Asymmetric halogenation/semipinacol rearrangement

Subsequently, organocatalytic asymmetric halogenation/semipinacol rearrangement sequences, both leading to chiral quaternary haloketones, have been reported by Tu and coworkers [61] and by Hermecke and coworkers [62]. The mechanism of these reactions probably involves an acid-catalyzed diastereoselective semipina-col rearrangement of a chiral halonium ion intermediate obtained by chiral tertiary amine-promoted asymmetric halogenation of an enone [63]. 

Chen Z-M, Zhang Q-W, Chen Z-H, Li H, Tu Y-Q, Zhang F-M, Tian J-M. Organocatalytic asymmetric halogenation/ semipinacol rearrangement highly efficient synthesis of chiral a-oxa-quatemary p-haloketones. J. Am. Chen. Soc. 2011 133(23) 8818-8821. 

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