Microwave-assisted reaction series for use in organic teaching laboratories: Application to the formation and Diels-Alder cycloaddition of tetraphenylcyclopentadienone

CHED 401

Steven G. Ballmer, ballmer.3@wright.edu and Daniel M. Ketcha, daniel.ketcha@wright.edu. Department of Chemistry, Wright State University, 3640 Col. Glenn Hwy, Dayton, OH 45435
The sequence involving initial aldol condensation of benzil and 1,3-diphenylacetone to afford tetraphenylcyclopentadienone, followed by the subsequent reaction of this diene with an acetylenic dienophile is a common series of experiments in many organic laboratory texts. The use of a polymer-supported base (Amberlyst A-26, OH form) was found to facilitate the aldol condensation in ethanol in a commercial monomode microwave (120 oC, 5 min). A corollary study of the resultant dienone was the Diels-Alder cycloaddition with dimethyl acetylenedicarboxylate as the dienophile, using microwave irradiation with concomitant extrusion of carbon monoxide to afford the corresponding benzenic product. Presented here is an optimized method for the utilization of this reaction series in an organic teaching laboratory.