A Three-Step Synthesis of 4H-Cyclopenta[def]phenanthrene from Pyrene

Abstract

4H-Cyclopenta[def]phenanthrene (CPP) is a valuable building block in the production of photoactive polymers, which find use in a wide range of organic electronic applications. Of particular importance is their use in the development of blue-colored, organic light-emitting diodes (OLEDs), which remains a challenge in the field. Unfortunately, commercial sources and synthetic procedures known in the literature are unable to provide enough CPP for large scale implementation. Herein, we report on the development of a novel, gram-scale synthesis of CPP in three steps, starting from pyrene. The key steps in our methodology are the ring contraction of pyrene-4,5-dione to oxoCPP in a single step, as well as the direct reduction of oxoCPP to CPP. Apart from the small number of synthetic steps, our methodology benefits from the use of relatively non-hazardous reagents, together with optimized purification procedures, making CPP accessible in useful quantities.