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Unsaturated Aldehydes as Alkene Equivalents in the Diels–Alder Reaction
Author(s) -
Taarning Esben,
Madsen Robert
Publication year - 2008
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/chem.200800003
Subject(s) - decarbonylation , chemistry , cycloaddition , alkene , crotonaldehyde , aldehyde , organic chemistry , lewis acids and bases , acrolein , boron trifluoride , diels–alder reaction , olefin fiber , styrene , medicinal chemistry , cyclopentadiene , rhodium , catalysis , copolymer , polymer
A one‐pot procedure is described for using α,β‐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.