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https://hdl.handle.net/2142/70299
Description
Title
Carbanion Accelerated Claisen Rearrangements
Author(s)
Harmata, Michael
Issue Date
1985
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Abstract
A new variant of the Claisen rearrangement has been invented in which an arylsulfonyl-stabilized carbanion attached to carbon 2 of the allyl vinyl ether provides great acceleration to the 3,3 sigmatropic rearrangement. Two methods are reported for the synthesis of the appropriate allyl vinyl ethers, both involving the base catalyzed addition of allylic alcohols to arysulfonyl allenes. The rearrangement is shown to proceed through an arylsulfonyl-stabilized allylic anion. A study of methyl substitution at various positions on the allyl vinyl ether gave qualitative kinetic results in agreement with both the empirical and theoretical findings of others. The reaction is highly regioselective and stereoselective. Allyl vinyl ethers substituted at carbon 3 gave ketonic products containing only E double bonds. A proposal is formulated to explain certain regiochemical anomalies observed with allyl vinyl ethers substituted at carbon 3. Qualitative rate studies are reported which show little solvent and counterion effects in the rearrangement process. A rationalization for the rate changes observed in THF as a function of counterion is given. With allyl vinyl ethers substituted at carbons 1 and 5, the rearrangement was shown to proced via a chair transition state and with diastereoselection as good or better than its thermal counterpart. A study of several other carbanion stabilizing groups is reported. It was found that the arylsulfonyl group is the most efficacious stabilizing group for this reaction. Preliminary studies on the synthesis of allyl vinyl ethers containing arylsulfilimine or arylsulfoximine functions as carbanion stabilizing groups are also reported. Rearrangement of the sulfilimine based allyl vinyl ether substituted at carbon 5 resulted in no diastereoselection. A Friedel-Crafts reaction between a sulfoximidoyl chloride and an acetylene is also reported.
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