Propargylic cation-induced intermolecular electrophilic addition–semipinacol rearrangement.

Lewis base mediated halogenation/semipinacol rearrangement of diazo compounds: new access to α-halo-quaternary ketones.

A novel halogenation/semipinacol rearrangement of α-diazo alcohol catalyzed by Lewis base has been developed through a carbene-free mechanism. This semipinacol transposition, initiated by an electrophilic halogenation (X = Cl(+), Br(+), and I(+)) of diazo carbon event, furnished a convenient synthetic route for the efficient synthesis of α-halo-quaternary ketones under mild conditions.

Stereoselective geminal difunctionalization of vinyl arenes mediated by the bromonium ion.

An anti-Markovnikov geminal oxyamination of styrenyl alkenes in an intermolecular fashion using the umpolung strategy mediated by the bromonium ion is reported. Isotope labeling studies confirm the migration of the phenyl group in the semipinacol rearrangement.

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

Gold-catalyzed intermolecular oxidation of carboxylates of primary or secondary propargylic alcohols are realized with excellent regioselectivity, which is ascribed to inductive polarization of the C-C triple bond by the electron-withdrawing carboxy group. The gold carbene intermediates thus generated undergo selective 1,2-acyloxy migration over a 1,2-C-H insertion, and the selectivities could ...

Asymmetric semipinacol rearrangement of 2,3-allenols with N-bromo-1,8-naphthalimide.

A method using quinidine and optically active binol-derived phosphoric acid as a cocatalyst to catalyze the asymmetric semipinacol rearrangement of 2,3-allenols forming optically active 3-bromo-3-enals that contain an all-carbon quaternary stereocenter has been developed. After some further treatments, the products with practical enantiomeric purity could be prepared.

A tandem semipinacol rearrangement/alkylation of alpha-epoxy alcohols: an efficient and stereoselective approach to multifunctional 1,3-diols.