Synthesis of 4-fluoroalkyl-substituted pyridazines from fluorinated diazodiketones |
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Authors: | Valerij A. Nikolaev Valerija M. Zakharova Lothar Hennig |
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Affiliation: | a Saint-Petersburg State University, Department of Organic Chemistry, University pr. 26, 198504 Saint-Petersburg, Russia b Universität Leipzig, Institut für Organische Chemie, Johannisallee 29, 04103 Leipzig, Germany |
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Abstract: | Two approaches are reported for the preparation of 3,4,6-trisubstituted pyridazines from fluoroalkyl-containing diazodiketones: the sequence of Wittig/Staudinger/diaza-Wittig and Staudinger/Wittig/diaza-Wittig reactions. The implementation of the Wittig reaction at the first stage gives rise to considerably higher yields of the targeted pyridazines than through initial phosphazines. In both approaches the final stages of the synthesis (the formation of vinylphosphazines and the subsequent diaza-Wittig reaction) occur as a tandem process. RF-activated carbonyls are much more reactive in Wittig olefination of diazodicarbonyl and 1,3-dioxophosphazine molecules, than non-fluorinated acyl and aroyl carbonyl groups (RFCO ? COAlk, COAr), and as a result non-fluorinated diazodiketones and their phosphazines do not produce pyridazines under the same conditions. |
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Keywords: | 2-Diazo-1,3-diketones Fluoroalkyl-containing vinyldiazoketones Phosphazines Diaza-Wittig reaction Pyridazines |
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