Expedient Syntheses of β‐Iodofurans by 5‐endo‐dig Cyclisations

Abstract 5‐endo‐dig cyclisations of 3‐alkyne‐1,2‐diols using iodine as the electrophile proceed smoothly to deliver excellent yields of the corresponding β‐iodofurans. The necessary precursors are available from a number of different approaches, notably regioselective bis‐hydroxylation of conjugated enynes and the addition of acetylides to α‐hydroxy carbonyl groups. The initial iodofurans can be homologated using a number of strategies, ranging from various transition metal‐catalysed couplings to halogen–metal exchange and subsequent coupling with an electrophile. Hence, this method overall represents a flexible, relatively brief and very efficient approach to a variety of highly substituted furans. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)