Palladium-catalyzed activation of E-E and C-E bonds in diaryl dichalcogenides (E = S, Se) under microwave irradiation conditions

The first example of palladium-catalyzed stereoselective addition of diphenyl disulfide and diphenyl diselenide to the triple bond of terminal alkynes under microwave irradiation conditions is described. It was found that both the element-element (E-E) and carbon-element bonds can be activated in the catalytic system studied. The products of both reactions were isolated in quantitative yields. According to quantum-chemical calculations, the reaction mechanism involves the oxidative addition of the E-E bond to Pd-0. Depending on the microwave power and reaction conditions, the next stage is either the reaction with alkyne or the carbon-element bond activation. The product of the oxidative addition of Ph2Se2 to Pd-0, namely, dinuclear complex [Pd-2(SePh)(4)(PPh3)(2)], was detected by P-31{H-1} NMR spectroscopy directly in the Ph2Se2/pph(3) melt formed under microwave irradiation conditions.