γ-Alumina as a recyclable catalyst for the four-component synthesis of 6-amino-4-alkyl/aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles in aqueous medium

An Efficient and Green Protocol for the Synthesis of Dihydropyrano [2,3-C] Pyrazoles in Aqueous Medium Using Thiamine Hydrochloride as a Catalyst

“…The crude product was purified by crystallization from ethanol to afford the desired product. The products (5a-m) were confirmed by comparing the physical and spectral data with those of the reported compounds 12,17 . …”

“…[11][12][13][14][15] Although, the reported methods are effective, they have limited applicability by the use of toxic catalysts, long reaction times, low yields of products and the use of toxic organic solvents. Recently, some environment-compatible catalysts such as L-proline, 16 γ-alumina, 17 per-6-amino-β-cyclodextrin 18 and imidazole 19 were also used to achieve this transformation, but mostly at elevated temperature. Inspite of many reported methods for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives, the development of a new synthetic strategy using easily accessible catalyst and mild reaction condition still demand a lot of attention.…”

Synthesis of Pyranopyrazoles Using Magnetically Recyclable Heterogeneous Iron Oxide‐silica Core‐shell Nanocatalyst

“…1 They exhibit appreciable biological activities such as analgesic, anti-tumor, anti-cancer, and anti-inflammatory properties, and also serve as potential inhibitors of human Chk1 kinase. 1 There have been reported some catalytic system, homogeneous and heterogeneous, for the preparation of pyrano [2,3-c]pyrazol-6-ones via multicomponent reactions, such as g-alumina, 1 Mg/Al hydrotalcite, ported methods suffer high reaction temperature, poor catalyst recoverability, and in some cases tedious procedure for catalyst recyclability and low reusability. Magnetic-assisted in recyclability of the catalyst can efficiently overcome the difficulty of catalyst recoverability.…”

A Rapid, Convient and Diversified-Multicomponent Synthesis and Characterization of Pyrano[2,3-<i>b</i>]Indoles

“…Kappusami and co-workers have developed solvent-free multicomponent synthesis of pyranopyrazoles using per-6-amino-β-cyclodextrin as a catalyst 17 . More recently Myrboh et al reported the synthesis of pyranopyrazoles using L-proline and γ-alumina as catalyst 18 . As a part of ongoing program on the development of novel methods in organic synthesis, we report herein a simple, rapid and high yielding one pot three component reaction protocol for the synthesis of pyrano [2,3-b]indoles derivatives employing environmentally friendly wide range of basic catalyst [19][20][21] .…”