Substitution of a nitro group by formyl or a chlorine atom in 3,6-dinitro-4-chlorocoumarin under vilsmeier-haack conditions
✍ Scribed by T. Ya. Mozhaeva; O. L. Samsonova; V. L. Savel'ev
- Publisher
- Springer US
- Year
- 1988
- Tongue
- English
- Weight
- 38 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0009-3122
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✦ Synopsis
Heating 3,6-dinitro-4-chlorocoumarin (I) with excess phosphorus oxychloride in absolute DMF unexpectedly led to two novel products, viz. 3-formyl-4-chloro-6-nitrocoumarin (II, mp 172-174~ and3,4-dichloro-6-nitrocoumarin (III, mp 168~IZ0~ which could be separated chromatographically on silica gel. Similar results were obtainedwith 3,6-dinitro-4-hydroxycoumarin but 3-nitro-4-chlorocoumarin was practically unchanged under these conditions.
CI CI CI l II III
The structures of II and III were confirmed by elemental analysis, IR and PMR spectra, and by an independent synthesis via nitration of 3-formyl-4-chlorocoumarin and 3,4-dichlorocoumarin respectively.
To our knowledge the formation of III is the first example of ipso-substitution of a nitro group by formyl under Vilsmeier-Haack conditions.