Angular Regioselectivity in the Reactions of 2-Thioxopyrimidin-4-ones and Hydrazonoyl Chlorides: Synthesis of Novel Stereoisomeric Octahydro[1,2,4]triazolo[4,3-a]quinazolin-5-ones

The regioselective synthesis of cis and trans stereoisomers of variously functionalized octahydro[1,2,4]triazolo[4,3-a]quinazolin-5-ones was performed. The 2-thioxopyrimidin-4-ones used in the synthesis reacted with hydrazonoyl chlorides in a regioselective manner to produce the angular regioisomers [1,2,4]triazolo[4,3-a]quinazolin-5-ones rather than the linear isomers [1,2,4]triazolo[4,3-a]quinazolin-5-ones. The synthesis process took place with electronic control. The angular regiochemistry of the products was confirmed by X-ray experiments and two-dimensional NMR studies.

Microwave-Assisted Regioselective Synthesis of Variously Functionalized [1,2,4]triazolo[3,4-b]quinazolin-5(1H)-ones

[1,2,4]Triazolo[3,4-b]quinazolin-5(1H)-ones with varied functionalization patterns were synthesized in a regioselective manner by reacting 2-thioxo-2,3- dihydroquinazolin-4(1H)-one (2) with variously functionalized hydrazonoyl chlorides (3ah). Linear regioselectivity of the formed products was confirmed by X-ray measurements. Under microwave conditions, the reactions were completed in a few minutes without a change in the regioselectivity.

Efficient Methods for the Synthesis of Novel Arylazothiazoles Based on Acetylferrocene or Adamantane

Background: Hydrazonoyl halides are convenient for the synthesis of arylazothiazoles. Materials and Methods: A series of novel arylazothiazoles were efficiently synthesized from the reaction of hydrazonoyl chlorides with 2-(adamantan-2-ylidene)hydrazinecarbothioamide or 2-(ferrocenyl-1-ylidene)hydrazinecarbo-- thioamide in dioxane used as an aprotic solvent because of its lower toxicity and higher boiling point (101 °C) and triethylamine at reflux. The reaction mechanistic pathway proceeded by the nucleophilic substitution reaction by the elimination of hydrogen chloride to give thiohydrazonates as intermediate, which in situ undergo intramolecular cyclization and loss of water molecule to afford the final product of novel arylazothiazoles. This method is simple with good yield and excellent purities. Results and Discussion: The synthetic schemes for the final products are proposed and discussed. The chemical structures of the final products were identified by different techniques, such as elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS). Conclusion: In this article, we prepared arylazothiazoles from the reaction of 2-(adamantan-2-ylidene)hydrazinecarbothioamide or 2-(ferrocenyl-1-ylidene)hydrazinecarbothioamide with hydrazonoyl halides.

Copper-Catalyzed Tandem Dehydrocyanation and [3+2] Cyclo­addition Reactions of Phenacylmalononitriles: Regioselective Synthesis of Functionalized 4-Benzoyl-5-cyanopyrazoles under Mild Conditions

A novel copper-catalyzed [3+2] cycloaddition reaction with concomitant in situ generation of benzoylacrylonitriles and nitrile imines from phenacylmalononitriles and hydrazonoyl chlorides, respectively, is reported. The reaction was performed using copper(I) chloride as catalyst and N-methylimidazole as a clean complexing agent/weak base to afford the functionalized 4-benzoyl-5-cyanopyrazoles in moderate to good yields and excellent regioselectivity under ambient conditions. This method provides rapid access to a wide range of highly functionalized 4-benzoyl-5-cyanopyrazoles.

Synthesis of fully substituted pyrazoles from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides via a [[3 + 3] − 1] pathway

Pyrazoles were synthesized from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides via an unusual [[3 + 3] − 1] pathway, involving a formal [3 + 3] cascade cyclization followed by a spontaneous ring-contraction/sulfur extrusion reaction.