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A Mild and Efficient Asymmetric Hetero‐Diels–Alder Reaction of the Brassard Diene with Aldehydes
Author(s) -
Fan Qian,
Lin Lili,
Liu Jie,
Huang Yaozong,
Feng Xiaoming
Publication year - 2005
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.200500126
Subject(s) - chemistry , enantioselective synthesis , diene , ligand (biochemistry) , schiff base , benzaldehyde , diels–alder reaction , alkoxy group , medicinal chemistry , substituent , aldol reaction , aldehyde , organic chemistry , stereochemistry , catalysis , receptor , biochemistry , natural rubber , alkyl
This paper describes the successful development of the hetero‐Diels–Alder (HDA) reaction of the Brassard diene with aldehydes in the presence of a series of titanium( IV ) tridentate Schiff‐base complexes under mild conditions. The influence of the substituent of the chiral Schiff‐base ligands on the enantioselectivities of the reaction was studied. It was found that ligand L13 is a highly enantioselective ligand for the Ti‐catalyzed HDA reaction, affording 6‐substituted 4‐ethoxy‐5,6‐dihydropyran‐2‐one in up to 99 % ee . The mechanism of the HDA reaction between the Brassard diene and benzaldehyde in the presence of the (Schiff base)Ti IV complex was investigated. The results indicate that the reaction pathway is influenced by reaction temperature: at higher temperature (0 °C), the reaction is mostly a Diels–Alder process, whereas at lower temperature (–78 °C) it is a Mukaiyama aldol process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)