Children learn through play, and they learn more than adults might expect. Science experiments are a great way to spark their curiosity, get their minds active, and encourage them to do something that doesn’t involve a screen. 1038-95-5, C21H21P. A document type is Article, introducing its new discovery., Application In Synthesis of Tri-p-tolylphosphine
Diastereomerically pure secondary alcohols epimerize to mixtures of diastereomers in C6H5R at 65-90 C in the presence of 10 mol % (eta5-C5R5)Re(NO)(PPh3)(OCH 3) (1; R = H, Me). The methoxide ligand of 1 first exchanges with the alcohol substrate to give alkoxide complexes (eta5-C5R5)Re(NO)(PPh 3)(OCHR?R?) (2). Authentic samples of diastereomerically and enantiomerically pure 2 are prepared, where OCHR?R? is derived from (+)- and (-)-, exo- and endo-borneol. NMR data show that epimerization occurs first at rhenium (ca. 35 C) and then at carbon (ca. 65 C). Substitution reactions and rate experiments show that PPh3 initially dissociates from 2 with anchimeric assistance by alkoxide oxygen lone pairs. An intermediate with a trigonal-planar rhenium, which can either return to 2 (with epimerization at rhenium) or undergo beta-hydride elimination to a ketone hydride complex (leading to epimerization at carbon), is proposed. Accordingly, rates of epimerization at carbon (but not rhenium) are strongly inhibited by added PPh3, and show a significant kH/kD.
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Phosphine ligand,
Chiral phosphine ligands in asymmetric synthesis. Molecular structure and absolute configuration of (1,5-cyclooctadiene)-(2S,3S)-2,3-bis(diphenylphosphino)butanerhodium(I) perchlorate tetrahydrofuran solvate