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Enantioselective Cyclopropanation Reactions with Planar‐Chiral Pyridinium Ylides: A Substituent Effect and a Remote Steric Effect
Author(s) -
Kanomata Nobuhiro,
Sakaguchi Ryo,
Sekine Kazuki,
Yamashita Satomi,
Tanaka Hiroko
Publication year - 2010
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201000079
Subject(s) - pyridinium , chemistry , steric effects , cyclopropane , cyclopropanation , substituent , enantioselective synthesis , triethylamine , planar chirality , density functional theory , stereochemistry , photochemistry , medicinal chemistry , computational chemistry , organic chemistry , catalysis , ring (chemistry)
Novel planar‐chiral pyridinium ylides were designed, and generated in situ from the corresponding pyridinium salts with triethylamine. Ylides with a common parapyridinophane skeleton reacted efficiently with electron‐deficient dicyanoalkenes, or malononitriles, to produce optically active cyclopropane derivatives with high enantioselectivity (up to 99% ee ). Remote steric effects were observed on the enantioselectivities, where the R 2 groups of the pyridinophane core resulted in higher ee values of the products. Density function theory (DFT) calculations are in good agreement with our experimental results: the energetically favored transition state leads to the major stereoisomer, namely the trans‐ cyclopropane products.