Visible Light-Enhanced [3 + 2] Cycloaddition of ,-Disubstituted Hydrazines with Organo-Cyanamides: Access to Polysubstituted 1,2,4-Triazol-3-amines.

Visible light-enhanced [3 + 2] cycloaddition of ,-disubstituted hydrazines with -cyano--aryl--toluenesulfonamides is an efficient reaction pathway to polysubstituted 1,2,4-triazol-3-amines. The reaction is performed under mild conditions without the addition of any transition metals. This strategy involves a C(sp)-H bond activation, a cyano cycloaddition, and the formation of two new C═N bonds.

Copper-Promoted Aerobic Oxidative [3+2] Cycloaddition Reactions of N,N-Disubstituted Hydrazines with Alkynoates: Access to Substituted Pyrazoles.

A copper-promoted aerobic oxidative [3+2] cycloaddition reaction for the synthesis of various substituted pyrazoles from N,N-disubstituted hydrazines with alkynoates in the presence of bases is developed. This work involves a direct C(sp)-H functionalization and the formation of new C-C/C-N bonds. In this strategy, inexpensive and easily available CuO serves as the promoter and air acts as the green oxidant.

Metal-Free Temperature-Controlled Intermolecular [3 + 2] Annulation to Access Benzo[]thiazole-2(3)-thiones and Benzo[]thiazol-2(3)-ones.

A facile access to benzo[]thiazole-2(3)-thiones and benzo[]thiazol-2(3)-ones has been developed through a temperature-controlled intermolecular [3 + 2] annulation of N,N-disubstituted arylhydrazines with CS in the presence of DMSO. This protocol can obviate the prefunctionalization of the starting materials. This direct C-S/C-N bond formation reaction was performed in the absence of any external catalysts, transition metals, bases, ligands, and oxidants with high step economy.

Copper-Catalyzed Phosphorylation of ,-Disubstituted Hydrazines: Synthesis of Multisubstituted Phosphorylhydrazides as Potential Anticancer Agents.

An efficient copper-catalyzed aerobic oxidative cross-dehydrogenative coupling reaction for the synthesis of multisubstituted phosphorylhydrazides from ,-disubstituted hydrazines and hydrogen phosphoryl compounds is accomplished. The reaction proceeds under mild conditions without the addition of any external oxidants and bases. This work reported here represents a direct P(═O)-N-N bond formation with the advantages of being operationally simple, good functional group tolerance, and high atom and step economy.

Metal- and Oxidant-Free Green Three-Component Desulfurization and Deamination Condensation Approach to Fully Substituted 1-1,2,4-Triazol-3-amines and Their Photophysical Properties.

A metal- and oxidant-free three-component desulfurization and deamination condensation of amidines, isothiocyanates, and hydrazines for the synthesis of structurally diverse fully substituted 1-1,2,4-triazol-3-amines is described. The reaction proceeds without the requirement of any external catalysts, metals, ligands, or oxidants. This [2 + 1 + 2] cyclization strategy involves C-N and C-S bond cleavage and the formation of new C-N bonds in one pot.

Synthesis of Purine Analogues: Photocatalyst-Free Visible-Light-Enhanced Annulation Approach to Pyrazolo[1,5-][1,3,5]triazine-2,4-diamines.

A new photocatalyst-free visible-light-enhanced strategy for the synthesis of pyrazolo[1,5-][1,3,5]triazine-2,4-diamines via the formation of electron donor-acceptor (EDA) complexes is reported. The generated pyrazolthiourea intermediates from 1-pyrazol-3-amines and isothiocyanates undergo formal [4 + 2] annulation with 1,1,3,3-tetramethylguanidines (TMG) to deliver the corresponding products involved in three C-N bond formations in a one-pot protocol. The formation of EDA complex from pyrazolthiourea and TMG is confirmed by UV-vis spectroscopy and H NMR experiments.