Kobalt-katalysiert Cycloadditionen von Alkinen und Nitrilen zu Pyridinen: Ein neuer Zugang zu Pyridoxin (Vitamin B6)
✍ Scribed by Rudolf E. Geiger; Michel Lalonde; Hansijörg Stoller; Kuno Schleich
- Publisher
- John Wiley and Sons
- Year
- 1984
- Tongue
- German
- Weight
- 674 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Cobalt‐Catalyzed Cycloaddition of Alkynes and Nitriles to Pyridines: A New Route to Pyridoxine (Vitamin B~6~)
A new synthesis of pyridoxine hydrochloride (1) based on a Co‐catalyzed cycloaddition of MeCN with substituted di(2‐propynyl) ethers (3 and 16) is described. The reaction sequences following cycloaddition and leading to 1 involve as key steps the rearrangement f the pyridine‐N‐oxide 6 to the 3‐hydroxypyridine 7 with Ac~2~O and a modified Curtius rearrangement of the acid 19 and subsequent diazotation and hydrolysis to the same pyridoxine precursor 7, respectively. The intermediate 7 is transformed to 1 by well‐known procedures.