Enantioselective addition of selenosulfonates to α,β-unsaturated ketones

2018 ◽  
Vol 16 (16) ◽  
pp. 2893-2901 ◽  
Author(s):  
Shilong Luo ◽  
Nan Zhang ◽  
Zhen Wang ◽  
Hailong Yan
Keyword(s):  
Unsaturated Ketones ◽  
Enantioselective Addition ◽  
First Time

An efficient organo-catalyzed enantioselective addition of selenosulfonates to α,β-unsaturated ketones was developed for the first time.

scholarly journals Palladium Catalyzed Alternating Cooligomerization of Ethylene and Carbon Monoxide to Unsaturated Ketones

1995 ◽  
Vol 50 (3) ◽  
pp. 430-438 ◽  
Author(s):  
Wilhelm Keim ◽  
Heiko Maas ◽  
Stefan Mecking
Keyword(s):  
Carbon Monoxide ◽  
Palladium Catalysts ◽  
Methylene Chloride ◽  
General Structure ◽  
Phosphine Ligands ◽  
Unsaturated Ketones ◽  
Palladium Catalyzed ◽  
First Time ◽  
Cationic Palladium

Cationic palladium catalysts have been used to cooligomerize ethylene and carbon monoxide. At high ethylene/CO ratios (m /m = 10:1) in methylene chloride as a solvent, unsaturated alternating cooligomers of the general structure R[C(O)CH2CH2]mH ( m ≥ 1 ; R ≡CH2=CH-, CH2=CHCH2CH2- and CH3CH = CHCH2-) were obtained for the first time. Single component catalyst precursors [(allyl)Pd(P^X )]+Y- (P^X = Ph2P(CH2)nC(= O )OR, Ph2P(CH2)2P(=O)Ph2, Ph2P(CH2)nPh2P(CH2)2S (=O )Ph, n = 1 - 3 , R = Me, Et; Y- = BF4-, SbF6- ) with bidentate P,O- and P,S-ligands as well as in situ catalysts with unfunctionalized phosphine ligands were used. With P"Bu3 as a ligand, selectivities for ethylvinylketone of 40% based on the CO converted were obtained. The hemilabile phosphino-ester and phosphinothiophene ligands behave like monodentate phosphines under catalytic conditions.

Metal-free enantioselective addition of nucleophilic silicon to aromatic aldehydes catalyzed by a [2.2]paracyclophane-based N-heterocyclic carbene catalyst

2017 ◽  
Vol 15 (15) ◽  
pp. 3202-3206 ◽  
Author(s):  
Ping An ◽  
Yuwen Huo ◽  
Zhen Chen ◽  
Chun Song ◽  
Yudao Ma
Keyword(s):  
Transition Metal ◽  
Aromatic Aldehydes ◽  
Metal Free ◽  
Enantioselective Addition ◽  
First Time

A transition metal-free enantioselective 1,2-silylation of aromatic aldehydes to yield chiral α-hydroxysilanes was developed for the first time.

scholarly journals Enantioselective direct Mannich-type reactions of 2-benzylpyridine N-oxides catalyzed by chiral bis(guanidino)iminophosphorane organosuperbase

2018 ◽  
Vol 9 (18) ◽  
pp. 4348-4351 ◽  
Author(s):  
Qiupeng Hu ◽  
Azusa Kondoh ◽  
Masahiro Terada
Keyword(s):  
Base Catalysis ◽  
Addition Reactions ◽  
Brønsted Base ◽  
Enantioselective Addition ◽  
First Time

2-Benzylpyridine N-oxides possessing less acidic α-protons were utilized as pronucleophiles for the first time in enantioselective addition reactions under Brønsted base catalysis.

scholarly journals Modular synthesis of chiral 1,2-dihydropyridines via Mannich/Wittig/cycloisomerization sequence that internally reuses waste

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bo-Shuai Mu ◽  
Xiao-Yuan Cui ◽  
Xing-Ping Zeng ◽  
Jin-Sheng Yu ◽  
Jian Zhou
Keyword(s):  
Enantioselective Synthesis ◽  
Side Reactions ◽  
Structural Components ◽  
Chiral Amine ◽  
Low Concentration ◽  
Unsaturated Ketones ◽  
Modular Synthesis ◽  
Enantioselective Addition ◽  
Product Water ◽  
Hydrolysis Of

