Catalytic application of a novel oxyammonium based nano ionic liquid at the preparation of pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyrans

Due to the presence of bulky and asymmetric ions within the structure of ionic liquids,compare with classical inorganic salts, they cannot form a crystalline structure andtherefore, melt at temperatures lower than 100 oC. At the present time, due to remarkable typical characteristics such as minor vapor pressure, large temperature window of molten state, excellent solvation properties, high chemical and thermal stability, lack of inflammability, wide electrochemical window, and respectable ion conductivity, ionic liquids emerged as an interdisciplinary area and found a critical place in various fields of science [1]. Fused 4H-pyran derivatives such as pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyran derivatives widely occur in various molecules exhibiting a broad range of pharmacological applications such as antiviral, anticonvulsant andantimicrobial, antileishmanial, antiproliferative, anticancer, anti-HIV, antituberculosis and anti-fungal agents. Therefore, it is expected that the preparation of theseversatile compounds being exposed to chemists [2-3]. Herein we wish to present a mild and clean procedure for synthesis of pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyrans in the presence a suitable ionic liquid. The scope and limitations of described methodology will be discussed.