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

The first examples of regioselective aryl -C-H functionalization with diphenyldiazomethane for the construction of C-N bonds were accomplished the activation of C-H bonds and the subsequent reaction of diphenyldiazomethane with the RE-C bond. The reactions of rare-earth metal monoalkyl complexes LRE(CHSiMe)(THF) (L = 2,5-(2-pyrrolyl)CPh) supported by a neutral -methylpyrrole anchored dipyrrolyl ligand with 2 equiv. of PhCN gave irreversibly unprecedented hydrazonato-functionalized imino rare-earth metal complexes LRE(PhCNNCH-(-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-C 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 C-N 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 C-N bond construction. Moreover, the experimental studies show that the formation of the C-N bonds is thermodynamically facile, which could be realized at room temperature easily.