N-heterocyclic carbene-Pd(II)-1-methylimidazole complex catalyzed C–H bond benzylation of (benzo)oxazoles with benzyl chlorides

The crystal structure of 1,3-bis(2,6-diiso-propylphenyl)imidazol-2-ylidene)-dibromido-(1-methyl-1H-imidazole-κ1N)palladium(II) – ethyl acetate – water (1/1/1), C31H42Br2N4Pd

“…For instance, the synthesis of [1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-2(3H)-ylidene]palladium complex, from easily available starting materials in a one-pot procedure was reported [1]. In addition, the applications of this complex have been fully investigated in Suzuki-Miyaura coupling [2,[11][12][13][14][15][16][17][18], C-N coupling [1,[19][20][21], α-arylation of carbonyl compounds [22][23][24][25][26], Hiyama coupling [27], Mizoroki-Heck reaction [28] and direct C-H bond functionalization of heteroaromatic compounds [29][30][31][32][33]. As its analogue, initial studies on the catalytic activity of the title complex showed that it is also an e cient catalyst in the C-N coupling between primary and secondary amines with aryl chlorides at very low catalyst loadings, implying that the anions on the complex may have no e ect on the catalytic activity.…”

Recent Developments in Transition-Metal Catalyzed Direct C–H Alkenylation, Alkylation, and Alkynylation of Azoles

“…NHC-Pd(II) complex-catalyzed benzylation of (benz)oxazoles with benzyl chlorides. Concurrently, Shao and coworkers reported a phosphine free NHC-Pd(II) complex-catalyzed direct C-H bond benzylation of (benz)oxazoles with benzyl chlorides [76]. The authors presented a broad substrate scope with good functional group tolerance (Scheme 44).…”

“…Such substitution decreases the Lewis basicity of nitrogen atom and renders the C-H bond more acidic, thus enabling the Pd-catalyzed regioselective C-H functionalization (Scheme 43) [75]. Concurrently, Shao and coworkers reported a phosphine free NHC-Pd(II) complex-catalyzed direct C-H bond benzylation of (benz)oxazoles with benzyl chlorides [76]. The authors presented a broad substrate scope with good functional group tolerance (Scheme 44).…”

“…In 2018, Pan and Wang explored the use of quaternary ammonium triflates as a coupling partner for the benzylation of (benz)oxazoles in the presence of a Pd/dcype/K 3 PO 4 -catalytic system [78]. Mechanistically, in situ generated Pd(0) undergoes oxidative addition with ArCH Concurrently, Shao and coworkers reported a phosphine free NHC-Pd(II) complex-catalyzed direct C-H bond benzylation of (benz)oxazoles with benzyl chlorides [76]. The authors presented a broad substrate scope with good functional group tolerance (Scheme 44).…”

Accessing Medicinally Relevant O‐Benzofused Heterocycles through C−X Activation: Recent Trends

“…These ligands work with remarkable efficiency and versatility which can be finely tuned through the modification of the size and type of ligands involved. Over the last two decades, the use of NHCs in different cross‐coupling transformation, has dramatically increased, and their application can also be extended to unactive C sp 3 −X bonds [8] . One pioneering example, includes their application in Negishi cross‐coupling transformations involving C−Br and C−Cl containing substrates using catalytic amounts of Pd‐PEPPSI‐I Pr (dichloro[1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene)](3‐chloropyridyl)palladium(II)), a catalyst which was developed by Organ et al., [9] for accessing a broad range of sterically encumbered biaryls and druglike heterocycles in high yields of up to 98 %.…”