Organocatalytic Synthesis of Highly Substituted Furfuryl Alcohols and Amines

摘要

Substituted furans are present in many natural products, bioactive compounds, and functional materials.Furans also serve as valuable building blocks for organic synthesis. Driven by this prevalence, many methods have been developed for the synthesis of substituted furans. In addition to traditional methods, metal-mediated furan syntheses are becoming common. In particular, a variety of metals have been used to induce intramolecular carbonyl oxycyclization onto alkynes; electrophilic activation of alkynes has been demonstrated by using Lewis acidic complexes of copper and zinc. Additionally, gold-mediated furan syntheses have been reported; these syntheses involve both intermolecular couplings, and intramolecular cyclization of a range of 4-and 5-oxygenated alkynyl substrates. Furthermore, gold-and silver-mediated cyclizations triggered by nucleophilic substrate activation have been reported. These metal-mediated procedures are predated by reports of electrophilic activation of enynones by Br0nsted acid (Scheme 1 a, X=H.