Highly selective and single step vapor phase synthesis of 2,6-bis(4-methylphenyl)pyridine over Al-MCM-41 molecular sieves

Abstract

Vapor phase synthesis of 2,6-bis(4-methylpheny)pyridine (2,6-BP), an important drug intermediate, was carried out by the cyclization of 4-methyl acetophenone (4-MAP), ethanol, formaldehyde and ammonia over different classes of molecular sieves, viz. HY, HZSM-5, HY and Al-MCM-41. The predominant product of cyclization 2,6-BP was obtained on Al-MCM-41with high selectivity. To understand the mechanism and to identify the suitable acid sites, we further studied the reaction by varying the Si/Al ratio and feed composition on Al-MCM-41. A plausible mechanism leading to the formation of 2,6-BP along with the other major by-products 2-(4-methylphenyl)pyridine (2-P) and 2,6-bis(4-methylphenyl)4-methyl pyridine (2,6-MBP), is proposed.