Open AccessAn Insoluble Copper(II) Acetylacetonate–Chiral Bipyridine Complex that Catalyzes Asymmetric Silyl Conjugate Addition in Water
Author(s) -
Taku Kitanosono,
Lei Zhu,
Chang Liu,
Pengyu Xu,
Shū Kobayashi
Publication year - 2015
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.5b11418
Subject(s) - chemistry , catalysis , conjugate , steric effects , protonation , bipyridine , copper , ligand (biochemistry) , silylation , 2,2' bipyridine , enantioselective synthesis , transition metal , polymer chemistry , organic chemistry , crystal structure , ion , mathematical analysis , biochemistry , receptor , mathematics
Acicular purplish crystals were obtained from Cu(acac)2 and a chiral bipyridine ligand. Although the crystals were not soluble, they nevertheless catalyzed asymmetric silyl conjugate addition of lipophilic substrates in water. Indeed, the reactions proceeded efficiently only in water; they did not proceed well either in organic solvents or in mixed water/organic solvents in which the catalyst/substrates were soluble. This is in pronounced contrast to conventional organic reactions wherein the catalyst/substrates tend to be in solution. Several advantages of the chiral Cu(II) catalysis in water over previously reported catalyst systems have been demonstrated. Water is expected to play a prominent role in constructing and stabilizing sterically confined transition states and accelerating subsequent protonation to achieve high yields and enantioselectivities.