The Hexadehydro-Diels–Alder (HDDA) Reaction-Enabled Bottom-up Synthesis of Elaborated Polycyclic Aromatics

Abstract

Polycyclic arenes are an important class of organic molecules with promising semiconducting properties. Their relatively low cost, band-gap tunability, and ease of fabrication render them suitable for a host of applications for the next-generation optoelectronics devices. The biggest challenge to realize the full potential of organic semiconductors is the chemical synthesis of atomically precise polycyclic aromatics. The current strategies to assemble these materials heavily rely on transition-metal catalyzed cross-coupling reactions of prefunctionalized arenes, which in a way limit the vision of material scientists when search for potential compounds. This thesis describes a complementary synthetic approach to polycyclic aromatic products from polyynes via the hexadehydro-Diels–Alder (HDDA) reaction. The HDDA reaction is a variant of the classic Diels–Alder reaction, which generates pristine benzyne intermediates purely thermally. This mechanistically intriguing transformation also has served as a great platform for many discoveries of fundamentally new reactivities. Here multiple aspects of the HDDA reaction are discussed: (1) reaction of perylenes with HDDA-benzynes and photochemical HDDA reactions, (2) accessing other reactive intermediates via HDDA-generated benzynes, (3) copper(I)- and BF3- catalyzed trapping reactions of benzynes, (4) rapid construction of polyacenes via the domino HDDA reaction, and (5) a cascade strategy for using classically generated benzynes as in situ diynophiles for accessing HDDA-naphthynes.