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

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 formed in one pot through [4 + 2] annulation reaction. Four C–N bonds were promoted by iodine additives. This work is highlighted two iodides sole nitrogen source.