Ni-Catalyzed Oxygen Transfer from N2O onto sp3-Hybridized Carbons
Shengyang Ni, Franck Le Vaillant, Ana Mateos-Calbet, Ruben Martin and Josep Cornella*
*Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany,
Email: cornella
kofo.mpg.de
S. Ni, F. Le Vaillant, A. Mateos-Calbet, R. Martin, J. Cornella, J. Am. Chem. Soc., 2022, 144, 18223-18228.
DOI: 10.1021/jacs.2c06227
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Abstract
A catalytic synthesis of cycloalkanols in the presence of N2O as an oxygen transfer agent onto sp3-hybridized carbons of simple precursors offers mild conditions and wide substrate scope. The reaction even enables to access carbocyclic compounds in an enantioselective manner.
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Enantioselective Carbohydroxylation of Olefins
Activated Zinc
A round bottom flask was charged with 5 g of Zinc powder (325 mesh, 99.9% (metal basis)). 20 ml HCl (1 M) was added, and the mixture was stirred for 3 min at rt. Then, the mixture was filtered under reduced pressure using a vacuum filter funnel and washed with water (50 mL×3), acetone (50 mL×3), and ether (50 mL×3). After that, the solid was left to dry in the funnel for 3 min. The solid was transferred to a vial, dried under reduced pressure overnight, and stored in the glovebox.
General Procedure for Ni-catalyzed oxygen transfer from N2O into sp3 hybridized carbons (racemic)
An oven- and heatgun-dried pressure Schlenk tube with a Teflon screw-cap equipped with a Teflon-coated stir bar were used. The Schlenk tube was brought into an argon-filled glovebox, and NiI2 (0.01 mmol, 10 mol%), ligand (0.015 mmol, 15 mol%), activated Zn (0.4 mmol, 4 equiv) and NaI (0.15 mmol, 1.5 equiv) were introduced into the pressure Schlenk. Then, outside the glovebox, using a T-connection, the Schlenk was evacuated and backfilled with N2O (three times). Under N2O flow, the Schlenk was opened and DMSO (0.4 mL) was added using a syringe. The substrate was added subsequently using a Hamilton syringe. The Schlenk was then closed, and the pressure of N2O was increased to 2.4 - 2.5 atm. The reaction mixture was kept stirring at 1000 rpm, for 40 h, at room temperature. After the completion of reaction, the mixture was diluted with MTBE, washed with aqueous solution of HCl (1 M) and brine, and dried over Na2SO4. Upon filtration, the organic layer was concentrated under reduced pressure (water bath at 40 °C) and purified by flash column chromatography (silica gel) or preparative TLC (pTLC) to afford the desired product.
General Procedure for Ni-catalyzed oxygen transfer from N2O into sp3 hybridized carbons (chiral)
An oven- and heatgun-dried pressure Schlenk tube with Teflon screw-cap equipped with a Teflon-coated stir bar were used. The Schlenk tube was brought into an argon-filled glovebox, and NiI2 (0.01 mmol, 0.2 equiv), activated Zn (0.4 mmol, 4 equiv) and NaI (0.225 mmol, 2.25 equiv) were introduced into the pressure Schlenk. Then, outside the glovebox, using a T-connection, the Schlenk was evacuated and backfilled with N2O (three times). Under N2O flow, the Schlenk was opened and a solution of chiral ligand (0.02 mmol, 0.2 equiv) in DMA (0.4 mL) was added using a syringe. The substrate was added subsequently using a Hamilton syringe. The Schlenk was then closed, and the pressure of N2O was increased to 1.3 – 1.35 atm. The reaction mixture was kept stirring at 1000 rpm, for 40 h, at room temperature. After the completion of reaction, the mixture was diluted with MTBE, washed with an aqueous solution of HCl (1 M) and brine, and dried over Na2SO4. Upon filtration, the organic layer was concentrated under reduced pressure (water bath at 40 °C) and purified by flash column chromatography (silica gel) or preparative TLC (pTLC) to afford the desired product.
Key Words
ID: J48-Y2022
