Unprecedented Reactivity of AgSCF3 with o‐Isocyanobiaryls: Synthetic and Mechanistic Insight

Abstract

AbstractThe work reports an unusual reaction of o‐isocyanobiaryls and AgSCF3, which led to the unexpected formation of 6‐(trifluoromethyl)phenanthridines and o‐biaryl isothiocyanates as products, instead of the expected 6‐((trifluoromethyl)thio)phenanthridines. Density functional theory (DFT) calculations on the relative free energy of β‐fragmentation and 6‐endo‐trig radical cyclization pathways of the key thioimidoyl radical intermediate suggested that β‐fragmentation of the S−CF3 bond is preferable, releasing CF3 radical and o‐biaryl isothiocyanate. The CF3‐imidoyl intermediate arising from the addition of CF3 radical to o‐isocyanobiaryl then underwent 6‐endo‐trig radical cyclization to provide 6‐(trifluoromethyl)phenanthridines. This work demonstrates the alternate application of AgSCF3 in generating trifluoromethylated and isothiocyanate products.