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THREE-COMPONENT SYNTHESIS OF 2-ACYL-2,3-DIHYDRO-4H-THIOCHROMENO[4,3-b]FURAN-4-ONES AND THEIR REDUCTIVE REARRANGEMENT INTO 4H,5H-THIOCHROMENO[4,3-b]PYRAN-5-ONES

Максим Р. Демидов, Анастасия Н. Доброквашина, Дмитрий В. Осипов, Виталий А. Осянин, Юрий Н. Климочкин
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Abstract


Three-component condensation of in situ generated pyridinium acyl methylides with aromatic aldehydes and 4-hydroxythiocoumarin led to a series of 2-acyl-2,3-dihydro-4H-thiochromeno[4,3-b]furan-4-ones. The reaction proceeds diastereoselectively with the formation of trans-isomers and represents a cascade process involving the Knoevenagel condensation, carbo-Michael reaction, and intramolecular nucleophilic substitution. The subsequent redox rearrangement of 2-acyl-2,3-dihydro-4H-thiochromeno[4,3-b]furan-4-ones by the action of Zn and ZrCl4 grants access to 4H,5H-thiochromeno[4,3-b]pyran-5-ones.

 


Keywords


2-acyl-2,3-dihydro-4H-thiochromeno[4,3-b]furan-4-ones; carbenes; 4-hydroxythiocoumarin; pyridinium ylides; 4H,5H-thiochromeno[4,3-b]pyran-5-ones; zirconium(IV) chloride; zinc; zinc carbenoids; multicomponent reactions; reductive rearrangement.

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