Synthesis of higher carboxylic acids from ethers, CO2 and H2.

Synthesis of higher carboxylic acids using CO2 and H2 is of great importance, because CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Herein we report a route to produce higher carboxylic acids via reaction of ethers with CO2 and H2. We show that the reaction can be efficiently catalyzed by an IrI4 catalyst with LiI as promoter at 170 °C, 5 MPa of CO2 and 2 MPa of H2. The catalytic system applies to various ether substrates. The mechanistic study indicates that the ethers are converted to olefins, which are further transformed into alkyl iodides. The higher carboxylic acids are produced by carbonylation of alkyl iodides with CO generated in situ via RWGS reaction. This report offers an alternative strategy of higher carboxylic acid synthesis and CO2 transformation.