Effet de la concentration en acide fluorohydrique dans la pyridine sur la stereoselectivite de la fluorobromation de cinnamates d'ethyle substitues.
作者:S. Hamman、C.G. Beguin
DOI:10.1016/s0022-1139(00)85136-2
日期:1983.12
Bromofluorination of six substituted ethylcinnamates (e.g. YC6H4CXCHCO2Et; 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
六个取代的肉桂酸酯(例如YC 6 H 4 CX = CHCO 2 Et; Y = X = H,E和Z异构体; Y = mNO 2,X = H; Y = pOCH 3,X = H;和Y = H ,X = Cl,E和Z异构体)与N-溴代琥珀酰亚胺(NBS)在氟化氢-吡啶或氟化氢-四氢呋喃中的摩尔比(几个摩尔比),这取决于以下几个因素,使Markovnikov型区域选择性具有立体选择性:取代基(X或Y),溶剂(吡啶或THF)和主要是氟化氢溶剂的摩尔比。碳正离子YC 6 H 4 C + XCHBrCO 2络合的重要性不同Et作为烯烃和NBS氟化氢之间的络合物可以解释这些因素对立体选择性的影响。