Ruthenium arylboronic acids with aryl

In 2013, Tang and coworkers [55] reported the use of other chiral ligands to catalyze the arylation of aldehydes with ruthenium precatalysts. The same group developed a series of chiral biaryl monophosphorous ligands (Scheme 7.37) that were found to catalyze the addition of arylboronic acids to aryl aldehydes. A series of chiral diarylmethanols were obtained in excellent yields (up to... 

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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