Synthesis of new enantiopure fluorinated phenylcyclopropanecarboxylates - Potential chiral dopants for liquid-crystal compositions

The reaction of alpha-fluorostyrene (1a) with methyl phenyldiazoacetate in the presence of Rh-2(OAc)(4) gave a 64:36 mixture of diastereomeric monofluorinated cyclopropanes 5a and 6a. When using chiral Rhn catalysts Rh-2(TBSP)(4) (7) and Rh-2(DOSP)(4) (8), the products were obtained enantioselectively in up to > 99% ee for both (1R,2R)-5a and (1R,2S)-6a. The fluorocyclopropane derivatives are of interest as dopants to induce chirality in liquid-crystal mixtures. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).