Functionalizations palladium bromide

Selective palladium(0)-catalyzed arylation can be performed with aryl iodides bearing a triflate function using an appropriate palladium catalyst. Under these conditions, aromatic iodotriflates like 59 can play the role of multi-coupling reagents [88]. Thus, the reaction of 59 with a functional arylzinc bromide provides the functionalized biphenyl triflate 60 (see Section 9.6.13 Scheme 9-48) [89]. 

Arylations of primary alkyl bromides with aryl and heteroarylstannane reagents have also been achieved using palladium catalysts. Fu reported that aryltributyl-stannanes could be used for the arylation of certain functionalized alkyl bromides and iodides (Equation 5.13). An electron-rich phosphine ligand PCy(l-pyrrolidi-nyl)2 showed a pronounced accelerating effect in this cross-coupling reaction. Notably, not only aryl-substituted stannanes but also a pyridinylstannane, was shown to participate in the functionalization reaction [15]. 

In 1993, Corriu et al. studied the synthesis of nitrogen-containing heterocycles from (Z)-3-(tribulylstannyl)allylamine, which was prepared by the reaction of Af-(trimethylsilyl)allylamine with 2 mol of ra-butyllithium followed by treatment with chlorotributyltin and subsequent hydrolysis. The unprotected (Z)-3-(tributylstannyl)allylamine underwent a palladium-catalyzed cross-coupling reaction with aromatic bromides affording a stereospecific preparation of substituted allylic amines with Z configuration of the carbon-carbon double bond. The reactions of o/t/zo-functionalized aryl bromides offer a one-step preparation of 7-membered nitrogen heterocycles in high yields (Scheme 4.18). 

Soderberg and coworkers have developed a palladium-phosphine-catalyzed reductive iV-het-eroannuladon of 2-nitrostyrenes forming indoles in good yields For example, reaction of 6-bromo-2-nitrostyrene with carbon monoxide in the presence of a catalytic amount of palladium diacetate (6 mol% and triphenylphosphine 124 mol% in acetonitrile at 30 gives 4-bromoindole in 86% yield fEq 10 62 Several functional groups, such as esters, ethers, bromides, tnflates, and additional nitro groups, have been shown to be compatible with the reaction conditions... 

Organotins. The organotin reagents have much lower nucleophilicity than that of the Grignard reagents, thus allowing the use of a variety of functionalized monomers for the polymerization. Aryl-alkenyl iodides, bromides and tosylates have been used as substrates. Palladium complexes are commonly employed as catalysts for the reaction. Because the catalysts can be destroyed... 

Fagnou and co-workers reported on the use of a palladium source in the presence of different phosphine ligands for the intramolecular direct arylation reaction of arenes with bromides [56]. Later, they discovered that new conditions employing palladium complex 27 promoted the direct arylation of a broad range of aryl chlorides to form six- and five-membered ring biaryls including different functionalities as ether, amine, amide and alkyl (Scheme 7.11) [57]. 

Table 3. Catalysis results for the Barbier reaction of benzaldehyde and allyl bromide in presence of homogeneous palladium catalyst (entry 1) and those prepared by complexing palladium to amine functionalized mesoporous silica (entry 2-4) [74]...

The bisamides and bisesters provide two different families of benzocyclobu-tene monomers and polymers derived from bromobenzocyclobutene 2. Heck and coworkers have demonstrated that aromatic bromides and iodides react with olefins in the presence of a palladium catalyst to afford products where the vinyl group is directly bonded to the aromatic ring [40,42,43], This technology has been used with 4-bromobenzocyclobutene 2 as the starting aromatic halide,in order to prepare more highly functional bis- and monobenzocyclobu-tenes (Fig. 4)... 

Coupling of aliyl bromides and allyhlannanes. This reaction is possible by catalysis with benzylchlorobis(triphenylphosphinc)palladium, which is probably converted into bis(triphenylphosphine)palladium(0), the actual catalyst. This Pd(0) complex is more effective than ietrakis(triphenylphosphine)palladium(0). Zinc chloride in certain cases can function as a catalyst alone or in combination with the Pd(Il) catalyst. ... 

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