4 research outputs found
Enantiodivergent Synthesis of Benzoquinolizidinones from L-Glutamic Acid
Benzoquinolizidinone systems were synthesized in both enantiomeric forms from L-glutamic acid. The key chiral arylethylglutarimide intermediate was synthesized from dibenzylamino-glutamate and homoveratrylamine. Aldol reaction of the glutarimide afforded a mixture of syn and anti-aldol adducts. Subsequent regioselective hydride reduction of the glutarimide carbonyl followed by N-acyliminium ion cyclization afforded a product with opposite absolute configurations at C3 and C11b. Cope elimination of the dibenzylamino group then converted the two diastereomers into enantiomers
A Photocatalytic Approach for the Synthesis of LâShape Bicyclic NHC Ligands
International audienceLâshape N âHeterocyclic Carbenes (NHCs) based on the imidazo[1,5â a ]pyridine (ImPy) scaffold have recently gained considerable interest as the true carbene ligand analogues of the popular dialkylbiarylphosphines, better known as Buchwald phosphines. Nevertheless, the substitution pattern of ImPy ligands is still rather limited due to synthetic access issues. We report herein an efficient and versatile visible light photocatalytic strategy to access Lâshape bifunctional ImPy ligands laterallyâfunctionalized by a phenol group. Mechanistic investigations supported by density functional theory (DFT) reveal that the excited state of the iridium photocatalyst undergoes either a reductive quenching (SET process) or an energyâtransfer quenching (EnT process) depending on the nature of the counterion of the 5âbromoimidazo[1,5â a ]pyridinium substrate salt. Moreover, the bifunctional character of these new family of Lâshape ImPy ligands is demonstrated by the preparation of a gold(I) complex exhibiting a free OH function capable of intermolecular hydrogen bonding. This work highlights the advantage of visible light photocatalysis in the synthesis of advanced NHC ligand structures, a strategy that has not yet been considered despite its potential benefits in terms of versatility, diversity and practicability
A Photocatalytic Approach for the Synthesis of LâShape Bicyclic NHC Ligands
Abstract Lâshape NâHeterocyclic Carbenes (NHCs) based on the imidazo[1,5âa]pyridine (ImPy) scaffold have recently gained considerable interest as the true carbene ligand analogues of the popular dialkylbiarylphosphines, better known as Buchwald phosphines. Nevertheless, the substitution pattern of ImPy ligands is still rather limited due to synthetic access issues. We report herein an efficient and versatile visible light photocatalytic strategy to access Lâshape bifunctional ImPy ligands laterallyâfunctionalized by a phenol group. Mechanistic investigations supported by density functional theory (DFT) reveal that the excited state of the iridium photocatalyst undergoes either a reductive quenching (SET process) or an energyâtransfer quenching (EnT process) depending on the nature of the counterion of the 5âbromoimidazo[1,5âa]pyridinium substrate salt. Moreover, the bifunctional character of these new family of Lâshape ImPy ligands is demonstrated by the preparation of a gold(I) complex exhibiting a free OH function capable of intermolecular hydrogen bonding. This work highlights the advantage of visible light photocatalysis in the synthesis of advanced NHC ligand structures, a strategy that has not yet been considered despite its potential benefits in terms of versatility, diversity and practicability