Palladium-catalyzed coupling reactions of (ArCH2)Ti(O-i-Pr)3 with aromatic or heteroaromatic bromides

Three benzyltitanium compounds of (ArCH2)Ti(O-i-Pr)3 (Ar = Ph (1a), 4-MeOC6H4 (1b), 4-FC6H4 (1c)) were prepared and used as benzyl nucleophiles for coupling reactions with aromatic or heteroaromatic bromides. The simple catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 worked efficiently for a wide variety of aromatic bromides, producing diarylmethanes in good to excellent yields of up to 96%. Coupling reactions of hindered aromatic bromides or aromatic bromides containing electron-withdrawing substituents were slower over longer reaction times of 3–6 h. Reactions of heteroaromatic bromides of bromopyridines, bromofurans, or bromothiophenes with benzyl reagents of 1a or 1b required either longer reaction times of 12–24 h or a higher reaction temperature of 80 °C, producing pyridyl-, furyl-, and thienyl-arylmethanes in moderate yields.

Coupling reactions of (ArCH2)Ti(O-i-Pr)3 with aromatic or heteroaromatic bromides have been investigated. The simple catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 are effective under a mild reaction temperature of 40 °C, affording diarylmethanes in high yields of up to 96%. For the synthesis of heteroaryl-arylmethanes, either longer reaction times or a reaction temperature of 80 °C is required.Figure optionsDownload as PowerPoint slide