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). 

Rayama, A., Rinoshita-Nagaoka, J., Rawano, H., Rameda, S. and Mukuriya, M. (1998) Cycloauration of 2-substituted pyridine derivatives. Synthesis, structure and reactivity of srx-membered cycloaurated complexes of 2-anilino-, 2-phenoxy- and 2-(phenylsulfanyl)-pyridine. Journal of the Chemical Society Dalton Transactions, (24), 4095. 

Zhu, Z., Cameron, B.R. and Skerlj, R.T. (2003) Cycloauration of substituted 2-phenoxypyridine derivatives and X-ray crystal structure of gold, dichloro[2-[[5-[(cyclopentylamino)carbonyl]-2-pyridinyl- N]oxy]phenyl- C]-, (SP-4-3)-. Journal of Organometallic Chemistry, 677, 57. 

Fuchita, Y, leda, H Tsunemune, Y, Rinoshita-Nagaoka, J. and Rawano, H. (1998) Synthesis, structure and reactivity of a new six-membered cycloaurated complex of 2-benzoylpyridine [AuCl2(pcp-C, N)] [pep = 2-(2-pyridylcarbonyl) phenyl]. Comparison with the qfcloaurated complex derived from 2-benzylpyridine. Journal of the Chemical Society, Dalton Transactions, (5), 791. 

Synthesis and crystal structure of the novel five-membered cycloaurated complex of l-efhyl-2-phenylimidazole. 

Kilpin, K.J., Henderson, W. and Nicholson, B.K. (2007) Synthesis, characterisation and biological activity of cycloaurated organogold(III) complexes with imidate ligands. Polyhedron, 26, 204. 

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,... 

II. Synthesis of Five-Membered Ring Cycloaurated Complexes. 208... 

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

Owing to the substantial body of knowledge that has now been developed in this field (with seminal contributions from a number of research groups, including those of Vicente, Parish, Abram, Fuchita, Minghetti, Manassero and Cinellu, to name but a few) it has not been possible to be fully comprehensive. Instead, an attempt has been made to survey the main types of cycloaurated complexes that have been synthesised by various methods, and to report on the use of these complexes as substrates for further reactivity studies. 

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. 

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