Exploration of the inverse-electron-demand Diels-Alder (IEDDA) reaction. Rapid access to benzocoumarins via IEDDA-driven domino reactions of coumarin-fused electron-deficient dienes with electron-rich dienophiles

Abstract

Chapter 1 overviews the general concepts of the Diels-Alder reaction, and particular attention is given to the inverse-electron-demand Diels-Alder reaction (IEDDA). Examples of all-carbon diene systems that contain electron-withdrawing groups at their 1- and 3-positions and their IEDDA reactivity are described. -- Chapter 2 presents the synthesis of a coumarin-fused diene that was produced in a single step. An oxidative cleavage of this diene produces 3-formylcoumarin, which can be used in the Homer-Wadsworth-Emmons reaction or the Knoevenagel condensation to afford other coumarin-fused dienes. -- Chapter 3 presents the IEDDA reactivity of methyl (E)-3-(2-oxo-2H-chromen-3-yl)acrylate with electron-rich dienophiles. Enamines undergo an IEDDA-driven domino reaction to produce benzocoumarins. The reaction procedure can be simplified by generating the dienophile in situ. -- Chapter 4 details the methodology development of the IEDDA-driven domino reactions. The methodology was used to synthesize a subunit of a new heterokekulene and efficiently generate benzocoumarins from the appropriate phenols. Preliminary results for producing azabenzcoumarins are also discussed. -- Chapter 5 contains details of a concise, high yielding total synthesis of a naturally occurring benzocoumarin by applying the methodology developed in Chapter 4. An IEDDA-driven domino reaction constitutes the key step of the synthesis.