Metal-catalysed cross-coupling reactions

Transition metal catalysed cross-coupling reactions of organometalUc reagents containing Zn, Si, Mg, Sn or B with organic electrophiles in the presence of group 8-10 metals, notably Ni and Pd, are routinely the method of choice, both in academia and industry, for the preparation of C-0, C-S, C-H, C-N and C-C bonds [1]. 

In the context of NHC/metal catalysed cross-coupling reactions, the only example of a Hiyama reaction was reported by Nolan using an in situ protocol by mixing Pd(OAc)j and IPr HCl for the formation of the catalyst. Activated aryl bromides and chlorides, such as 2-chloropyridine, were coupled with phenyl and vinyl-trimethoxysilane in good yields [123] (Scheme 6.39). 

Another very important aspect of these transition metal-catalysed cross-coupling reactions stems from the high selectivity observed with stereo-defined vinyl sulfides. Applications to the stereoselective syntheses of pheromones were straightforward (see [321] and references therein), as shown in the two-step synthesis of muscalure from (Z)-l-bromo-2-phenylthioethylene [322] involving its sequential coupling through the bromo and phenylthio substituents with the appropriate derivatives. 

Stang, P. J. and Diederich, F., Metal Catalysed Cross-Coupling Reactions, Wiley, Chichester, 1997. 

K. Sonogashira, Metal-catalysed Cross-coupling Reactions, Wiley-VCH, Weinheim, 1997, p. 203. 

For reviews see (a) Mitchell TN. In Diedrich F, Stang PG, eds. Metal Catalysed Cross-Coupling Reactions. Weinheim Verlag GmbH, Wiley VCH, 1988 197-202 (b) Farina V, Krishnamurthy V, Scott WJ. In Paquette LA, ed. The Stille Reaction. Organic Reactions 1997, Vol. 50. New York John Wiley Sons, Inc., 1997 1-676. 

Table 7.1 Transition-metal catalysed cross-coupling reaction of alkyl halides with grignard reagents in the presence of 1,3-butadiene.

Due to the importance of aryl triflates and related compounds in modern organic chemistry, including metal catalysed cross-coupling reactions, an efficient procedure for the triflation or nonaflation of phenols has been developed by the combination of PS-TBD (3 equiv.) and a perfluoroalkanesulfonyl transfer reagent (3 equiv.) such as p-nitrophenyl triflate or nonaflate [30] (Scheme 6.2). In this case, the free PS-TBD reagent could be recovered by washing successively with diluted acid, base, water and organic solvents, and almost comparable results were obtained with use of the recycled catalyst. 

P. Diederich and P. Stang (Eds.), Metal-Catalysed Cross-Coupling Reactions Wiley VCH, New York (1998). 

Prominent Transition Metal Catalysed Cross Coupling Reactions for the Aryl-Aryl Bond... 

Scheme 27 Metal-catalysed cross-coupling reactions of a 6-fluoropurine nucleoside derivative...

The scope of transition metal-catalysed cross-coupling reactions involving N-tosylhydrazones has been broadened. While IV-tosylhydrazones cross-couple with trialkylsilylethynes to form C -C s bonds under Cu(I) catalysis,i° Pd(0) catalysis has been used to induce (i) their oxidative cross-coupling reactions with allylic alcoholsi and (ii) their cross-coupling with cyclopropyl halides, giving rise to... 

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