Efficient preparation of chiral non-racemic sulfur compounds

2007 ◽  
Vol 85 (9) ◽  
pp. 603-618 ◽  
Author(s):  
Joannie Minville ◽  
Mélina Girardin ◽  
Claude Spino
Keyword(s):  
Sulfur Compounds ◽  
Sigmatropic Rearrangement ◽  
Chiral Auxiliary ◽  
Quaternary Carbon ◽  
Ring Closing Metathesis ◽  
Sulfur Containing

p-Menthane-3-carboxaldehyde serves as an efficient chiral auxiliary in the preparation of chiral non-racemic S-alkylthiocarbamates or S-dithiocarbonates via the 3,3-sigmatropic rearrangement of the corresponding alkylthionocarbamates or xanthates. The transfer of chirality during rearrangement is complete, and the final products possess a chiral tertiary or quaternary carbon bearing sulfur. The rearranged products are then transformed into enantiopure cyclic or acyclic sulfur-containing products, depending on the means of clivage of the auxiliary. The synthesis of a potent MMP-13 inhibitor is presented.Key words: 3,3-sigmatropic rearrangement, p-menthane-3-carboxaldehyde, S-alkylthiocarbamate, S-dithiocarbonate, alkylthionocarbamate, xanthate, ring-closing metathesis.

scholarly journals New Gas-Phase Catalytic Oxidative Processes for Desulfurization of Diesel Fuel

2015 ◽  
Vol 17 (2) ◽  
pp. 119 ◽  
Author(s):  
Z.R. Ismagilov ◽  
M.A. Kerzhentsev ◽  
S.A. Yashnik ◽  
S.R. Khairulin ◽  
A.V. Salnikov ◽  
...  
Keyword(s):  
Gas Phase ◽  
Diesel Fuel ◽  
Ambient Pressure ◽  
Oxidative Desulfurization ◽  
Sulfur Compounds ◽  
Deep Desulfurization ◽  
Oxidative Processes ◽  
Laboratory Reactor ◽  
Sulfur Containing ◽  
Regeneration Processes

<p>An effective gas-phase oxidative desulfurization (ODS) process was proposed. The process was studied in a laboratory reactor with a proprietary catalyst at 300-400 ºС and ambient pressure with model fuels represented by thiophene, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) dissolved in octane, isooctane or toluene. The reactivity of different sulfur containing molecules in ODS was shown to increase in the sequence: thiophene &lt; DBT &lt; DMDBT. The main sulfur containing product of oxidation of these compounds was SO<sub>2</sub>. During the gas-phase ODS both processes of sulfur species oxidation and processes of their adsorption were observed and studied. Based on the conducted studies, different ODS process designs comprising its integration with adsorption and regeneration processes and with conventional hydrodesulfurization (HDS) process were proposed. One scheme is based on alternating regimes of ODS and catalyst regeneration in two reactors: sulfur is removed from organic feedstock by oxidation and adsorption in one reactor while simultaneous regeneration of the catalyst that has accumulated sulfur  compounds takes place in another reactor. Two other schemes are based on joint use of ODS and HDS. The conventional HDS process is most effective for removal of low-boiling sulfur containing compounds reactive with respect to hydrogen, while removal of refractory sulfur compounds, such as DMDBT is more easily achieved by gas phase ODS. Thus the combination of these processes is expected to be most efficient for deep desulfurization of diesel fuel.</p>

scholarly journals Sulfur and Sulfur Compounds in Plant Defence

2012 ◽  
Vol 7 (3) ◽  
pp. 1934578X1200700 ◽  
Author(s):  
Ifeanyi D. Nwachukwu ◽  
Alan J. Slusarenko ◽  
Martin C. H. Gruhlke
Keyword(s):  
Natural Products ◽  
New Technologies ◽  
Plant Defence ◽  
Sulfur Compounds ◽  
Oxidation States ◽  
Chemical Structures ◽  
Wide Range ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

The multiplicity of chemical structures of sulfur containing compounds, influenced in part by the element's several oxidation states, directly results in diverse modes of action for sulfur-containing natural products synthesized as secondary metabolites in plants. Sulfur-containing natural products constitute a formidable wall of defence against a wide range of pathogens and pests. Steady progress in the development of new technologies have advanced research in this area, helping to uncover the role of such important plant defence molecules like endogenously-released elemental sulphur, but also deepening current understanding of other better-studied compounds like the glucosinolates. As studies continue in this area, it is becoming increasingly evident that sulfur and sulfur compounds play far more important roles in plant defence than perhaps previously suspected.

