Premium
Development of an Unusually Highly Enantioselective Hetero‐Diels‐Alder Reaction of Benzaldehyde with Activated Dienes Catalyzed by Hypercoordinating Chiral Aluminum Complexes
Author(s) -
Simonsen Klaus B.,
Svenstrup Niels,
Roberson Mark,
Jørgensen Karl Anker
Publication year - 2000
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/(sici)1521-3765(20000103)6:1<123::aid-chem123>3.0.co;2-l
Subject(s) - diels–alder reaction , steric effects , enantioselective synthesis , chemistry , benzaldehyde , catalysis , lewis acids and bases , yield (engineering) , asymmetric induction , lewis acid catalysis , diene , chiral ligand , ligand (biochemistry) , organic chemistry , materials science , biochemistry , natural rubber , receptor , metallurgy
The effect of Lewis acid catalysis of the hetero‐Diels‐Alder reaction between benzaldehyde and activated dienes (e.g. the Danishefsky's diene) has been investigated. In the present work we decided to study a series of chiral aluminum complexes as potential catalysts for the hetero‐Diels‐Alder reaction in order to gain a better understanding of the effect on the chiral induction of varying the steric and electronic environment of the metal ion. The results of this study prompted us to conclude that steric effects in the ligand coordination sphere and hypercoordination are strongly contributing factors to the optical yield of the reaction. Optimization of the reaction culminated in the synthesis of the hetero‐Diels‐Alder product in 99.4 % ee and 97 % yield of the isolated product. Based on the experimental results the mechanism for the hetero‐Diels‐Alder reaction is discussed and it is postulated that hypercoordination to the chiral aluminum Lewis acid center is of importance for the reaction.