Catalytic Asymmetric Hydrocarboxylation and Hydrohydroxymethylation. A Two-Step Approach to the Enantioselective Functionalization of Vinylarenes
摘要:
A method for the catalytic asymmetric hydrocarboxylation and hydrohydroxymethylation of vinylarenes is reported. By separating the step in which asymmetry is installed from the one where carbon-carbon bond formation takes place, a highly enantioselective and regioselective synthesis of Ibuprofen and its analogs is achieved. Stereochemistry is installed via an enantioselective hydroboration reaction, catalyzed by cationic rhodium BINAP complexes, and the homologation is carried out with halomethyllithium reagents. If CH2Cl2/n-BuLi is used as the homologating reagent, carboxylic acids are produced after oxidation. On the other hand, if CH2ClBr is used in combination with n-BuLi, the corresponding primary alcohol is produced. This latter transformation represents a previously unknown asymmetric hydrohydroxymethylation reaction. In both cases, complete retention of stereochemistry is observed, yielding products in up to 97% ee. Superior results are obtained if the initially formed catecholate is converted into a pinacolate prior to homologation.
Catalytic Asymmetric Hydrocarboxylation and Hydrohydroxymethylation. A Two-Step Approach to the Enantioselective Functionalization of Vinylarenes
摘要:
A method for the catalytic asymmetric hydrocarboxylation and hydrohydroxymethylation of vinylarenes is reported. By separating the step in which asymmetry is installed from the one where carbon-carbon bond formation takes place, a highly enantioselective and regioselective synthesis of Ibuprofen and its analogs is achieved. Stereochemistry is installed via an enantioselective hydroboration reaction, catalyzed by cationic rhodium BINAP complexes, and the homologation is carried out with halomethyllithium reagents. If CH2Cl2/n-BuLi is used as the homologating reagent, carboxylic acids are produced after oxidation. On the other hand, if CH2ClBr is used in combination with n-BuLi, the corresponding primary alcohol is produced. This latter transformation represents a previously unknown asymmetric hydrohydroxymethylation reaction. In both cases, complete retention of stereochemistry is observed, yielding products in up to 97% ee. Superior results are obtained if the initially formed catecholate is converted into a pinacolate prior to homologation.
Cobalt-Catalyzed Enantioselective Hydroboration of 1,1-Disubstituted Aryl Alkenes
作者:Lei Zhang、Ziqing Zuo、Xiaolong Wan、Zheng Huang
DOI:10.1021/ja5093908
日期:2014.11.5
We report the synthesis of cobalt complexes of novel iminopyridine-oxazoline (IPO) ligands and their application to the asymmetric hydroboration of 1,1-disubstitutedarylalkenes. The new catalysts afforded α-alkyl-β-pinacolatoboranes with exclusive regioselectivity in high yields with up to 99.5% ee. Furthermore, we have applied this method to an efficient synthesis of naproxen.
Highly regio- and enantioselective catalytic asymmetric hydroboration of α-substituted styrenyl derivatives
作者:Clément Mazet、David Gérard
DOI:10.1039/c0cc01547d
日期:——
The catalytic asymmetric hydroboration of a variety of 1,1-disubstituted olefins has been achieved with excellent yields, perfect regioselectivity and in some cases, high levels of enantioselectivity using readily accessible iridium catalyst.