SYNTHESIS OF NOVEL SYMMETRICAL AND NONSYMMETRICAL 6-MEMBERED HETEROCYCLES WITH PENDANT ELECTRON-RICH ORGANOIRON SUBSTITUENTS

Abstract

The functionalized complexes [(dppe)Cp*Fe(CºC)]₂–(Py)(Py = 2,6-C₅H₃N and 3,5-C₅H₃N (dppe = 1,2-bis(diphenylphosphino)ethane) were isolated in good yields from reaction of the chloro complex (dppe)Cp*FeCl with the protected bis-acetylenic heterocyclic precursor. These electron-rich pyridyl ligands constitute interesting examples of organometallic heterocycles bearing redox-active substituents. Attempts to find an alternative route starting from the alkynyl complex [(dppe)Cp*Fe(CºCH)] and the corresponding dibromopyridines using a Sonogashira cross-coupling reaction are also described. By this route, the monofunctionalized products [(dppe)Cp*Fe(CºC)]-2,6-Py-Br and [(dppe)Cp*Fe(CºC)]-3,5-Py-Br could be cleanly isolated. These compounds open the way to the generation of heteroaromatics featuring nonequivalent alkyne substituents such as [(dppe)Cp*Fe(CºC)]-2,6-Py-[(CºC)SiMe₃] or [(dppe)Cp*Fe(CºC)]-3,5-Py-[(CºC)SiMe₃] by further coupling.

Also published in Chemistry of Heterocyclic Compounds, 1999, 35 (9), pp 1063-1074

http://link.springer.com/article/10.1007/BF02251798