Solid-Supported Organotin Reagents

1 Supported Organotin Reagents on Insoluble Polystyrene Matrix 

An alternative type of insolnble polystyrene matrix is obtained with lower amonnts of DVB (0.5 to 2%), affording microporons polymers or so-called gel-type resins. These polymers are characterized by the absence of permanent pores and by a low external area. Accordingly, the swelling of the resin in the solvent is of great importance to achieve chemical reactions in appropriate conditions and for this purpose, solvents such as toluene, dichloromethane or THF are generally the more suitable ones. It is also worth noting that this type of structure increases the sensitivity to mechanical abrasive effects and to osmotic pressure.  

The synthesis of these snpported organotin reagents can be achieved according to two routes  

It should also be mentioned that polymers A-D have to be washed correctly in order to remove the soluble organotin species resulting from the synthesis. This aspect has been studied in detail for polymer C and when it was used for the reduction of organic halides, soluble organotin residues 

Through this route, several reagents have been prepared with a tin incorporation that depends on the nature of the SnXs moiety. A loading of 0.9 mmol g was obtained for SnBrs compared with 0.7 mmol g for Sn(OMe)3,1 mmol g for SnCl(OMe)2 and 1.5 mmol g for SnBr(OMe)2.  

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New Trends in the Synthesis of Solid-Supported Organotin Reagents 607... 

New Trends in the Synthesis of Solid-Supported Organotin Reagents and Interest of their Use in Organic Synthesis in a Concept of Green Chemistry... 

One of the first cross-coupling reactions performed on solid supports was the Stille reaction [250] which is a paUadium-catalyzed reaction of a trialkylaryl or trialkylalkenyl stannane with an aromatic iodide, bromide or triflate. In contrast to the process in liquid-phase, the organotin reagent is easily removed from the solid-phase because of the subsequent washing processes. Immobilized aryl halides have been frequently coupled with aryl and alkenylstannanes, whereas stan-nanes attached to the solid support have been used less frequently for the StiUe reaction. An example is the synthesis of a benzodiazepine library by EUman et al. Recently, a Stille cross-couphng reaction has been employed in the synthesis of al-kenyldiarylmethanes (ADAM) series of non-nucleoside HlV-1 Reverse Transcriptase Inhibitors (Scheme 3.14) [251]. 

Some interesting procedures are being developed to make the present protocol more useful as a synthetic tool. Directing to the combinatorial synthesis, solid-phase syntheses have currently been under development using polymer-supported stannanes (Scheme 69) [263-268] or electrophiles (Scheme 70, Scheme 71) [149, 269-272]. In the latter case, unreacted organotin reagent as... 

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