Sulfamic Acid Catalysed One-Pot Three-Component Condensation for the Synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles

Abstract

A clean and simple synthesis of 6-amino-4-aryl-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles was accomplished in good to excellent yields via the one-pot three component condensation of 3-methyl-1-phenyl-2-pyrazolin-5-one, an aromatic aldehyde, and malononitrile catalysed by sulfamic acid in ethanol.

Sulfamic Acid and Its N- and O-Substituted Derivatives

“…277 6-Amino-4-aryl-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles 50 were synthesized via a one-pot 3component reaction with sulfamic acid in EtOH. 278 Yields vary from 30% to 90% in the 3-component synthesis of various 1,4dihydropyridines containing a pyrazole ring 51. 279 Two Friedlander quinolone syntheses have been reported.…”

“…Several pyrazole derivatives have been synthesized, all employing sulfamic acid as catalyst. − Thus, synthesis of various benzochromeno-pyrazoles and pyrano-pyrazoles have been reported by the same group. For synthesis by the latter two routes were used: one with sulfamic acid in ACN and the second without sulfamic acid but using microwave irradiation .…”

“…For synthesis by the latter two routes were used: one with sulfamic acid in ACN and the second without sulfamic acid but using microwave irradiation . 6-Amino-4-aryl-3-methyl-1-phenyl-1,4-dihydropyrano[2,3- c ]pyrazole-5-carbonitriles 50 were synthesized via a one-pot 3-component reaction with sulfamic acid in EtOH . Yields vary from 30% to 90% in the 3-component synthesis of various 1,4-dihydropyridines containing a pyrazole ring 51 …”

Facile and One-Pot Access of 3,3-Bis(indol-3-yl)indolin-2-ones and 2,2-Bis(indol-3-yl)acenaphthylen-1(2H)-one Derivatives via an Eco-Friendly Pseudo-Multicomponent Reaction at Room Temperature Using Sulfamic Acid as an Organo-Catalyst

“…It exists in the zwitterionic state rather than the aminosulfonic acid form as evidenced from X-ray and neutron diffraction experiments . Sulfamic acid has been successfully used as an effective catalyst in carrying out certain useful organic reactions including Friedel–Crafts reaction, Aldol condensation, Michael addition, Mannich-type reactions, − Strecker reaction, Biginelli reaction, one-pot synthesis of triazolo­[5,1- b ] quinazolines, dihydropyridines, 1,4-dihydropyrano­[2,3- c ]­pyrazoles, esterification reaction, and many others. − This successful prehistory of sulfamic acid as a commercially available low-cost and environmentally benign ogano-catalyst with an intrinsic zwitterionic property encouraged us to investigate its further applications in some other carbon–carbon bond forming reactions. In this paper, we wish to extend the synthetic applicability of this unique catalyst in the one-pot synthesis of both the 3,3-bis­(indol-3-yl)­indolin-2-one ( 3 ) and 2,2-di­(1 H -indol-3-yl)­acenaphthylen-1­(2 H )-one ( 5 ) scaffolds of pharmacological interest under the same optimized reaction conditions.…”

HClO4-SiO2 Nanoparticles: An Efficient and Versatile Catalyst for Synthesis of 1,4-Dihydropyrano[2,3-c]Pyrazoles

“…Organic reactions in water without using hazardous organic solvents have attracted a great deal of interest in both academic and industrial research because, in addition to environmental concerns, there are beneficial effects of aqueous solvents on the rate and selectivity of important organic transformations. 1 There are a many procedures described to prepare 1,4-dihydropyrano [2,3-c]pyrazoles such as one-pot threecomponent condensations of malononitrile, aldehyde and 3-methyl-1-phenyl-2-pyrazolin-5-one using KF/Al 2 O 3 in DMF at room temperature, 2 sulfamic acid in ethanol, 3 CsF, 4 solvent-free reaction conditions along with microwave irradiation technique using piperidine as the base have also been introduced for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles. 5 but most of them are toxic.…”