Synthesis of Some New 3, 5-Bis (substituted) Pyrazoles and Isoxazoles Based on (N’1E, N’3E)- N’1, N’3-Bis (3, 4, 5-substitutedbenzlidene) Malonohydrazide under Solvothermal Conditions
Journal Title: International Journal of Biomedical Science (IJBS) - Year 2010, Vol 6, Issue 1
Abstract
Synthesis of pyrazole and isoxazole derivatives has been a subject of consistent interest because of the wide applications of such heterocycles in pharmaceutical as well as agrochemical industry. Numerous compounds containing pyrazole and isoxazole moieties have been shown to exhibit antihyperglycemic, analgesic, anti-inflammatory, antipyretic antibacterial, antiviral, antitumor, antifungal and antidepressant activities (1-13). They are also useful intermediate for many industrial products (14, 15). A lot of synthetic methods for pyrazoles and isoxazoles have been developed. However these methods are usually carried out in organic solvents and many of them reactions require long reaction times, high temperatures, or inconvenient reaction condition for their execution and are often accompanied by tedious chromatographic techniques for purification of the desired products. Recently Rai et al have developed a simple method for the organic synthesis in the presence of asalen metal catalyst. The chemistry of solvothermal reactions involves two major factors namely, high temperature and pressure. “Solvothermal reactions can be defined as reaction in closed system, in the presence of solvent at a temperature higher than its boiling point. Consequently these reactions can be developed in supercritical or in sub critical conditions” (16). Some of the reactions, which proceed at slow rates under normal pressure, can be enhanced by increasing the pressure. This can be achieved by heating the reaction mixture under sealed condition. The development of solvothermal reaction is of interest because they offer the possibility of environmentally benign reaction conditions by reducing the burden of organic solvent disposal. Solvothermal process involves the heterogeneous chemical reaction, which occur at solid-liquid or solid-liquid-gas interfaces under high temperature and high pressure. Rai and Linganna successively used thiourea as thionating agent for (i) the conversion of 1,3,4-oxadiazole to1,3,4-thiadiazole under solvothermal condition (17) by heating in a sealed tube at 100°C. (ii) the conversion of esters to thioesters under solvothermal condition using More’s autoclave (18). Besides, Rai et al (19) successfully converted aldehyde semicarbazones to bishydrazones by thermolysis under pressure using ethanol as solvent in a sealed tube. These facts prompted us to apply this technology for the synthesis of 3,5-bis(substituted)pyrazoles and isoxazoles based on cyclocondensation of (N’1E, N’3E)- N’1, N’3-bis (3,4,5-substitutedbenzylidene)malonohydrazide with hydrazine hydrate and hydroxylamine hydrochloride via solvothermal mode (Figure 1).
Authors and Affiliations
Musad Ebraheem, Lokanatha Rai Kuriya , Byrappa Kullaiah
Keywords
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