Peculiarity of methoxy group-substituted phenylhydrazones in Fischer indole synthesis |
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Authors: | Murakami Yasuoki |
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Institution: | Faculty of Pharmacy, Chiba Institute of Science, Shiomi-cho 15-8, Choshi, Chiba 288-0025, Japan. ymurakami@cis.ac.jp |
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Abstract: | We found that the Fischer indole synthesis of ethyl pyruvate 2-methoxyphenylhydrazone (5) with HCl/EtOH gave an abnormal product, ethyl 6-chloroindole-2-carboxylate (7), as the main product, with a smaller amount of ethyl 7-methoxyindole-2-carboxylate (6) as the normal product. This abnormal reaction was the result of a cyclization on the side with the substituent (methoxy group) of a benzene ring on phenylhydrazone, which was not previously observed. In this initial investigation, we focused on 1) the application of the above-mentioned abnormal Fischer indole synthesis, 2) the details of this reaction of phenylhydrazone with other kinds of substituents, 3) the mechanism of the first step of the Fischer indole synthesis, 4) the abnormal reaction in methoxydiphenylhydrazones, and 5) a synthetic device to avoid an abnormal reaction. The results of these studies are summarized herein. |
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Keywords: | Fischer indole synthesis methoxy group abnormal reaction phenylhydrazone reaction mechanism natural product |
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