Platinum-catalyzed reactions

In Scheme 10, HMG-CoA reductase inhibitor 92 was synthesized via a Suzuki coupling approach. Hiyama s group also carried out a Hiyama coupling to make the same compound (93TL8263). Vinylsilane 119 was prepared by platinum-catalyzed reaction from terminal alkyne 89. 

Some other types of interaction were reported by Gamica Meza and Spiro in their study of the platinum-catalyzed reaction... 

For a recent review on platinum-catalyzed reactions Clarke, M. L. Polyhedron 2001, 20, 151-164. 

Other ligands have been examined to improve the performance of platinum-catalyzed reactions,40 and bicyclic aminophosphines (Scheme 7, G) are a sterically demanding structural class that has been employed to afford very high regioselectivities41... 

Ishikawa and coworkers have studied the unique reactivity of strained cyclic disilanes (Equation 9.11) [35]. Transition metals, especially those of Group 10, readily insert into the Si—Si bond of disilacyclobutene 118 and can catalyze the addition of that bond across a variety of unsaturated acceptors. In the case of Ni(0)-catalyzed reactions of 118 with trimethylsilyl alkynes, insertion was found to occur both in a 1,2-and in a 1,1-fashion. The latter of these pathways implies a 1,2-silyl-migration, presumably occurring at the metal center. A nickel vinylidene intermediate was therefore proposed, though efforts to prove its existence were inconclusive. Similar vinylidene intermediates have been proposed by Ishikawa and coworkers to account for migrations observed in related palladium- and platinum-catalyzed reactions [36]. 

The platforming catalyst was the first example of a reforming catalyst having two functions.43 44 93 100-103 The functions of this bifunctional catalyst consist of platinum-catalyzed reactions (dehydrogenation of cycloalkanes to aromatics, hydrogenation of olefins, and dehydrocyclization) and acid-catalyzed reactions (isomerization of alkanes and cycloalkanes). Hyrocracking is usually an undesirable reaction since it produces gaseous products. However, it may contribute to octane enhancement. n-Decane, for example, can hydrocrack to C3 and C7 hydrocarbons the latter is further transformed to aromatics. 

Asymmetric hydroformylation of the three isomeric straight-chain butenes provided evidence that asymmetric induction in both rhodium- and platinum-catalyzed reactions occurs during and before the formation of the alkylmetal intermediate.66 67... 

The formulation ofmoisture-ujriiig silicones includes a silicone polymer, filler, a moisture-reactive cross-linker, and sometimes a catalyst. A newer class of silicone sealants are known as the silicone latex sealants. These sealants are silicone-in-water emulsions that cure by evaporation of the emulsifying water. Addition-curing silicones in general are two-part systems that cure by the platinum-catalyzed reaction of a silicone hydride with typically a vinyl group attached to silicon. Because no by-products are generated by the cure, there are few volatiles and no shrink in thick sections. 

The general pattern of compensation behavior found for platinum-catalyzed reactions was appreciably different from that described above for nickel and palladium. Moreover, since some of the trends were less well defined, these may not represent meaningful obedience to Eq. (2). 

Similar schemes have been accepted for the rhodium57> and the platinum-catalyzed reaction 58). For cobalt, a possible alternative that, following activation of hydrogen molecules, both hydrogen atoms necessary for hydroformylation are incorporated in the first step 65 was excluded 66). 

Self-oscillations of the rate in high-vacuum experiments have been found only for the platinum-catalyzed reactions (NO + CO) [61] and (CO + 02) [88]. 

The platinum-catalyzed reaction of alkanes with chlorine leads to alkyl chlorides and alcohols (Table 6, entry 46) with modest rates and conversions [50], Cydooctane can be easily dehydrogenated (Table 6, entry 47) in the presence of a stabilized vinylalkane by use of the neutral rhenium compound ReH7(PR3)2 [51]. By employing an iridium-based catalyst, the photochemical dehydrogenation of methylcydohexane to methylenecyclohexane is performed at room temperature... 

Methylene cyclopropanes are of interest as the substrate having high reactivity originated from the strained structure. The platinum-catalyzed reaction of diboron proceeded through the proximal bond cleavage of the cyclopropane ring (Equation (27)).223 Addition of diborons to enones provided 1,4-addition products in the presence... 

Although the platinum-catalyzed reactions are not as practical as palladium used for the same purpose, several types of unique discoveries still are noteworthy. Besides electrophihc C-H activation, the platinum complexes are efficient catalysts for hydrosilation see Hydrosilation Catalysis) that is important to silicon polymer industry. Platinum carbene catalysts are prepared from Karstedt catalyst (9) and imidazolium salts. The trials of model hydrosilylation reactions show very high yields of regioselective products (<1% impurity) with remarkable TON (see Turnover) (<30ppm catalyst load) (Scheme 81). ... 

Experimental and theoretical studies on gold- and platinum-catalyzed reactions " explained the mechanism of this phenol synthesis. Oxepines and arene oxides have been observed in the reaction catalyzed by Au(III). ... 

A conceptual model depicting the sequences of steps in this platinum-catalyzed reaction is shown in Figure 10-10. Figure lO-lOis only a schematic representation of the adsorption of cumene a more realistic model is the formation of a complex of the -it orbitals of benzene with the catalytic surface, as shown in Figure 10-11. 

Furthermore, the principle of interception (Section II,E,1) is well illustrated if we consider the methylcyclopentane — methylcyclopentadiene reaction as the platinum catalyzed reaction as being diverted by the F-com-ponent, through the intermediate cyclo-olefin (here grossly detectable). 

Conversions with platinum catalysts usually give better optical inductions than with rhodium catalysts if the same phosphane ligand is used. On the other hand, regioselectivities towards the chiral iso-product, however, are usually better with rhodium catalysts. In platinum-catalyzed reactions a combination of platinum(II) chloride with tin(II) chloride is generally used together with the chiral ligand, such as Diop, DIPHOL, BPPM and many others (Table 4). 

Thermolysis of (44) in the presence of alkynes results in 1,4-disilanaphthalenes <9lOM3l73>. As already mentioned, they can be formed in higher yields during the nickel <92JOM(439)l9) and platinum catalyzed reactions <930M4987> of the (44) with diphenylalkyne and ethene respectively. Platinum-complex catalyzed dehydrogenative double silylation of alkynes, alkenes, and dienes with... 

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