Metal-mediated Heterocyclization: Synthesis of Heterocyclic Compounds Containing More Than One Heteroatom Through Carbon-Heteroatom Bond Forming Reactions

Heterocyclic compounds are versatile building blocks in organic synthesis. These are important part in various natural products and bioactive compounds. Several methodologies have been developed to synthesize these heterocyclic compounds. This review article covers an updated (published during 2005 to 2008) summary of transition-metal catalyzed approaches for the syntheses of commonring heterocycles containing more than one heteroatom via the selective formation of carbon-heteroatom bonds. The five-membered ring heterocycles with two nitrogen atoms include imidazoles, pyrazoles, indazoles, imidazoindolones etc. and heterocycles with one nitrogen and one oxygen atoms include oxazoles, isoxazolines, isoxazolidines etc. Other five-membered heterocycles with one nitrogen and one sulfur atoms as well as one oxygen and one phosphorus/sulfur/silicon atoms have also been included here. Six-membered heterocycles containing two nitrogen atoms such as pyrimidines, pyrazines, phenazines, quinoxazolines etc. have been incorporated. Other six-membered heterocycles containing one nitrogen and one oxygen/sulfur atoms as well as one oxygen and one phosphorus atoms have also been included. Some heterocycles containing three or more heteroatoms have been discussed.