Improved Protocols for the Molybdenum-Catalyzed Hydrostannation of Alkynes

In the molybdenum-catalyzed hydrostannation of alkynes the addition mode of tributyltin hydride has a strong effect on the outcome of the reaction. Slow addition increases the yield, even if the amount of tributyltin hydride is reduced to only one equivalent. Microwave irradiation speeds up the reaction dramatically, sometimes at the cost of regioselectivity.