Hydrometallation. reviews

In this review, an attempt is made to exhaustively catalog the rapidly growing subset of metal-catalyzed reductive C-C bond formations comprising the hydrometallative and hydrogenative carbocyclization of 7t-unsaturated substrates, and application of these methods in target-oriented synthesis. Content is organized on the basis of reaction... 

In this chapter, recent advances in asymmetric hydrosilylations promoted by chiral transition-metal catalysts will be reviewed, which attained spectacular increase in enantioselectivity in the 1990s [1], After our previous review in the original Catalytic Asymmetric Synthesis, which covered literature through the end of 1992 [2], various chiral Pn, Nn, and P-N type ligands have been developed extensively with great successes. In addition to common rhodium and palladium catalysts, other new chiral transition-metal catalysts, including Ti and Ru complexes, have emerged. This chapter also discusses catalytic hydrometallation reactions other than hydrosily-lation such as hydroboration and hydroalumination. 

There are a few reports of the catalysis of the hydrostannation of active alkenes by soluble palladium catalysts,105- 106 but, with less active alkenes, the major product is the hexaalkyldistannane. Good yields of hydrostannation products, however, can be obtained with heterogeneous catalysts, and Table 4-2 shows examples of the hydrostannation of alkenes in the presence of a PdjOHVC catalyst.107 A recent, thorough, survey in Chemical Reviews is available.108 The mechanism of the palladium-catalysed hydrostannation is not known in detail, but presumably it involves oxidative addition and insertion of the alkene by stannylmetallation (or hydrometallation) as shown, followed by reductive elimination (Scheme 4-4). 

---