Free radical addition of para-~oluenesulfonyl iodide 10 alkenols occurs readily 10 give functionalised Piodosulfones as single regioisomers. Cyclisation fo give cyclic ethers is effected by treatment with potassium carbonate in methanol. An anomalous reaction, where a substimed alkenol cyclises direcrly lo give an iodoretrahydropyran, is also discussed.
In recent years many natural product syntheses have incorporated, as key strategic elements in the elaboration of complex molecular frameworks, highly stereo-and regio-selective free radical reactions.1 Of increasing importance is the extension of radical methodology to allow for the introduction, transfer or retention of functionality for further synthetic operations. 2 As a part of a programme directed towards the development of new routes to functionalised oxygenated heterocycles, we elected to investigate the radical addition ofpara-toluenesulfonyl iodide3 (tosyl iodide, TsI) to unsaturated alcohols and ethers (Scheme), such that the products could be amenable to further ionic reactions. The recently published work of Serra and da Silva Corrta4 on novel radical displacement reactions has prompted us to communicate our preliminary results in this area. The different stereoelectronic constraints of free radical versus ionic reactions will ensure