Combinatorial chemistry Stille reactions

Although solid-phase synthesis revolutionized synthetic organic chemistry and triggered the development of combinatorial chemistry, it still exhibits several shortcomings originating from the nature of heterogeneous conditions, such as lower reaction rates and difficulties in reaction monitoring. 

Recent advances in the use of Lawesson s reagent include its application in microwave assisted solvent-free syntheses, solid-phase synthesis and combinatorial chemistry.165 Despite the ubiquity of Lawesson s reagent for organic thionation reactions, there are still some classes of compounds that it does not... 

Cornforth (1992) describes synthesis as the intentional construction of molecules by means of chemical reactions." This is certainly the case in modern multistep synthesis of organic compounds because the common practice is to select a target compound to be synthesized and then to decide the sequence of chemical reactions needed to complete the synthesis. Here, intention most often (though not always) means the intention to create a compound of particular structure rather than one having particular (molar) properties. It is possible that the inclusion of the newly developing area of combinatorial chemistry as a synthetic approach would change the precise meaning of "intent" still more because the specific structural features of products of those syntheses may not be of interest unless and until they are shown to have some desired molar property. 

At the other end of the scale, products can be isolated on single beads of resin produced by combinatorial chemistry, involving sequential splitting and mixing batches of beads between reaction steps such that single beads contain only one product. Spectroscopic methods have been developed for the non-destructive characterisation of products while still on the bead. ... 

In an interesting development for combinatorial chemistry, Sm -promoted radical cyclizations have been adapted for use on solid support [27], The procedures developed have some inherent advantages over -Bu3SnH-mediated reactions and sometimes even to the corresponding solution phase SmE-promoted reactions. Unfortunately, they still appear to lack the consistency necessary for general use in the synthesis of chemical libraries. 

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