Isoprene: A Promising Coupling Partner in C–H Functionalizations

Abstract

Five-carbon dimethylallyl units, such as prenyl and reverse-prenyl, are widely distributed in natural indole alkaloids and terpenoids. In conventional methodologies, these valuable motifs are often derived from substrates bearing leaving groups, but these processes are accompanied by the generation of stoichiometric amounts of by-products. From an economical and environmental point of view, the basic industrial feedstock isoprene is an ideal alternative precursor. However, given that electronically unbiased isoprene might undergo six possible addition modes in the coupling reactions, it is difficult to control the selectivity. This article summarizes the strategies we have developed to achieve regioselective C–H functionalizations of isoprene under transition-metal and acid catalysis.1 Introduction2 Catalytic Coupling of Indoles with Isoprene3 Catalytic Coupling of Formaldehyde, Arenes and Isoprene4 Catalytic Coupling of 4-Hydroxycoumarins with Isoprene5 Catalytic Coupling of Cyclic 1,3-Diketones with Isoprene6 Conclusion and Outlook