"Goldilocks Effect" of Water in Lewis-Brønsted Acid and Base Catalysis

Benedict J. Barron, Wing Tak Wong, Pauline Chiu, King Kuok Hii

Research output: Journal article publicationJournal articleAcademic researchpeer-review

10 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)4189-4194
Number of pages6
JournalACS Catalysis
Volume6
Issue number7
DOIs
Publication statusPublished - 1 Jul 2016
Externally publishedYes

Keywords

  • asymmetric catalysis
  • aza-Michael reactions
  • Brønsted acid and base
  • deactivation
  • Lewis acid
  • phenylenediamine
  • water-effect

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Cite this