Metal-Catalyzed Synthesis of Functionalized 1,2,4-Oxadiazoles from Silyl Nitronates and Nitriles

Article abstract of DOI:10.1002/adsc.201601378

The metal-catalyzed cycloaddition of silyl nitronates and nitriles leading to 1,2,4-oxadiazoles is described. Silver(I) triflate (AgOTf) and and ytterbium(III) triflate [Yb(OTf)₃] are suitable catalysts. A variety of functional groups is tolerated in the nitrile. The reaction works well for alkenyl and aryl silyl nitronates while the use of alkyl silyl nitronates is less efficient. Mechanistic studies are in favour of an elimination of tert-butyl(dimethyl)silanol (TBSOH) after the cycloaddition step. The new approach has also been applied for the synthesis of the drug ataluren. (Figure presented.).