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Catalytic Asymmetric Epoxidation of α,β‐Unsaturated Esters with Chiral Yttrium–Biaryldiol Complexes
Author(s) -
Kakei Hiroyuki,
Tsuji Riichiro,
Ohshima Takashi,
Morimoto Hiroyuki,
Matsunaga Shigeki,
Shibasaki Masakatsu
Publication year - 2007
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200600309
Subject(s) - yttrium , chemistry , catalysis , ligand (biochemistry) , cyclohexene oxide , triphenylphosphine oxide , aryl , triphenylphosphine , enantioselective synthesis , enantiomer , enantiomeric excess , triphenylarsine , alkyl , chiral ligand , organic chemistry , medicinal chemistry , oxide , cyclohexene , biochemistry , receptor
Abstract The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(O i Pr) 3 –biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee ). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(O i Pr) 3 –binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee ). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (−)‐ragaglitazar, a potential antidiabetes agent.