Unprecedented Reactivity of AgSCF3with o‐Isocyanobiaryls: Synthetic and Mechanistic Insight

The 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−CF3bond is preferable, releasing CF3radical and o‐biaryl isothiocyanate. The CF3‐imidoyl intermediate arising from the addition of CF3radical to o‐isocyanobiaryl then underwent 6‐endo‐trig radical cyclization to provide 6‐(trifluoromethyl)phenanthridines. This work demonstrates the alternate application of AgSCF3in generating trifluoromethylated and isothiocyanate products. The reaction ofo‐isocyanobiarylsand AgSCF3led to unexpected formation of 6‐(trifluoromethyl)phenanthridines and o‐biaryl isothiocyanates as the products, instead of the expected 6‐((trifluoromethyl)thio)phenanthridines. DFT calculations were performed to better understand the mechanistic details and unprecedented reactivity of AgSCF3with o‐isocyanobiaryls.