Convenient Synthesis of a New Series of 3-Triazolonyl Iminocoumarins

3-Cyano-7-diethylamino-N-ethoxycarbonyl-iminocoumarin reacted with different hydrazines as N-nucleophiles to afford, in one step, a new series of 2-N-substituted 3-triazolonyl-iminocoumarins in good yields. In two cases, N-unsubstituted derivatives were also obtained. The structures of all the products obtained were confirmed by infrared, ¹H NMR, ¹³C NMR, and elemental analysis. The optical properties of three of these compounds in dichloromethane and ethanol were reported.     

Three-component one-pot synthesis of N-arylsulfonyl-2-iminocoumarins

A one-pot, synthesis of N-arylsulfonyl-2-iminocoumarins is developed at ambient temperature by the reaction of 2-hydroxybenzaldehydes, arylacetonitriles, and aryl sulfonyl chlorides using DABCO as a base in a bio-mass-derived green solvent 2-MethylTHF. A simple telescoped process in which 2H-chromen-2-imines are formed in situ by the condensation of 2-hydroxybenzaldehyde and arylacetonitriles. The formed imines are further reacted with arylsulfonyl chlorides in a one-pot approach to obtain the target compounds. This protocol provides access to 3-aryl-N-arylsulfonyl-2-iminocoumarins in a practical and environmentally benign way avoiding cumbersome steps of intermediate syntheses and purifications.     

A room temperature one-pot Knoevenagel-Chan-Evans-Lam coupling reaction for synthesis of N-aryl-2-Iminocoumarins in bio-mass-derived green solvent 2-methylTHF

An efficient approach for the synthesis of biologically interesting N-aryl-2-iminocoumarins by a copper-catalyzed one-pot procedure has been developed by the reaction of 2-hydroxybenzaldehydes, malononitrile and arylboronic acids using triethylamine as a base in a bio-mass-derived green solvent 2-MethylTHF at room temperature. This protocol allows access to several N-aryl-2-iminocoumarins in high yields in a relatively short period of time under mild reaction conditions. The procedure operates by a simple telescoped process wherein 2-imino-2H-chromene-3-carbonitriles are formed in situ by the reaction of 2-hydroxybenzaldehyde, malononitrile, and TEA. Further a subsequent one-pot reaction of imine with the arylboronic afforded the target compounds. To understand the reaction mechanism, MALDI-ESI studies were performed, which showed the in situ generated iminocoumarins to be in ligation cooper to form a copper-iminocoumarin complex thus facilitating the smooth formation of N-aryl-2-iminocoumarins in the reaction. Overall, this protocol is practically valuable, useful in organic synthesis, shows good functional group tolerance and provides access to a diverse array of N-aryl-2-iminocoumarins derivatives.