Mild and highly efficient deacetylation of acetamido and acetoxy coumarins: A convenient and expeditious synthesis of substituted 3-aminocoumarins

A convenient protocol for efficient and cost-effective method for synthesis of substituted 3-aminocoumarins has been developed. The synthetic route involves expeditious and fast quantitative deacetylation of readily available acetamido derivative under anhydrous acidic conditions, employing thionyl chloride in methanol, without formation of undesired substituted 3-hydroxycoumarins. The method is suitable for derivatives bearing electron-donating as well as electron-withdrawing groups at position 7 of the coumarin scaffold. Under these conditions, a series of acetoxy substituted 3-dialkylaminocoumarins has been also successfully deacetylated to afford easily isolable corresponding hydroxy derivatives in high yields.