ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis of pyranopyrazoles, benzopyrans, amino-2-chromenes and dihydropyrano[c]chromenes using ionic liquid with dual Brønsted acidic and Lewis basic sites

Davood Habibi, Atefeh Shamsian, and Davood Nematollahi

Department of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838683 Iran

E-mail: davood.habibi@gmail.com

Abstract: An efficient ionic liquid with both Brønsted acidic and Lewis basic sites, namely 1,4-dimethyl-1- (4-sulphobutyl)piperazinium hydrogen sulphate (IL1), was synthesised and characterised. IL1 is a “green”, homogeneous and reusable catalyst for: i) the synthesis of pyranopyrazoles (Va-Vj) and benzopyrans (VIa-VIj and VIIa-VIIf) at ambient temperature under solvent-free conditions and ii) the synthesis of amino-2-chromenes (VIIIa-VIIIi and IXa-IXi) and dihyropyrano[c]chromenes (Xa- Xi) at 80◦C under solvent-free conditions. The reactions were rapid with excellent product yields. In addition, the double Brønsted acid, 1,4-dimethyl-1,4-bis(4-sulphobutyl)piperazinium hydrogen sulphate (IL2), was prepared to evaluate the cooperation efficiency of their Brønsted acidic and Lewis basic sites as compared with the double Brønsted acidic sites in IL1

Keywords: ionic liquid – synthesis – pyranopyrazoles – benzopyrans – amino-2-chromenes – dihydropyrano[ c]chromenes

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0066

Chemical Papers 69 (4) 586–595 (2015)