Multicomponent synthesis of allomaltol containing 2-aminooxazoles and acid-catalyzed recyclization into substituted furo[3,2-b]pyrans

For the first time we elaborated the efficient one-step approach for the preparation of substituted 2-aminooxazoles containing 3-hydroxy-4H-pyran-4-one moiety. The considered method includes multicomponent condensation of allomaltol derivatives with alpha-ketoaldehydes and cyanamide. The distinctive feature of the proposed protocol is formation of 2-aminooxazole core in contrast to related previously described approach leading to urea containing condensed furans. The advantages of this synthesis include readily available starting materials, mild reaction conditions, atom economy and easy workup procedure, which can avoid chromatographic purification. Wherein, it was found that obtained 2-aminooxazoles undergo previously unknown acid-catalyzed recyclization into N-(2-aryl-5-methyl-7-oxo-7H-furo[3,2-b]pyran-3-yl)acetamides. The structures of one 2-aminooxazole derivative and one substituted furo[3,2-b]pyran were confirmed by X-ray diffraction. (C) 2022 Elsevier Ltd. All rights reserved.