Nickel-Catalyzed C–H Bond Functionalization Utilizing an N,N′-Bidentate Directing Group

Abstract

This review discusses the use of nickel catalysts and N,N 0 -bidentate directing groups, such as 2-pyridinylmethylamine, 8-aminoquinoline, and derivatives thereof, which constitute a powerful combination for the chelation-assisted functionalization of C-H bonds.

Benzothiazole Nickelation: An Obstacle to the Catalytic Arylation of Azoles by Cyclopentadienyl Nickel N-Heterocyclic Carbene Complexes

“…The latter was indeed characterized by typical signals for its IMes and Cp groups, but which are shifted compared to those of 3, as well as by two apparent triplets centered at 7.11 and 6.97 ppm, which integrate for one proton each relative to the Cp and IMes signals and correspond to the H(5) and H(6) protons of a benzothiazolyl unit. However, the signals of the H(4) and H (7) overlapped with those of unreacted benzothiazole and were not unambiguously observed. Complex 7 was also observed in the attempted couplings with the cationic complex 6 ( Figure S3), highlighting a general behaviour for these CpNi(NHC) species thereof.…”

“…They instead form a C(2)-metallated benzothiazolyl complex that constitutes a potential energy well that quenches all further reactivity. Although benzothiazolyl complexes are often proposed as possible intermediates in such biaryl couplings, the isolated complex, [NiCp(C 7 H 4 NS)(IMes)] (7), is to our knowledge a very rare example of fully characterized C(2)-benzothiazolyl-nickel complex.…”

“…The recent trend to use 3d transition metal catalysts, that is driven by economic and environmental concerns, has led to a re-assessment of nickel's reactivity [1][2][3][4]. In particular, nickel catalysts have emerged as promising candidates for C-H bond functionalization [5][6][7][8], and nickel-catalyzed reactions between (hetero)arenes and aryl halides [9][10][11][12], phenol derivatives [13][14][15][16][17][18], aryl or alkenyl esters [19][20][21] or even alkyl halides [22,23] have been shown to be reliable atom-economical alternatives to palladium-catalyzed cross-couplings. In this context, we have recently reported that the unsaturated T-shaped nickelacycle 1, that bears a mono-anionic C,C-NHC-cyanoalkyl chelate (NHC = N-heterocyclic carbene), shows moderate activity for the coupling of benzothiazole with aryl iodides (Scheme 1) [24].…”

Cross-Coupling of Heteroatomic Electrophiles

“…Murai followed up this report in 1995 with a cross-coupling similar to his previous report, but utilizing organozinc reagents instead of alkynyl stannanes. 198 This multicomponent reaction featured an expanded substrate scope in regards to the terminal alkyne and the dialkyl organozinc reagent. Additional silyl groups could be introduced both on alkyne or zinc reagent.…”

“…Bower found that the substituent on the carbamate (R 1 in Figure 49) could be varied with the 5-exo substrates (e.g. [198][199][200]. However, for the 6-exo and 7-exo substrates (201)(202)(203) only the tert-butyl substituent on the carbamate provided the optimal yields.…”