Continuous‐Flow Oxidative Cyanation of Primary and Secondary Amines Using Singlet Oxygen |
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Authors: | Dr Dmitry B Ushakov Dr Kerry Gilmore Dr Daniel Kopetzki Prof?Dr D Tyler McQuade Prof?Dr Peter H Seeberger |
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Institution: | 1. Department für Biomolekulare Systeme, Max‐Planck‐Institut für Kolloid‐ und Grenzfl?chenforschung, Am Mühlenberg 1, 14476 Potsdam (Germany);2. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (USA);3. Institut für Chemie und Biochemie, Freie Universit?t Berlin, Arnimallee 22, 14195 Berlin (Germany) |
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Abstract: | Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable‐temperature continuous‐flow LED‐photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α‐Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α‐aminonitriles. Primary α‐aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at –50 °C. This atom‐economic and protecting‐group‐free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert‐leucine hydrochloride from neopentylamine. |
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Keywords: | amines C H activation flow chemistry photooxidation Strecker reaction |
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