A Sandmeyer-type difluoromethylation process has been developed that allows the straightforward conversion of (hetero-)arenediazonium salts into the corresponding difluoromethyl (hetero-)arenes under mild conditions. The actual difluoromethylating reagent, a difluoromethyl-copper complex, is formed in situ from copper thiocyanate and TMS-CF2H. The diazonium salts are either preformed or generated in situ from broadly available aromatic amines.

Aromatic and heteroaromatic diazonium salts were efficiently converted into the corresponding trifluoromethylthio- or selenoethers by reaction with Me4 NSCF3 or Me4 NSeCF3 , respectively, in the presence of catalytic amounts of copper thiocyanate. These Sandmeyer-type reactions proceed within one hour at room temperature, are applicable to a wide range of functionalized molecules, and can optionally be combined with the diazotizations into one-pot protocols.

A copper-CF2 H complex generated in situ from copper thiocyanate and TMSCF2 H smoothly converts organothiocyanates into valuable difluoromethyl thioethers. This reaction step can be combined with several thiocyanation methods to one-pot protocols, allowing late-stage difluoromethylthiolations of widely available alkyl halides and arenediazonium salts. This strategy enables the introduction of difluoromethylthio groups-a largely unexplored substituent with highly promising properties-into drug-like molecules.

An AlCl3 -catalyzed CH thiocyanation was discovered and combined with a Langlois-type trifluoromethylation to afford aryl trifluoromethyl thioethers directly from arenes, N-thiocyanatosuccinimide (NTS) and Ruppert-Prakash reagent. An analogous combination with a copper-mediated difluoromethylation gives access to aryl difluoromethyl thioethers. Both processes proceed with exceptional regioselectivity for the most electron-rich, sterically least hindered position of the arene. The sulfur and fluoroalkyl groups originate from different sources, so that the use of expensive, preformed fluoroalkylthiolation reagents is avoided.

Scheme 1. Dehydrogenative alkoxylation of arenes. DG = directing group, FG = functional group, Alk = alkyl.[*] Dr. Scheme 2. Dehydrogenative alkoxylation of an C sp 3ÀH bond.Scheme 3. Determination of the kinetic isotope effect.Scheme 4. Evidence against the formation of hydroxyarene intermediates.Scheme 5. Proposed dehydrogenative alkoxylation mechanism. Angewandte Chemie