Evaluation of Catalyst Acidity and Substrate Electronic Effects in a Hydrogen Bond-Catalyzed Enantioselective Reaction
作者:Katrina H. Jensen、Matthew S. Sigman
DOI:10.1021/jo1013806
日期:2010.11.5
A modular catalyst structure was applied to evaluate the effects of catalystacidity in a hydrogen bond-catalyzed hetero Diels−Alder reaction. Linear free energy relationships between catalystacidity and both rate and enantioselectivity were observed, where greater catalystacidity leads to increased activity and enantioselectivity. A relationship between reactant electronic nature and rate was also
1′-binaphthyl, and the structure was proved via X-ray analysis of its salicyl-aldehyde Schiff base, which was tested in the enantioselective titanium-catalyzed hetero-Diels-Alderreaction of Danishefsky’s diene with aldehydes. The reaction provided dihydropyranone in moderate to high yield (up to 99%) and enantioselectivities (up to 84.5% ee).
Optically active 3-oxobutylideneaminatocobalt(III) complexes were developed as effective catalysts for the enantioselective hetero Diels–Alder reaction of aromatic and aliphatic aldehydes with 3-(t-butyldimethylsilyloxy)-1-methoxy-1,3-butadiene. In the presence of the highly active cationic cobalt(III) complex, the hetero Diels–Alder reactions proceeded to afford the corresponding dihydropyran-4-ones