Single Enantiomer Epoxides by Bromomandelation of Prochiral Alkenes

Abstract

A combination of mandelic acid and N-bromosuccinimide efficiently converts prochiral alkenes into a readily separable 1:1 mixture of the bromomandelates. The diastereomerically pure bromomandelates are then converted into a variety of enantiomerically pure products. Terminal alkenes are converted into enantiomerically pure epoxides. Cyclohexene is converted into enantiomerically pure cis-2-azidocyclohexanol and cis-2-phenylthiocyclohexanol.

Fluorinated Isatin Derivatives. Part 2. New N-Substituted 5-Pyrrolidinylsulfonyl Isatins as Potential Tools for Molecular Imaging of Caspases in Apoptosis

“…Hz, N-CH 2 CF=CH 2 ), 111. 1,124.6,137.5 (isatinArCH), 5.85 (ddt, 1H, 3 J Ha,H =5. 5 Hz, 3 J Ha,Hb =17.…”

Toward the total synthesis of ritterazine N

“…The diastereomeric mandelates were separated by column chromatography. The structures were assigned by 1 H NMR analysis, following our earlier precedent [13]. This assignment was confirmed by X-ray analysis of the mesylate 22 (Scheme 6).…”

“…To arrive at the enantiomerically pure epoxide 2, we exposed (Scheme 5) racemic 16 to mandelic acid and N-bromosuccinimide in the presence of 2,6-lutidine [13]. As expected, just two diastereomeric bromomandelates were formed, the product of Br (+) complexation to the more accessible face of the alkene followed by diaxial opening with mandelate anion.…”

Novel C2-symmetric chiral ligands: enantioselective transformation of cyclic 1,2-diols into 1,2-bis(phenylsulfenyl) and 1,2-bis(phenylselenyl) derivatives

“…Recently, this enantiomeric product has also been obtained via bromomandelation of cyclohexene. 9 We were also interested in the preparation of the corresponding 1,2-bis(phenylselenyl) derivatives. Thus, (1S,2S)-trans-1,2-cyclopentanediol 1 reacted smoothly with PhSeCN/Bu 3 P according to Grieco protocol 10 and stereoselectively gave both, mono-6 (37%) and bis-substituted 7 (43%) products (>98% de, >95% ee).…”