Reaction of .ALPHA.,.BETA.-unsaturated ketones with hydrazine derivatives.

Fused heterocycles 11.1 Synthesis of tricyclic fused pyrazolines by the reaction of 3-arylidenechromanones and 3-arylidene-1-thiochromanones with hydrazine

“…On the basis of the literature data on the synthesis of 2-pyrazolines by the reaction of α,β-unsaturated ketones with hydrazines under acidic conditions, [32][33][34] we assume a plausible mechanism (Scheme 2) for the formation of compounds 8-21. As the first step, a hydrazone type intermediate is formed and a Michael type addition of its amino group provides the pyrazoline ring.…”

Introduction

“…For example, the reaction of hydrazides of some organic acids with chalcone in the presence of acetic acid involves the carbonyl group of the unsaturated ketone, while basic catalysis (piperidine) promotes -addition [45]. An analogous influence of the acidity on the direction is observed in reactions with binucleophiles [46].…”

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

“…A general procedure for the synthesis of 2-substituted hexahydroindazoles is based on reaction of benzylidenecyclohexanones with hydrazine derivatives in the presence of hydrochloric [5,9] or acetic acid [6], as well as in the absence of a catalyst in alcoholic medium [7]. Syntheses under basic conditions are less common [10]; in these cases, alternative products are formed [11][12][13].We found that the reactivity of initial ketones II toward various hydrazine derivatives is considerably lower than the reactivity of 2,6-bis(arylmethylidene) cyclohexanones. Both ketones II and 2,6-bis(arylmethylidene)cyclohexanones readily reacted with hydrazine and methylhydrazine, whereas the former failed to react with phenylhydrazine and thiosemicarbazide.…”

“…A general procedure for the synthesis of 2-substituted hexahydroindazoles is based on reaction of benzylidenecyclohexanones with hydrazine derivatives in the presence of hydrochloric [5,9] or acetic acid [6], as well as in the absence of a catalyst in alcoholic medium [7]. Syntheses under basic conditions are less common [10]; in these cases, alternative products are formed [11][12][13].…”