Carbopalladation reactions in solid-phase syntheses

Heck reactions on solid supports have been extensively applied because of the easy accessibibty of starting materials such as polymer-bound haloalkenes or haloarenes and alkenes. The most frequently used reaction conditions are either the standard Heck conditions (Pd(OAc)2, PPhj, or P(o-Tol)3, DMF, 80-100°C, 

2-24h) [3] or the protocol developed by Jeffery (PdlOAcJj, PPh, BU4NCI, KjCOj, DMF, 20-80°C) [223]. The yields obtained under the Jeffery conditions were frequently enhanced by the addition of 10% of water to the reaction mixture. In some cases, PdjIdbaJj-CHCl, was found to be far more effective than PdJOAcJj [579]. The Heck reaction was performed on immobilized aryl halides, mostly iodides, or aryliodonium salts with soluble alkenes [122, 209, 210, 580-590] or on immobihzed alkenes with soluble aryl hahdes [IlOe, 217a, 601-606] as well as with soluble aryhodonium salts [217b]. When performed on the same type of resin and with the same catalyst system, the immobilization of the aryl iodide appears to be more beneficial than that of the alkene [210]. 

Similarly, a 20-membered ring of a tetrapeptide derivative containing a 3-substituted cinnamic acid template was closed on a solid support [593]. This methodology was also applied in the synthesis of a small library (15 examples) of cyclic RGD mimics having a diverse array of amino acids, with a variety of ring sizes [594]. 

Besides the preparation of macrocycles, cyclizations to give heteroatom-containing five-, six-, and seven-membered rings have been investigated [211, 595-599]. Thus, the construction of indoles, benzofurans, dihydroisoquinoHnes, and benzazepines has been reported. Starting from aryl iodides with appropriate 

R = Ph, Bu. cPent, CH2CH2Ph, CH2CH2CH20(m-Me02CC6H4), CH2N(Me)CO(p-MeOC6H4) 

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