Controllable chemoselectivity in the coupling of bromoalkynes with alcohols under visible-light irradiation without additives: synthesis of propargyl alcohols and α-ketoesters
作者:Ke Ni、Ling-Guo Meng、Hongjie Ruan、Lei Wang
DOI:10.1039/c9cc04090k
日期:——
The chemoselectivity of visible-light-induced coupling reactions of bromoalkynes with alcohols can be controlled by simple changes to the reaction atmosphere.
Transition-metal-catalyzed cross-coupling of propargylic electrophiles and Grignardreagents provides densely functionalized products that are extremely useful synthetic intermediates. However, examples of conversion of propargylic derivatives to form propargyl compounds remain limited due to the challenging regioselectivity. We use LaCl3·2LiCl to catalyze propargylation of Grignardreagents in the absence of
过渡金属催化的炔丙基亲电子试剂和格氏试剂的交叉偶联提供了高度官能化的产物,是极其有用的合成中间体。然而,由于具有挑战性的区域选择性,将炔丙基衍生物转化为炔丙基化合物的例子仍然有限。我们使用LaCl 3 ·2LiCl在没有配体的情况下催化格氏试剂的炔丙基化,具有高区域选择性和立体特异性。该方法显示了使用烷基或(杂)芳基格氏试剂和具有不同离去基团的炔基亲电子试剂的广泛底物范围。我们的方案进一步应用于叶毛多辛 B 的正式合成。利用天然丰富且相对无毒的镧催化剂的方法值得探索。
Silver Mediated Banert Cascade with Carbon Nucleophiles
作者:Juliana R. Alexander、Paul V. Kevorkian、Joseph J. Topczewski
DOI:10.1021/acs.orglett.1c01032
日期:2021.4.16
Nickel-Catalyzed Asymmetric Friedel–Crafts Propargylation of 3-Substituted Indoles with Propargylic Carbonates Bearing an Internal Alkyne Group
The nickel-catalyzed highly enantioselective Friedel Crafts propargylation of 3-substituted indoles with propargylic carbonates bearing an internal alkyne group was developed. A wide array of the propargylic carbonates as well as 3-substituted indoles can be applicable to the asymmetric nickel catalysis, providing the corresponding chiral C-3 propargylated indolenine derivatives bearing two vicinal chiral centers in up to 89% yield with up to >99% ee and 94:6 dr (24 examples).