ChemInform Abstract: (2,3)-Thia-Wittig Rearrangements of α-Lithiated Sulfides via De- Aromatized Cyclohexadiene Intermediates Proceed with Inversion of Configuration at the Carbanionic Center.
Abstract
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ChemInform Abstract
BuLi-induced Sn/Li-exchange reaction on readily achieved, diastereomeric stannylated sulfides, syn-(VI) and anti-(IX), provides the corresponding α-lithiated sulfides which undergo (2,3)-thia- Wittig rearrangement via dearomatized cyclohexadiene intermediates. Aqueous work-up of product mixtures derived from (VI) or (IX) gives the ortho-functionalized toluene derivatives (VII) and (VIII) in exactly opposite selectivity. The Wittig rearrangements presumably proceed with total inversion of configuration at the carbanion center. The incomplete stereoselectivity of the overall process is explained by an epimerization, that is 3.3 times slower than the rearrangement, of the anti/syn-α-lithio sulfides.
