Highly fluorinated 2,3-dihydro-1,3,4-thiadiazole derivatives via [3+2]-cycloadditions of tertiary thioamides with nitrile imines derived from trifluoroacetonitrile

[Display omitted] •Fluorinated, non-enolisable thioamides react smoothly with N-aryl trifluoroacetonitrile imines.•Observed [3 + 2]-cycloaddition reactions occur with complete regioselectivity.•Fluorine-rich 2,3-dihydro-1,3,4-thiadiazoles were isolated as stable compounds in high yields.•Two electron-deficient reagents form the 5-membered N,N,S-heterocycle.•Observed [3 + 2]-cycloadditions belong to the Type II according to Sustmann’s classification. Fluorine-rich 1,3,4-thiadiazole derivatives were prepared by 1,3-dipolar cycloaddition of the in situ generated N-aryl-trifluoroacetonitrile imines with tertiary polyfluoroalkanethioamides (N,N-dialkyl thioamides). Reactions were performed under mild conditions in THF solutions at room temperature. The 1,3,4-thiadiazole derivatives were formed in a fully regioselective manner in high yields. In a competition experiment, the non-fluorinated 1-(morpholin-4-yl)ethanethione was shown to be more reactive towards a model nitrile imine than its 2,2,2-trifluoromethylated analogue.