Synthesis and stereochemistry of substituted bi- and tri-cyclic 4,5-dihydropyrazoles

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

“…6,7 Synthesis of tricyclic fused pyrazolines by the reaction of exocyclic α,β-unsaturated ketones and hydrazines has also been studied by several research groups. 1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] As a continuation of our activity on the investigation of the reaction of …”

Novel 3, 3a, 4, 5, 6, 7‐Hexahydroindazole and Arylthiazolylpyrazoline derivatives as Anti‐inflammatory Agents

“…In contrast to the above results, Jacquier and Maury synthesized dihydropyrazoles derivatives in a two-step reaction of 2-alkylidene and 2-benzylidenecycloalkanones with hydrazine and obtained both the cis and trans diastereoisomers [37]. Moreover, reactions of 2,6-diarylidenecycloalkanones with thiosemicarbazide under acidic catalysis yielded only one diastereoisomer of the 3-H, 3a-H cis, while the reaction with semicarbazide afforded a mixture of trans and cis diastereoisomers, which have been separated [38,39]. In the present work, compound 2 was synthesized by the reaction of 2,6-bis-benzylidenecyclohexanone (1) [40] with thiosemicarbazide in presence of NaOH afforded a mixture of the 3-H, 3a-H trans (major) 2 and cis (minor) 2 a diastereoisomers which have been separated by fractional recrystallization from methanol.…”

“…These chair and boat-like forms with out-of-plane C-5 and C-7a atoms are both distorted approaching the sofaarrangement with coplanar C-7a. It is to be noted that the inversion of the six-membered ring hardly influences the envelope form of the pyrazoline ring (with an out-ofplane C-3 atom) bearing the aryl (phenyl, substituted phenyl, thienyl) group in a quasi-equatorial position [38].…”

“…One of the two product components, apparently the minor one, was matched properly with the cis isomer 2 a and the other component, which seemed to be the major one, is considered to be the trans diastereoisomer 2.The confirmation of the trans isomer can also be achieved by the melting point differences between the two products 2 and 2 a and by oxidation of the 2-thiocarbamoyl group in compound 2 a with hydrogen peroxide according to the previously described method [41] leading to the published compound trans 7-benzylidene-2-carbamoyl-3,3a,4,5,6,7-hexahydro-3-phenyl -2H-indazole (2 c) [38].…”

Synthesis of exocyclic α,β-unsaturated ketones

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Another versatile utilization is the reaction of exocyclic α,β-enones with dinucleophiles to afford polycyclic fused ring systems, e.g. tricyclic pyrazolines, [23][24][25][26][27][28][29][30][31][32][33][34][35][36] tetracyclic benzothiazepines, [37][38][39][40] tetracyclic benzodiazepines, 41,42 thiazines, [43][44][45][46] pyrimidines, 47-50 quinazolines [51][52][53][54][55][56][57][58][59] and so on. In the present review article the most common and useful procedures for the preparation of select...…”