B(OH)₃-Catalyzed Dual Friedel-Crafts Type Reaction of Anilines and Aldehydes to Access Di- or Triarylmethanes (TRAMs)

The catalytic influences of boric acid have been introduced on dual Friedel-Crafts reaction between arylamines and aldehydes to install the Csp(3)-center that leads to the formation of di- or tri-substituted methanes. The described reaction conditions have directed the transformation to favor the para-para substitution pattern to deliver the major products rather than the corresponding ortho-para functionalization process. The devised transformation was examined by DFT calculation, which shows the favorable activation energy of transition states (TS) for the generation of highly substituted molecular scaffolds. The method was applicable over diversely substituted aldehydes and arylamines to afford the final products in excellent yields (60-92 %) and selectivity. The proposed mechanism is supported by suitable control experiments, GC-MS studies, and DFT calculations.