A Sequential Suzuki Coupling Approach to Unsymmetrical Aryl s-Triazines from Cyanuric Chloride

A practical approach has been developed for efficient synthesis of unsymmetrical aryl s-triazines via highly selective sequential Suzuki coupling of cyanuric chloride (2,4,6-trichlorotriazine) with aryl or vinyl boronic or diarylborinic acids catalysed by 0.1-0.5 mol% Pd(PPh3)(2)Cl-2 under mild conditions. The second and third Suzuki couplings for unsymmetrically trisubstituted aryl s-triazines could be more practically conducted in one-pot procedure. An electron-withdrawing conjugate group at phenyl ring of arylboronic acids was unexpectedly found to completely block the coupling while steric hindrance from an ortho electron-donating substituent could be overcome.