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Fringuelli, F.; Piermatti, O.; Pizzo, F.; Vaccaro, L., Science of Synthesis, (2010) 47, 701.
The first report of a Diels–Alder reaction performed in supercritical water appeared in 1997,[517] and it showed that cycloadditions carried out under these conditions are generally fast, and may occur in good yields (Scheme 138). Thus, cyclohexenecarbonitriles are obtained in a few minutes from suitable starting materials. Similarly, the cycloaddition of ethyl acrylate to cyclopentadiene is complete within 2 hours in supercritical water, while in water at 50°C 8 hours is required. The configuration of the dienophile is sometimes crucial for the success of the reaction; for example, while diethyl maleate reacts with cyclopentadiene within an hour at 337°C to afford the required adduct in 86% yield, under the same reaction conditions its diastereomer diethyl fumarate gives only 10% of the corresponding adduct.[517]
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References
[517] | Meeeeeeee, M. M.; Meeee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |