Copper-Catalyzed Oxidative Decarboxylative Couplings of Sulfoximines and Aryl Propiolic Acids
Daniel L. Priebbenow, Peter Becker and Carsten Bolm*
*Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany, Email: carsten.bolmoc.rwth-aachen.de
D. L. Priebbenow, P. Becker, C. Bolm, Org. Lett., 2013, 15, 6155-6157.
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A copper-catalyzed decarboxylative coupling of sulfoximines with aryl propiolic acids enables the preparation of N-alkynylated sulfoximines. Various substituents on both the sulfoximidoyl moiety as well as the aryl group of the propiolic acid were tolerated.
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General Procedure for the preparation of N-alkynylated sulfoximines:
To an oven dried Schlenk tube was added sulfoximine (1.5 equiv, 0.60 mmol), CuBr (6 mg, 10 mol%), pyridine (6.3 mg, 20 mol %), K3PO4 (93 mg, 1.1 equiv, 0.44 mmol) and PhMe (3 mL). The resultant solution was heated to 80°C, and then aryl propiolic acid (1.0 equiv., 0.40 mmol) was added portion wise over 2 minutes. The Schlenk tube was left open to the air and the reaction mixture was heated at 80°C for 16 hours. After this time, the mixture was cooled to room temperature and the solvent was evaporated. The product was purified on basic alumina oxide (initially activity stage I – deactivated by adding 10 mL deionized water per 200 mL Al2O3) using gradient elution [100% pentane (50 mL), then 1:9 EtOAc/pentane (50 mL), then 1:2 EtOAc/pentane (150 mL)] to afford the N-alkynylated sulfoximine (typical Rf = 0.5 in 2:3 EtOAc/pentane).