Catalytic Use of Elemental Gallium for Carbon–Carbon Bond Formation
作者:Bo Qin、Uwe Schneider
DOI:10.1021/jacs.6b06767
日期:2016.10.12
The first catalytic use of Ga(0) in organic synthesis has been developed by using a Ag(I) cocatalyst, crownether ligation, and ultrasonic activation. Ga(I)-catalyzed C-C bondformations between allyl or allenyl boronic esters and acetals, ketals, or aminals have proceeded in high yields with essentially complete regio- and chemoselectivity. NMR spectroscopic analyses have revealed novel transient Ga(I)
A highly efficient metal-free aldol-type reaction of various acetals or ketals with fluorinated silylenolethers catalysed by less than 1 mol% HClO4 (70 wt%, aq.) is developed. This provides expedient access to a wide array of valuable fluoroalkyl ethers featuring a ketone carbonyl functionality in good to excellent yields (40 examples). Furthermore, the thus obtained adducts are readily elaborated
Enantioselective Copper-Catalyzed Alkynylation of Benzopyranyl Oxocarbenium Ions
作者:Harathi D. Srinivas、Prantik Maity、Glenn P. A. Yap、Mary P. Watson
DOI:10.1021/acs.joc.5b00364
日期:2015.4.17
We have developed highly enantioselective, copper-catalyzedalkynylations of benzopyranyl acetals. By using a copper(I) catalyst equipped with a chiral bis(oxazoline) ligand, high yields and enantioselectivities are achieved in the alkynylation of widely available, racemic isochroman and chromene acetals to deliver α-chiral oxygen heterocycles. This method demonstrates that chiral organometallic nucleophiles
Copper-catalyzed oxidative cross-dehydrogenative coupling of 2<i>H</i>-chromenes and terminal alkynes
作者:Fei Yang、Yangshan Li、Paul E. Floreancig、Xiaoyan Li、Lei Liu
DOI:10.1039/c8ob00949j
日期:——
An efficient copper-catalyzedcross-dehydrogenativecoupling of 2H-chromenes and terminal alkynes mediated by DDQ has been established. A protic additive, EtOH, proved to be crucial for harmonizing the oxidation with a subsequent alkynylation step by retaining the oxidation state of an oxocarbenium ion in the form of acetal. The CDC reaction exhibits a good substrate scope, with a range of terminal
Kinetic Resolution and Dynamic Kinetic Resolution of Chromene by Rhodium‐Catalyzed Asymmetric Hydroarylation
作者:Qingjing Yang、Yanbo Wang、Shihui Luo、Jun (Joelle) Wang
DOI:10.1002/anie.201900721
日期:2019.4.8
A highly efficient kineticresolution and dynamickineticresolution of chromene is reported for the first time and they procced by a rhodium‐catalyzed asymmetric hydroarylation pathway. This new approach offers versatile access to various chiral 2,3‐diaryl‐chromanes containing vicinal stereogenic centers, as well as the recovered chiral flavenes, in high yields with excellent ee values (s factor up