Recherches dans la série des azoles

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.…”

TADDOLs, Their Derivatives, and TADDOL Analogues: Versatile Chiral Auxiliaries

“…The rac-cyclohexenone, [135] as a ™neutral∫ compound, would not have been subject to ™classical∫ resolution through diastereomeric salts; the rac-pyrazoline [134] had previously been separated by chromatography on a triacetylcellulose column. [136] cited literature describes many additional examples. Thus, separations have been accomplished with enantiomer mixtures of nitrogen-(amines, nitrosamines, N-heterocycles), oxygen-(alcohols, phenols, ethers, ketones, esters, lactones, anhydrides), and sulfur-containing compounds (sulfoxides), as well as such multifunctional materials as esters of hydroxy or amino acids, cyanohydrins, alkoxylactones, and oxaziridines.…”

A theoretical study of the mechanism of oxidation of 1H-pyrazolines to 1H-pyrazoles by molecular bromine

“…The experiments were carried out on 3,5,5-trimethyl-2-pyrazoline (7, Scheme 4) and on 5-methyl (11) and 3-methyl-2-pyrazoline (13,Scheme 5). Scheme 5.…”

“…The 1 H NMR data agree much better with 18 than with 8 even assuming no N-Br inversion in the latter. At that time (1962-1966), 13 C and 15 N NMR were not accessible preventing a straightforward identification. Although, the information on 12/22 is scarce (only 1 H NMR) it appears that the structure should be 22.…”

“…11 Afterwards, we reported that this coupling is dependent on the 1-substituent and that in some cases vanished. 13 It cannot be excluded that the bromine substituent affects 4 J 34 to the point to be not observable.…”