Cross-coupling reactions transition metal catalysts, carbon

To make the transformation even more useful, different carbon electrophiles should be connected sequentially in a stepwise manner. For this purpose, a transition-metal-catalyzed cross-coupling reaction opened the way. As shown in Scheme 22, cinnamyl chloride is treated with bis(iodozincio)methane (3) in the presence of palladium catalyst with various phosphine ligands. Phosphine ligands, having an electron-withdrawing group, such as tris[3,5-bis(trifluoromethyl)phenyl]phosphine and tris(2-furanyl)phosphine, show excellent results47. 

Selective cross-coupling reactions between C(sp ) and C(5p ) centers had been one of the most difficult tasks in carbon-carbon bond synthesis until the early 1970s, when it was first reported that iron, nickel, palladium and copper - catalysts are extremely effective for cross-coupling of Grignard reagents with organic halides. Now, nearly 20 years later, transition metal catalyz cross-coupling has become the reaction of first choice for this purpose. 

Representing the third important method of C-C bond formation covered in Chapter 12, cross-coupling reactions constitute one of the most powerful and widely used tools available today to the synthesis chemist. Equation 12.52 shows the general overall reaction, which involves combination of two carbon fragments (R and R ), one typically originating from an organohalide and the other from a metal hydrocarbyl compound. A transition metal complex serves as catalyst and template for the coupling to occur. 

Carbon-carbon bond formation is one of the most important reaction in organic synthesis [20]. However, most of the reactions require relatively large amounts of a costly transition metal catalyst and its removal from the reaction mixture is difficult. With the perfluoroalkyl substituted triarylphosphane 27 palladium catalyzed cross-coupling reactions of aryl iodides 28 with arylzinc... 

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