Synthesis of Novel Chiral (Thio)ureas and Their Application as Organocatalysts and Ligands in Asymmetric Synthesis
作者:Marcos Hernández-Rodríguez、Claudia Gabriela Avila-Ortiz、Jorge M. del Campo、Delia Hernández-Romero、María J. Rosales-Hoz、Eusebio Juaristi
DOI:10.1071/ch08116
日期:——
The synthesis of novel chiral (thio)ureas 1–10 and 14–26 is described. These (thio)ureas incorporate chiral auxiliaries derived from (R)- or (S)-α-phenylethylamine, (R)-phenylglycine, or (1R,2S)-ephedrine. The phenylethyl group in compounds 1–10 and 21–24 adopts a particular orientation in the molecular structure as a consequence of 1,3-allylic strain with the (thio)carbonyl group. Ureas 1–10 were
weed Amaranthus retroflexus, four new sesquiterpeneglucosides were isolated from the methanolic extract of the plant. The structures of these metabolites are determined on the basis of the mass spectrometry, and 1D and 2D NMR spectroscopies (DQ-COSY, TOCSY, HSQC, HSQC–TOCSY, HMBC, and NOESY). Two compounds are characterized by a new aglycone and differed from the site of glucosylation. The other two
Enantioselective catalytic rearrangement of cyclohexene oxide with new homochiral bis-lithium amide bases
作者:Olivier Equey、Alexandre Alexakis
DOI:10.1016/j.tetasy.2004.02.030
日期:2004.4
Cyclohexeneoxide can be rearranged with good levels of induction (up to 68% ee) with substoichiometric amounts of chiral bases derived from readily available diamines. The influence of the steric bulk of the amine substituents on the rearrangement enantioselectivity has also been studied.
Enantioselective copper catalysed 1,4-conjugate addition reactions using chiral N-heterocyclic carbenes
作者:Caroline L. Winn、Frédéric Guillen、Julien Pytkowicz、Sylvain Roland、Pierre Mangeney、Alexandre Alexakis
DOI:10.1016/j.jorganchem.2005.07.024
日期:2005.12
The preparation of a variety of chiral N-heterocyclic carbene (NHC) precursors is described. The relative merits of imidazolinium salts and silver carbenes as NHC precursors are discussed with respect to their synthesis, stability and performance in the copper catalysed conjugate addition of dialkyl zinc reagents to a variety of Michael acceptors. Enantioselectivities of up to 93% were achieved using
Palladium complexes of bis(acyclic diaminocarbene) ligands with chiral N-substituents and 8-membered chelate rings
作者:Yoshitha A. Wanniarachchi、Sri S. Subramanium、LeGrande M. Slaughter
DOI:10.1016/j.jorganchem.2009.06.007
日期:2009.9
with N,N′-bis[(R)-1-(1-naphthyl)ethyl]-1,3-diaminopropane did not lead to an isolable bis(carbene) complex, instead forming significant amounts of bis(ammonium) salt as a decomposition product. However, reaction of the same palladium isocyanide precursor with a mixture of all diastereomers of N,N′-bis[1-(1-naphthyl)ethyl]-1,3-diaminopropane provided an achiral, Cs-symmetric palladium bis(acyclic diaminocarbene)