New benzothiazine heterocycles have been formed from thiourea derivatives by using different gold catalysts. The catalyst and the conditions were optimised towards the selective synthesis of six‐membered benzothiazine heterocycles, characterised by X‐ray diffraction. Interestingly, these organic compounds evolved under gold catalysis in basic medium to achieve the formation of amino thioquinolines through an unprecedented aromatisation process of the heterocycle. The reaction was also carried out stoichiometrically by reaction with gold complexes to afford thioquinolines coordinated to the gold fragment. Benzothiazine, amino thioquinoline heterocycles and gold‐derived species have a great potential for biological applications.
This work represents the first example of a gold-catalyzed
formation
of 1,3-thiazine/1,3-thiazinane by means of a catalytic approach and
further uncommon isolation of the two tautomers. The developed protocol
gives rise to a broad scope of 1,3-thiazine derivatives with excellent
yields in short reaction times. Interestingly, different isomers could
be obtained depending on the state of the compound, and in the crystal
state the 1,3-thiazinane isomer is obtained, while in solution the
1,3-thiazine is the unique isomer. This work represents an interesting
approach for the synthesis of potential biologically relevant molecules
and a crucial precedent in tautomerism isolation and characterization.
The reaction of propargylamines with isothiocyanates results in the selective formation of iminothiazolidines, aminothiazolines or mixed thiazolidine-thiourea compounds under mild conditions. It has been observed that secondary propargylamines lead to...
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