Reaction cycloauration

The N-coordinated compound [AuCljL] (L= l-ethyl-2-phenylimidazole) with silver tetrafluoroborate gives the cycloaurated species 102, which on further reaction with triphenylphosphine and sodium tetrafluoroborate or ammonium hexafluorophosphate forms the cationic complexes 103 (X = BF., PF,) (00JCS(D)271). 

Most of the substrates that give both types of cycloaurated complexes are limited to pyridine derivatives, although recently a few exceptions have been reported with thiazoles and imidazoles. The reaction of substituted pyridine ligands such as phpy,1 49,1924 2-benzoyl pyridine,1924 2-anili-nopyridine,1925,1926 l-(2-pyridylamino and 2-pyrimidinylamino)naphthalene, 7 2-phenoxypyri-dine,1811 2-(phenylsulfanyl)pyridine,1925 2-(2-thienyl)pyridine, 8 2-(3-thienyl)pyridine,1928 2-(alkylsulfanyl)pyridine,1929 or papavorine1930 at room temperature yields the nonmetallated compounds which, upon heating, are transformed into the metallated complexes [Au(N,C)Cl2], The process with phpy is illustrated in Scheme 21. 

However, cycloauration is, sometimes, difficult to achieve with direct activation of a C—H bond and transmetallation reaction of organomercury or organotin compounds with the appropriate gold compounds is, hence, frequently used. This procedure has been used with azobenzene, 36 A, A -dimethylbenzilamine,1937,1938 4,4 -dimethyl-2-phenyl-l, 3-oxaazoline,1938 1 - (dii zene,... 

K. Reactions Involving Complete Displacement of the Cycloaurated Ligand. 258... 

This section describes the various reaction pathways that lead to the formation of five-membered ring cycloaurated complexes six-membered cycloaurated ring... 

In a related system, reaction of 6-(2"-thienyl)-2,2,-bipyridine (HL) with [AuCLJ-was initially reported by Constable et al.15,16 to give a cycloaurated product, but subsequent work by the same group identified this assignment as incorrect. Reaction of the ligand with Na[AuCl4] in aqueous MeCN gave the non-cycloaurated complex AuC13(HL). 

As described in Section II.A, the complex 2-(3-thienyl)pyridineAuCl3 6 undergoes direct cycloauration in refluxing MeCN/H20, but the 2-thienyl isomer 7 does not.14 However, reaction of 7 with Ag[BF4] in dichloromethane did give the desired product 9. 

Bipyridine-derived cycloaurated complexes have also been synthesised through the transmetallation route. Conversion of 6-phenyl-2,2 -bipyridine to its organomercury derivative 58, followed by reaction with Na[AuCl4] gave the cycloaurated complex 59 in 38% yield as its [AuC14] salt.39... 

Other bis(cycloaurated) complexes related to 61 have been synthesised by closely related chemistry reaction of equimolar amounts of 29 and [Me4N][AuCl4] gave [Au(azo)2Cl] 62, which with Ag[C104] gave the corresponding cationic bis(cycloaurated)... 

One of the most facile, direct cycloauration reactions is that of an [AuC14] source with (commercially available) 2-anilinopyridine. Reaction of Na[AuCl4] with... 

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