Silver‐Catalyzed Enantioselective Sulfimidation Mediated by Hydrogen Bonding Interactions

Abstract

An enantioselective sulfimidation of 3-thiosubstituted 2-quinolones and 2-pyridones was achieved with astoichiometric nitrene source (PhI=NNs) and as ilver-based catalyst system. Keytothe success of the reaction is the use of achiral phenanthroline ligand with ah ydrogen bonding site.T he enantioselectivity does not depend on the size of the two substituents at the sulfur atom but only on the binding properties of the heterocyclic lactams.Atotal of 21 chiral sulfimides were obtained in high yields (44-99 %) and with significant enantiomeric excess (70-99 %e e). The sulfimidation proceeds with high site-selectivity and can also be employed for the kinetic resolution of chiral sulfoxides. Mechanistic evidence suggests the intermediacy of ah eteroleptic silver complex, in whichthe silver atom is bound to one molecule of the chiral ligand and one molecule of an achiral 1,10-phenanthroline.Support for the suggested reaction course was obtained by ESI mass spectrometry,DFT calculations,and aHammett analysis.

Cation–anion confined hydrogen-bonding catalysis strategy for ring-closing C–O/O–H metathesis of alkoxy alcohols under metal-free conditions

“…1a and S2,† the cations [HO-EtN 111 ] + , [HO-EtMIm] + , and [EMIm] + serve as HB donors to form HBs with the ether O atom of 1a with the HB lengths following the order: [HO-EtN 111 ] + < [HO-EtMIm] + < [EMIm] + ; especially, the HB lengths of 1a with [HO-EtN 111 ] + and with [HO-EtMIm] + are less than 2.0 Å, suggesting very strong hydrogen bonding interaction. 40,41 The anions [OTf] − , [PF 6 ] − , Cl − serve as HB acceptors to form HBs with the hydroxyl H of 1a , and the HB lengths are as follows: [OTf] − < [PF 6 ] − < Cl − , indicating the strongest ability of [OTf] − to form HB with 1a . Additionally, the NBO charges of the methylene C atom in –CH 2 OCH 3 and the hydroxyl O atom in 1a were calculated to get information on electron transfer caused by hydrogen bonding (Fig.…”

Remote Enantioselective Epoxidation Reactions Catalyzed by Chiral Iron Porphyrin Complexes with a Hydrogen-Bonding Site

“…Our group has for some time studied transition-metal complexes which are attached via a V-shaped carbon scaffold to a lactam unit. 5 6 Two-point hydrogen bonding serves to recruit a prochiral lactam substrate and this motif was found to open viable pathways for enantioselective oxygenation, 6a,c amination, 6b sulfoxidation, 6d sulfimidation, 6e aziridination, 7 and epoxidation reactions. 3-Alkenylquinolin-2(1 H )-ones (3-alkenylquinolones), such as compound 1 for example, underwent a clean and highly enantioselective epoxidation at the alkenyl group employing 2,6-dichloropyridine- N -oxide as the stoichiometric oxidant and ruthenium porphyrin complex 3 as the catalyst (Figure 1 ).…”

Combined Approach of Hypervalent Iodine Reagents and Transition Metals in Organic Reactions

“…It was found that the enantioselectivity is not function of the size of the two substituents on sulfur atom but only on the binding properties of heterocyclic lactams. The reaction afforded high yields (44–99%), high enantiomeric excess (70–99% ee ) and high site‐selectivity [109] …”

“…The reaction afforded high yields (44-99%), high enantiomeric excess (70-99% ee) and high site-selectivity. [109]…”