Premium
Asymmetric Boron Conjugate Additions to Enones in Water Catalyzed by Copper(0)
Author(s) -
Kitanosono Taku,
Kobayashi Shū
Publication year - 2013
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.201300201
Subject(s) - chemistry , transmetalation , enone , protonation , catalysis , copper , conjugate , boron , kinetic isotope effect , substrate (aquarium) , medicinal chemistry , redox , photochemistry , catalytic cycle , deuterium , combinatorial chemistry , inorganic chemistry , organic chemistry , ion , mathematical analysis , physics , oceanography , mathematics , quantum mechanics , geology
The use of copper(0) powder in water enables chiral induction as well as high catalytic activity. Water plays a prominent role to determine both the catalytic activity and enantioselection. Elevated temperature is indispensable for the regular reaction pathway, and an active species tends to aggregate after the completion of the reaction. Selective deuteration implies enantiofacial differentiation of the deuteron toward an O ‐enolate intermediate. Strict substrate specificity suggests the vital interaction between copper(0) and an enone. A very weak isotope effect is indicative of instantaneous protonation. Accordingly, a redox copper cycle (0→II) is tentatively proposed, in which transmetalation of a cyclometalated enone with diboron would furnish a boron enolate, followed by hydrolysis and reductive elimination. However, a single electron transfer process cannot be excluded on the available evidence and a more detailed mechanistic study is under way.