Pyridines, dihydro-, lithiation

Carbene complexes have also been prepared by transmetallation reactions. Lithiated azoles react with gold chloride compounds and after protonation or alkylation the corresponding dihydro-azol-ylidene compounds, e.g., (381) or (382), are obtained.22 9-2264 Silver salts of benz-imidazol have also been used to obtain carbene derivatives.2265 Mononuclear gold(I) carbene complexes also form when trimeric gold(I) imidazolyl reacts with ethyl chlorocarbonate or ethyl idodate.2266,2267 The treatment of gold halide complexes with 2-lithiated pyridine followed by protonation or alkylation also yields carbene complexes such as (383).2268 Some of these carbene complexes show luminescent properties.2269-2271... 

Regioselective lithiation.1 This complex undergoes selective lithiation at the orf/io-position, which can be trapped by methylation to give (2-methylpyridine)tri-carbonylchromium. The disilyl complex 2 undergoes selective lithiation at C4 because of steric effects. Reduction (DIBAH) of 1 provides (l,2-dihydro-pyridine)tri-carbonylchromium (3) after quenching (MeOH). Reaction of 1 with RLi followed by alkylation with CH3I provides the complex 4. 

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