RESUMO
A one-pot tandem Pd-catalyzed hydrostannylation/Stille coupling protocol for the stereoselective generation of vinyltins and their subsequent union, employing only catalytic amounts of tin, is described. By recycling the organotin halide Stille byproduct back to organotin hydride, a hydrostannylation/cross-coupling sequence can be carried out with catalytic amounts of tin. Such a process is most effective with Me(3)SnCl serving as the tin source. This protocol allows a 94% reduction of the tin requirement, while maintaining good yields (up to 90%) for a variety of Stille products. Furthermore, since one cycle requires the tin to undergo at least four transformations, each moiety of trialkyltin is experiencing a minimum of 60 reactions over the course of the hydrostannylation/Stille sequence.
Assuntos
Compostos Orgânicos de Estanho/química , Compostos Orgânicos de Estanho/síntese química , Compostos de Estanho/química , Estanho/química , Paládio/química , EstereoisomerismoRESUMO
A new tin recycling method for Stille couplings catalytic in tin is reported. PMHS made hypercoordinate by KF((aq)) allows Me(3)SnH to be efficiently recycled during a Pd(0)-catalyzed hydrostannation/Stille cascade. Relative to previously disclosed protocols, reaction times are shorter and because this process is believed to proceed through a Me(3)SnF intermediate the hazards and problems associated with trimethyltins are also diminished.[reaction: see text]
Assuntos
Fluoretos de Estanho/química , Compostos de Trimetilestanho/química , Catálise , Paládio/químicaRESUMO
In a fraction of the time required by conventional methods, microwave-accelerated one-pot hydrostannylation/Stille coupling allows 1-alkynes to be efficiently transformed into 1,3-dienes or styrenes.
