Application of Photoclick Chemistry for the Synthesis of Pyrazoles via 1,3-Dipolar Cycloaddition between Alkynes and Nitrilimines Generated In Situ
作者:Richard Remy、Christian G. Bochet
DOI:10.1002/ejoc.201701225
日期:2018.1.23
The photolysis of tetrazoles leads to the extrusion of dinitrogen and forms a reactive nitrile imine intermediate. The latter can then react in situ with alkynes in a [3+2] cycloaddition providing pyrazoles. Some reactivity trends were identified, such as a preference for electron‐poor alkynes. On the tetrazole part, there is a clear preference for either aromatic or conjugated substituents.
An unprecedented facile oxidation of 1,3,5-trisubstitutedpyrazolines and Hantzsch 1,4-dihydropyridines (DHPs) to the corresponding pyrazoles and pyridines was observed, mediated by 3,4-dihydro-2H-pyran in air. The reaction showed excellent reactivity, functional group tolerance, and high yield without using any metal and/or halogen based oxidizing agents.
Divergent Synthesis of Pyrazoles via Manganese Pincer Complex Catalyzed Acceptorless Dehydrogenative Coupling Reactions
作者:Koushik Sarkar、Pramod Kumar、Arjun Mule、Biplab Maji
DOI:10.1002/chem.202401105
日期:2024.6.25
defined Mn(I)-complex catalyzed acceptorless dehydrogenative coupling (ADC) reactions employing alcohols as the carbon source enabled the synthesis of multi-substituted pyrazoles. Symmetrical pyrazoles were made via the coupling of 1,3-diols with hydrazines. The unsymmetrically substituted pyrazoles were created using the ADC reaction of primary alcohols with hydrazones.