A Review of Ruthenium-catalyzed C-N Bond Formation Reactions for the Synthesis of Five-membered N-heterocycles

The field of heterocyclic chemistry has been revolutionized using transition metal catalysts in recent years. Various research groups have focused on the development of general protocols to achieve better functional group compatibilities and greater levels of molecular complexity under mild reaction conditions, using easily available starting substrates. The methodologies used earlier for their synthesis were less approachable to organic chemists because of their high cost, highly specified instrumentation and inconvenient methods. For both stereoselective and regioselective synthesis of five-membered nitrogen- containing heterocycles, cyclic reactions that are Ru-catalyzed have known to be very efficient. These methods have many advantages as compared to alternative pathways involved in the synthesis of heterocyclic compounds. In this review article, we concentrated on the synthesis of nitrogen-containing five-membered heterocycles in the presence of a ruthenium catalyst. This review mostly covers the literature published during the period from 1977-2019.