Chemists can now be picky about organosulfur compounds

When hearing someone describe the typical preparation of organosulfur compounds, it’s clear the approach is not a very sustainable one. Mixtures of sulfur compounds naturally found in crude oil are first treated with hydrogen in a catalytic refinery process to remove the sulfur—the goal is to pull out as much sulfur as possible to create cleaner transportation fuels. The ­hydrogen sulfide that forms in this hydrodesulfurization step is converted to elemental sulfur. Chemists then pair this sulfur with selected reactants to reconstruct desired organosulfur compounds one product at a time. Overall, the energy-intensive, multistep process is costly and generates a significant amount of waste. A new strategy reported by Valentine P. Ananikov of the Russian Academy of Sciences’ Zelinsky Institute of Organic Chemistry and coworkers enables unprecedented direct C–H functionalization and separation of only one sulfur component at a time from mixtures of organosulfur compounds (ACS Omega 2017, DOI: 10.1021/acsomega.7b00137). The Russian ­researchers use palladium acetate along with oxygen and silver trifluoroacetate as a combination oxidant to couple an olefin, such as ethyl acrylate, to an aryl or heteroaryl sulfur compound. The reaction’s selectivity centers on the sulfur acting as a directing group to guide the C–H activation and alkenylation. Benzyl compounds provide the most favorable geometry for palladium binding, followed by compounds with longer alkyl chains, which leads to exclusive functionalization of one component at a time in a mixture.