efficient and selective approach for the synthesis of functionalized pyranocoumarins has been developed via a gold(III)-catalyzed tandem conjugate addition/annulation reaction of 4-hydroxycoumarins with α,β-unsaturatedketones.
Efficient synthesis of pyrano[3,2-c]coumarins has been achieved via copper(II) triflate catalyzed tandem reaction of 4-hydroxycoumarin with α,β-unsaturated carbonyl compounds in high yields. The catalytic reaction proceeded very smoothly under solvent-free conditions and showed high regioselectivity. The synthetic potential of this methodology was explored to 4-hydroxy-6-methyl-2-pyrone successfully
吡喃并[3,2- c ]香豆素的有效合成已通过三氟甲磺酸铜(II)催化4-羟基香豆素与α,β-不饱和羰基化合物的串联反应以高收率实现。在无溶剂条件下,催化反应进行得非常顺利,并具有很高的区域选择性。该方法的合成潜力已成功地探索为4-羟基-6-甲基-2-吡喃酮。