The synthesis of chiral imidazolidinones on mesoporous silica nanoparticles, exploiting two different anchoring sites and two different linkers, is reported. Catalysts 1-4 were prepared starting from l-phenylalanine or l-tyrosine methyl esters and supporting the imidazolidinone onto silica by grafting protocols or azide-alkyne copper(I)-catalyzed cycloaddition. The four catalysts were fully characterized by solid-state NMR, N2 physisorption, SEM, and TGA in order to provide structural assessments, including an evaluation of surface areas, pore dimensions, and catalyst loading. They were used in organocatalyzed Diels-Alder cycloadditions between cyclopentadiene and different aldehydes, affording results comparable to those obtained with the nonsupported catalyst (up to 91% yield and 92% ee in the model reaction between cyclopentadiene and cinnamic aldehyde). The catalysts were recovered from the reaction mixture by simple filtration or centrifugation. The most active catalyst was recycled two times with some loss of catalytic efficiency and a small erosion of ee.
|Titolo:||Chiral Hybrid Inorganic-Organic Materials: Synthesis, Characterization, and Application in Stereoselective Organocatalytic Cycloadditions|
|Settore Scientifico Disciplinare:||Settore CHIM/06 - Chimica Organica|
Settore CHIM/02 - Chimica Fisica
|Data di pubblicazione:||2013|
|Digital Object Identifier (DOI):||10.1021/jo401852v|
|Appare nelle tipologie:||01 - Articolo su periodico|