Wall effects, microwave-assisted

In 1996, the first examples of intermolecular microwave-assisted Heck reactions were published [85]. Among these, the successful coupling of iodoben-zene with 2,3-dihydrofuran in only 6 min was reported (Scheme 75). Interestingly, thermal heating procedures (125-150 °C) resulted in the formation of complex product mixtures affording less than 20% of the expected 2-phenyl-2,3-dihydrofuran. The authors hypothesize that this difference is the result of well-known advantages of microwave irradiation, e.g., elimination of wall effects and low thermal gradients in the reaction mixture. 

Dallinger D, Irfan M, Suljanovic A, Kappe CO. An investigation of wall effects in microwaves-assisted ring-closing metathesis and cyclotrimerization reactions. J. Org. Chem. 2010 75 5278-5288. 

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