Aryl C–H bond functionalization with diphenyldiazomethane induced by rare-earth metal alkyl complexes.

The first examples of regioselective aryl ortho-C–H functionalization with diphenyldiazomethane for the construction of Caryl–Nhydrazinato bonds were accomplished via the activation of C–H bonds and the subsequent reaction of diphenyldiazomethane with the RE–Caryl bond. The reactions of rare-earth metal monoalkyl complexes LRE(CH2SiMe3)(THF)2 (L = 2,5-[(2-pyrrolyl)CPh2]2(N-Me-pyrrole)) supported by a neutral N-methylpyrrole anchored dipyrrolyl ligand with 2 equiv. of Ph2CN2 gave irreversibly unprecedented hydrazonato-functionalized imino rare-earth metal complexes LRE(Ph2C＝NNC6H4-(o-C＝NHPh) (RE = Y (2a), Lu (2a′)) in good yields involving a rather complex process including the interaction of a diazo unit with a RE–Calkyl bond, a β-H elimination, a N–N cleavage, 1,4-hydrogen transfer and the subsequent C–N coupling with another diphenyldiazomethane. More important is that regioselective aryl C–H bond functionalization with diphenyldiazomethane to construct the Caryl–Nhydrazinato bonds can be easily achieved by three-component reactions of rare-earth metal monoalkyl complexes, a wide range of substituted imines (including aldimines, ketimines or analogous 2-phenylpyridine) and diphenyldiazomethane, affording various hydrazonato-functionalized phenyl, thienyl imino or pyridyl rare-earth metal complexes 2b–2j at room temperature. A further study indicated that the substituents on the phenyl ring have a great effect on the reaction pathway and governed the Caryl–Nhydrazinato bond construction. Moreover, the experimental studies show that the formation of the Caryl–Nhydrazinato bonds is thermodynamically facile, which could be realized at room temperature easily. [ABSTRACT FROM AUTHOR]