EFFET DE LA CONCENTRATION EN ACIDE FLUOROHYDRIQUE DANS LA PYRIDINE SUR LA STEREOSELECTIVITE DE LA FLUOROBROMATION DE CINNAMATES D'ETHYLE SUBSTITUTES.

Article abstract of DOI:10.1016/S0022-1139(00)85136-2

Bromofluorination of six substituted ethylcinnamates (e. g.YC6H4CX=CHCO2Et; Y = X = H, E and Z isomers; Y = mNO2, X = H; Y = pOCH3, X = H; and Y = H, X = Cl, E and Z isomers) with N-bromosuccinimide (NBS) in hydrogen fluoride-pyridine or hydrogen fluoride-tetrahydrofuran (several molar ratios), giving the Markovnikov-type regioselectivity has a stereoselectivity depending on several factors: the nature of the substituent (X or Y), the solvent (pyridine or THF) and mainly the hydrogen fluoride-solvent molar ratio.The variable importance of the complexation of the carbenium ion YC6H4C⁺XCHBrCO2Et as a complex between the olefin and NBS-hydrogen fluoride can give an interpretation of the influence of these factors on stereoselectivity.