Novel Domino Routes for the Synthesis of N-Heterocycles via Reductive Cyclization of β-(N-2-Nitroaryl)-α,β-unsaturated Ketones

An efficient and operational simple synthetic method has been developed towards the preparation of important biologically active N-heterocyclic scaffolds. The present method associated with the use of inexpensive and easy to prepare nitroaromatics as substrates. The key step of the developed protocol rely on the reductive cyclization of nitro-compounds in presence of Mo (VI) as catalyst and phosphine as deoxygenative agent. It has been shown that depending on the nature of substrates two distinct heterocyclic scaffolds such as 1-hydroxyphenazines and quinoxalines can be synthesized in high yields. It is envisaged that both 1-hydroxyphenazines and quinoxalines exhibits potential pharmacological profiles and offers novel landscapes in medicinal chemistry, and drug discovery research. Considering the limited number of methods available in literature for the preparation of 1-hydroxyphenazines, the present method serves an efficient and economical alternative towards this scaffold.