Saturated oxygen and nitrogen heterocycles: Via oxidative coupling of alkyltrifluoroborates with alkenols, alkenoic acids and protected alkenylamines

Abstract

Saturated heterocycles are important components of many bioactive compounds. The method disclosed herein enables a general route to a range of 5-, 6- and 7-membered oxygen and nitrogen heterocycles by coupling potassium alkyltrifluoroborates with heteroatom-tethered alkenes, predominantly styrenes, under copper-catalyzed conditions, in the presence of MnO2. The method was applied to the synthesis of the core of the anti-depressant drug citalopram. The reaction scope and observed reactivity is consistent with a polar/radical mechanism involving intermolecular addition of the alkyl radical to the alkene followed by [Cu(iii)]-facilitated C-O (or C-N) bond forming reductive elimination.