首次成功开发了一种基于廉价过渡金属镍的高效催化体系,用于挑战性环状烯基砜,3-取代的苯并[ b ]噻吩1,1-二氧化物的不对称加氢。以高收率(95-99%)和优异的对映选择性(90-99%ee)获得了一系列氢化产物,手性2,3-二氢苯并[ b ]噻吩1,1-二氧化物。根据非线性效应研究,氘标记实验和DFT计算研究的结果,为这种镍催化的不对称氢化提供了合理的催化机理,表明该氢化产物中两个加成的氢原子可能来自H 2。 通过插入Ni–H和随后的氢解反应。
Continuous-Flow Synthesis of Biaryls by Negishi Cross-Coupling of Fluoro- and Trifluoromethyl-Substituted (Hetero)arenes
作者:Stefan Roesner、Stephen L. Buchwald
DOI:10.1002/anie.201605584
日期:2016.8.22
continuous‐flow method for the regioselective arylation of fluoroarenes and fluoropyridines has been developed. The telescoped procedure reported here consists of a three‐step metalation, zincation, and Negishi cross‐coupling sequence, providing efficient access to a variety of functionalized 2‐fluorobiaryl products. Precise temperature control of the metalation step, made possible by continuous‐flow technology
first example of near-room-temperature α-arylation of benzo[b]thiophenes is reported. The discovery rests on the observation of a switch in α-/β-regioselectivity at different loadings of Pd2(dba)3·CHCl3 in the coupling between benzo[b]thiophene and 4-iodotoluene. We show that this unprecedented regioselectivity switch is driven by a Ag(I)-mediated C–H activation at the α-C–H position, which becomes the
A new strategy for the synthesis of 2‐aryl‐ and 2‐heteroaryl fluoroarenes has been developed. An intermolecular domino Grignard‐coupling–fluorination sequence affords a range of 2‐fluorobiaryls from aryl bromides under mild conditions. This methodology can be further extended to the synthesis of 2′‐aryl‐2‐fluorobiphenyls.