Synthesis of Symmetric Bis(N‑alkylaniline)triarylmethanes via Friedel–Crafts-Catalyzed Reaction between Secondary Anilines and Aldehydes

The first general protocol for the preparation of symmetric triarylmethanes bearing secondary anilines by ytterbium-catalyzed Friedel–Crafts reaction of hetero­(aryl) aldehydes and secondary anilines is reported. Mechanistic studies indicated that the iminium ion intermediate is the electrophilic partner. The reaction is greatly accelerated by high pressure (9 kbar) and showed a broad substrate scope on the hetero­(aryl) aldehyde. The new triarylmethanes exhibited activity against HT-29 cancer cell lines, with the best result scoring an IC50 of 1.74 μM.