'Goldilocks effect’ of water in Lewis-Brønsted Acid and Base catalysis

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Title: 'Goldilocks effect’ of water in Lewis-Brønsted Acid and Base catalysis
Authors: Barron, BJ
Wong, WT
Chiu, P
Hii, KM
Item Type: Journal Article
Abstract: © 2016 American Chemical Society.Different catalytic protocols were evaluated in the enantioselective Pd-catalyzed aza-Michael reaction involving monoprotected phenylenediamine (PDA) derivatives. The use of these nucleophilic amines leads to the poisoning of the (monomeric) Lewis acidic catalyst, and significant competitive formation of side products were observed. In contrast, good yields and enantioselectivities can be attained by employing the Brønsted basic-Lewis acidic dimeric Pd catalyst, in combination with PDA derivatives protonated by triflic acid. In this case, the presence of the right amount of water was found to be critical for success ( Goldilocks effect ). The results were rationalized on the basis of delicately balanced acid-base equilibria, dependent upon the nature of the catalyst and the amine.
Issue Date: 20-May-2016
Date of Acceptance: 20-May-2016
URI: http://hdl.handle.net/10044/1/32920
DOI: https://dx.doi.org/10.1021/acscatal.6b00800
ISSN: 2155-5435
Publisher: American Chemical Society
Start Page: 4189
End Page: 4194
Journal / Book Title: ACS Catalysis
Volume: 6
Issue: 7
Copyright Statement: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acscatal.6b00800
Publication Status: Published
Appears in Collections:Chemistry
Catalysis and Advanced Materials
Faculty of Natural Sciences

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