Optically Active 1,1′-Spirobiindane-7,7′-diol (SPINOL)-Based Phosphoric Acids as Highly Enantioselective Catalysts for Asymmetric Organocatalysis

2011 ◽  
Vol 76 (10) ◽  
pp. 4125-4131 ◽  
Author(s):  
Chun-Hui Xing ◽  
Yuan-Xi Liao ◽  
Jaclynn Ng ◽  
Qiao-Sheng Hu
Keyword(s):  
Optically Active ◽  
Asymmetric Organocatalysis ◽  
Enantioselective Catalysts ◽  
Phosphoric Acids

Preparation of ( R )‐3‐aminopiperidine by resolution with optically active cyclic phosphoric acids

Chirality ◽  
2021 ◽  
Author(s):  
Yujuan Sun ◽  
Beibei Hu ◽  
Yongshuai Jing ◽  
Jialiang Wu ◽  
Maochao Zhou ◽  
...  
Keyword(s):  
Optically Active ◽  
Phosphoric Acids

Formation of Quaternary Stereogenic Centers by Wagner-Meerwein Rearrangement – Synthesis of Optically Active Cyclopentadienyl Complexes from Borneol and Fenchol

2009 ◽  
Vol 64 (1) ◽  
pp. 25-40 ◽  
Author(s):  
Christian Färber ◽  
Gotthelf Wolmershäuser ◽  
Helmut Sitzmann
Keyword(s):  
Optical Purity ◽  
Alkyl Substituent ◽  
Optically Active ◽  
Titanocene Dichloride ◽  
High Yield ◽  
The Novel ◽  
Group 4 ◽  
Stereogenic Centers ◽  
Cyclopentadienyl Complexes ◽  
Enantioselective Catalysts

The development of optically active cyclopentadienyl complexes as enantioselective catalysts calls for simple synthetic procedures for cyclopentadienes with optically active alkyl substituents. While exo-bornyl chloride and exo-fenchyl bromide do not react or exclusively eliminate hydrogen halide with cyclopentadienylmetal compounds in ether solvents or ammonia, they undergo Wagner- Meerwein rearrangement and substitution with cyclopentadienylmagnesium chloride in toluene. The bornyl cation yields racemic exo-bornylcyclopentadiene and partially racemized isocamphylcyclopentadiene, but for the fenchyl cation no racemization pathway is available, and the main diastereomer among the lithium salts of the ensuing substituted cyclopentadienes can be isolated in 95% diastereomeric purity by solvent extraction. This material with the IUPAC name lithium (2R)- 2,5,5-trimethylbicyclo[2.2.1]hept-2-ylcyclopentadienide carries an alkyl substituent having no trivial name so far. Exo-norbornylcyclopentadiene could be synthesized in high yield with a similar procedure. The same protocol works with 1-bromoadamantane. The novel alkylcyclopentadienes have been converted to ferrocenes and molybdenum complexes of the type [CpRMo(CO)3CH3]. (2R)- 2,5,5-Trimethylbicyclo[2.2.1]hept-2-ylcyclopentadiene with an optical purity of 78% ee (the optical purity of the starting material fenchol) was converted into an optically active titanocene dichloride and tested in the catalytic hydrogenation of 2-phenyl-1-butene. The hydrogenation product was obtained with 31% ee, which compares favorably with results obtained with other group 4 metallocene dichlorides with one optically active alkyl substituent on each ring ligand. Facile procedures for the synthesis of the starting compounds exo-bornyl chloride and exo-fenchyl bromide based on the tosylate method have been developed with a tosylate melt or with toluene serving as solvents.

