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|Title:||Stereoselective alkylations and rearrangements of chiral phosphonic and phosphinic acid derivatives|
|Author(s):||Dorow, Roberta L.|
|Doctoral Committee Chair(s):||Denmark, Scott E.|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The stereochemical course of carbon migration from phosphorus to nitrogen and oxygen were investigated. Optically active ($\geq$99.9% e.e.) phosphonic and phosphinic azides were prepared and photolyzed in methanol to effect the phosphorus analogues of the carbonyl-Curtius rearrangement. These studies showed that carbon migration in the phosphinoyl-Curtius rearrangement proceeds with 99% net retention of configuration while the migration in the first example of the phosphonoyl-Curtius rearrangement occurs with 99.4% net retention of configuration.
The stereoselectivity in the alkylation reactions of various chiral phosphorus-stabilized benzylic carbanions was also examined. Both racemic and scalemic 2-benzyl-1,3,2-oxazaphosphorinane-2-oxides were employed. The effects of solvent, base, additive, and electrophile were studied. The diastereoselectivity of alkylation is dependent on the phosphorus-stabilized carbanion which is used, but high diastereoselectivity (98:2-95:5) was realized.
Multinuclear NMR spectroscopy was used to gain insight into the solution state structure of both symmetrical and unsymmetrical heterocyclic phosphorus-stabilized benzylic carbanions. The spectral data is consistent with a charge-alternating structure that has a planar anionic carbon. Information about the conformation of the anion as well as the ring form was obtained. Much information about the structure of phosphorus-stabilized carbanions was obtained through X-ray crystallographic studies of the first lithiated phosphonoyl-stabilized carbanion.
|Rights Information:||Copyright 1990 Dorow, Roberta L.|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9026171|