Contents 1.0Introduction
1.1 Polystyrene Supports as Carriers for Reagents and Catalysts
1.2 Catalyst and Reagent Attachment to Polymer Supports
2.0C-C Bond Formation Using Recyclable Resin-Based Reagents and Catalysts
2.1 Palladium-Catalyzed Coupling Reactions
2.2 Other Transition Metal Catalyzed Reactions
2.3 Resin-Supported Olefin Metathesis
2.4 Resin-Mediated Cycloaddition Reactions
2.4.1 Diels-Alder Cycloadditions
2.4.2 Resin-Based Catalysts for 1,3-Dipolar Cycloadditions
2.5 Immobilized Chiral Ligands for Diethylzinc Additions to Aldehydes
2.6 Miscellaneous: Other C-C Bond Forming Reactions
3.0Immobilized Oxidants
3.1Oxidation with Immobilized Transition Metal Complexes
3.2 Alcohol Oxidation
3.3 Alkene Oxidation
3.3.1 Dihydroxylation
3.3.2 Epoxidation
3.3.3 Asymmetric Epoxidation
3.3.4 Other Alkene Oxidation Reactions
3.4 Potpourri: Other Immobilized Oxidants
4.0Immobilized Resin-Based Reductants
4.1 General Reduction Processes
4.2 Asymmetric Reduction of Ketones
4.3 Alkene Reduction
4.4 Resin-Based Tin and Germanium Reductants
5.0Conclusions
6.0Abbreviations
7.0Acknowledgments
8.0References

Recoverable Catalysts and Reagents Using Recyclable Polystyrene-Based Supports

Poly(1,6-heptadiyne)-Based Materials by Metathesis Polymerization.

As part of the dramatic changes associated with the need for preparing compound libraries in pharmaceutical and agrochemical research laboratories, industry searches for new technologies that allow for the automation of synthetic processes. Since the pioneering work by Merrifield polymeric supports have been identified to play a key role in this field however, polymer-assisted solution-phase synthesis which utilizes immobilized reagents and catalysts has only recently begun to flourish. Polymer-assisted solution-phase synthesis has various advantages over conventional solution-phase chemistry, such as the ease of separation of the supported species from a reaction mixture by filtration and washing, the opportunity to use an excess of the reagent to force the reaction to completion without causing workup problems, and the adaptability to continuous-flow processes. Various strategies for employing functionalized polymers stoichiometrically have been developed. Apart from reagents that are covalently or ionically attached to the polymeric backbone and which are released into solution in the presence of a suitable substrate, scavenger reagents play an increasingly important role in purifying reaction mixtures. Employing functionalized polymers in solution-phase synthesis has been shown to be extremely useful in automated parallel synthesis and multistep sequences. So far, compound libraries containing as many as 88 members have been generated by using several polymer-bound reagents one after another. Furthermore, it has been demonstrated that complex natural products like the alkaloids (+/-)-oxomaritidine and (+/-)-epimaritidine can be prepared by a sequence of five and six consecutive polymer-assisted steps, respectively, and the potent analgesic compound (+/-)-epibatidine in twelve linear steps ten of which are based on functionalized polymers. These developments reveal the great future prospects of polymer-assisted solution-phase synthesis.

Functionalized Polymers—Emerging Versatile Tools for Solution-Phase Chemistry and Automated Parallel Synthesis

Solution-phase synthesis of diaryl selenides using polymer-supported borohydride.

The current interest in solid-phase organic synthesis has led to a renewed interest in a complementary technique in which solid supported reagents are used in solution phase chemistry. This technique obviates the need for attachment of the substrate to a solid-support, and enables the chemist to monitor the reactions using familiar analytical techniques. The purpose of this review is to increase awareness of the wide range of useful transformations which can be accomplished using solid-supported reagents.

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Solid-Supported Reagents in Organic Synthesis

Exchange of quaternary ammonium type anion exchange beads with NaBH4 leads to useful reducing agents possessing the advantage of easy work-up.

Chemical modification of polymers. Borohydride reducing agents derived from anion exchange resins

The synthesis and initial characterization of a new free-standing dopable electrically conducting polyene film, poly(hepta-1,6-diyne), are reported.

F. Courtney Bailey

Papers

Chemical modification of polymers. Borohydride reducing agents derived from anion exchange resins

A new free-standing dopable electrically conducting polyene film