Search

A rare example of the palladium-catalyzed sp 3 C-H bond activation in a monoterpene-based compound has been observed in the reaction of PdCl 2 with a (+)-3-carene-based ligand HL (HL=N-((1aS,3S,7bR)-1,1,3-trimethyl-7-phenyl-5-(pyridin-2-yl)-1a,2,3,7b-tetrahydro-1H-cyclopropa[f]quinolin-3-yl)acetamide), which yielded the [PdLCl] complex. In contrast to the vast majority of C(sp 3 )-H activation reactions which require prolonged heating and mixing due to the inert character of the corresponding bond, the reaction reported herein proceeds rapidly under mild conditions. A theoretical insight into the ligand deprotonation has been performed by DFT calculations. The mechanism of the C-H activation involves (i) simultaneous coordination of the CH 3 group of HL to the Pd 2+ ion and decoordination of the Cl - anion with consequent formation of a Cl⋅⋅⋅H-N hydrogen bond with the amide group, (ii) approximation of the out-of-sphere Cl - anion to one of the hydrogen atoms of the CH 3 group mediated by the crane motion of the amide group and (iii) the ejection of the HCl molecule, which increases the entropy of the system and serves as a driving force for the reaction., (© 2024 Wiley-VCH GmbH.)