Clarification of the Stereochemical Course of Nucleophilic Substitution of Arylsulfonate-Based Nucleophile Assisting Leaving Groups
2009; American Chemical Society; Volume: 74; Issue: 16 Linguagem: Inglês
10.1021/jo900991z
ISSN1520-6904
AutoresD. Christopher Braddock, Rebecca H. Pouwer, Jonathan W. Burton, Phillip Broadwith,
Tópico(s)Chemical Reaction Mechanisms
ResumoSecondary alcohols modified as tosylates, PEG-sulfonates, or quisylates undergo inversion of configuration at the reacting center when treated with lithium halide in acetone at reflux, where the PEG-sulfonates and quisylates are substantially more reactive. In sterically hindered cases, elimination is a competing process. In contrast, when treated with TiCl(4), simple secondary sulfonates give chloride products with partial inversion of configuration. Any observed retention of configuration in a given alkyl sulfonate substrate under these conditions is likely due to neighboring group participation or diastereoselective attack on a carbocation (or ion pair) rather than an S(N)i mechanism.
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