Synthesis of (3S)-(tert-butyldimethylsilyloxy)methylcyclopentan-1-one as a key intermediate of sphingosine 1-phosphate-1 receptor agonists
摘要:
Herein we report the asymmetric synthesis of (3S)-(tert-butyldimethylsilyloxy)methylcyclopentan-1-one (S)-3 as a practical chiral synthon for a wide range of pharmaceutical and/or natural products, using Lipshutz's asymmetric copper-catalyzed conjugate reduction. This method makes it feasible to prepare a conformationally constrained cyclopentane analogue 12, which is one of the key intermediates for the synthesis of novel sphingosine 1-phosphate-1 receptor agonists. (C) 2013 Elsevier Ltd. All rights reserved.
In tandem or alone: a remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts
作者:Grzegorz Krzysztof Zieliński、Cezary Samojłowicz、Tomasz Wdowik、Karol Grela
DOI:10.1039/c4ob02480j
日期:——
A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity.
New robust and air-stable ruthenium(II) indenylidene type second-generation precatalysts with unsymmetrical N-heterocycliccarbene (NHC) ligands were synthesized. The reaction profiles of these complexes were studied in commercial-grade solvents in air with model substrates leading to the di-, tri-, and tetrasubstituted olefins. In addition, application of selected precatalysts for olefin metathesis
Thermal Switchability of N-Chelating Hoveyda-type Catalyst Containing a Secondary Amine Ligand
作者:Karolina Żukowska、Anna Szadkowska、Aleksandra E. Pazio、Krzysztof Woźniak、Karol Grela
DOI:10.1021/om2011062
日期:2012.1.9
An investigation of aza analogues of the popular Hoveyda–Grubbs catalystcontaining a secondaryamineligand is presented, proving the crucial impact of steric as well as electronic factors on the catalyst’s stability and performance. The issue of latency in the reactivity profile of studied catalysts is examined, followed by structural and application studies.
A low-waste, time-economical, and scalable semiheterogeneous purification protocol for the removal of ruthenium residues from olefinmetathesis (OM) reactions has been developed. It is based on the non-covalent immobilization of the commercially available isocyanide 1,4-bis(3-isocyanopropyl)piperazine (QA) on unmodified silica gel. The use of the heterogeneous scavenger [email protected]2 synthesized
Five Hoveyda–Grubbs‐type complexes bearing cyclopropyl to cycloheptyl ether moieties in the chelating benzylideneligand have been synthesized and investigated by spectroscopic and crystallographic methods. Their experimentally measured catalytic activity in model ring‐closing metathesis (RCM) reactions was studied at catalyst loading down to 10 ppm and compared with DFT calculations. The latter can