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Desililujące sprzęganie winylosilanów i etynylosilanów w sekwencjach reakcji w syntezie organicznej

Prukała W.

Wiadomości Chemiczne

2008

[Z] 62, 9-10

779-826

An efficient formation of carbon-carbon bonds belongs to one of the most important transformations in synthetic chemistry. The reaction is predominantly catalyzed by the late transition metals [1, 2]. Traditional methods that have been employed, to accomplish this transformation include Stille and Suzuki reactions. However, due to a number of drawbacks inherent to the substrates used in these reactions, organosilicon reagents have emerged as competitive alternatives (the facility of preparation and purification of silanes, their high stability, and low-molecular weight). Because of the low polarizability of the C-Si bond, the silicon function must undergo nucleophilic activation to induce migration of a transferable group onto the organopalladium species (transmetallation) [3-8]. The family of palladium-based catalysts, used in the desilylative coupling reaction (DC), tolerates the presence of the majority of functional groups. The paper gives a review of literature focused on the application of desilylative coupling in sequential reactions published till the end of 2007. The activity of different catalytic systems based on palladium compounds in desilylative coupling reactions has been characterized. The influence of some substituents and activators on the reaction as well as their mechanisms has been presented [36, 41, 94-104]. It is remarkable, that the two entirely different mechanisms can be operative for both fluoride and fluoride-free silanolate couplings [104-110], and that both are highly efficient room temperature reactions. Alkenylsilanes, used in sequential reactions, can be efficiently prepared by several stereo- and regioselective methodologies involving classical stoichiometric routes from organometallic reagents and, more recently, transition-metal-catalyzed transformations of alkynes and silylalkynes (via the hydrosilylation, Sonogashira reaction), alkenes (the dehydrogenative silylation [10, 12, 13], cross-metathesis [9-11], Heck reaction), and other silicon derivatives. Moreover, the paper provides a characterization of the desilylative coupling reaction (DC) conditions. Several independent sequential reactions (one-pot, tandem reaction), e.g. RCM/DC, Stille/DC, Heck/DC, Sonogashira/DC, cross-metathesis/DC, silylative coupling/DC etc., and their applications to the synthesis of biologically active compounds have been presented. The paper is completed with a list of the most important, in the author's opinion, monographs and review works on the application of the desilylative coupling catalysed by palladium compounds in organic synthesis.