Pyrazole and (pyrazol-1-yl)metal complexes as carbon–carbon coupling catalysts

Synthesis of substituted-3-iodo-1H-pyrazole derivatives and their further modification under Sonogashira cross coupling reaction conditions

“…As pyrazoles themselves are known as ligands for transition metals, 4 protection of N-H group of 3-iodo-1H-pyrazole derivatives were necessary in our investigations of cross-coupling reactions. 1H-Pyrazoles 1-5 were protected using Boc anhydride and ethyl vinyl ether.…”

“…After 1 hour of stirring at the same temperature dimethylformamide (1.5 equiv) was added to the reaction mixture dropwise and left to warm to room temperature overnight. Then saturated NH 4 Cl (5 equiv) solution in deionized water were added to the reaction mixture, organic layer was separated and NH 4 Cl solution was extracted with dichloromethane (for 1 mol of pyrazole 0.5 L of dichloromethane were used) twice. Organic layers were combined, washed with deionized water (for 1 mol of pyrazole 0.5 L of water were used), dried with anhydrous Na 2 SO 4 and evaporated under reduced pressure.…”

“…Then dimethylformamide (5.5 mol) were added to the reaction mixture (at -78 ºC) and left to warm to the room temperature, and then additionally stirred at room temperature overnight. Then reaction was cooled down to 5 ºC and 5L of saturated NH 4 Cl solution in water was added, organic layer was separated, and concentrated under reduced pressure. Crude product was dissolved in 2.5 L dichloromethane and extracted with NH 4 Cl solution in water (same NH 4 Cl solution with was used for quenching), water layer was washed with dichloromethane (2×250 mL).…”

“…3 Substituted pyrazole derivatives may be used as ligands for transition metal-catalyzed reactions. 4 Moreover, they are very useful synthetic intermediates for other heterocyclic systems such as substituted bis(pyrazolo [4,3-d] [1,2]diazepinones, 5 substituted octahydro-1H-benzo[g]indazole derivatives, 6 substituted 1H-pyrazolo[3,4-c]pyridines 7 and other.…”

Novel directed synthesis of functionalized pyrazole derivatives via regioselective solvent-free thiylation of 3-alkenylpyrazoles with arenethiols

“…18 Some pyrazole ligands can be used in transition metal-catalyzed reactions. 19 Pyrazoles are used in supramolecular 20 and polymer chemistry, 21 in the food industry, as cosmetic colorings 22 and UV stabilizers 23 and some possess liquid crystal properties. 24,25 They are also applied in the design of complexes with unusual magnetic properties.…”