[TBP] 2 SO 4 ionic liquid catalyst for 4MCR of pyridazinoindazole, indazolophthalazine and pyrazolophthalazine derivativ
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ORIGINAL ARTICLE
[TBP]2SO4 ionic liquid catalyst for 4MCR of pyridazinoindazole, indazolophthalazine and pyrazolophthalazine derivatives Najmeh Amirmahani1,2 · Nosrat O. Mahmoodi3 · Mohammad Malakootian2 · Abbas Pardakhty4 Received: 22 August 2020 / Accepted: 23 October 2020 © Springer Nature Switzerland AG 2020
Abstract Tetrabutyl phosphonium sulfate ([TBP]2SO4), as novel room-temperature ionic liquid (RTIL), was synthesized by a simple cost-effective method, characterized by 1H, 13C, 31P NMR and FT-IR spectrophotometry. The newly prepared catalyst was used as an efficient catalyst in some four multicomponent reactions (4MCRs) e. g., to synthesis pyridazino[1,2-a]indazole, indazolo[2,1-b]phthalazine and pyrazolo[1,2-b]phthalazine. This green method has several advantages such as short reaction time, using simple methods to prepare catalysts and products, easy operation and high efficiency of products. In addition, the catalyst can be easily recovered and reused several times with reduced average activity. Graphic abstract
Keywords Tetrabutylphosphonium sulfate ( [TBP]2SO4) · Ionic liquids · Pyridazino[1,2-a]indazoles · Indazolo[2,1-b] phthalazines · Pyrazolo[1,2-b]phthalazines · Recyclable catalyst
Introduction * Nosrat O. Mahmoodi [email protected] Extended author information available on the last page of the article
The development of environmentally benign and economical methods for the synthesis of heterocyclic compounds is one of the fundamental goals in current organic synthesis and medicinal chemistry. Organic chemists in both academia
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and industry are always challenged to consider more green processes for the preparation of these types of molecules. In this regard, multicomponent reactions (MCRs) have played an important role [1–4]. In these methods, three or more reactants are combined in one-step to produce the desired products in one-pot. The MCRs offer exceptional advantages such as high yields compared to multistep synthesis, Reduce costs, time, energy, and waste generation, simpler procedures, and better selectivity [5–9]. Nitrogen-bearing heterocycles are widely found in nature, fine chemicals, agrochemicals, and pharmaceutically active compounds [10–12]. Among a large variety of N-containing heterocyclic compounds, great focus has been directed toward bridgehead nitrogen-containing heterocycles, especially those containing the hydrazine moiety as ‘fusion site’ because of their pharmacological properties and clinical applications [13, 14]. The pyridazino[1,2-a]indazole, 2H-indazolo[2,1-b]phthalazine-trione and pyrazolo[1,2-b] phthalazine derivatives are important classes of bridgehead N-containing compounds that the development of an efficient method for the preparation of these derivatives. It is an active research area. In this regard, several strategies have been developed for the synthesis of these types of compounds using different catalysts [14–22]. The reported methods exhibit various levels of advantages as well as disadvantages. Hence, the development
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