Solid supported organic synthesis

In these reactions, the reactants are stirred in a suitable solvent (for example, water, alcohol, methylene chloride etc.). The solution is stirred thoroughly with a suitable adsorbent or solid support like silica gel, alumina, phyllosilicate (M -montomorillonite etc.). After stirring, the solvent is removed in vacuo and the dried solid support on which the reactants have been adsorbed are used for carrying the reaction under microwave irradiation. 

Some of the important applications of solid support synthesis are given as follows. 

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Those people who have tried here to summarise solid-supported organic synthesis in a hopefully clear and comprehensive way agree ... 

Historical landmarks in solid-supported organic synthesis... 

J. A. Bristol, Ed., Applications of Solid-Supported Organic Synthesis in Combinatorial Chemistry. Pergamon Press, Oxford, 1997. 

C. Blackburn, Polymer supports for solid-phase organic synthesis, Biopolymers 47 311-351 1998. 

Kobayashi S, Aoki Y. />-Benzyloxybenzylamine (BOBA) resin. A new polymer-supported amine used in solid-phase organic synthesis. Tetrahedron Lett 1998 39 7345-7348. 

Schiemann K, Showalter HDH. Development of polymer-supported benzotriazole as a novel traceless linker for solid-phase organic synthesis. J Org Chem 1999 64 4972 1975. 

Hu Y, Porco JA, Jr, Labadie JW, Gooding OW, Trost BM. Novel polymer-supported trialkylsilanes and their use in solid-phase organic synthesis. J Org Chem 1998 63 4518 1521. 

One of the key technologies used in combinatorial chemistry is solid-phase organic synthesis (SPOS) [2], originally developed by Merrifield in 1963 for the synthesis of peptides [3]. In SPOS, a molecule (scaffold) is attached to a solid support, for example a polymer resin (Fig. 7.1). In general, resins are insoluble base polymers with a linker molecule attached. Often, spacers are included to reduce steric hindrance by the bulk of the resin. Linkers, on the other hand, are functional moieties, which allow the attachment and cleavage of scaffolds under controlled conditions. Subsequent chemistry is then carried out on the molecule attached to the support until, at the end of the often multistep synthesis, the desired molecule is released from the support. 

Solid-phase organic synthesis (SPOS) exhibits several shortcomings, due to the nature of the heterogeneous reaction conditions. Nonlinear kinetic behavior, slow reactions, solvation problems, and degradation of the polymer support due to the long reaction times are some of the problems typically experienced in SPOS [2], Any technique which is able to address these issues and to speed up the process of solid-... 

Allylic amination is important for the solid-phase organic synthesis.15 The solid-phase allylic aminations are devised into the G-N bond formation on solid support and the deprotection of allyl ethers. As a novel deprotection method, the palladium-catalyzed cyclization-cleavage strategy was reported by Brown et al. (Equation (4)).15a,15b The solid-phase synthesis of several pyrrolidines 70 was achieved by using palladium-catalyzed nucleophilic cleavage of allylic linkages of 69. 

The proper choice of the solid support and the connected linker is important for the success of solid-phase organic synthesis. To date, the possibihty of reactions on the resins have been limited by the number of linkers, because most of them were initially developed for peptide synthesis. 

There are only few examples for oxidation reactions on solid supports, because most linkers or polymeric supports are sensitive towards some reagents suitable for classical transformations. Classical oxidation reagents are not soluble in most solvents used in the solid-phase organic synthesis step (but e.g. Scheme 3.10). 

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