Widdowson, Katherine (1992) Silicon-directed carbon-carbon bond forming reactions. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:09282011-115011728
It is shown that O-silyl ketene N,O-acetals react with aldehydes, without catalysis, to form aldol-type products with high diastereoselectivity. For example, the prolinolderived O-silyl ketene N,O-acetal 7 reacts with benzaldehyde to form the anti aldol product 9 with >98% diastereoselectivity. Mechanistic studies are presented which support a scheme involving formation of trigonal bipyrarnid (tbp) G, pseudorotation to form tbp T_(boat), and rate-determining C-C bond formation to produce 9.
It is shown that aldehydes react with pyridine, benzeneselenol, dichlorodimethylsilane, and an allylic alcohol to form O-allyloxy dimethylsilyl hemiselenoacetals in high yield. These derivatives undergo efficient free radical-mediated cyclization upon treatment with BU_3SnH, as exemplified by the transformation of 7→8. Together these steps provide an efficient method for carbon-carbon bond formation between the carbonyl carbon of an aldehyde and the terminus of an allylic alcohol.
2,3-Epoxy alcohols are transformed to C2-inverted cyclic carbonates upon treatment with cesium carbonate under an atmosphere of carbon dioxide (e.g., 5→6).The reaction is completely stereospecific, within experimental error, and forms only 5-membered ring cyclic carbonates.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Chemistry and Chemical Engineering|
|Thesis Availability:||Restricted to Caltech community only|
|Defense Date:||2 March 1992|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||John Wade|
|Deposited On:||28 Sep 2011 22:35|
|Last Modified:||26 Dec 2012 04:38|
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