Stille Couplings Catalytic in Tin:  The “Sn−O” Approach

Abstract

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.

Organotin Reagents in Cross‐Coupling Reactions

“…A mixture of Bu 3 SnCl (catalytic amount), polymethylhydrosiloxane (PMHS) and aqueous sodium carbonate (to convert the chloride to bis(tri-n-butyltin)oxide that reacts with PMHS to give Bu 3 SnH in situ) in combination with Pd 2 (dba) 3 and trifurylphosphine leads to diene formation. Use of Me 3 SnCl instead of the tributyltin chloride [73] improves yields drastically (to up to 90%). Further improvement is obtained in the third protocol reported [74a,b], which was used to prepare (E)-alkenes and dienes in shorter reaction times: sodium carbonate is replaced by aqueous KF and catalytic tetrabutylammonium fluoride, which are suggested to render both PMHS and the intermediate trimethylstannylalkene ''hypercoordinate'' (Scheme 6.17).…”

Polymers for Green C–C Couplings

“…The authors attribute this effect to the elimination of the residual palladium that is deposited in the polymer after the first reaction. Polystyrene-supported stannanes have also been used in the Stille reaction catalytic in tin developed several years ago by Maleczka et al [107,117] This reaction is a Stille coupling of organic electrophiles and vinyl tin derivatives that uses substoichiometric amounts of the tin derivative (5-10 %). The vinylstannane is generated in situ by hydrostannation of alkynes, and the required tin hydride is generated in the course of the reaction by reduction with a polysiloxane (Scheme 14).…”

Use of polymer-supported phenyltin for the creation of aryl–aryl or aryl–heteroaryl bonds via Stille cross-coupling reactions

“…In this context, various methodologies concerning the Stille cross-coupling reaction including the elimination of tributyltin halides as tributyltin fluoride [18,19], the use of monoorganotin reagents [20][21][22], a catalytic amount of organotin reagent [23][24][25], a biphasic system like a fluorous phase [26][27][28] or ionic liquids [29][30][31], have been reported. In addition, the concept of tin reagent grafted on a matrix has also been developed.…”