ORGN 665 |
| Javier Santos and Michael A. Meador. Ohio Aerospace Institute and Polymers Branch, Materials Division, NASA Glenn Research Center, 21000 Brookpark Road, M.S. 49-1, Cleveland, OH 44135 |
| A broad range of synthetic strategies have been reported for the preparation of benzofurans. Among them is the photocyclization of alkoxyphenyl ketones and base mediated reactions. Often the photocyclization approach generate a hydrobenzofuranol derivative that needs to be dehydrated in order to gets the desired benzofuran. However, base mediated cyclizations usually do not require dehydration. A number of bases have been employed for the cyclization of alkoxyphenyl ketones to afford the desired benzofuran, for example: sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium ethoxide, potassium tert-butoxide, and recently a phosphazene base. Here we disclose the capability of cyanide ions to deprotonate acidic benzyl positions by means of cyclocondensation of alkoxyphenyl ketones affording the corresponding benzofurans. It was found that the cyanide anions are regenerated during the reaction allowing its continuing activity as a base. The use of cyanide ions is suitable for the preparation of benzofuran derivatives containing substituents that are sensitive to other bases and photolysis. Under this condition benzofurans were obtained in good to excellent yield, depending on substituents and the nature of the carbonyl group. |
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New Reactions, Methodology, Heterocycles, Aromatics
8:00 PM-10:00 PM, Wednesday, August 25, 2004 Pennsylvania Convention Center -- Hall D, Poster
Division of Organic Chemistry |