An Unexpected Michael-Aldol-Smiles Rearrangement Sequence for the Synthesis of Versatile Optically Active Bicyclic Structures by Using Asymmetric Organocatalysis

2010 ◽  
Vol 16 (14) ◽  
pp. 4337-4346 ◽  
Author(s):  
Nicole Holub ◽  
Hao Jiang ◽  
Marcio W. Paixão ◽  
Caterina Tiberi ◽  
Karl A. Jørgensen
Keyword(s):  
Optically Active ◽  
Smiles Rearrangement ◽  
Asymmetric Organocatalysis

On the synthesis of a novel chiral phosphorodiamidic acid containing the α-phenylethyl moiety: Insights in its conformation and reactivity

Synthesis ◽  
2021 ◽  
Author(s):  
Carlos Alberto Cruz-Hernández ◽  
Eusebio Juaristi
Keyword(s):  
Present Report ◽  
The Novel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multistep Synthesis ◽  
Asymmetric Organocatalysis ◽  
Synthetic Methodologies ◽  
Chiral Brønsted Acids ◽  
Heterocyclic Moiety ◽  
Phosphoric Acids

A few years ago, the synthesis of chiral phosphoric acids supported on chiral BINOL frameworks was accomplished by T. Akiyama and M. Terada. Subsequent relevant applications demonstrated the importance of chiral phosphoric acids as privileged chiral inducers in asymmetric organocatalysis. In the present report we discuss the development of novel chiral phosphorodiamidic acids derived from C2-symmetric trans-1,2-diaminocyclohexane aliphatic frameworks. The preparation of the new chiral Brønsted acids, based on the intermediacy of a 1,3,2-diheterophospholan-2-oxide moiety, turned out to be challenging since several plausible synthetic methodologies proved to be ineffective. Furthermore, the five membered heterocyclic moiety turned out to be easily hydrolyzed when exposed to nucleophilic alcohols or water. Complementary to the successful multistep synthesis reported here, it was possible to obtain crystals of the key precursor of the desired phosphorodiamidic acid, which proved suitable for X-ray diffraction analysis and hence to establish important conformational characteristics of the novel heterocycle.

Optical analysis of ink and other contaminants in process waters

TAPPI Journal ◽  
2012 ◽  
Vol 11 (8) ◽  
pp. 51-58
Author(s):  
ANTTI HAAPALA ◽  
MIKA KÖRKKÖ ◽  
ELISA KOIVURANTA ◽  
JOUKO NIINIMÄKI
Keyword(s):  
Optically Active ◽  
Process Water ◽  
Paper Machine ◽  
Optical Analysis ◽  
Direct Process ◽  
Active Components ◽  
Water Contaminants ◽  
Dependent Measurement ◽  
Measurement Methodology

Analysis methods developed specifically to determine the presence of ink and other optically active components in paper machine white waters or other process effluents are not available. It is generally more interest¬ing to quantify the effect of circulation water contaminants on end products. This study compares optical techniques to quantify the dirt in process water by two methods for test media preparation and measurement: direct process water filtration on a membrane foil and low-grammage sheet formation. The results show that ink content values obtained from various analyses cannot be directly compared because of fundamental issues involving test media preparation and the varied methodologies used to formulate the results, which may be based on different sets of assumptions. The use of brightness, luminosity, and reflectance and the role of scattering measurements as a part of ink content analysis are discussed, along with fine materials retention and measurement media selection. The study concludes with practical tips for case-dependent measurement methodology selection.

Microscopic Structure of Er-Related Optically Active Centers in Si

2003 ◽  
Vol 770 ◽  
Author(s):  
H. Przybylinska ◽  
N. Q. Vinh ◽  
B.A. Andreev ◽  
Z. F. Krasil'nik ◽  
T. Gregorkiewicz
Keyword(s):  
Ground State ◽  
Photoluminescence Spectrum ◽  
Zeeman Effect ◽  
Optically Active ◽  
Single Type ◽  
Active Centers ◽  
Mbe Growth ◽  
Spectral Components ◽  
Er Doped ◽  
Successful Observation

AbstractA successful observation and analysis of the Zeeman effect on the near 1.54 μm photoluminescence spectrum in Er-doped crystalline MBE-grown silicon are reported. A clearly resolved splitting of 5 major spectral components was observed in magnetic fields up to 5.5 T. Based on the analysis of the data the symmetry of the dominant optically active center was conclusively established as orthorhombic I (C2v), with g‼≈18.4 and g⊥≈0 in the ground state. The fact that g⊥≈0 explains why EPR detection of Er-related optically active centers in silicon may be difficult. Preferential generation of a single type of an optically active Er-related center in MBE growth confirmed in this study is essential for photonic applications of Si:Er.

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