利用二氧化碳(CO 2 )作为一种可持续、丰富且无害的C1源来催化合成对映体富集的羧酸长期以来被认为是合成化学中的一项关键任务。在此,我们提出了一种电流驱动的镍催化还原羧化反应与CO 2固定,通过避免对湿气敏感的有机金属试剂的处理来促进C(sp 3 )–C(sp 2 )键的形成。该电还原方案作为一个实用平台,为从外消旋炔丙碳酸酯和CO 2合成对映体富集的炔丙羧酸(对映体过量高达98%)铺平了道路。这种转化的功效通过其成功用于( S )-芦笋酸、( R )-PIA、( S )-chizhine D、( S )-cochlearin G 和 ( S , S ) 的不对称全合成来证明。 -alexidine,从而强调了不对称电合成可持续实现复杂分子结构的潜力。
Rapid Asymmetric Synthesis of Disubstituted Allenes by Coupling of Flow-Generated Diazo Compounds and Propargylated Amines
作者:Jian-Siang Poh、Szabolcs Makai、Timo von Keutz、Duc N. Tran、Claudio Battilocchio、Patrick Pasau、Steven V. Ley
DOI:10.1002/anie.201611067
日期:2017.2.6
We report herein the asymmetric coupling of flow‐generated unstabilized diazo compounds and propargylated amine derivatives, using a new pyridinebis(imidazoline) ligand, a copper catalyst and base. The reaction proceeds rapidly, generating chiral allenes in 10–20 minutes with high enantioselectivity (89–98 % de/ee), moderate yields and a wide functional group tolerance.
The cobalt(II) complexes prepared with a series of enantiopure ligands (1-3) containing the bis(oxazolinyl)pyridine unit have been studied. The ligands form high spin octahedral complexes as shown by the X-ray crystal structure of the homochiral complex [Co(R,R-1)2](ClO4)2(CH3CN)3. The diastereoselectivity of complex formation has been studied: equimolar mixtures of RR and SS ligands show mixtures
已经研究了用一系列含有双(恶唑啉基)吡啶单元的对映体纯配体 (1-3) 制备的钴 (II) 配合物。配体形成高自旋八面体配合物,如同手性配合物 [Co(R,R-1)2](ClO4)2(CH3CN)3 的 X 射线晶体结构所示。已经研究了复合物形成的非对映选择性:RR 和 SS 配体的等摩尔混合物显示 2 和 3 的纯手性和异手性复合物的混合物,但苯基取代的配体 1 显示了异手性物种的排他性形成。这种选择性与配合物的结构和电子特性相关。
Synthesis, characterization and 1,3-butadiene polymerization studies of cobalt dichloride complexes bearing pyridine bisoxazoline ligands
of [CoL2]2+ can be described as distorted octahedron. In combination with ethylaluminum sesquichloride, these cobalt complexes displayed high catalytic activity and cis-1,4-selectivity towards 1,3-butadiene polymerization. The selectivity of the catalytic system can be tuned to predominantly 1,2-fashion via addition of PPh3. The effects of reaction parameters and the ligand environment on the polymerization
We have developed a photoredox/Cu dual catalyzed enantioselective remote cyanation via1,4-heteroarylmigration. Experimental and computational studies have been carried out to reveal the reaction mechanism and explain the origins of the regio- and enantioselectivities of the remote cyanation process. This methodology exhibits mild conditions, a broad substrate scope and good regio- and enantioselectivities
The first catalytic asymmetric 1,4-addition reactions of azlactones with acrylic esters have been developed. A chiral coordinative calcium catalyst was found to be effective for these reactions, and the desired 1,4-adducts were obtained in good yields and enantioselectivities. The product was converted to the corresponding alpha-alkylated glutamic acid by acid hydrolysis. (C) 2010 Elsevier Ltd. All rights reserved.