Regioselective Synthesis of 1,4 & 1,5-Enynes through a Ca(II)- Catalyzed Cross-Dehydrative-Coupling of Styrenes and Propargyl alcohols

A chemo and regioselective C(sp(3)) - C(sp(2)) and C(sp(3)) - C(sp(3)) bond formation through a Cross-Dehydrative-Coupling of styrenes and propargyl alcohols is described for the synthesis of 1,4 and 1,5-enynes. The first direct coupling of cyclic alkenes with oxindole derived propargylic alcohols is achieved for the synthesis of quaternary centered enynes under mild reaction conditions and demonstrated the gram scale synthesis. This approach meets the sustainable criterion of chemical synthesis due to its air-tolerance, atom economic (water is the only by-product), solvent free and use of less expensive and more abundant Ca(II) as the promoter.