AbstractRuthenium(II)‐phosphine complexes‐catalyzed [3+2] cycloadditions were conducted to synthesize a variety of dihydrofurans by reactions of cyclic or acyclic diazodicarbonyl compounds with olefins. This method represents a direct and efficient one‐pot synthesis for multi‐substituted dihydrofurans under mild reaction conditions with an excellent regioselectivity. Furthermore, to reduce reaction times and increase yields of dihydrofurans, microwave‐assisted tris(triphenylphosphine)ruthenium(II) chloride/ 1‐butyl‐3‐methylimidazolium tetrafluoroborate {Ru(PPh3)3Cl2/[Bmim]BF4}‐catalyzed reactions were also developed. The synthesized dihydrofurans can be readily converted into biologically interesting tetrahydroindoles.magnified image
Electrochemical oxidation of 1,3-diketones in the presence of olefins afforded the formal [3+2] cycloaddition products, dihydrofuran derivatives or tetrahydrofuran derivatives. A mechanism involving attack of a radical intermediate to an olefin has been proposed.