An Efficient Synthesis of Five-Membered N-Heterocycles

Significance

An effective synthetic method of preparing five-membered N-heterocycles was developed by using montmorillonite K-10 catalyst. Thus, microwave-assisted reaction of amines 1 with 2,5-hexanedione 2 in the presence of montmorillonite K-10 under solvent-free conditions gave the corresponding pyrroles 3 in 91-98% yield (eq. 1). Under similar reaction conditions, pyrroles 4 underwent reaction with 2 to afford the corresponding indoles 5 in 75-98% yield (eq. 2), and indoles 6 were converted into the corresponding carbazoles 7 in 86-96% yield (eq. 3). All reactions were completed within very short reaction times (2-25 minutes).