High‐Speed Reduction of Triarylpyrylium Salts Using Zn(BH4)2/SiO2 as an Efficient and Regiospecific Reducing Reagent

The regiospecific reduction of some triarylpyrylium salts in the presence of modified hydride donors was investigated. Among these reagents, Zn(BH 4 ) 2 /SiO 2 performed the best results. The major advantages of this reagent are the cheapness, availability, simplicity in operation, very short reaction time and much improved regioselectivity in comparison with the other reducing reagents.