One pot synthesis of 6,12-dihydro-1,3,7,9-tetramethyl-5H, 11H-dipyrido[1,2-a:1′,2′-d]pyrazine-2,8-dione by hilbert-johnson reaction of 2-chloromethyl-3,5-dimethyl-4-methoxypyridine

✍ Scribed by Marina Orešić; Aleksandar Danilovski; Miljenko Dumić; Nada Košutić-Hulita

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2001
• Tongue: English
• Weight: 100 KB
• Volume: 38
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570380342

✦ Synopsis

Abstract

By heating 2‐chloromethyl‐3,‐5‐dimethyl‐4‐methoxypyridine (1) either neat or in solution methoxy group cleavage was achieved, followed by dimerisation to poorly soluble 6,12‐dihydro‐1,3,7,9‐tetramethyl‐5__H__,11__H__‐dipyrido[1,2‐a:1′,2′‐d]pyrazine‐2,8‐dione (3) in almost quantitative yield with methyl chloride evolution. To our knowledge this is the first example of such Hilbert‐Johnson preparation of dipyridopyrazine‐diones. Recrystallization of 3 from the hydrochloric acid yielded 6,12‐dihydro‐2,8‐dihydroxy‐1,3,7,9‐tetramethyl‐dipyrido[1,2‐a:1′,2′‐d]pyrazinediylium dichloride (4), neutralization of which gave back the pyrazine‐2,8‐dione 3. The molecular structures of both compounds 3 and 4 have been unambiguously confirmed by single crystal X‐ray structure analysis.