Abstract
The reactivity of α-azidochalcones has been explored for the preparation of highly substituted oxazoles via a 2H-azirine intermediate. The azidochalcones, when treated with potassium thiocyanate in the presence of potassium persulfate, lead to 2,4,5-trisubstituted oxazoles in good yields. Incidentally, 2-aminothiazoles are the products when ferric nitrate is employed instead of persulfate in the above reaction.
Highlights
Vinyl azide is one of the most versatile and potent building blocks explored in the synthesis of several heterocycles [1,2,3,4,5]
Some oxazoles play a significant role in biological properties such as TRPV1 antagonistical activity, antifungal, analgesic, antiinflammatory, antiproliferative, antileukemia, anticancer [2732] and enzyme inhibitory activities [33,34,35,36,37,38,39,40,41,42]. 2,4,5-Trisubstituted oxazoles are embedded in some natural products and pharmaceuticals with a broad range of biological activities prompting the development of efficient synthetic strategies for this useful heterocycle [43,44] (Figure 1)
The synthesis of oxazoles with an arylimino substituent has been accomplished in this work
Summary
Vinyl azide is one of the most versatile and potent building blocks explored in the synthesis of several heterocycles [1,2,3,4,5]. In continuation, employing α-azidochalcones as the precursor [9], we report the preparation of highly substituted oxazoles and thiazoles. It is shown that highly substituted oxazoles and aminothiazoles could be accessed directly from the reaction of substituted α-azidochalcones with potassium thiocyanate. The initial attempts employing iodine, CAN and ZnCl2 upon refluxing in acetonitrile for 6 hours did not yield any product (Table 1, entries 1, 2 and 4).
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