Sc(OTf)3-catalyzed, solvent-free domino synthesis of functionalized pyrazoles under controlled microwave irradiation

4,5-Dihydro-1H-pyrazole: an indispensable scaffold

“…Although routes B and G use the same reactants 3, route B follows microwave irradiation 46 unlike route G in which the reactants are subjected to heating at 120 C. Route B employed an efficient, rapid, and green synthesis under solventfree conditions in the presence of scandium triflate [Sc(OTf) 3 ] resulting pyrazoline (1) in yield ranging from 74 to 92% in 5 min and silica chloride (route G) catalyzed one pot cyclocondensation 47 afforded yield of 80% in 2 h. Suzuki-Miyaura reaction 48 exploiting Pd (OAc) 2 (5 mol %) as a catalyst in the presence of SPhos (10 mol %) in an aqueous solution of K 2 CO 3 (2 M) (route C) afforded pyrazoline in 60-66% yield in 8 h. Yet another strategy employed included solvent-free synthesis 49 as in route D which used equivimolar concentration of methanesulphonic acid and 5 at 80 C giving a yield of 95% in 45 min. Route E followed asymmetric synthesis 50 through an enantioselective phase transfer organocatalytic addition of N-Boc hydrazine to 2 followed by a transprotection sequence allowing N-Boc transformation into N-Ac or other functional groups resulting in 1.…”

An Efficient, Green, and Solvent‐free Multi‐component Synthesis of Benzimidazolo/Benzothiazolo Quinazolinone Derivatives Using Sc (OTf)3 Catalyst Under Controlled Microwave Irradiation

“…Usually, most of the traditional Lewis acid and mineral acid cause some ruthless environmental problems in chemical industries, and Sc (OTf) 3 is supposed to resolve these problems. Sc (OTf) 3 has been widely used as a catalyst for various organic transformations .…”

Synthesis and Antimicrobial Activity of Some New 3,4‐Disubstituted Pyrroles and Pyrazoles

“…Some of the drugs viz., celecoxib, antipyrine, phenylbutanone, novalgine, ramfenazone, fipronil, and rimonabant contain pyrazole moiety. The 1,3‐dipolar cycloaddition methodology is prominent for the synthesis of pyrazoles using alkynes, nitrile imines , diazo compounds , reaction of chalcones with hydrazines, a three‐component coupling of hydrazine, aldehyde, ethyl acetonate , and direct condensation of 1,3‐diketones and hydrazines . In addition, furan, thiophene, and pyridine derivatives are fundamentally important heterocyclic cores and are present in many natural products and pharmaceuticals with wide spectrum of biological activities .…”