbene oxide by SiC14, albeit in modest enantiomeric excess.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Tao, Beata, 1973-

Advisor dc:contributor.advisor

• Gregory C. Fu.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8047

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8047