Heteroaryl compounds coupling reactions

Fused pyrazole compounds have been prepared from A-alkyl substituted pyrazoles. For example, a palladium-catalyzed/norbornene-mediated sequential coupling reaction involving an aromatic sp2 C-H functionalization as the key step has been described, in which an alkyl-aryl bond and an aryl-heteroaryl bond were formed in one pot <060L2043>. A variety of highly substituted six-membered annulated pyrazoles 59 were synthesized in a one-step process in moderate yields from IV-bromoalkyl pyrazoles 57 and aryl iodides 58. 

A similar cross-coupling reaction between triarylbismuth(V) compounds and aryl-, heteroaryl-, or styryltributylstannanes smoothly proceeded under the same reaction conditions as those for the iodonium salts (Scheme 17) [34]. Homocoupling side products were not mentioned. 

Carbonylative cross-coupling reaction between triarylbismuth(V) compounds and organostannanes is smoothly catalyzed by PdCl2 under 1 atm CO at room temperature (Scheme 48) [34]. Not only arylstannanes, but also heteroaryl-, alkynyl-, and vinyltributylstannanes were employed efficiently. 

As described in Section in.B.4.d, a palladium catalyst was required to couple ArZnX with AFX. Indeed, the remaining nickel(II) complex in the medium was unable to catalyze this coupling reaction even if it was reduced to the corresponding zero-valent nickel complex. In contrast, with 2-chloropyridine as the heteroaryl halide added in the second stage, the coupling reaction was efficiently catalyzed by Ni°(bpy). 2-Arylpyridine compounds were obtained in good yields. Results are reported in Table 5. 

The organometallic-substituted 85 (M = a derivative of B, Zn, Sn) and halogeno-substituted siloles 85 (M = C1, Br, I) are suitable starting compounds for cross-coupling reactions. Pd-catalyzed coupling of 91 (R = Me, Ph) with 4-amino- and 4-heteroaryl-bromobenzenes affords the siloles 92 in high yield <20040M6205>. 

A number of ligand coupling reactions involving the treatment of an heteroaryllithium reagent with triphenylsulfonium salts leading to phenyl-heteroaryl compounds [(14) - (17) for example] have also... 

Organoindium(III) compounds can be prepared under very similar conditions to these organozincs and have an even greater tolerance of functional groups they are compatible with alcohols and phenols. Di-(heteroaryl) zincs, for use in coupling reactions, can be prepared by direct exchange of iodides, for example 5-iodofurfural, with (i-Pr)2Zn in the presence of a Li(acac) catalyst. ... 

The heteroaryl derivatives of boron, silicon, and tin, which show related patterns of reactivity, have found considerable application in synthesis. Unlike lithium compounds, they are generally fairly stable to air and water but will undergo a range of selective reactions under relatively mild conditions. Heteroaryl boronic acids and stannanes are particularly useful as the organometallic component in palladium-catalysed coupling reactions (section 2.7.2.2) heteroaromatic silanes such as 2-... 

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