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Enantioselective Addition of Cyclic Enol Silyl Ethers to 2‐Alkenoyl‐Pyridine‐ N ‐Oxides Catalysed by Cu II –Bis(oxazoline) Complexes
Author(s) -
Livieri Alessandro,
Boiocchi Massimo,
Desimoni Giovanni,
Faita Giuseppe
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201201214
Subject(s) - silylation , chemistry , enol , oxazoline , silyl enol ether , enantioselective synthesis , adduct , pyridine , medicinal chemistry , reagent , furan , organic chemistry , catalysis
Asymmetric reactions involving ( E )‐3‐aryl‐1‐(pyridin‐2‐yl‐ N ‐oxide)prop‐2‐en‐1‐ones and cyclic enol silyl ethers show good yields and excellent enantioselectivities (up to 99.9 % ee ) when catalysed by bis(oxazoline)–Cu II complexes. Different reaction pathways can be followed by different enol silyl ethers: with 2‐(trimethylsilyloxy)furan, a Mukaiyama–Michael adduct is obtained, whereas a hetero Diels–Alder cycloadduct was formed by using (1,2‐dihydronaphthalen‐4‐yloxy)trimethylsilane. In the latter reaction, the absolute configuration of the product is consistent with a reagent approach to the less hindered Re face of the coordinated substrate in the reactive complex.