Expedient syntheses of β-iodofurans by 5-endo-dig cyclisations

5-endo-dig cyclisations of 3-alkyne-1,2-diols using iodine as the electrophile proceed smoothly to deliver excellent yields of the corresponding beta-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 a-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. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).