Metal catalyzed reaction with

The uncatalyzed hydroboration-oxidation of an alkene usually affords the //-Markovnikov product while the catalyzed version can be induced to produce either Markovnikov or /z/z-Markovnikov products. The regioselectivity obtained with a catalyst has been shown to depend on the ligands attached to the metal and also on the steric and electronic properties of the reacting alkene.69 In the case of monosubstituted alkenes (except for vinylarenes), the anti-Markovnikov alcohol is obtained as the major product in either the presence or absence of a metal catalyst. However, the difference is that the metal-catalyzed reaction with catecholborane proceeds to completion within minutes at room temperature, while extended heating at 90 °C is required for the uncatalyzed transformation.60 It should be noted that there is a reversal of regioselectivity from Markovnikov B-H addition in unfunctionalized terminal olefins to the anti-Markovnikov manner in monosubstituted perfluoroalkenes, both in the achiral and chiral versions.70,71... 

The development of microwave-heated reactions using aryl chlorides has attracted the interest of several research groups. Transition metal-catalyzed reactions with aryl chlorides were elusive for a long time and were generally only successful with very high reaction temperatures and special reaction conditions. Lately, new catalytic systems, most notably those presented by Fu [48], have spurred the development of several schemes for the microwave-assisted activation of aryl chlorides. 

The metal catalyzed reaction with ammonia or amines likely proceeds by the SNAr mechanism. This reaction, with phase-transfer catalysis, has been used to synthesize triarylamines. Copper ion catalysts (especially cuprous oxide or iodide) also permit the Gabriel synthesis (10-41) to be applied to aromatic substrates. Aryl bromides or iodides are refluxed with potassium phthalimide and... 

The conversion of acid chlorides to aldehydes has been achieved by platinum metal-catalyzed reaction with silanes. The general reaction. 

In order to achieve a similar metal-catalyzed reaction with methylenecyclopropanes, het-erocumulenes X = C=Y, rather than heteroalkenes C = X, have to be employed as substrates. However, when ketenes are used (X = O Y = CR R ), the reaction proceeds readily even in the absence of metal catalysts and mainly yields [2 + 2] homo- and codimers of the ketene with methylenecyclopropane (see Section 2.2.2.3.1. for details). ... 

Table 3.5. Alkene Epoxidation by Transition Metal Catalyzed Reaction with Alkyl Hydroperoxides SS...

Several different transition metal-catalyzed reactions with the 2(li-f)pyrazinone template have been evaluated. The Suzuki-Miyaura coupling was efficient in introducing aryl groups to both the 3 and the 5-positions of the heterocycle. The 3-arylated product could be isolated in 75% yield by using 1.1 equivalents of boronic acid and sodium carbonate as base whereas use of 2.2 equivalents of boronic acid with cesium carbonate yielded the 3,5-disubstituted compound in 52% yield (Scheme 15.21) [56]. Efforts to widen the utility of this Suzuki-Miyaura reaction to include solid-phase reactions met with difficulties, because the reaction was problematic to drive to completion [57]. Other teams have also reported problems with Suzuki-Miyaura couplings on polymeric supports [44, 58]. 

To this end, monodentate phosphine or bidentate PX (X=P, N, O) ligands have usually been employed as ancillary ligands for transition-metal-catalyzed reactions, with bulky tertiary alkyl phosphines proving particularly effective. Significant advances have been achieved in the use of less active aryl chlorides (bond strength C-Cl>C-Br>C-I) as chemical feedstock [5], with a number of processes mediated by palladium-bulky phosphine systems. This success is often explained by the effect of bulk and electron richness at the metal center along the catalytic cycle depicted in Fig. 1 [6]. 

The proposed mechanism involves the initial formation of the palladacycle 118 via the Catellani reaction sequence between the aryl iodide and norbornene (Scheme 3.32). Coordination of the aziridine 125 followed by oxidative addition of the N-C single bond by Pd leads to the intermediate 129. The fission of N-C single bond is commonly observed in transition-metal-catalyzed reactions with aziridines. Chemoselective C-C bond formation gives 130, which on decarbopalladation affords palladacycle 131 and extrudes norbornene. Reductive elimination furnishes... 

Other metal-catalyzed reactions with five-membered pincers include asymmetric aldol-type condensations [26, 28-30], cyclopropanations [31], enantioselective allylations [32], reductive eUminations [33], transfer hydrogenations [28-30, 34], hydroaminations [28], and polymerizations [26, 28, 35]. 

Nielson KD et al (2005) Development of the ReaxEF reactive force field for describing transition metal catalyzed reactions, with application to the initial stages of the catalytic formation of carbon nanotubes. J Phys Chem A 109(3) 493-499... 

By merging a transition metal-catalyzed reaction with an organocatalytic cascade sequence into a cycle-specific cascade catalysis, Simmons et al. developed a new... 

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