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Abstract
Investigation of the reaction of (chlorocarbonyl)phenyl ketene with 1,3-dinucleophiles such as Schiff bases which were prepared from acetophenone and aryl amides led to the discovery of new synthetic pathways towards 4-hydroxy-3,6-disubstituted-2(1H)–pyridinones and 2,5-diaryl6-oxo-5-phenyl-6H-1,3-oxazin-3-ium-4-olates respectively. These reactions provide a new route to produce 2-pyridinones and cross - conjugated heterocyclic mesomeric betaines in good to excellent yields in a short reaction time.
Highlights
(Chlorocarbonyl)phenyl ketene 2, first described by Nakanishi, represents a highly reactive equivalent of phenylmalonic acid.[1]
Due to our interest in preparing structures containing the 2(lH)-pyridinone skeleton[17] as exhibited in Scheme 1 the 4-hydroxy-3,6-disubstituted-2(1H)–pyridinone derivatives were prepared in a one step procedure from readily availablephenyl ketene and Schiff bases such as N-phenyl-N-[(E)-1-phenylethylidene]amine, N-[(E)-1-(4-methylphenyl) ethylidene]-N-phenylamine, N-benzyl–N-[-[(E)-1-phenylethylidene]amine, N- [(E)-1-(4-chlorophenyl)ethylidene)](phenyl)methaneamine and N- [(E)-1-(4-chlorophenyl)ethylidene)](4-methylphenyl)methaneamine
We have reported the synthesis of 6-chloro-2,3,5-triphenyl-1,3-oxazine-4-one from the reaction of ketene 2 with N-benzilideneaniline (Schiff base of benzaldehyde) which were refluxed under a nitrogen stream
Summary
(Chlorocarbonyl)phenyl ketene 2, first described by Nakanishi, represents a highly reactive equivalent of phenylmalonic acid.[1]. The synthesis of 6-chloro-2,3,5-triphenyl-1,3-oxazine-4-one from the reaction of ketene 2 with N-benzylideneaniline (Schiff base of benzaldehyde) as a [4+2] cycloaddition product has been reported.[11] In continuing our previous work on the reaction of chlorocarbonyl ketenes (CCKs) with dinucleophiles,[12,13,14,15,16] we wish to describe the condensation of (chlorocarbonyl)phenyl ketene with 1,3-dinucleophiles such as Schiff bases prepared from acetophenone and N-substituted benzamides to afford 4-hydroxy-2-(1H)-pyridinone and mesoionic 1,3-oxazinium olate derivatives respectively.
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