Abstract1,2-Dihydropyridines are valuable and reactive synthons, and particularly useful precursors to synthesize piperidines and pyridines that are among the most common structural components of pharmaceuticals. However, the catalytic enantioselective synthesis of structurally diverse 1,2-dihydropyridines is limited to enantioselective addition of nucleophiles to activated pyridines. Here, we report a modular organocatalytic Mannich/Wittig/cycloisomerization sequence as a flexible strategy to access chiral 1,2-dihydropyridines from N-Boc aldimines, aldehydes, and phosphoranes, using a chiral amine catalyst. The key step in this protocol, cycloisomerization of chiral N-Boc δ-amino α,β-unsaturated ketones recycles the waste to improve the yield. Specifically, recycling by-product water from imine formation to gradually release the true catalyst HCl via hydrolysis of SiCl4, whilst maintaining a low concentration of HCl to suppress side reactions, and reusing waste Ph3PO from the Wittig step to modulate the acidity of HCl. This approach allows facile access to enantioenriched 2-substituted, 2,3- or 2,6-cis-disubstituted, and 2,3,6-cis-trisubstituted piperidines.

ChemInform Abstract: Sc(III)-Catalyzed Enantioselective Addition of Thiols to α,β-Unsaturated Ketones in Neutral Water.

ChemInform ◽  
2011 ◽  
Vol 42 (37) ◽  
pp. no-no
Author(s):  
Simona Bonollo ◽  
Daniela Lanari ◽  
Ferdinando Pizzo ◽  
Luigi Vaccaro
Keyword(s):  
Unsaturated Ketones ◽  
Neutral Water ◽  
Enantioselective Addition

Sc(III)-Catalyzed Enantioselective Addition of Thiols to α,β-Unsaturated Ketones in Neutral Water

2011 ◽  
Vol 13 (9) ◽  
pp. 2150-2152 ◽  
Author(s):  
Simona Bonollo ◽  
Daniela Lanari ◽  
Ferdinando Pizzo ◽  
Luigi Vaccaro
Keyword(s):  
Unsaturated Ketones ◽  
Neutral Water ◽  
Enantioselective Addition

Annulate lamellae in the Sertoli cells of guinea pig testis after unilateral torsion of the spermatic cord

1984 ◽  
Vol 42 ◽  
pp. 196-197
Author(s):  
J. Chakraborty ◽  
A. P. Sinha Hikim ◽  
J. S. Jhunjhunwala
Keyword(s):  
Sertoli Cells ◽  
Guinea Pigs ◽  
Spermatic Cord ◽  
Present Report ◽  
Cell Types ◽  
Annulate Lamellae ◽  
Spermatogenic Cells ◽  
Electron Microscopic ◽  
Structural Details ◽  
First Time

Although the presence of annulate lamellae was noted in many cell types, including the rat spermatogenic cells, this structure was never reported in the Sertoli cells of any rodent species. The present report is based on a part of our project on the effect of torsion of the spermatic cord to the contralateral testis. This paper describes for the first time, the fine structural details of the annulate lamellae in the Sertoli cells of damaged testis from guinea pigs.One side of the spermatic cord of each of six Hartly strain adult guinea pigs was surgically twisted (540°) under pentobarbital anesthesia (1). Four months after induction of torsion, animals were sacrificed, testes were excised and processed for the light and electron microscopic investigations. In the damaged testis, the majority of seminiferous tubule contained a layer of Sertoli cells with occasional spermatogonia (Fig. 1). Nuclei of these Sertoli cells were highly pleomorphic and contained small chromatinic clumps adjacent to the inner aspect of the nuclear envelope (Fig. 2).

Electron spectroscopic imaging and diffraction

1991 ◽  
Vol 49 ◽  
pp. 706-707
Author(s):  
M. Rühle ◽  
J. Mayer ◽  
J.C.H. Spence ◽  
J. Bihr ◽  
W. Probst ◽  
...  
Keyword(s):  
Materials Science ◽  
Electron Spectroscopic Imaging ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Illumination System ◽  
Probe Size ◽  
Diffraction Patterns ◽  
Fritz Haber ◽  
Koehler Illumination ◽  
First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

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