Cobalt-Catalyzed Deoxygenative Coupling of Ethers to Alkanes

Alkanes have extensive applications in diverse fields and their natural abundance is dwindling. Ethers are prevalently present in biomolecules and synthetic compounds; however, despite recent progress in their transformations they are considered as unreactive functionalities, and widely used as solvents in transition metal-catalyzed reactions. Hence, catalytic synthesis of alkanes from bio-ample ethers is highly desirable. A simple cobalt-catalyzed double C-O bond activation of ethers is attained now; diverse symmetrical and unsymmetrical arylmethyl ethers (ArCH₂OCH₂Ar') are selectively transformed to 1,2-diaryl alkanes. This protocol is extended toward unsymmetrical arylmethyl alkyl ethers which furnished linear alkyl arenes. Synthesis of biologically active compounds is also achieved utilizing this catalytic method. Consumption of ethers in catalytic deoxygenative coupling to alkanes follows first-order kinetics. Mechanistic studies indicate that the reactions proceed through molecular intermediates and involve arylmethyl and alkyl radicals. DFT analysis reveals that the in situ generated radical either abstracts a proton from silane, resulting in C-H bond formation or attacks the aryl silyl ether, leading to C-C coupling. The reaction mechanism involves intermediates with different spin multiplicities and spin crossover through minimum energy crossing points (MECPs).