An N-Fluorinated Imide for Practical Catalytic Imidations
Yuno Oe, Ryuhei Yoshida, Airi Tanaka, Akiya Adachi, Yuichiro Ishibashi, Takashi Okazoe, Kohsuke Aikawa* and Takuya Hashimoto*
*The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656; Chiba University, 1-33, Yayoi, Inage, Chiba 263-8522, Japan, Email: aikawag.ecc.u-tokyo.ac.jp, takuya.hashchiba-u.jp
Y. Oe, R. Yoshida, A. Tanaka, A. Adachi, Y. Ishibashi, T. Okazoe, K. Aikawa, T. Hashimoto, J. Am. Chem. Soc., 2022, 144, 2107-2113.
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N-Fluoro-N-(fluorosulfonyl)carbamate (NFC) can act as a modular synthetic handle for one-step derivatization to amines, sulfonamides, and sulfamides. In comparison to NFSI, NFC also offers a superior reactivity in copper-catalyzed imidations of benzene derivatives and imidocyanation of aliphatic alkenes.
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NFSI and NFC in catalytic imidation
Preparation of NFC lithium (fluorosulfonyl)((neopentyloxy)carbonyl)amide
To an argon-purged flask, acetonitrile (50 mL), chlorosulfonyl isocyanate (110 mmol, 9.77 mL, 98.0%) and neopentyl alcohol (100 mmol, 8.82 g) were added at 0 ░C. After stirring for 1 h at room temperature, potassium hydrogenfluoride (120 mmol, 9.37 g) was added to the flask at room temperature. After stirring for 2 h at the same temperature, the reaction was quenched with water (150 mL) and extracted with hexane/EtOAc (1:1) (100 mL Î 3). The combined organic layers were washed with brine, dried over anhydrous Na2SO4 and evaporated under reduced pressure. To the residue, MeOH (100 mL) and lithium carbonate (110 mmol, 8.13 g) were added. The mixture was stirred for 15 min at room temperature and the solvent was removed under reduced pressure. The residue was diluted with EtOAc, filtered through Celite pad and concentrated. The residue was washed with CH2Cl2 to give the title compound as a white solid in 80% yield (79.9 mmol, 17.5 g) for 2 steps.
The solution of 1 (6.00 g, 27.38 mmol) in a mixture of acetonitrile (142.5 g) and H2O (7.5 g) was stirred in a 250 mL PFA vessel and cooled to 0 ░C. A gaseous mixture of 4% F2 in N2 (volume percent) was introduced at a rate of 100 mL/min to the solution for 162.3 min (F2: 1.0 eq.). N2 gas was introduced to remove the residual F2 gas for 30 min. The yield of the compound was determined by 19F NMR analysis using benzotrifluoride as an internal standard (19F NMR yield 89%). The insoluble solid was filtrated, and the filtrate was evaporated under reduced pressure (50 mmHg). The resulting crude product was extracted with n-hexane (30 mL, 3 times). The collected organic phase was concentrated under reduced pressure (50 mmHg) at ambient temperature and gave the product 2 (4.85 g, 77% yield) as a colorless liquid.
Cu-catalyzed Imidation of Heteroarenes and PAHs - General Procedure
To an argon-purged Schlenk tube, calcium carbonate (200 Ámol, 20.0 mg), copper(I) chloride (20.0 Ámol, 2.1 mg, 95.0%), 6,6'-dimethyl-2,2'-bipyridine (20.0 Ámol, 3.8 mg, 98.0%), 1,2-dichloroethane (1.00 mL), substrate arenes (200 Ámol) and neopentyl N-fluoro-N-(fluorosulfonyl)carbamate (NFC) (280 Ámol, 64.7 mg, >98%) were added. After stirring for 5 h at 70 ░C, the mixture was cooled to room temperature. The crude solution was filtered through a pad of Al2O3 eluting with EtOAc and concentrated under vacuum. The residue was purified by column chromatography on silica gel.