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 C aryl -N hydrazinato bonds were accomplished via the activation of C-H bonds and the subsequent reaction of diphenyldiazomethane with the RE-C aryl bond. The reactions of rare-earth metal monoalkyl complexes LRE(CH 2 SiMe 3 )(THF) 2 (L = 2,5-[(2-pyrrolyl)CPh 2 ] 2 ( N -Me-pyrrole)) supported by a neutral N -methylpyrrole anchored dipyrrolyl ligand with 2 equiv. of Ph 2 CN 2 gave irreversibly unprecedented hydrazonato-functionalized imino rare-earth metal complexes LRE(Ph 2 CNNC 6 H 4 -( 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-C alkyl 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 aryl -N hydrazinato 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 aryl -N hydrazinato bond construction. Moreover, the experimental studies show that the formation of the C aryl -N hydrazinato bonds is thermodynamically facile, which could be realized at room temperature easily.