[4+1] cyclization of α-diazo esters and mesoionic N-heterocyclic olefins.

Prompted by the recent stepwise mechanistic proposal for the Huisgen [3+2] cycloaddition reaction between enamine and α-diazo ester, where the nucleophilic addition of the enamine carbon onto the terminal nitrogen of diazo ester is crucial, we examined the possible use of N-heterocyclic olefins (NHOs) as highly electron-rich dipolarophiles in these reactions. The mesoionic NHOs derived from 1,2,3-triazoles undergo fast [4+1] cycloaddition to give 3-(triazolium-4-yl)-(3)-pyrazol-4-olates at room temperature. The reaction mechanism has been explored through experimental and DFT computational studies.

RhNPs supported on -functionalized mesoporous silica: effect on catalyst stabilization and catalytic activity.

Amine and nicotinamide groups grafted on ordered mesoporous silica (OMS) were investigated as stabilizers for RhNPs used as catalysts in the hydrogenation of several substrates, including carbonyl and aryl groups. Supported RhNPs on functionalized OMS were prepared by controlled decomposition of an organometallic precursor of rhodium under dihydrogen pressure. The resulting materials were characterized thoroughly by spectroscopic and physical techniques (FTIR, TGA, BET, SEM, TEM, EDX, XPS) to confirm the formation of spherical rhodium nanoparticles with a narrow size distribution supported on the silica surface.