Ready Available Chiral Azapyridinomacrocycles N-Oxides; First Results as Lewis Base Catalysts in Asymmetric Allylation of p-Nitrobenzaldehyde
摘要:
We report here the straightforward synthesis of the first series of enantiomerically pure azapyridinomacrocycles N-oxides containing a cyclohexyl chiral moiety. These compounds were readily obtained in good overall yields by a convergent synthesis using natural amino acids as starting building blocks and macrocyclisation as the key step. This method is rapid, efficient and suitable for the introduction of various substituents at the macrocyclic skeleton. Finally, the compounds were tested as organocatalysts for the enantioselective allylation of p-nitrobenzaldehyde with allyltrichlorosilane.
Catalytic oxidation of alcohols with novel non-heme <i>N</i><sub>4</sub>-tetradentate manganese(<scp>ii</scp>) complexes
作者:Vincent Vermaak、Desmond A. Young、Andrew J. Swarts
DOI:10.1039/c8dt03808b
日期:——
non-heme N4-tetradentate Mn(OTf)2 complexes of the type, [(L)MnOTf2], where L = R,R and S,S enantiomers of BPMCN, its 6-methyl and 6-bromo derivatives as well as the novel ligand BMIMCN (BPMCN = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-(R,R/S,S)-1,2-diaminocyclohexane, BMIMCN = N,N′-dimethyl-N,N′-bis(1-methyl-2-imidazolemethyl)-(R,R/S,S)-1,2-diaminocyclohexane). Solid state structural analysis of the BMIMCN-ligated
IrCl(COD)PPh3 and chiral [SNNS]-type ligands, were employed in the asymmetric transfer hydrogenation of aromaticketones under mild reaction conditions. The corresponding optically active alcohols were obtained in high yield and good to excellent enantioselectivities (up to 96% ee). The chiral Ir(I) complexes with the ligands of [SNNS]-type were also prepared and characterized, which showed good enantioselectivity
2R)-diphenylethylene and (aR)-binaphthylene linkers have been designed and synthesized in 30–94% yield. Ten chiral bis(NHC) palladium complexes 20–28 have been synthesized and characterized by NMR, HRMS, elemental analysis and further confirmed by X-ray single crystal analysis. These bis(NHC)-Pd complexes showed obviously different catalytic properties in the asymmetric Suzuki–Miyaura coupling reactions. The
N-Heterocyclic Carbene-Mediated Enantioselective Addition of Phenols to Unsymmetrical Alkylarylketenes
作者:Carmen Concellón、Nicolas Duguet、Andrewâ D. Smith
DOI:10.1002/adsc.200900538
日期:2009.11
Chiral N-heterocyclic carbenes (NHCs) mediate the enantioselectiveaddition of 2-phenylphenol to unsymmetricalalkylarylketenes, delivering α-alkyl-α-arylacetic acid derivatives with good levels of enantiocontrol (up to 84% ee). Enantiodivergent stereochemical outcomes are observed using 2-phenylphenol and benzhydrol in the NHC-promoted esterification reaction using a triazolium precatalyst derived
of the salenMn(III) complex (complex 4). All of the synthesized complexes were well characterized, and their performance in the enantioselectiveepoxidation of styrene was investigated systematically. Under optimum reaction conditions, a 99% styrene epoxide yield with 50% enantiometric excess (ee) could be obtained over the complex 2. Furthermore, the IL-functionalized chiral salenMn(III) complexes