Triazoles, arylboronic acid coupling

Table 9 Reaction of arylboronic acids with 3,5-dihalo-1,2,4-triazole derivatives under Suzuki coupling conditions (Equation 25)...

This sequence could be further extended to the synthesis of 1,4,5-triaryl-l,2,3-triazoles 44—46 (Scheme 7.16) by assembling the 5-iodotriazole and immediately employing Pd(0)-catalyzed cross-coupling with an appropriate arylboronic acid. This simple stepwise construction obviates purification of any intermediates and simultaneously provides complete control over the placement of substituents around the 1,2,3-triazole core, allowing facile access to all regioisomeric permutations of trisubstituted triazoles 44—46. Similar regiocontrolled synthesis would not be possible via thermal or ruthenium-catalyzed reaction due to the steric and electronic similarity of the aryl substituents (phenyl, tolyl, and p-methoxyphenyl). 

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