Cross-coupling reactions organotin compounds

Organotin compounds can be effectively used as substrates in the palladium-catalyzed cross-coupling reactions of alkenyliodonium salts [66,67]. For example, the reaction of alkenyliodonium triflate 84 with 5-stannylated uracil 83 proceeds smoothly to provide cross-coupled products 87 in moderate yield. The same products 87 are obtained in almost quantitative yield in the palladium-catalyzed cross-coupling of uracil iodonium triflate 85 and vinyltin 86 (Scheme 39) [67]. 

The cross-coupling reaction of alkenyl(fluoro)silanes with aryl halides sometimes produces, in addition to the desired ipso-cowpled products, small amounts of cmc-coupled products [14]. The czne-coupling is often striking in the reaction with organotin compounds. The isomer ratio of products produced by the reaction of l-fluoro(dimethyl)silyl-l-phenylethene with aryl iodides is found to depend on the electronic nature of a substituent on aryl iodides (Eq. 11) an electron-withdrawing group like trifluoromethyl and acetyl favors the formation of the ipso-coupled product. To explain the substituent effect, the mechanism depicted in Scheme 3 is proposed for the transmetalation of alkenylsilanes with palladium(ll) complexes. It is considered that an electron-donating substituent on Ar enhances... 

Palladium-catalyzed cross-coupling reaction between organotin compounds and various electrophUes provides a vast range of carbon skeletons. 

Keywords. Organotin compounds. Palladium catalyst. Cross-coupling reaction, Carbonylative coupling... 

Organotin compounds are used widely in Pd-catalyzed cross-coupling reactions, where the tin reagents serve to deliver an organic group to Pd . In effect, an R-for-halide exchange takes place and, although Pd-Sn species are not detected, the reaction proceeds by an oxidative-addition reductive-elimination sequence. 

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