Aims and Objective: 1-Alkynes are the important precursors for the CuAAC click chemistry. The hybrid of 1,2,3-triazole ring to the chromene ring and sugar moiety could bring some remarkable biological properties. Propargyl derivatives are usually used in the click chemistry. This article reported the synthesis of 2-amino-4-aryl-7-propargyloxy-4-aryl-4H-chromene-3-carbonitriles using propargyl bromide as alkylation agent. The use of potassium carbonate and sodium hydride as bases in the conversion of 2-amino-4-aryl-7-hydroxy-4-aryl-4H-chromene-3-carbonitriles into corresponding propargyl ethers in Williamson’s ether synthesis.
Materials and Method: The use of CTAB for synthesis of benzylidene malononitriles and anhydrous potassium carbonate as a catalyst in absolute ethanol in the synthesis of 2-amino-7-hydroxy-4H-chromene-3-carbonitriles. This is the efficient and simple synthetic methods. Propargyl ether compounds of these 4H-chromene-3-carbonitriles were obtained from the alkylation reaction by propargyl bromide. Two procedures were applied: K2CO3 as a base in acetone solvent (Procedure A) and NaH as a base in DMF solvent (Procedure B). The single-crystal X-ray structure of propargyl ether 5e has been study.
Results: The use of K2CO3 and NaH as bases in the Williamson’s ether synthesis from 2-amino-7-hydroxy-4H-chromene-3-carbonitriles showed that Procedure B was better route and gave the ethers in the higher yields. 2-Amino-4-aryl-7-propargyloxy-4-aryl-4H-chromene-3-carbonitriles were obtained from corresponding 7-hydroxy-4H-chromene-3-carbonitriles. Yields of ethers 5a-i were 70−89% and 80−96%, respectively in depending on the used procedures.
Conclusion: The described methods are the simple, clean and environmentally friendly alternatives for the preparation of 2-amino-4-aryl-7-hydroxy-4H-chromene-3-carbonitriles. The conditions for the transformation of these compounds into propargyl ethers were dried DMF as a solvent, NaH as a base and the reaction time of 2 h at the room temperature. A series of 2-amino-4-aryl-7-hydroxy-4-aryl-4H-chromene-3-carbonitriles were obtained based on investigated reaction condition.