Synthetic Studies on the Reactions of Hydrazine and Aroylhydrazide with 5-Phenyl-1,3,4-Oxadiazol-2-thione

One‐pot PTC synthesis of polyfused pyrazoles

“…Treatment of compound 1 with CS 2 under PTC conditions afforded pyrazole dithioc acid, which was allowed to react in situ with equimolar ratio of active nitriles including ethyl cyanoacetate or malononitrile to give 6-amino-5-ethoxycarbonyl-2-phenyl-4-thioxo-3,3a,4,7-tetrahydro-2H-pyrazolo- [3,4- (17), respectively (Scheme 3).…”

“…In an extension of our recent studies [17][18][19][20][21][22][23] on the application of PTC in heterocyclic synthesis, starting with an active methylene compounds containing ␣-keto or ␣-cyano group, herein we report the synthesis of some new fused and spiro pyrazole heterocycles starting with 3-amino-1-phenyl-2pyrazolin-5-one (1). Compound 1 was allowed to react with CS 2 and a variety of halo compounds having an active methylene, including chloroacetonitrile, ethyl chloroacetate, or phenacyl bromide in 1:1:1 molar ratio, under PTC conditions [K 2 CO 3 / dioxane/tetrabutylammonium bromide (TBAB)], where 3-amino-1-phenyl-4-thioxo-3a,4-dihydro-1Hthieno [3,4-c]pyrazol-6-ylcarbonitrile (2), ethoxy(3amino-1-phenyl-4-thioxo-3a,4-dihydro-1H-thieno [3, 4-c]pyrazo-6-yl)-1-methanone (3) or 3-amino-1phenyl-4-thioxo-3a,4-dihydro-1H-thieno [3,4-c]pyrazol-6-ylphenyl-1-methanone (5), and 3-hydroxy-2phenyl-4-thioxo-2,4-dihydro-1H-thieno [3,4-c]-pyrazol-6-ylphenyl-1-methanone (6) were obtained.…”

“…The reaction of compound 1 with CS 2 and alcoholic KOH in 2:1:1 molar ratio gave 5-hydroxy-4mercapto-2,6-diphenyl-2,3,6,8-tetrahydrodipyrazolo-SCHEME 1 [3,4-b:4,3-e]pyridin-3-one (12), which was treated with ethyl chloroacetate under the proceeding PTC conditions to give ethoxy(8-hydroxy-3,7diphenyl-5,7-dihydro-3H-1-thia-3,4,5,6,7-pentaazacyclopenta[cd]-s-indacen-2-yl)-1-methanone (14). On the other hand, 6-phenyl-2,4-dithioxo-2,6,7,8tetrahydropyrazolo [1,5 -c] [ 1,3,5 ]-thiadiazin-7-one (13) was obtained by treating compound 1 with CS 2 and alcoholic KOH in 1:2:2 molar ratio, which was reacted with hydrazine hydrate [16,17] in refluxing ethanol, where H 2 S gas was evolved to afford 3-amino-6-phenyl-2,4-dithioxo-2,3,4,6,7,8hexahydropyrazolo [1,5-a] [1,3,5]triazin-7-one (15) (Scheme 2). The structure of these compounds were confirmed using IR, 1 H-NMR, MS, and elemental analysis ( Table 1).…”

“…The precipitate was collected by filtration and crystallized from ethyl alcohol to give compound 15 as yellow needles. [3,4-b]pyridin-3-one (16) and 3a,4, [3,4-b]pyridin-5-yl Carbonitrile (17) A mixture of 1 (0.01 mol), anhydrous potassium carbonate (3 g), a catalytic amount of TBAB, dioxane (40 ml), carbon disulfide (0.01 mol) and ethyl cyanoacetate or malononitrile (0.01 mol) was stirred for 4 or 2 h at 60…”

Rapid, microwave accelerated synthesis of [1,2,4]triazolo[3,4- b ][1,3,4]oxadiazoles from 4-acylamino-1,2,4-triazoles

“…In nearly all approaches to 1 the oxadiazole is first prepared and the triazole is formed in the final step. For instance, 1,3,4-oxadiazoles functionalized at the 2-position with acylhydrazines ( 2 ), 19,23-25 hydrazones ( 3 ), 26-27 and unsubstituted hydrazines ( 4 ) 20,28-29 can be directly converted to 1 via triazole cyclization. The triazole has also been formed by reacting hydrazine hydrate with either EtOH and amino oxadiazoles ( 5 ), 21 N -substituted oxadiazolines ( 6 ), 30 or N -acylated oxadiazolones ( 7 ).…”