Beilstein J. Org. Chem.2020,16, 2108–2118, doi:10.3762/bjoc.16.178
058, India Department of Inorganic and Physical Chemistry, Indian Institute of Science (IISc), Bangalore-560 012, India 10.3762/bjoc.16.178 Abstract The reactivity of α-azidochalcones has been explored for the preparation of highly substituted oxazoles via a 2H-azirine intermediate. The
substituted α-azidochalcones with potassium thiocyanate. Thiocyanate is a known ambident reagent with two potential sites of attack, enabling the selective and efficient construction of C–C and C–N bonds towards biologically important heterocyclic skeletons [62][63][64].
Results and Discussion
Previously, we
have reported the TMSOTf-catalyzed synthesis of highly substituted imidazoles from α-azidochalcones under mild conditions [65]. As a sequel, the synthesis of oxazoles with an arylimino substituent has been accomplished in this work. The biologically important arylimino group [66][67][68][69] integrated
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Graphical Abstract
Figure 1:
Examples of biologically active oxazole and aminothiazole scaffolds.
Beilstein J. Org. Chem.2015,11, 2021–2028, doi:10.3762/bjoc.11.219
Abstract The reaction of α-azidochalcones with carboxylic acids has been investigated resulting in the formation of α-amido-1,3-diketones under microwave irradiation via in situ formation of 2H-azirine intermediates. An interesting reaction is described wherein, with trifluoroacetic acid at lower
temperature, it affords highly substituted 2-(trifluoromethyl)oxazoles. These flexible transformations proceed under solvent free conditions in good to excellent yields without any catalyst.
Keywords: α-amido-1,3-diketones; α-azidochalcones; carboxylic acids; 2H-azirines; oxazoles; Introduction
α
character of the C(2)–N double bond is higher than a normal imine (Figure 1) [10][26][27]. The generated substituted aziridines A2 may undergo further ring opening reactions. The α-azidochalcones 1 are suitable as precursors for the generation of 2H-azirines A1, though several other methods are available