Transition-metal-catalyzed approaches

Moreover, PFS block co-polymers can be accessed via transition metal-catalyzed ROP of silicon-bridged [l]ferro-cenophanes (Section 12.06.3.3.4) in the presence of a polymer terminated with a reactive Si-H bond. This technique has been used successfully for the synthesis of both diblock and triblock co-polymers. For example, water-soluble PFS-/ -PEO 106 (PEO = poly(ethylene oxide)) has been prepared from monomer 72 and commercially available poly(ethylene glycol) modified at the end group (Scheme 9). In such cases, the polydispersity of the PFS blocks is higher than that obtained from anionic ROP (typically, PDI = 1.4) and the polydispersity of the co-block is determined by that of the original Si-H functionalized material. Nevertheless, block co-polymer syntheses that use the transition metal-catalyzed approach are very convenient, as the stringent purification and experimental requirements for living anionic polymerizations are unnecessary. 

Transition metal-catalyzed approaches to boron-nitrogen compounds are potentially of significant importance. Very interestingly. Manners et ah have reported the catalytic dehydrocoupling of primary or secondary amine-borane adducts... 

Kamal and co-workers used a transition metal-catalyzed approach in their synthesis of desoxyvasicinone. Treatment of an aromatic azide with iron(IIl) chloride in the presence of sodium iodide and acetonitrile gave the desired product in high yield. Derivatives containing 6,6,6- (n = 2) and 6,6,7-fused (n = 3) systems were also reported in high yield. 

Transition Metal Catalyzed Approaches to Lactones Involving C—O Bond Formation... 

Despite its obvious limitation to the requisite preparation of copper(I) acetylides, this seminal work greatly influenced progress in the development of transition metal-catalyzed approaches for the preparation of benzofuran units, as well as other heterocyclic cores. Furthermore, since its original discovery, this protocol was featured in a number of syntheses of an array of multisubstituted benzofuran derivatives, including the preparation of various biologically active molecules and valuable intermediates [112-116]. 

Transition-metal-catalyzed approaches were investigated in the preparation of indazoles.Arylhydrazones 22 were transformed to substituted inda-zoles 23 under non- and metal-catalyzed conditions, which are represented in the table below. 

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