Palladium‐ and Rhodium‐Catalyzed Dynamic Kinetic Resolution of Racemic Internal Allenes Towards Chiral Pyrazoles
作者:Lukas J. Hilpert、Simon V. Sieger、Alexander M. Haydl、Bernhard Breit
DOI:10.1002/anie.201812984
日期:2019.3.11
resolution (DKR) of racemic allenes leading to N‐allylated pyrazoles is described. Such compounds are of enormous interest in medicinal chemistry as certified drugs and potential drug candidates. The new methods feature high chemo‐, regio‐ and enantioselectivities aside from displaying a broad substrate scope and functional group compatibility. A mechanistic rational accounting for allene racemization and trans‐alkene
Carbonylation of 1,1-disubstituted propargyl acetates in a cat.PdCl2/CuCl2/MeC(OMe)3/MeOH system under CO atmosphere (balloon) gave γ-acetoxy-β-methoxy-α,β-unsaturated esters.
mediated by Pd(II) afforded cyclic orthoesters, which were hydrolyzed into γ-acetoxy-β-ketoesters. Based on the NMR experiments, it was presumed that the cyclization reaction was initiated by a nucleophilic attack of carbonyl oxygen to the alkyne carbon coordinated to palladium(II). When the γ-acetoxy-β-ketoesters were treated with a basic condition, Knoevenagel–Claisen type condensation took place, and
The resolution of tertiary α-acetylene- acetate esters by the lipase from candida cylindracea
作者:David O'Hagan、Naveed A. Zaidi
DOI:10.1016/0957-4166(94)80062-6
日期:1994.6
The resolution of tertiary alcohols using the Candida cylindracea lipase is explored. In particular strategies are deployed to limit nonenzymatic hydrolysis of the tertiary acetate substrates in buffer, such that a full range of the steric requirements and limitations for successful resolutions can be explored.
Copper-catalyzed Z-selective semihydrogenation of alkynes with hydrosilane: a convenient approach to cis-alkenes
A copper catalyst generated in situ from widely available copper salt and imidazolium salt in the presence of t-BuOK showed high efficiency for the semihydrogenation of a wide range of internal and terminal alkynes to their corresponding alkenes without obvious over-reduction. Functional groups, such as hydroxyl, nitro, halides, and amino, etc. were tolerated. The Z/E ratios of the obtained alkenes were generally >99%. Finally, semireduction of bulky alkynes also went smoothly. (C) 2014 Elsevier Ltd. All rights reserved.