Support was provided by the National Natural Science Foundation of China (NSFC, Grant Numbers 21772087 and 22001118) and the Natural Science Foundation of Jiangsu Province (Grant Numbers BK20200300 and BK20201245).
We report a ligand-controlled nickel-catalyzed reductive hydroarylation of styrenes with predictable and controllable regioselectivity. With a diamine ligand, the reaction produces selective linear hydroarylation products. Alternatively, with a chiral PyrOx ligand, branch-selective enantioenriched 1,1-diarylalkane products are obtained. Preliminary mechanistic results are consistent with a reductive Heck process.
13 For an elegant example of ligand-controlled regiodivergent hydroarylation of terminal alkenes, see:
Li Z.-Q,
Fu Y,
Deng R,
Tran VT,
Gao Y,
Liu P,
Engle KM.
Angew. Chem. Int. Ed. 2020; 59: 23306
141-Methoxy-4-phenethylbenzene (3a) – General Procedure A
In a nitrogen-filled glove box, to an oven-dried 8 mL screw-cap vial equipped with a magnetic stir bar were added NiBr2·3H2O (2.73 mg, 0.010 mmol, 5 mol%), L1 (2.55 mg, 0.012 mmol, 6 mol%), CsF (60.8 mg, 0.40 mmol, 2.0 equiv), and 0.40 mL anhydrous THF. The mixture was stirred for 5 min, at which time PMHS (30 μL, 0.50 mmol, 2.5 equiv) was added, and the stirring was continued for another 5 min at r.t. Styrene (1a, 31.2 mg, 0.30 mmol, 1.5 equiv) and 4-methoxyphenyl trifluoromethanesulfonate (2a, 51.2 mg, 0.20 mmol, 1.0 equiv) were added to the resulting mixture in this order. The tube was sealed with a Teflon-lined screw cap, removed from the glove box and stirred at 25 °C for up to 24 h. The reaction was quenched upon the addition of H2O, and the mixture was extracted with EtOAc (3 ×). The organic layer was concentrated to give the crude product. n-Dodecane (20 μL) was added as an internal standard for GC analysis. The product was purified by chromatography on silica gel for each substrate. The crude material was purified by flash column chromatography (PE–EtOAc = 100:1) to provide the title compound as a white solid in 85% yield (36.0 mg). The analytical data are consistent with values reported in the literature.10e
15(S)-1-Methoxy-4-(1-phenylethyl)benzene (4a) – General Procedure B
In a nitrogen-filled glove box, to an oven-dried 8 mL screw-cap vial equipped with a magnetic stir bar were added NiCl2·glyme (2.20 mg, 0.010 mmol, 5 mol%), L4 (4.27 mg, 0.012 mmol, 6 mol%), K3PO4·H2O (92.1 mg, 0.40 mmol, 2.0 equiv), methanol (3.2 mg, 0.10 mmol, 0.5 equiv), and mixed solvent (Et2O–toluene = 3:1, 0.40 mL). The reaction mixture was stirred for 5 min, at which time PMHS (30 μL, 0.50 mmol, 2.5 equiv) was added, and the stirring was continued for another 5 min at r.t. Styrene (1a, 31.2 mg, 0.30 mmol, 1.5 equiv) and 4-methoxyphenyl trifluoromethanesulfonate (2a, 51.2 mg, 0.20 mmol, 1.0 equiv) were added to the resulting mixture in this order. The tube was sealed with a Teflon-lined screw cap, removed from the glove box and stirred at 0 °C for up to 24 h. The reaction was quenched upon the addition of H2O, and the mixture was extracted with EtOAc (3 ×). The organic layer was concentrated to give the crude product. n-Dodecane (20 μL) was added as an internal standard for GC analysis. The crude material was purified by flash column chromatography (PE–EtOAc = 100:1) to provide the title compound as a colorless oil in 55% yield (23.3 mg), 94:6 rr. HPLC analysis (OJ-H, 5% iPrOH/hexane, 1.0 mL/min, 220 nm) indicated 95% ee, tR (major) = 16.9 min, tR (minor) = 18.1 min. The analytical data are consistent with values reported in the literature.2f
16 Under branch-selective reaction conditions, when (Bpin)2 was used instead of PMHS, the regioreversed arylboration product was obtained in 36% yield, 94:6 rr, 94% ee.
17 For similar Heck-type reaction, see:
Chen L.-A,
Lear AR,
Gao P,
Brown MK.
Angew. Chem. Int. Ed. 2019; 58: 10956
