2000 Alfred Bader Award LectureIn the footsteps of Pasteur: asymmetric induction in the photochemistry of crystalline ammonium carboxylate salts

2001 ◽  
Vol 79 (4) ◽  
pp. 349-357 ◽  
Author(s):  
John R Scheffer
Keyword(s):  
Solid State ◽  
Asymmetric Synthesis ◽  
Ammonium Ion ◽  
Chiral Auxiliaries ◽  
Organic Salts ◽  
Space Groups ◽  
Chiral Induction ◽  
Organic Amines ◽  
Asymmetric Environment ◽  
Optically Pure

This review describes the development of a new, synthetically useful method of asymmetric synthesis in organic photochemistry. Similar in many ways to the Pasteur procedure for resolving racemic carboxylic acids and organic amines, the method relies on the use of crystalline organic salts in which the enantioselectivity of a photochemical reaction of an achiral organic ion (for example, a carboxylate anion) is governed in the solid state by the presence of an optically pure counterion (for example, an optically active ammonium ion). Such optically pure counterions are termed ionic chiral auxiliaries. Salts containing ionic chiral auxiliaries are required to crystallize in chiral space groups, which provide the asymmetric environment necessary for chiral induction. Using this methodology, we have obtained near-quantitative optical yields in a wide variety of photochemical reactions.Key words: photochemistry, solid state, chiral auxiliaries, asymmetric synthesis, crystal structure–reactivity relationships.

Article

1998 ◽  
Vol 76 (11) ◽  
pp. 1616-1632
Author(s):  
Bozena Borecka-Bednarz ◽  
Alan V Bree ◽  
Brian O Patrick ◽  
John R Scheffer ◽  
James Trotter
Keyword(s):  
Solid State ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Crystallographic Analysis ◽  
Organic Salts ◽  
Harmonic Intensity ◽  
Space Groups ◽  
Order Of Magnitude ◽  
Optically Pure

Second-harmonic generation in the solid state is restricted to materials that crystallize in non-centrosymmetric space groups. Unfortunately, the vast majority of solids crystallize in centrosymmetric space groups and are therefore SHG-inactive. The requirement for solid-state asymmetry is addressed in a new series of organic salts. The acid p-nitrophenylglycine, SHG-inactive due to its centrosymmetric (P1) packing, was coupled to six optically pure amines to form salts and (or) complexes that, by virtue of their chiral counterion, crystallized in non-centrosymmetric space groups. The 1064 nm output from a Nd:YAG laser produced 532 nm second-harmonic generation from each of the six salts, with three of the salts producing second-harmonic intensities at least an order of magnitude greater than that of our standard, urea. X-ray crystallographic analysis was carried out on five of the six salts, and an attempt was made to rationalize the second-harmonic intensity of each of these five salts based on the orientation of its molecular charge-transfer axis in the unit cell and on its chromophore density.Key words: second-harmonic generation, nonlinear optics, chiral organic salts, crystal structures.

scholarly journals Cellulose recycling as a source of raw chirality

2013 ◽  
Vol 85 (8) ◽  
pp. 1683-1692 ◽  
Author(s):  
Valeria Corne ◽  
María Celeste Botta ◽  
Enrique D. V. Giordano ◽  
Germán F. Giri ◽  
David F. Llompart ◽  
...  
Keyword(s):  
Organic Chemistry ◽  
Organic Carbon ◽  
Asymmetric Synthesis ◽  
Building Blocks ◽  
Biologically Active ◽  
Raw Material ◽  
Chiral Auxiliaries ◽  
High Chemical ◽  
Chiral Structure

Modern organic chemistry requires easily obtainable chiral building blocks that show high chemical versatility for their application in the synthesis of enantiopure compounds. Biomass has been demonstrated to be a widely available raw material that represents the only abundant source of renewable organic carbon. Through the pyrolitic conversion of cellulose or cellulose-containing materials it is possible to produce levoglucosenone, a highly functionalized chiral structure. This compound has been innovatively used as a template for the synthesis of key intermediates of biologically active products and for the preparation of chiral auxiliaries, catalysts, and organocatalysts for their application in asymmetric synthesis.

An Ultimate Stereocontrol in Asymmetric Synthesis of Optically Pure Fully Aromatic Helicenes

2015 ◽  
Vol 137 (26) ◽  
pp. 8469-8474 ◽  
Author(s):  
Michal Šámal ◽  
Serghei Chercheja ◽  
Jiří Rybáček ◽  
Jana Vacek Chocholoušová ◽  
Jaroslav Vacek ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Optically Pure

scholarly journals Influence of Organic Ammonium Derivatives on the Equilibria Between of NH4+, NO2- and NO3- Ions in River Waters

2021 ◽  
Author(s):  
Petru Spataru
Keyword(s):  
River Water ◽  
Nitrogen Concentration ◽  
Inhibitory Effect ◽  
Ammonium Nitrogen ◽  
Ammonium Ion ◽  
Organic Radical ◽  
Stress Effect ◽  
River Waters ◽  
Carbon Radicals ◽  
Organic Amines

Abstract The braking effect of the ammonium derivatives on the natural aquatic environment varies dramatically with the number and nature of organic radical substitutions at nitrogen atom, particularly with their structure, composition and genesis. The most common discrepancy in their toxic effect are showing the natural and synthetic amines. For instance, the values of the maximum allowable concentration (MAC) of the derivatives of the natural origin for drinking water exceed the MAC of the synthetic ones by two orders. On the other hand, it has been found out that 1- naphtylamine (1-NA) inhibitory effect is associated to its toxicity. The Diethylamine (DEA) braking impact on the nitrification process is effectively lower than that of the toxicity. Our experiments show that the carbon-radicals of organic amines act as reducing agents. It is found that DEA decomposition leads to a high NH4+ ions (approx. 3.8 mg/L ammonium nitrogen) concentration in river water samples. By laboratory simulations two types of fixations by microbial organisms have been established: 1) absorption-desorption, the hydromicrobiotic reaction to ammonium (HMBRA) at the instantaneous increase of the concentration of ammonium ion in the river water (so-called shock/stress effect); 2) nitrogen fixation stimulated by a certain concentration (0.05mg/L) of a 1-NA and other amines.

Sign in / Sign up

Export Citation Format

Share Document