Four-Component Domino Strategy for the Combinatorial Synthesis of Novel 1,4-Dihydropyrano[2,3-c]pyrazol-6-amines

Abstract

An efficient one-pot four-component domino protocol for the combinatorial synthesis of novel 1,4-dihydropyrano[2,3-c]pyrazol-6-amines has been achieved. This transformation presumably occurs via cyclization-Knoevenagel condensation-Michael addition-tautomerism-intramolecular O-cyclization-elimination sequence of reactions. The significant features of this reaction include expedient one-pot process, short reaction time, no column chromatographic purification, excellent yield, and readily available starting materials.

NitroketeneN,S-acetals: synergistic building blocks for the synthesis of heterocycles

“…52 Kanchithalaivan and his group developed an effective one- . 53 The scope of the abovementioned protocol was also envisaged in the cyclic system (2-hydroxy-1,4-naphthoquinone) 67 with aromatic aldehydes and NMSM using ethanol under reux conditions. This reaction afforded the corresponding products even in the absence of a base.…”

Green, Rapid, Simple, and an Effective One-Pot Multicomponent Strategy for Synthesis of Novel Dihydropyrano[2,3-C]pyrazol-6-Amines in Aqueous Medium

“…Water offers several benefits such as control over exothermic reactions, salting in and salting out, as well as variation of pH range 21 . Recently, organic reactions in water without use of hurtful organic solvents have drawn much more attention, because water is cheap, safe and environment friendly solvent 36 . In continuation of current efforts to find and develop a new routes for the synthesis of biologically active heterocyclic molecules using inexpensive, readily available, and environmentally benign catalysts 37-43 , thus herein, we wish to report a mild, efficient method for the synthesis of some novel and simple one-pot four-component synthesis of dihydropyrano [2, 3-c] pyrazol-6-amines using green chemistry principles.…”

A green and efficient protocol for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives via a one-pot, four component reaction by grinding method

“…Kumar et al have reported a catalytic and solvent free multi-component reaction involving the grinding the components [4] . Multi-component reactions (MCRs) are ecofriendly process as they obey green chemistry principles [5] . MCR has emerged as an efficient green tool for the synthesis of simple and complex building blocks, thus allowing the generation of several bonds in a single operation with offer significant advantages such as convergence, facile automation, no time consuming workup, easy purification processes, atom economy, low cost, shorter reaction time and minimum wastage [6] , [7] , replacement of volatile organic solvents by non-flammable, non-volatile, non-toxic and economical “green solvents” [8] .…”

“…As part of our attempt to develop biologically important pyranopyrazole by a new synthetic method, a detailed literature survey revealed that only few numbers of grinding methods published for synthesis of pyranopyrazole [17] . A large number of catalysts stimulated this transformation at various reaction conditions [5] , [3] , [15] , [32] , [33] , [34] , [35] , [36] , [37] ( Table 1 , entry 1–8). The above mentioned results indicate that l -proline proved to be an efficient catalyst for this conversion.…”