A new ring synthesis for 3- and polysubstituted furans; directing effects of a 3-(arenesulfonyl) group in metalation and Friedel-Crafts processes
✍ Scribed by S.W. McCombie; B.B. Shankar; A.K. Ganguly
- Book ID
- 104227273
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- French
- Weight
- 242 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Primary and secondary a-bromoketones react with the potassium salt (3) to afford Z-[E-2-(p-toluenesulfonyl)-ethenyloxyl-ketones. On treatment with LDA followed by p-TsOH, good yields of the corresponding 3-or 2,3-substituted-4-tosylfuran are obtained, from which the 4-substituent may be reductive1.y removed. 3-Aryl or alkyl-4-tosylfurans undergo regiospecific metalation at C-5 and Friedel-Crafts acylation at C-2. These processes permit the conversion of bromoketones to 2,3-, 2,4-or 2,3,5_substituted furans.
The furan nucleus occurs in a variety of natural products from land and marine 1 sources , 3-and 2,3_substitution being common. Furans are also useful synthetic