Journal article
Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction
A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no electron-withdrawing substituents.
In this way, the aldehyde group serves as a traceless control element to direct the cycloaddition reaction. The Diels-Alder reactions are performed in a diglyme solution in the presence of a catalytic amount of boron trifluoride etherate. Subsequent quenching of the Lewis acid, addition of 0.3% of [Rh-(dppp)(2)Cl] and heating to reflux achieves the ensuing decarbonylation to afford the product cyclohexenes.
Under these conditions, acrolein, crotonaldehyde and cinnamaldehyde have been reacted with a variety of 1,3-dienes to afford cyclohexenes in overall yields between 53 and 88%. In these transformations, the three aldehydes serve as equivalents of ethylene, propylene and styrene, respectively.
Language: | English |
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Publisher: | WILEY-VCH Verlag |
Year: | 2008 |
Pages: | 5638-5644 |
ISSN: | 15213765 and 09476539 |
Types: | Journal article |
DOI: | 10.1002/chem.200800003 |
ORCIDs: | Madsen, Robert |