Asymmetric hydrogenation as a general route to polypropionates has been
explored for allylic alcohols, acids, and derivatives, which has led to the generation of
2,4-dimethylated hexane derivatives. Quantitative yields in most cases and
enantioselectivities greater than 98% were obtained. A remarkable stereofacial inversion
was observed when an ester or acid was present in the allylic position instead of an
alcohol or alcohol derivative. This led to the construction of all four diastereomers of
the hexanol series from a single enantiomer of hydrogenation catalyst. Also described
are an attempted synthesis of (-)-lardolure, a formal synthesis of the methyl ester portion
of the preen gland extract from the domestic goose Anser anser, and a total synthesis of
an extract from the fungi A. cruciatus. The synthesis of these compounds demonstrated
shortcomings of the known catalyst system showing enantioselectivities for
polymethylated compounds was high, while diastereoselectivity was low. Methodology
to develop new N-heterocyclic carbene catalysts was developed using the cyanide
coupling of aldimines to generate electronically tunable 1,3,4,5-tetraaryl complexes, and
X-ray, IR, and calculations were used to elucidate their electronic characteristics. These
studies indicate that the 4,5-positions have as great an influence on the metal-ligand
bond as the 1,3-positions. In addition, they are among the most electron-donating 2-
metalated N-heterocyclic carbenes found thus far. An intrinsic relationship between
catalytic activity and electron donating ability was found in transfer hydrogenations.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3126 |
| Date | 15 May 2009 |
| Creators | Ogle, James William |
| Contributors | Burgess, Kevin, Miller, Stephen A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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