2026-09-18T19:30:32Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/96362021-07-05T14:03:20Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022
Stephen L. Buchwald.
Troutman, Malisa V. (Malisa Vaughn), 1970-
Massachusetts Institute of Technology. Department of Chemistry
2005-08-19T19:05:58Z
2005-08-19T19:05:58Z
1998
1998
http://hdl.handle.net/1721.1/9636
42363676
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1998.
Includes bibliographical references (leaves 97-98).
A highly reactive chiral catalyst for the asymmetric hydrogenation of aryl trisubstituted olefins was generated by combining the complex (EBTHI)MMe2 (EBTHI = ethylenebistetrahydroindenyl, M = Ti, Zr) with [PhMe2NH]+[(BC6F5)4]- under a hydrogen atmosphere. A number of unfunctionalized trisubstituted olefins could be hydrogenated rapidly at room temperature under 80 psig H2 with a wide range of ee's (7 97% ). Reduction of some substrates under a deuterium atmosphere revealed that olefins which gave low ee's were being isomerized to 1, 1-disubstituted olefins prior to reduction. In some cases, additional deuterium was introduced at nonolefinic carbon atoms, indicating that the metal complexes also catalyze directed C-H activation. The zirconium-based catalyst was also applied to the first highly enantioselective hydrogenations of unfunctionalized tetrasubstituled olefins. Hydrogenations of l ,2- dimethyi-3,4-dihydronaphthalene proceeded with high enantioselectivity, but were accompanied by side reactions. At 80 - 2000 psig H2, hydrogenations of a number of fully substituted unfunctionalized indenes proceeded cleanly to give mostly cis products with ee's of 78 - 99%; rates and enantioselectivities increased with increasing pressure. Again, deuteration experiments showed that isomerization processes may occur under the reaction conditions.
by Malisa V. Troutman.
Ph.D.
99 leaves
6080049 bytes
6079805 bytes
application/pdf
application/pdf
eng
Massachusetts Institute of Technology
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http://dspace.mit.edu/handle/1721.1/7582
Chemistry
Asymmetric hydrogenation of unfunctionalized trisubstituted and tetrasubstituted olefins
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<Abstract>A highly reactive chiral catalyst for the asymmetric hydrogenation of aryl trisubstituted olefins was generated by combining the complex (EBTHI)MMe2 (EBTHI = ethylenebistetrahydroindenyl, M = Ti, Zr) with [PhMe2NH]+[(BC6F5)4]- under a hydrogen atmosphere. A number of unfunctionalized trisubstituted olefins could be hydrogenated rapidly at room temperature under 80 psig H2 with a wide range of ee's (7 97% ). Reduction of some substrates under a deuterium atmosphere revealed that olefins which gave low ee's were being isomerized to 1, 1-disubstituted olefins prior to reduction. In some cases, additional deuterium was introduced at nonolefinic carbon atoms, indicating that the metal complexes also catalyze directed C-H activation. The zirconium-based catalyst was also applied to the first highly enantioselective hydrogenations of unfunctionalized tetrasubstituled olefins. Hydrogenations of l ,2- dimethyi-3,4-dihydronaphthalene proceeded with high enantioselectivity, but were accompanied by side reactions. At 80 - 2000 psig H2, hydrogenations of a number of fully substituted unfunctionalized indenes proceeded cleanly to give mostly cis products with ee's of 78 - 99%; rates and enantioselectivities increased with increasing pressure. Again, deuteration experiments showed that isomerization processes may occur under the reaction conditions.</Abstract>
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