Another nice report on the utility of ionic liquids:  an organic synthetic approach to tetrahydrobenzo[a]xanthen-11-ones. This was a nice idea to combine the ionic liquid with an acid functionality to see if the combination of the two would promote the 3 component sequence with attack of the aldehyde, alpha to the OH on the arene, spitting out water and reaction with the enol for of dimedone and intramolecular attack for the OH to give the desired Xanthene product.

Green Chemistry Letters and Reviews 2011

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3 component reaction with catalytic IL

In addition to using the IL (or Task Specific as referred to in the article), they wanted the reaction to be catalytic in the acid — so the IL was studied in mole percent/time to develop the chemistry (5-20%, so not a solution phase reaction) for 10 min provided comparable results.

The approach was nice enough, but I get a little chapped when I don’t see temperatures defined as part of an optimization. Isn’t that a pretty key variable? Was this a multimode microwave? With a time of reaction from 8-15 minutes, temperatures can get pretty high, especially in the presence of an IL as part of the medium…….I get the utility, but would just like a little care given to pushing a technique. Anyway not to end on a down note, they did note some standard conditions with the current method and have shown a significant reduction in time while maintaining high yields.

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