Multicomponent catalyst promotes multistep reactions

Brown University chemists have developed a new composite catalyst that can perform four separate reaction steps in sequential order in the same vessel, generating compounds that are useful as intermediates for making antibiotics, anticancer drugs, and other pharmaceuticals (J. Am. Chem. Soc. 2017, DOI: 10.1021/jacs.7b01983). A collaboration between the groups of Christopher T. Seto and Shouheng Sun, the researchers led by postdoc Chao Yu and graduate student Xuefeng Guo set out with a goal of creating greener reactions amenable to industrial applications—ones that use smaller amounts of less expensive and less toxic solvents and reagents and generate less waste but still lead to complex molecules. The team first created the catalyst by growing silver-palladium nanoparticles on the surface of oxygen-deficient tungsten oxide nanorods. They then designed a reaction worthy of the catalyst: formic acid dehydrogenation followed by hydrogenation of nitrophenol to an amine and then condensation of the amine with an aldehyde to form an intermediate that undergoes ring closing to form benzoxazoles (shown). The entire reaction was carried out under mild conditions (dioxane/water solvent at 80 °C). The procedure also works for preparing related quinazolines.