The formation of acylimino-derivatives of indoles and pyrroles by reactions with nitrilium salts

✍ Scribed by Stephen C. Eyley; Robert G. Giles; Harry Heaney

• Book ID: 104228928
• Publisher: Elsevier Science
• Year: 1985
• Tongue: French
• Weight: 212 KB
• Volume: 26
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)98776-8

✦ Synopsis

Sumnary: N-Methylnitrilium fluoroborates are prepared rapidly by warming trimethyloxonium fluoroborat?? with a slight excess of the nitrile, subsequent addition of indoles and pyrroles at low temperatures (-50" to -20") gives iminium salts (and hence ketones) in high yields. Although Z-acetylpyrrole' and 1,3-diacetyl-' or 3-acetyl-3 indole can be prepared by the reaction of acetic anhydride with pyrrole and indole respectively, high yields of C-acylated products can only be obtained by indirect methods.4 Thus, the well known reactions of pyrryl-5 and indolyl-6 magnesium chlorides with acyl haliaes have been improved by recent methodology in which E-pyridylthiol esters have been shown to give Z-acylpyrroles in yields of 80 to 95%.' The reactions of nitriles with both pyrroles and indoles in the presence of hydrogen chloride also result, after hydrolytic work-up, in the formation of acceptable yields of C-acylated products.8'g We now report some of our results of reactions of nitrilium salts with pyrrole and indole and some of their derivatives.