Transition-metal catalysis of cyclocarbonylation and cycloisomerization reactions

Chapter 1. The asymmetric Pauson-Khand cyclization of nitrogen-containing enynes using carbon monoxide and a catalytic amount of (EBTHI)TiMe2 was examined. The influence of the nitrogen substituent and the concentration of the catalyst on the enantioselectivity of this cyclization was explored. It has been found that enynes with an octyl-, benzyl-, or allyl-amino group, positioned [beta] to the alkyne and the olefin, were cyclized with a high degree of enantioselectivity. Substrates with bulky and/or electron-withdrawing nitrogen substituents were converted to products in low to moderate enantioselectivity. Chapter 2. The first example of an early transition-metal-catalyzed enyne cycloisomerization is described. Titanocene dicarbonyl was shown to catalyze the cycloisomerization of enynes and dienynes to 1,4-dienes and allylic allenes, respectively. Examination of the scope of the reaction demonstrates that only trans-substituted enynes were cyclized. The products were exclusively 1,4-dienes and the reaction was completely diastereoselective for a chiral substrate with a substituent [gamma] to the alkyne. Chapter 3. A variety of monocyclopentadienyl-titanium-aryloxide complexes were used to catalyze or mediate cyclization reactions of alkynes, dienes, and enynes. Structural analysis, by X-ray crystallography, provided steric parameters, including wedge angles, for the aryloxide ligands. A titanium metallacycle was prepared from a sterically-hindered enyne containing a trisubstituted olefin. A monocyclopentadienyl titanium (2,6-dipheyl)phenoxide was used to promote a Pauson-Khand reaction of trimethylsilyl-substituted enynes,

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Sturla, Shana Jocette, 1975-

Advisor dc:contributor.advisor

• Stephen L. Buchwald.

• 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/1721.1/8249

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8249