羰基化合物的催化对映选择性α-氟化反应是构建光学活性α-氟化羰基化合物的最有效,最有效的合成方法之一。然而,由于α-非支链羧酸衍生物的α-氢原子的p K a值相对较高,并且随后不进行差向异构化就很难进行合成转化,因此α-非支链羧酸衍生物的α-氟化仍然是一个很大的挑战。本文显示了3-(2-萘基)-1-丙氨酸衍生的酰胺的手性铜(II)络合物是N-(α-芳基乙酰基)和N的对映体和定点α-氟化的高效催化剂-(α-烷基乙酰基)3,5-二甲基吡唑。转化的底物范围非常广泛(25个实例,其中包括季铵化α-氟化α-氨基酸衍生物)。α-氟化产物几乎没有差向异构化地转化为相应的酯,仲酰胺,叔酰胺,酮和醇。
羰基化合物的催化对映选择性α-氟化反应是构建光学活性α-氟化羰基化合物的最有效,最有效的合成方法之一。然而,由于α-非支链羧酸衍生物的α-氢原子的p K a值相对较高,并且随后不进行差向异构化就很难进行合成转化,因此α-非支链羧酸衍生物的α-氟化仍然是一个很大的挑战。本文显示了3-(2-萘基)-1-丙氨酸衍生的酰胺的手性铜(II)络合物是N-(α-芳基乙酰基)和N的对映体和定点α-氟化的高效催化剂-(α-烷基乙酰基)3,5-二甲基吡唑。转化的底物范围非常广泛(25个实例,其中包括季铵化α-氟化α-氨基酸衍生物)。α-氟化产物几乎没有差向异构化地转化为相应的酯,仲酰胺,叔酰胺,酮和醇。
suppressing effect for α-chlorination and -bromination due to undesired halogenbonding. This strategy provides facile access to α-halogenated compounds in high yield with excellent enantioselectivity. X-ray crystallographic and ESR analyses of the catalyst complexes suggest that the release of two counteranions (2TfO–) from the copper(II) center might be crucial for the efficient activation of N-acyl-3
描述了新型手性 π-铜 (II)-π 配合物催化的N-酰基-3,5-二甲基吡唑的对映选择性 α-氯化和 -溴化。Cu(OTf) 2与 3-(2-萘基) -l-丙氨酸衍生的酰胺的 π-铜(II)-π 络合极大地增加了路易斯酸度并在没有外部碱的情况下触发了烯醇化物的原位生成,由于不希望的卤素键合,它对α-氯化和-溴化具有抑制作用。该策略提供了以高产率轻松获得α-卤代化合物的方法,并具有出色的对映选择性。催化剂配合物的 X 射线晶体学和 ESR 分析表明,释放了两种抗衡阴离子(2TfO-) 来自铜 (II) 中心可能对N-酰基-3,5-二甲基吡唑的有效活化至关重要。
Rationally Designed Amide Donors for Organocatalytic Asymmetric Michael Reactions
作者:Bin Tan、Gloria Hernández-Torres、Carlos F. Barbas
DOI:10.1002/anie.201200996
日期:2012.5.29
Amide nucleophiles on demand: Rationallydesigned pyrazoleamides function as Michaeldonors in urea‐catalyzed asymmetricMichaelreactions with excellent chemical and optical yields (see scheme). The pyrazoleamide group performs as an ester equivalent, a directing group, an activating group, and functions as a good leaving group in further transformations of the product.
N-acyl pyrazoles were efficiently and selectively prepared through the 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed reaction of nitrosoarenes with N-acyl pyrazoles via an N-nitroso aldol reaction/dehydration sequence. The α-imino acyl pyrazoles were demonstrated to be new versatile intermediates for practical one-pot syntheses of α-imino amides, dipeptide precursors, esters, and β-amino alcohols
2‐a]‐pyrazole‐1,7‐diones, bearing up to three stereocentres, by reacting ready available N,N′‐cyclic azomethineimines and pyrazoleamides under catalytic loading of commercial 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD), has been developed. The products are obtained in good yields and high diastereoselectivity, working at room temperature. Preliminary bioassay showed the products to inhibit growth of Gram‐positive