Pyridine Syntheses. II. Condensation Routes Toward Streptonigrin Ring C

✍ Scribed by J. Michael Robinson; Masood Ahmed; Nicky J. Alaniz; Timothy R. Boyles; Chris D. Brasher; Kimberly A. Floyd; Preston L. Holland; Laura D. Maruffo; Terry L. Mcmahan; Stan Middleton; Kevin D. O'Hara; Marcia J. Pack; Brandon D. Reynolds; Romelia R. Rodriquez; Dennis E. Sawyer; Elena Sharp; Sharai L. Simpson; Clint L. Vanlandingham; Rebecca S. Velasquez; Brian M. Welch; C. David Wright

• Publisher: Journal of Heterocyclic Chemistry
• Year: 1998
• Tongue: English
• Weight: 365 KB
• Volume: 35
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570350113

✦ Synopsis

Alternative complimentary syntheses of penta-substituted pyridine rings with full regiochemical control of substituents were studied as a method for the synthesis of Streptonigrin (1). Various (\alpha)-substituted acetophenones 2 were reacted with enones 3 in acetic acid/ammonium acetate and air to afford penta-substituted pyridines 4. (\alpha)-Substituents that could provide a source of exocyclic nitrogen at position 3 of these Steptonigrin ring-C models proved to be the limiting factor. However, an inverse " (3+2+1) " cyclocondensation of (\alpha)-cyanochalcone (5 \mathrm{c}) with 2-furyl ethyl ketone (6b) afforded the desired model 6-(2-furyl)-5-methyl2,4-diphenyl-3-pyridinecarbonitrile (\mathbf{( 4 g}) ) in (75 %) yield.