Chelate ring size effects of Ir(P,N,N) complexes: Chemoselectivity switch in the asymmetric hydrogenation of α,β-unsaturated ketones
作者:Zsófia Császár、Eszter Z. Szabó、Attila C. Bényei、József Bakos、Gergely Farkas
DOI:10.1016/j.catcom.2020.106128
日期:2020.11
led to the conclusion that the activity, chemo- and enantioselectivity in the hydrogenation of α,β-unsaturatedketones are highly dependent on the combination of the two bridge lengths. It has been found that a minor change in the ligand's structure, i. e. varying the value of m from 1 to 0, can switch the chemoselectivity of the reaction, from 80% CO to 97% CC selectivity.
Copper-Catalyzed Borylation of Cyclic Sulfamidates: Access to Enantiomerically Pure (β-and γ-Aminoalkyl)boronic Esters
作者:Nina Ursinyova、Robin B. Bedford、Timothy Gallagher
DOI:10.1002/ejoc.201501492
日期:2016.2
Abstract Cyclicsulfamidates undergo borylation under copper‐catalyzed conditions using B2pin2 to give enantiomerically (and diasteromerically) defined (aminoalkyl)boronicesters. External iodide is essential, but the intermediacy of simple alkyl iodides has been excluded; N‐sulfated intermediates are key in the borylation sequence. Based on stereochemical studies and trapping experiments, the involvement
Application of a lanthanide shift reagent in 17O n.m.r. spectroscopy to determine the stereochemical course of oxidation of cyclic sulphite diesters to cyclic sulphate diesters with ruthenium tetroxide
作者:Gordon Lowe、Salvatore J. Salamone
DOI:10.1039/c39830001392
日期:——
Cyclic sulphite diesters are rapidly oxidized to cyclic sulphate diesters with ruthenium tetroside in good yield; diastereotopically labelled cyclic [17O] sulphate diesters obtained by oxidation of diastereoisomeric cyclic sulphite diesters with ruthenium [17O] tetroxide are shown, by the effect of a lanthanide shift reagent on their 17O n.m.r. signals, to be formed with retention of configuration
环式亚硫酸二酯与四溴化钌可快速氧化为环式硫酸二酯,收率良好。通过镧系元素转移试剂对其17 O nmr信号的影响,显示了通过用钌[ 17 O]四氧化物氧化非对映异构环状亚硫酸二酯而得到的非对位标记的环状[ 17 O]硫酸二酯。硫。
Desymmetrization of bicyclo[3.3.0]octane-3,7-dione by the Schmidt reaction: am easy synthesis of tecomanine
selective Schmidt reaction to give the the 3-azabicyclo[4.3.0]noanmine buildingblock 3b which was employed in a short synthesis of (±)-tecomanine 4. AsymmetricSchmidt reaction on 1, employing (2S,4R)-2-azido-4-hydroxypentane 14 as a chiral inducer, showed encouraging levels of enantiotopic methylene group stereo differentiation.
A general and convenient two-step synthetic method has been developed for the preparation of a novel class of aminoalkyl-phosphine type compounds, which involves nucleophilic ring-opening of cyclic sulfate esters. The ring-opening step was performed using several different aliphatic and aromatic amines to produce aminoalkyl sulfates that were reacted with LiPPh2 to give the corresponding P,N-ligands