Microwave-promoted efficient synthesis of 2-phosphabicyclo[2.2.2] octadiene- and octene-2-oxides under solvent-free conditions in Diels-Alder reaction

The microwave-induced and solvent-free Diels - Alder reaction of 1,2-dihydro-phosphinine oxides ( 1 and 5) and dimethyl acetylenedicarboxylate or N-phenylmaleimide afforded 2-phosphabicyclo[2.2.2] octadiene-( 2 and 6) and phosphabicyclo[ 2.2.2] octene oxides ( 4 and 7), respectively, almost quantitatively and in a fast reaction in an ecofriendly manner.