Regioselective synthesis of 3-trifluoromethyl 1,2,4-triazoles via photocycloaddition of sydnone with CF3CN

A general and regioselective synthesis of 3-trifluoromethyl 1,2,4-triazoles has been achieved through photocycloaddition of sydnone with trifluoroacetonitrile. This method employed trifluoroacetaldehyde O-(aryl)oxime as the CF3CN precursor and tolerated various functional groups to furnish 3-trifluoromethyl 1,2,4-triazole products in moderate to good yields. Mechanistic experiments revealed an energy transfer from photocatalyst 4-CzIPN to the sydnone substrates.