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First Synthesis, Isolation and Characterization of Enantiomerically Pure and Inherently Chiral Resorc[4]arenes by Lewis Acid Cyclization of a Resorcinol Monoalkyl Ether
Author(s) -
Klaes Michael,
Agena Ceno,
Köhler Markus,
Inoue Maki,
Wada Takehiko,
Inoue Yoshihisa,
Mattay Jochen
Publication year - 2003
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/ejoc.200390197
Subject(s) - chemistry , diastereomer , resorcinol , enantiomer , phenol , lewis acids and bases , ether , organic chemistry , chiral auxiliary , enantioselective synthesis , catalysis
Cyclization of resorcinol monoalkyl ethers with aliphatic aldehydes leads to the corresponding racemic mixtures of C 4 ‐symmetric rccc ‐resorc[4]arenes. Separation of these isomers was achieved by mono‐ O ‐functionalization of the rccc ‐2,8,14,20‐tetramethylresorc[4]arene ( 2 ) with ( S )‐( + )‐10‐camphorsulfonyl chloride leading to a diastereomeric mixture of ( + )‐5a and (− )‐5b . After removal of the chiral auxiliary the inherently chiral pure enantiomers ( + )‐2 and (−)‐2 were obtained. Further enantiomerically pure rccc ‐resorc[4]arenes were obtained by cyclization of (+)‐3‐[(2 S )‐2‐methylbutoxy]phenol ( 6 ) followed by chromatographic separation. The resulting diastereomeric resorc[4]arenes (+)‐7a and (−)‐7b were examined by CD spectroscopy, showing a perfect mirror image in all solvents examined. This indicates that the resorcarene cavities of (+)‐7a and (−)‐7b are essentially enantiomers of each other. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)