A1 Refereed original research article in a scientific journal
Asymmetric Synthesis of Amino-Bis-Pyrazolone Derivatives via an Organocatalytic Mannich Reaction
Authors: Chauhan P, Mahajan S, Kaya U, Peuronen A, Rissanen K, Enders D
Publisher: AMER CHEMICAL SOC
Publication year: 2017
Journal: Journal of Organic Chemistry
Journal name in source: JOURNAL OF ORGANIC CHEMISTRY
Journal acronym: J ORG CHEM
Volume: 82
Issue: 13
First page : 7050
Last page: 7058
Number of pages: 9
ISSN: 0022-3263
DOI: https://doi.org/10.1021/acs.joc.7b01113
Abstract
A new series of N-Boc ketimines derived from pyrazolin-5-ones have been used as electrophiles in asymmetric Mannich reactions with pyrazolones. The amino-bis-pyrazolone products are obtained in excellent yields and stereo-selectivities by employing a very low loading of 1 mol % of a bifunctional squaramide organocatalyst. Depending on the substitution at position 4 of the pyrazolones, the new protocol allows for the generation of one or two tetrasubstituted stereocenters, including a one-pot version combing the Mannich reaction with a base-mediated halogenation.
A new series of N-Boc ketimines derived from pyrazolin-5-ones have been used as electrophiles in asymmetric Mannich reactions with pyrazolones. The amino-bis-pyrazolone products are obtained in excellent yields and stereo-selectivities by employing a very low loading of 1 mol % of a bifunctional squaramide organocatalyst. Depending on the substitution at position 4 of the pyrazolones, the new protocol allows for the generation of one or two tetrasubstituted stereocenters, including a one-pot version combing the Mannich reaction with a base-mediated halogenation.
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