Synthetic analogs of natural flavolignans. XII. Synthesis of 3,5-diarylsubstituted pyrazolines based on 1,3-benzodioxane and 1,4-benzodioxane chalcone analogs

Abstract

NH 2 NH 2 OH R 1 R 2 R 3 N NH Het 5 -8 5c, d, f, g, Het = A; 6d, g, Het = B; 7g, Het = C; 8a, e, f, g, h, Het = D a: R 1 = R 2 = R 3 = H; c: R 1 = R 3 =H, R 2 = CH 3 d: R 1 = R 3 = H, R 2 = OMe; e: R 1 = R 3 = H, R 2 = Cl f: R 1 = R 2 = H, R 3 = Cl; g: R 1 = R 2 = H, R 3 = F h: R 1 = R 2 = Cl, R 3 = H Het: A = O O Cl O O Br B = C = O O HOOC O O Het R 3 R 2 R 1 OH O 547.814.5 3,5-Diarylsubstituted pyrazolines were synthesized by reaction of 1,3-benzodioxane and 1,4-benzodioxane chalcone analogs with hydrazine hydrate. The structures of the products were confirmed by PMR spectroscopy.

Chalcones as Versatile Synthons for the Synthesis of 5- and 6-membered Nitrogen Heterocycles

“…The most common approach for the synthesis of 2-pyrazolines starting from chalcones involves the reaction with hydrazines in refluxing ethanol [93,113,[198][199][200][201][202][203][204][205][206][207][208][209] or methanol [113,125,133,210]. Under these conditions, a large variety of substituents can be found in the synthesis of functionalized 2-pyrazolines such as benzodioxane [211], benzofuran [118,212,213], coumarin [214], indenoquinoxaline [215], naphthalene [125], quinoline [216,217], 1,3-thiazole [218] and thiophene [219][220][221]. The introduction of bases such as pyridine [122,[222][223][224], piperidine [129,225,226], triethylamine [227,228], KOH [107], NaOH [229][230][231][232][233]…”