An efficient and green approach for the synthesis of 2,4-dihydropyrano[2,3- c]pyrazole-3-carboxylates using Bi2O3/ZrO2 as a reusable catalyst

Sandeep V H S Bhaskaruni; Suresh Maddila; Werner E van Zyl; Sreekantha B Jonnalagadda

doi:10.1039/c8ra01994k

An efficient and green approach for the synthesis of 2,4-dihydropyrano[2,3- c]pyrazole-3-carboxylates using Bi₂O₃/ZrO₂ as a reusable catalyst

RSC Adv. 2018 May 3;8(29):16336-16343. doi: 10.1039/c8ra01994k. eCollection 2018 Apr 27.

Authors

Sandeep V H S Bhaskaruni¹, Suresh Maddila¹, Werner E van Zyl¹, Sreekantha B Jonnalagadda¹

Affiliation

¹ School of Chemistry & Physics, University of KwaZulu-Natal Westville Campus, Chiltern Hills Durban-4000 South Africa jonnalagaddas@ukzn.ac.za +27 31 2603091 +27 31 2607325.

Abstract

A novel material of bismuth loaded on zirconia (Bi₂O₃/ZrO₂) is synthesized by simple wet-impregnation method and characterized by several techniques (P-XRD, TEM, SEM, BET, etc.). Bi₂O₃/ZrO₂ proved to be a good catalyst for the four-component, one-pot reaction to produce a new series of 2,4-dihydropyrano[2,3-c]pyrazole-3-carboxylate derivatives with excellent yields (91 to 98%) under mild conditions at RT with short reaction times (≈20 min). The structures of the target molecules were confirmed by ¹H NMR, ¹³C NMR, ¹⁵N NMR, HRMS and FT-IR. The catalyst is easily separable and can be reused for six cycles without ostensible loss of activity. This method is inexpensive, atom-efficient and no chromatographic separations are needed.