Addition von Acetylendicarbonsäuredimethylester an Imidazole; Aminierung der Addukte: neue Synthesen von 3-(2-Imidazolyl)-2-pyridon-4,5-dicarbonsäureamiden und Pyrido[1,2-a]pyrazinen
✍ Scribed by Franz Troxler; Hans Peter Weber; André Jaunin; Hans-Rudolf Loosli
- Publisher
- John Wiley and Sons
- Year
- 1974
- Tongue
- German
- Weight
- 763 KB
- Volume
- 57
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The reaction between dimethyl acetylene dicarboxylate and 2‐amino‐1‐methylimidazole affords dimethyl 2‐amino‐1‐methyl‐1,3‐diazepine‐5,6‐dicarboxylate in low yield. This 1:1 – adduct was formed by addition of the acetylenic compound to the enamine double bond of the imidazole ring followed by ring enlargement. On the other hand, 2:1 – adducts to the imine bond are isolated in moderate yield when dimethyl acetylene dicarboxylate is treated with either 1‐methyl‐2‐methylmercapto‐imidazole or 1‐methyl‐2‐methylmercapto‐imidazoline. These adducts behave differently on heating with ethylamine: the adduct of the imidazole series cyclizes to the pyridone 15 with concomittant loss of one carboxamide group whereas that of the imidazoline series forms a pyrido[1,2‐a]pyrazine derivative 20, both in high yield. The possible reaction mechanisms are discussed. ^13^C–NMR.‐spectroscopy and X‐ray analysis were used in the determination of several structures.