A Traceless Heterocyclic Amine Mediator in Regioselectivity−Switchable Formal [1 + 2 + 2] Cycloaddition Reaction to 1,3,4- and 1,4,5-Trisubstituted Pyrazoles

Abstract

Switchable multicomponent reactions have been attractive tools for the construction of compound libraries with skeleton diversity and complexity by slightly changing the reaction conditions. Described herein is a regioselectivity-switchable formal [1 + 2 + 2] cycloaddition reaction from difluoroalkyl compounds, enaminones, and RNHNH 2 , ultimately using 1methylindazol-3-amine as a traceless mediator to switch the inherent regioselectivity of 1,3,4-trisubstituted pyrazole formation to 1,4,5-trisubstituted pyrazoles. Remarkable features of this work include mild conditions, simple operation, and broad scopes.

Recent advances in the electrochemical generation of 1,3-dicarbonyl radicals from C–H bonds

“…6 The reductive dehalogenation of prefunctionalized C–X bonds has become an efficient method for generating carbon-centered radicals. 7 Direct transformations of simple and easily available C–H bonds are more economical and competitive in organic synthesis. 8 1,3-Dicarbonyl radicals can be formed via the single electron oxidation of C–H bonds using stoichiometric metal reagents or oxidants and have been studied extensively.…”

Activation of Ethanol via Conjunction of a Photocatalyst and a HAT Reagent for the Synthesis of Benzimidazoles

“…Alternatively, photo-mediated transformation is found to be more remarkable as it eliminates the need for harsh reaction conditions and elevated reaction temperature. − In the last few years, there have been few reports for the synthesis of benzimidazoles under photocatalytic conditions using aldehydes. − Undoubtedly, instead of using expensive and unstable aldehydes, its synthesis using alcohols is highly desirable. The synthesis of benzimidazoles from aliphatic alcohols under photocatalytic conditions was first reported by Shiraishi’s group using Pt@TiO 2 .…”

One Stone, Three Birds: One-Pot Synthesis of Pyrido[3,2-a]phenoxazin-5-one Derivatives from o-Aminophenols with Triple Roles, Paraformaldehyde, and Enaminones via the Povarov Reaction

“…Over the past 10 years, our group has performed detailed studies of the Povarov reactions of arylamines with two reactive sites in an I 2 –DMSO system . However, the Povarov reactions involving o -aminophenol with more active sites have rarely been reported.…”