Annulative π‐Extension (APEX): Rapid Access to Fused Arenes, Heteroarenes, and Nanographenes

Abstract

The annulative π‐extension (APEX) reaction has the potential to have a tremendous impact on the fields of materials science and bioimaging, as well as on the pharmaceutical/agrochemical industries, since it allows access to fused aromatic systems from relatively simple aromatic compounds in a single step. Typically, an APEX reaction facilitates a one‐pot π‐extension without the need to prefunctionalize the aromatic compounds. This advantageous feature is extremely useful for tuning and modifying molecular properties in the last step of a synthesis. In this Review, the progress and applications of APEX reactions of unfunctionalized arenes and heteroarenes are described.

C−H Alkenylation of Pyrroles by Electronically Matching Ligand Control

“…For example, C3‐alkenylation of 4 g with Pd(OAc) 2 and Cu(OAc) 2 afforded 4,5‐dialkenyl pyrrole 7 a having different alkenyl groups (Scheme ) . Subsequent thermal 6π‐electrocyclization and oxidation facilitated ring closure, producing the multi‐substituted indole 7 b …”

Polycyclic Aromatic Hydrocarbons as Potential Building Blocks for Organic Solar Cells

“…In addition to their intrinsically high band gap values, these units are generally “electronically neutral”, meaning that they cannot be part of a donor‐acceptor complex, which is the predominant strategy used to prepare low band gap organic materials. One of the best ways to decrease the band gap value of a given PAH is to perform annulation reactions that will extend its effective conjugation length . Depending on the nature of the annulated unit and the direction of the π extension, significant change can be induced on the electronic properties.…”

A Highly Warped Heptagon‐Containing sp2 Carbon Scaffold via Vinylnaphthyl π‐Extension

“…This provides an addition to other important p-extension reactions of unfunctionalized hydrocarbons such as bay-or Kregion annulations. [21] X-ray crystallography and DFT studies reveal that compound 2 is highly warped and adopts a cisoid saddle-shaped structure with planes of rings on either side of the p-scaffold intersecting at angles less than 828 8.D FT calculations and NMR spectroscopic studies suggest high flexibility of the scaffold. Compound 2 is highly soluble, exhibits visible range absorption and emission in solution, and is reversibly oxidized at mild potentials.W ea nticipate that this new,straightforward way to incorporate heptagonal rings into sp 2 -hybridized carbon frameworks will offer access to other exciting new structures and studies of these are underway in our laboratories.…”