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|Title:||Phosphorus-Stabilized, Carbanion-Accelerated Claisen Rearrangements: Asymmetric Induction via 1,3,2-Oxazaphosphorinanes|
|Author(s):||Marlin, John Emory, II|
|Doctoral Committee Chair(s):||Denmark, Scott E.|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The carbanion-accelerated Claisen rearrangement has been extended to include phosphorus carbanion-stabilizing groups. The appropriately substituted allyl vinyl ethers are synthesized by the nucleophilic addition of allyloxides to phosphorus-substituted allenes, which are obtained in one step from simple starting materials. The phosphorus-stabilized, carbanion-accelerated Claisen rearrangements proceed rapidly at room temperature in high yield, and the rearrangements are regiospecific and highly stereoselective. Most importantly, the first examples of asymmetric induction in the Claisen rearrangement with chiral phosphorus anion-stabilizing groups are documented. The observed asymmetric induction, which is highly dependent on the metal counterion involved, is explained in terms of both internal and relative diastereoselectivity. The sense of asymmetric induction is established by degradation of the Claisen rearrangement products to ($R$)- and ($S$)-dimethyl methylsuccinates. Two limiting transition state models are proposed to rationalize the high levels of observed diastereoselectivity.
Methods of cleaving the phosphorus-carbon bond are examined. Phosphorus-carbon bond cleavage is observed only under harshly acidic conditions.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
|Date Available in IDEALS:||2014-12-15|