Osyanin VA, Osipov DV, Semenova IA, Korzhenko KS, Lukashenko AV, Demidov OP, Klimochkin YN. Eco-friendly synthesis of fused pyrano[2,3-
b]pyrans
via ammonium acetate-mediated formal oxa-[3 + 3]cycloaddition of 4
H-chromene-3-carbaldehydes and cyclic 1,3-dicarbonyl compounds.
RSC Adv 2020;
10:34344-34354. [PMID:
35514419 PMCID:
PMC9056786 DOI:
10.1039/d0ra06450e]
[Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 08/26/2020] [Indexed: 11/21/2022] Open
Abstract
Various substituted polycyclic pyrano[2,3-b]pyrans were synthesized via the condensation of 4H-chromene-3-carbaldehydes and their areno-condensed analogues with hetero- and carbocyclic 1,3-dicarbonyl compounds in acetic acid. Ammonium acetate was used as a green catalyst for the reaction. The process also involves the subsequent Knoevenagel condensation and 6π-electrocyclization of the 1-oxatriene intermediates formed. Fused pyridines were isolated as the products of the conjugated addition of ammonia to 1-oxatriene intermediates while using carbocyclic 1,3-dicarbonyl compounds and increasing the reaction time, indicating the reversibility of the electrocyclization stage. The calculated values of the Gibbs free energies and reaction rate constants for the 1-oxatriene - 2H-pyran equilibrium also testified to the irreversibility of pyrano[2,3-b]pyran formation in the case of using of heterocyclic 1,3-dicarbonyl compounds.
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