Titanocene-Mediated Dinitrile Coupling: A Divergent Route to Nitrogen-Containing Polycyclic Aromatic Hydrocarbons

J Am Chem Soc. 2018 Feb 21;140(7):2450-2454. doi: 10.1021/jacs.7b13823. Epub 2018 Feb 6.

Abstract

A general synthetic strategy for the construction of large, nitrogen-containing polycyclic aromatic hydrocarbons (PAHs) is reported. The strategy involves two key steps: (1) a titanocene-mediated reductive cyclization of an oligo(dinitrile) precursor to form a PAH appended with di(aza)titanacyclopentadiene functionality; (2) a divergent titanocene transfer reaction, which allows final-step installation of one or more o-quinone, diazole, or pyrazine units into the PAH framework. The new methodology enables rational, late-stage control of HOMO and LUMO energy levels and thus photophysical and electrochemical properties, as revealed by UV/vis and fluorescence spectroscopy, cyclic voltammetry, and DFT calculations. More generally, this contribution presents the first productive use of di(aza)metallacyclopentadiene intermediates in organic synthesis, including the first formal [2 + 2 + 2] reaction to form a pyrazine ring.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Molecular Structure
  • Nitriles / chemical synthesis*
  • Nitriles / chemistry
  • Nitrogen / chemistry*
  • Organometallic Compounds / chemistry*
  • Polycyclic Aromatic Hydrocarbons / chemical synthesis*
  • Polycyclic Aromatic Hydrocarbons / chemistry

Substances

  • Nitriles
  • Organometallic Compounds
  • Polycyclic Aromatic Hydrocarbons
  • titanocene
  • Nitrogen