RESUMO
X-ray crystal structures of two [(diphosphine)Au2 Cl2 ] complexes (in which diphosphine=P-Phos and xylyl-P-Phos; P-Phos=[2,2',6,6'-Tetramethoxy-4,4'-bis(diphenylphosphino)-3,3'-bipyridine]) were determined and compared to the reported structures of similar atropisomeric gold complexes. Correlations between the Auâ â â Au distances and torsional angles for the biaryl series of ligands (MeOBIPHEP, SEGPhos, and P-Phos; BIPHEP=2,2'-bis(diphenylphosphino)-1,1'-biphenyl, SEGPhos=[(4,4'-bi-1,3-benzodioxole)-5,5'-diyl]bis[diphenylphosphine]) can be made; these measurements appear to be very dependent upon the phosphorous substituent. Conversely, the same effect was not observed for ligands based on the binaphthyl (BINAP) series. The catalytic activity of these complexes was subsequently assessed in the enantioselective cycloisomerisation of 1,6-enynes and revealed an over-riding electronic effect: more-electron-rich phosphines promote greater enantioselectivity. The possibility of silver acting as a (co-)catalyst was ruled out in these reactions.
Assuntos
Complexos de Coordenação/química , Ouro/química , Fosfinas/química , Compostos de Bifenilo/química , Catálise , Complexos de Coordenação/síntese química , Cristalografia por Raios X , Dioxóis/química , Isomerismo , Conformação Molecular , Prata/químicaRESUMO
A family of new chiral zwitterionic phosphorus-containing heterocycles (zPHC) have been derived from methylene-bridged bis(imidazolines). These structures were unambiguously determined, including single-crystal XRD analysis for two compounds. The stability, acid/base and electronic properties of these dipolar phosphorus heterocycles were subsequently investigated. zPHCs can be successfully employed as a new class of chiral solvating agents for the enantiodifferentiation of chiral carboxylic and sulfonic acids by NMR spectroscopy. The stoichiometry and binding constants for the donor-acceptor complexes formed were established by NMR titration methods.
Assuntos
Compostos Heterocíclicos/síntese química , Fósforo/química , Espectroscopia de Ressonância Magnética/métodos , Metilação , Modelos Moleculares , Estrutura Molecular , Solventes/química , EstereoisomerismoRESUMO
The first asymmetric synthesis of a synthetic cannabinoid levonantradol was accomplished, and the 3-D solution structure of its core architecture was confirmed by NMR and computational methods.