Ruthenium-Catalyzed trans-Selective Hydrostannation of Alkynes†
M. Sc. Stephan M. Rummelt
Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany)
Search for more papers by this authorCorresponding Author
Prof. Alois Fürstner
Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany)
Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany)Search for more papers by this authorM. Sc. Stephan M. Rummelt
Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany)
Search for more papers by this authorCorresponding Author
Prof. Alois Fürstner
Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany)
Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany)Search for more papers by this authorGenerous financial support from the MPG and the Fonds der Chemischen Industrie is gratefully acknowledged. We thank Dr. B. Sundararaju for preliminary studies and Dr. C. Farès for NMR support.
Graphical Abstract
Unorthodox: Ruthenium catalysts allow stannanes to be added in a trans fashion across the triple bonds of terminal, internal, silylated, and chlorinated alkynes. This pattern violates the basic mechanism of transition-metal catalysis which otherwise secures high cis selectivity in hydrometalations. Cooperative effects between the ruthenium species and protic functionality render reactions of unsymmetrical substrates regioselective. Cp*=η5-C5Me5.
Abstract
In contrast to all other transition-metal-catalyzed hydrostannation reactions documented in the literature, the addition of Bu3SnH across various types of alkynes proceeds with excellent trans selectivity, provided the reaction is catalyzed by [Cp*Ru]-based complexes. This method is distinguished by a broad substrate scope and a remarkable compatibility with functional groups, including various substituents that would neither survive under the conditions of established Lewis acid mediated trans hydrostannations nor withstand free-radical reactions. In case of unsymmetrical alkynes, a cooperative effect between the proper catalyst and protic functionality in the substrate allows outstanding levels of regioselectivity to be secured as well.
Supporting Information
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