Chiral Calcium VAPOL Phosphate Mediated Asymmetric Chlorination and Michael Reactions of 3-Substituted Oxindoles
作者:Wenhua Zheng、Zuhui Zhang、Matthew J. Kaplan、Jon C. Antilla
DOI:10.1021/ja109824x
日期:2011.3.16
We disclose a novel high yielding and highlyenantioselectivechiralcalciumVAPOL phosphate-catalyzed chlorination of 3-substituted oxindoles with N-chlorosuccinimide (NCS). The reaction conditions are also shown to be effective for the catalyticenantioselective Michael addition of 3-aryloxindoles to methyl vinyl ketone.
Design of Highly Stable Iminophosphoranes as Recyclable Organocatalysts: Application to Asymmetric Chlorinations of Oxindoles
作者:Xing Gao、Jianwei Han、Limin Wang
DOI:10.1021/acs.orglett.5b02323
日期:2015.9.18
A new family of tartaric acid derived chiral iminophosphoranes has been developed as highly effective organocatalysts in the asymmetric chlorinations of 3-substituted oxindoles with a high level of enantioselectivity. Importantly, these catalysts are air- and moisture-stable. Recovery of the catalyst after simple chromatographic separation for reuse in the model reaction was achieved; the catalyst can be recycled six times without loss of any enantioselectivity. Several advantages of this catalytic process are high conversion after a very short reaction time at ambient temperature, low catalytic loading, and scale-up to multigram quantities with an excellent enantiomeric excess value of >99%, which meets the enantiomeric purity required for pharmaceutical purposes.