Direct formylation of phenols using difluorocarbene as a safe CO surrogate.

A convenient method to prepare aryl formates is reported herein that exploits difluorocarbene to serve as a CO surrogate. This reaction is proposed to occur through a sequential O-difluoromethylation of phenol, followed by α-C-F bond functionalization of the resulting aryl difluoromethyl ether intermediate by phenol or moisture through fluorosemiacetal or orthoformate intermediates. Late-stage modification of biologically and materially active compounds is demonstrated.

Three-Component Coupling of Anilines, Amines, and Difluorocarbene to Access Formamidines.

A one-pot three-component reaction of two anilines (or one aniline and one alkylamine) and in situ-generated difluorocarbene is developed herein to enable efficient construction of formamidines. Crucial formimidoyl fluoride intermediate RN═CHF is proposed from the reaction of a primary aniline and difluorocarbene. Ensuing nucleophilic iminyl substitution of this intermediate with a second amine allows cross-condensation of the two amines to produce formamidines. When only one type of primary aniline is used as the substrate, the difluoromethylated homo-condensation products can also be produced under a 1:1 molar ratio of aniline/difluorocarbene. Intramolecular variant of this method allows concise synthesis of benzimidazoquinazolines and nitrogen-fused/spirocyclic compounds, showing the potential of this method in organic synthesis. More interesting reactions are anticipated by exploiting the reactivity of difluorocarbene and primary amines to isocyanides or the formimidoyl fluoride intermediates.

Direct Arene Trifluoromethylation Enabled by a High-Valent CuIII -CF3 Compound.

Direct C-H trifluoromethylation of arenes and heteroarenes poses an important synthetic challenge that is highly desirable. High-valent CuIII -CF3 compounds have often been invoked in copper-mediated trifluoromethylation reactions, but the fundamental reactivity toward arenes is elusive. Herein, direct C-H trifluoromethylation of arenes/heteroarenes by a high-valent CuIII -CF3 compound is disclosed for the first time. The CuIII -CF3 compound serves CF3 radical and a CuII oxidant by homolytic cleavage of a CuIII -CF3 bond, which engage synergistically in a SE Ar type reaction with arenes. The presence of K2 S2 O8 co-oxidant can significantly improve the reaction yields. This reaction shows good efficiency, broad functional group tolerance, and the potential in late-stage functionalization. The reactivity of high-valent CuIII -CF3 compounds disclosed in this study represents an important progress in organofluorine and CuIII chemistry.