Visible-Light-Induced Photocatalytic Synthesis of β-Keto Dithiocarbamates via Difunctionalization of Styrenes
Ramesh Kumar Vishwakarma, Saurabh Kumar and Krishna Nand Singh*
*Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, India, Email: knsinghbhu.ac.in
R. K. Vishwakarma, S. Kumar, K. N. Singh, Org. Lett., 2021, 23, 4147-4151.
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A facile photocatalyzed strategy for difunctionalization of styrenes in the presence of CS2 and amines provides β-keto dithiocarbamates. However, 4-nitrostyrene and 2-vinylpyridine can only be converted to 2-arylethylthiocarbamates.
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General Experimental Procedure:
A mixture of amine (1.2 mmol), carbon disulfide (2.4 mmol) and DMF (2 mL), contained in a 25-mL borosilicate RB flask, was stirred at room temperature for 5 minutes followed by the addition of styrene (1 mmol), rhodamine B base (3 mol%) and aq. TBHP (2 equiv.). The contents were stirred and irradiated by Luxeon rebel blue LED (470 nm) under ambient conditions for 36 h. The distance from the light source to the irradiation vessel was approximately 2 cm and no filters were used. After completion of the reaction (monitored through TLC), a cold brine solution (10 mL) was added to the mixture, and then extracted with ethyl acetate (3×10 mL). The combined organic phase was dried over Na2SO4 and concentrated using rotary vacuum evaporator. The residue was purified by column chromatography using ethyl acetate/n-hexane as eluent to afford pure product.
LED set up