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Abstract
A specific tautomer of 1,3-thiazinone and 1,3-oxazinone derivatives were prepared in a one step procedure from condensation of chlorocarbonyl ketenes (CCKs) such as (chlorocarbonyl)phenyl ketene and (chlorocarbonyl)benzyl ketene with thiobenzamide, thioacetamide , cinnamide , benzamide, 2-phenylacetamide and acetamide . This method provides an easy route to prepare 2,5-disubstituted 4-hydroxy-1,3-thiaizin-6-ones and 2, 5-disubstituted 4-hydroxy 1, 3-oxazin-6ones in good to excellent yields in a short experimental time.
Highlights
The study of α-oxoketenes and their reactions, were investigated because these compounds contain two active functional groups. α-Oxoketenes are highly reactive molecules which usually cannot be isolated under ordinary reaction conditions, several examples have been reported that the ketene bands of the α-oxoketenes have been detected at low temperature by infrared spectroscopy technique.[1,2,3,4]some of these ketenes can be stabilized both sterically and electronically
We have recently reported the reaction ofphenyl ketene with 1,3-diketones as 1,3-dinucleophiles to produce 2-pyrone derivatives.[10]
The cycloaddition reaction of ketenes with dinucleophiles such as hydrazones,[11] oximes,[12] imidazoles and substituted arylthioamides were reported in the literature.[13,14,15]
Summary
The study of α-oxoketenes (acyl ketenes) and their reactions, were investigated because these compounds contain two active functional groups. α-Oxoketenes are highly reactive molecules which usually cannot be isolated under ordinary reaction conditions, several examples have been reported that the ketene bands of the α-oxoketenes have been detected at low temperature by infrared spectroscopy technique.[1,2,3,4]some of these ketenes can be stabilized both sterically and electronically. The attempted reaction of (chlorocarbonyl)phenyl ketene and (chlorocarbonyl)benzyl ketene with several N-unsubstituted amides and thioamides at ambient temperature or even in boiling solvent such as dry THF have been mostly unsuccessful. In the present protocol as exhibited in scheme 2 the cycloaddition of chlorocarbonyl ketenes 1a-b with N-unsubstituted thioamides 2a-b only afforded 4-hydroxy-2,5-disubstituted-1,3thiazin-6-ones (II) as a specific tautomer of 1,3-thiazinone, in boiling dry toluene as a solvent.
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