Structure–activity relationship of N‐heterocyclic carbene–Pd(II)–imidazole complexes in Suzuki–Miyaura coupling between 4‐methoxyphenyl chloride and phenylboronic acid

Abstract

A series of N-heterocyclic carbene-PdCl 2 -imidazole [NHC-Pd(II)-Im] complexes were synthesized and the structure of most of them was unambiguously determined by X-ray single-crystal diffraction. The structure-activity relationship of these complexes was investigated for the Suzuki-Miyaura coupling between 4-methoxyphenyl chloride and phenylboronic acid, and the effect of the NHCs and Im moieties were fully discussed. The sterically hindered IPr-based complex showed the highest catalytic activity.

Pd–PEPPSI: a general Pd–NHC precatalyst for Buchwald–Hartwig cross-coupling of esters and amides (transamidation) under the same reaction conditions

“…Complexes 4b, 4c and 4e were prepared by procedures reported in the literature. 10,11 Spectroscopic data match those reported in the literature.…”

“…00, 151.54, 146.77, 137.49, 135.24, 130.36, 125.13, 124.15, 124.12, 28.86, 26.43, 23.38. Synthesis of 4c. 11 On a benchtop, a vial equipped with and a stir bar was charged with PdCl2 (17.7 mg, 0.10 mmol), IPrHCl (0.12 mmol), K2CO3 (0.10 mmol), and 1-methylimidazole (0.40 mmol), placed under a positive pressure of argon, and subjected to three evacuation/backfilling cycles under high vacuum. THF (0.15 M) was added, the reaction mixture was placed in a preheated oil bath at 65 °C and stirred for 20 h at 65 °C.…”

Crystal structure of dichlorido(1,3-bis(2,6-dimethyl-phenyl)-1H-3λ4-imidazol-2-yl)(isoquinolinyl)palladium(IV), C28H27Cl2N3Pd

“…In addition, both of them are longer than that of its i-propyl analogue, that of which are 1.960(3) and 2.093(3) Å, respectively [1]. Therefore, it maybe draw the conclusion that stronger σ e ect exsits in the latter complex, and may be the result of its higher catalytic activity [13].…”

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.…”

“…The title product was prepared by modi cation of the literature known methods [1,2]. Under a nitrogen atmosphere, 1,3-bis(2,6-diisopropylphenyl)-1H-imidazolium bromide (0.7 mmol), palladium acetate (0.7 mmol), sodium bromide (0.7 mmol), potassium carbonate (0.7 mmol), tetrahydrofuran (5.0 mL) and 1-methylimidazole (2.5 mmol) were successively added into a Schlenk tube.…”