Journal of Molecular Catalysis A-Chemical, Vol.214, No.1, 33-44, 2004
Recyclable palladium(0)-catalysed silylstannation of terminal alkynes in ionic liquids
The palladium(0)-catalysed addition of silylstannanes Bu3SnSiMe3 and Bu3SnSiMe2Ph to terminal alkynes has been shown to proceed in the ionic liquids 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) and 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4). These reactions generally proceed in excellent yields to give 1-trialkylsilyl-2-tributylstannyl-1Z-alkenes regio- and stereoselectively as a single product with reaction times comparable to those reported for reactions performed in tetrahydrofuran (THF). The reaction has been shown to tolerate remote functionality on the alkyne. Each of the ionic liquids containing the immobilised palladium catalyst has been recycled up to 10 times without loss of activity, allowing extensive reuse of the expensive solvent/catalyst system. A catalyst activation stage involving mild heating of the palladium catalyst in the ionic liquid/diethyl ether solvent system decreased reaction time in the first cycle once all reagents were added, indicating the formation of a catalytically active palladium species other than tetrakis(triphenylphosphine)palladium(0). (C) 2004 Elsevier B.V. All rights reserved.