%0 Journal Article
%T Solvent-Free Green and Efficient One-Pot Synthesis of Dihydropyrano[3,2-c]chromene Derivatives
%A Shubha Jain
%A Deepika Rajguru
%A Balwant S. Keshwal
%A Aman D. Acharya
%J ISRN Organic Chemistry
%D 2013
%R 10.1155/2013/185120
%X A rapid, clean, and highly efficient method for synthesis of dihydropyrano[3,2-c]chromene derivatives by one-pot, three-component condensation of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin using DABCO as catalyst in solvent-free neat conditions is described. The present method has the advantages of mild reaction conditions, short reaction times, easy isolation of products, and excellent yields. 1. Introduction Multicomponent reactions (MCRs) are very important in organic synthesis due to the formation of carbon-carbon and carbon-hetero atom bonds in one pot [1¨C3]. Simple procedures, high bond forming efficiency, time and energy saving, and low expenditures are among the advantages of these reactions [4]. Over the past several years, chemists have been aware of the environmental implications of their chemistry. Nowadays, they are trying to develop new synthetic methods, reaction conditions, and uses of chemicals that reduce the risks to humans and the environment. Organic solvents are high on the list of hazardous chemicals because they are used in large amounts and are usually volatile liquids. Therefore, in recent years, solventless organic reactions have attracted great interest. They have many advantages such as high efficiency and selectivity, operational simplicity, low costs, mild reaction conditions, and reduced pollution [5¨C7]. Pyrano[3,2-c]chromenes are a class of important heterocycles with a wide range of biological properties [8] such as spasmolytic, diuretic, anticoagulant, anticancer, and antianaphylactic activity [9]. Moreover, they have been used as cognitive enhancers, for the treatment of neurodegenerative diseases, including Alzheimer¡¯s disease, Parkinson¡¯s disease, Huntington¡¯s disease, amyotrophic lateral sclerosis, AIDS associated dementia, and Down¡¯s syndrome as well as for the treatment of schizophrenia and myoclonus [10]. In addition, aminochromene derivatives exhibit a wide spectrum of biological activities including antihypertensive and anti-ischemic behavior [11¨C13]. Several methods have been reported for the synthesis of pyrano[3,2-c]chromene derivatives. 2-Amino-4-aryl-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitriles have previously been prepared from aromatic aldehydes, malononitrile, and 4-hydroxycoumarin in the presence of organic bases like piperidine or pyridine in an organic solvent, that is, ethanol and pyridine [14]. They have also been prepared in the presence of diammonium hydrogen phosphate (DAHP), (S)-proline [15], K2CO3 under microwave irradiation [16], TBAB [17], MgO [18], H6P2W18O62 18H2O [19],
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2013/185120/