Palladium and electrophilic cyclization approaches to carbo- and heterocyclic compounds

Abstract

2,3-Disubstituted benzo[6]furans are readily prepared under very mild reaction conditions by the palladium/copper-catalyzed cross-coupling of o-iodoanisole and terminal alkynes, followed by electrophilic cyclization using 12, Br2, PhSeCl and /?-02NC6H4SCl. Aryland vinylic-substituted alkynes undergo electrophilic cyclization in excellent yields. Biologically important furopyridines can be prepared by this approach in high yields. Introduction The benzo[e]furan nucleus is prevalent in a wide variety of biologically active natural and unnatural compounds.1 Many 2-arylbenzofuran derivatives are well known to exhibit a broad range of biological activities, such as anticancer,2 antiproliferative,3 antiviral,4 antifungal,5 immunosuppressive,6 antiplatelet,7 antioxidative,8 insecticidal,9 anti­ inflammatory,10 antifeedant,11 and cancer preventative activity.12 These compounds are also important calcium blockers13 and phytoestrogens.14 For instance, XH-1415 was the first