Solid support catalysts Suzuki coupling

The use of solid supported, recyclable catalysts, is a well-assessed technique in classic organic chemistry, and many exhaustive reviews dealing with this subject are available [105, 115]. The use of solid supported catalysts for library synthesis in solution has also been reported. Among others, Kobayashi et al. presented the use of a new supported scandium catalyst for 3CC reactions leading to solution libraries of amino ketones, esters, and nitriles (24-member model discrete library) [116], or to quinolines (15-member model discrete library) [117], and Jang [118] presented a polymer bound Pd-catalyzed Suzuki coupling of organoboron compounds with halides and triflates. This area was also briefly reviewed recently [119]. 

Applications of Suzuki and Heck cross-coupling reactions were adopted by Gallop and coworkers [131] to prepare diverse biaryl- and styryl-substituted (3-lactams on solid support. The catalyst system, [PdCl2(dppf)]-TEA, was found to be efficient to promote C-C bond formation around a (3-lactam template (Schemes 26 and 27). 

Ellman utilized the Suzuki coupling twice between a support-bound vinyl bromide and an alkyl 9-BBN derivative in a solid-phase synthesis of E- and F-series prostaglandins. The Suzuki reaction was performed in situ, with the hydroboration of a terminal olefin being followed by the palladium-mediated step. This sequence is attractive in library synthesis because of the wide range of suitable commercially available alkenes. The inspiration behind this chemistry was the solution-phase work of Johnson and Braun, where the couplings of 35 with 2-iodo-4-(silyloxy)cyclopent-2-enone 36 went well at room temperature with PdCljCdppO-AsPhj as catalyst (Scheme 41). The modular chemistry demonstrated in this paper was clearly amenable to adaptation to a solid-phase strategy. 

Another solid-support Suzuki coupling is the hydroboration of vinyl polystyrene with 9-BBN in THF to provide [29] polymer supported borane. This borane is coupled to give different aryl, vinyl, or alkyl iodides. Pd(OAc)2 is employed as the catalyst for aryl iodides and PdCl2(dppf) in other cases to yield the coupled adduct in 55-85% yield (Scheme 31.7) on the basis of the mass of the product cleaved or by comparison with IR integration to standards. 

Due to the substantial amount of literature, even when excluding supported catalysts, only selected articles on the solid phase Suzuki reaction are mentioned here, concentrating on the more recent publications. Apart from the general palladium reviews cited in Sect. 5, some examples of solid phase synthesis can be found in a review of apphcations of the Suzuki-Miyaura cross-coupling reactions in organic synthesis by Kotha in 2002 [114]. 

---