Synthesis and application of 1,1-divinylallene

Abstract

Cross-conjugated hydrocarbons possess the innate ability to rapidly generate polycyclic frameworks through sequences of diene-transmissive Diels-Alder reactions. Chapter 1 of this thesis reviews the application of this chemistry in synthesis, with particular attention given to those examples that best exemplify the state of the art. Despite many remarkable contributions, this examination highlights how little this methodology has been applied in target-orientated synthesis. Chapter 2 reports the first synthesis of 1,1-divinylallene. The arrangement of alkenes in this highly reactive cross-conjugated molecule permits a new diene-transmissive triple Diels-Alder cycloaddition sequence. This enables the synthesis of a fused tricyclic phenalene ring system in just one step. Controlled single additions have also been achieved, enabling the synthesis of diverse polycyclic compounds. The phenalene framework is embedded in a number of natural products, of which the pseudopterosins are perhaps the most well known. This family of biologically active glycosylated terpenes enjoy a rich synthetic history, and a comprehensive review of their total and formal syntheses is presented in Chapter 3. Finally, Chapter 4 details the successful application of a triple Diels-Alder sequence of a substituted 1,1-divinylallene in total synthesis. The enantioselective synthesis of the pseudopterosin (-)-G-J aglycone was accomplished using a new Kumada cross-coupling route to axially chiral vinylallenes, enabling the synthesis of the natural product in only eleven steps. This represents the most step economic synthesis of a pseudopterosin to date. Show more