Solvent-free Robinson Annulation

Robinson annulation is a reaction sequence consisting of a Michael addition of a cycloalkanone a-carbanion to an a,[3-unsaturated ketone derivative, followed by al-dol condensation to form the final product, a 2-cyclohexenone ring fused to the 

A solvent-free self-assembly offullerene Cjq using high-speed vibration milling has been described [19]. This simple, efficient, and green pathway to the synthesis of a supramolecular complex in the solid state opened a new avenue for the application of solventless reactions. 

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Rajagopal, D., Narayanan, R., Swaminathan, S. Enantioselective solvent-free Robinson annulation reactions. Proc. - Indian Acad. Sci., Chem. Scl. 2001, 113, 197-213. 

One-pot syntheses of diaryl-a-tetralones by Michael condensation and subsequent Robinson annulation reactions of isophorone with chalcones were performed efficiently in a solvent-free PTC system under the action of MW irradiation. Compared with conventional heating substantial rate enhancements were observed, within very short reaction times, by use of microwaves (Eq. 59 and Tab. 5.31). They were far better than those achieved by the classical method (NaOEt in EtOH under reflux for 24 h 40-56%). 

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