The preparation of pharmaceutically active 2-amino-4H-chromene derivatives has been achieved using a nano powder of natural clinoptilolite (CP) zeolite. A wide range of these worthy structures having diverse substituents on the 4H-chromene ring were efficiently synthesized via the reaction of an aromatic aldehyde and variety of enolizable C–H activated acidic compounds. Nano sized natural clinoptilolite
DBU: a highly efficient catalyst for one-pot synthesis of substituted 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2-amino-4H-benzo[h]chromenes and 2-amino-4H benzo[g]chromenes in aqueous medium
作者:Jitender M. Khurana、Bhaskara Nand、Pooja Saluja
DOI:10.1016/j.tet.2010.05.082
日期:2010.7
We have reported DBU catalyzedone-potsynthesis of 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2-amino-4H-benzo[h]chromenes and 2-amino-4H-benzo[g]chromenes from aldehydes, active methylene compounds malononitrile/ethyl cyanocacetate, and 4-hydroxycoumarin/4-hydroxy-6-methylpyrone/1-naphthol/2-hydroxynaphthalene-1,4-dione in water under reflux. The attractive features of this process
我们已经报道了DBU催化一锅合成3,4-二氢吡喃并[3,2- c ]苯并二氢吡喃并[4,3- b ]吡喃,2-氨基-4 H-苯并[ h ]苯并二胺回流下得自醛,活性亚甲基化合物丙二腈/氰基乙酸乙酯和4-羟基香豆素/ 4-羟基-6-甲基吡喃酮/ 1-萘酚/ 2-羟基萘-1,4-二酮的-4 H-苯并[ g ]色酮。该方法的吸引人的特征是温和的反应条件,反应介质的可重复使用性,较短的反应时间,易于分离的产物以及优异的产率。
“One-pot” access to dihydrofurans via tandem oxidative difunctionalization and ring contraction of aminopyrans
An operationally simple and efficient protocol for the construction of dihydrofuran derivatives has been accomplished via a sequential addition of N-chlorosuccinimide and a base to 2-amino-4H-pyran derivatives in alcohol medium. The one-pot protocol proceeding via tandem oxidative difunctionalization and ring contraction provides an entirely new strategy for the construction of the dihydrofuran skeleton.
Glycerol is applied as a green, biodegradable and reusable promoting medium for one-pot three component synthesis of 4H-pyrans under catalyst-free conditions. A broad range of substrates including aromatic and heteroaromatic aldehydes, isatine derivatives, acenaphthenequinone and ninehydrine are condensed with carbonyl compounds possessing a reactive α-methylene group and alkylmalonates. All reactions are completed in short times, and the products are obtained in good to excellent yields. The reaction medium could be recycled and reused several times without any loss of efficiency.
the preparation of a series of 4 H -benzo[b]pyran derivatives. SBPPSP was used as a recyclable heterogeneous solid base catalyst for the synthesis of 3,4-dihydropyrano[c]chromenes, 2-amino-4H -pyrans, 1,4-dihydropyrano[2,3-c]pyrazoles, and 2-amino-4H -benzo[e]-chromenes via the condensation reaction of dimedone, ethyl acetoacetate, 3-methyl-1-phenyl-1 H -pyrazol-5(4 H )-one, and α-naphthol, respectively