Four-Component Synthesis of 9<i>H</i>-Pyrimido[4,5-<i>b</i>]indoles Using Ammonium Iodide as the Nitrogen Source

Abstract

A four-component synthesis of 2-phenyl-9H-pyrimido[4,5-b]indoles was developed using indole-3-carboxaldehydes, aromatic aldehyde and ammonium iodide as the raw materials under transition-metal-free conditions. The pyrimidine ring was formed in one pot through [4 + 2] annulation reaction. Four C–N bonds were formed in one pot promoted by iodine and iodide additives. This work is highlighted by using two ammonium iodides as the sole nitrogen source.

Keywords

• 9<i>H</i>-pyrimido[4,5-<i>b</i>]indole
• aromatic aldehyde
• ammonium salt
• cycloaddition
• transition metal free