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α-Chlorierte Benzoylacetanilide 2a–c lassen sich ebenso wie β-chlorierte Brenztraubensaure- Derivate 2d–f mit Urethan in aprotischen Losungsmitteln zu 2-Oxo-4-carbonsaure Derivaten 3 cyclisieren. Die aus 3d, f uber die Saurechloride 4d, f dargestellten 4-Oxazolin-5-carboxamide 5g-j kuppeln mit N,N-Diethyl-p-phenylendiamin unter Ringoffnung und CO2 Abspaltung zu Azomethinfarbstoffen 7, wobei die Kupplung jetzt am ursprunglichen keto-C-Atom erfolgt. Umpolung of Coupling Position via Oxazoline Ring Closure α-Chlorinated benzoylacetanilides 2a–c as well as β-chlorinated pyruvic acid derivatives 2d–f can be cyclised with urethane in aprotic solvents to give 2-oxo-4-oxazoline-4-carboxylic acid derivatives 3. From 3d, f the acyl chlorides 4d, f are prepared which yield the 4-oxazoline-5- carboxamides 5g–j. These react with N,N-diethyl-p-phenylenediamine to azomethin dyestuffs 7 under ring opening and elimination of CO2. The coupling position is now shifted to the original keto C-atom. |
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