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Copper(II)‐Bisoxazoline‐Catalysed Asymmetric Diels−Alder Reactions of α‐Thioacrylates
Author(s) -
Aggarwal Varinder K.,
Jones D. Elfyn,
MartinCastro Ana M.
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200008)2000:16<2939::aid-ejoc2939>3.0.co;2-k
Subject(s) - chemistry , cyclopentadiene , ethyl acrylate , moiety , cycloaddition , ligand (biochemistry) , diels–alder reaction , catalysis , yield (engineering) , enantioselective synthesis , medicinal chemistry , organic chemistry , chiral ligand , acrylate , stereochemistry , polymer , monomer , receptor , biochemistry , materials science , metallurgy
A range of C 2 ‐symmetric, chiral Cu II ·bisoxazoline complexes were tested as catalysts for the asymmetric Diels−Alder cycloaddition between cyclopentadiene and a range of α‐sulfenylacrylates. The optimum acrylate was ethyl α‐phenylthioacrylate and the optimum catalyst was the bisoxazoline derived from phenylalanine which, upon complexation with Cu(SbF 6 ) 2 , gave the cycloadducts in 92% yield, 88% de and >95% ee for the endo product. The α‐phenylthio ester moiety was easily converted into a carbonyl group furnishing (1 S ,4 S )‐norbornenone with high enantioselectivity. Attempts to improve the diastereoselectivity by changing the bite angle of the ligand were unsuccessful. An attempt is made to rationalise our findings in terms of the transition‐state structure of the ligand−metal−dienophile complex.