Cyclopalladation organic synthesis

The cyclopalladated complexes have limited practical value in organic synthesis because of the high cost of die stoichiometric amount of palladium required. Some compensation for their expense may be obtained, however, if several steps can be saved compared with an alternate method and, of course, the palladium may be recovered relatively easily.18... 

Finally, there are two examples of intramolecular C,P chelates, viz. LPd k2-C,P-2-CH2C6H4P(o-To1)2 (L = Tp 468, Bp 469), both prepared by cleavage of the halide bridged dimer with KL (Scheme 46). 43 These complexes were targeted to explore their potential in the guise of catalysts for organic synthesis, a role to which the cyclopalladated tris(o-tolyl) phosphane precursor had been previously applied. However, this preliminary study revealed these materials to be unreactive toward electrophiles (see also Section III.C.3.b), and no further investigations have been reported. 

Ryabov, A. D. Cyclopalladated complexes in organic synthesis. Synthesis 1985, 233-252. Grigg, R. MacLachlan, W. S. MacPherson,... 

Cyclopalladated complexes in organic synthesis , Ryabov, A. D., Synthesis, 1985, 233 Mechanisms of intramolecular activation of C-H bonds in transition metal complexes , idem, Chem. Rev., 1990, 90, 403. 

Cyclopalladated complexes, which are most conunonly prepared from tetrachloropaUa-date(II) and appropriate amines or imines, have drawn the attention of inorganic, coordination, and organometallic chemists since the first report in 1965 (for imines) and in 1968 (for amines) by Cope and co-workers. ° These palladacycle species can easily be transformed into chiral form by employing corresponding chiral amines or imines. Two representative examples of the chiral cyclopalladated species are illustrated in Figure 1. This section will describe three examples that represent applications of these chiral orthometallated palladium complexes in organic synthesis. 

R.F. Heck, Best Synthetic Methods - Palladium Reagents in Organic Synthesis, Academic Press, London and Orlando FL, 1985. A.D. Ryabov, The Application of Cyclopalladated Compounds in Synthesis, Russ.Chem. Rev., 1985, 153. 

M. Pfeffer, Reel. Trav. Chim. Pays-Bas, 1990, 109, 567-576. Reactions of Cyclopalladated Compounds and Alkynes New Pathways for Organic Synthesis ... 

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