Equilibrium Analysis on Sulfur Material in Oxyfuel Combustion

2014 ◽  
Vol 986-987 ◽  
pp. 67-71
Author(s):  
Hai Ping Xiao ◽  
Gao Yan Han ◽  
Yu Kun Dai ◽  
Lin Dong
Keyword(s):  
Thermodynamic Equilibrium ◽  
Formation Rate ◽  
Equilibrium Concentration ◽  
Sulfur Compounds ◽  
Equilibrium Analysis ◽  
Conventional Combustion ◽  
Gas Formation ◽  
Oxyfuel Combustion ◽  
Excess Air Coefficient ◽  
Sulfur Containing

To study migration and transformation of sulfur species in oxyfuel combustion, the study attempts to analyze distribution of sulfur compounds with thermodynamic equilibrium. Results show that sulfur-containing gases predominantly are SO2 and SO3, the maximum thermodynamic equilibrium concentration of those in oxyfuel combustion respectively increase by 3.4 and 4.5 times compared with the conventional combustion. Furthermore, SO2 gas formation rate decreases while SO3 increases under oxyfuel combustion. Sulfur-containing gases are generally more sensitive to temperature and excess air coefficient. The amount of sulfur compounds significantly increases in oxyfuel combustion.

Water-promoted claisen sigmatropic rearrangement using glyco-organic substrates. Chiral auxiliary-mediated induction

1990 ◽  
Vol 31 (29) ◽  
pp. 4147-4150 ◽  
Author(s):  
André Lubineau ◽  
Jacques Augé ◽  
Nathalie Bellanger ◽  
Sylvie Caillebourdin
Keyword(s):  
Sigmatropic Rearrangement ◽  
Chiral Auxiliary ◽  
Organic Substrates

Part 2: Efficient strategies for the construction of variably substituted bicyclo[5.3.1]undecenones (AB-taxane ring systems) and their conversion to tricyclo[9.3.1.03,8]pentadecenones (ABC taxane ring systems) and bicyclo[2.2.2]octanones

2004 ◽  
Vol 82 (2) ◽  
pp. 227-239 ◽  
Author(s):  
Nidia P Villalva-Servín ◽  
Alain Laurent ◽  
Alex G Fallis
Keyword(s):  
Lewis Acid ◽  
Sigmatropic Rearrangement ◽  
Diels Alder ◽  
Direct Access ◽  
Cope Rearrangement ◽  
Ring Closing Metathesis ◽  
Ring Systems ◽  
Sigmatropic Rearrangements ◽  
Key Words Magnesium ◽  
Cope Rearrangements

The extension of our strategies for the construction of cyclic molecules containing variably substituted bicyclo[5.3.1]undecenones (AB taxane ring systems) for the synthesis of the tricyclo[9.3.1.03,8]pentadecenone (ABC taxane ring system) and bicyclo[2.2.2]octanones are described. These routes employ a multi-component coupling protocol that employs sequential magnesium-mediated carbometallation of allyl-substituted propargyl alcohols followed by diastereoselective Lewis acid catalyzed intramolecular Diels–Alder reactions (IMDA). Subsequent ring-closing metathesis (RCM) afforded the ABC taxane core structure. Enone accelerated [3,3] sigmatropic rearrangements (Cope rearrangements) generated the bicyclo[2.2.2]octanone nucleus. In the presence of a Lewis acid, the dienophile precursor underwent a tandem reaction via the adduct directly to the bicyclo[2.2.2]octanones. This is the first example of a novel enone accelerated carbocycle Cope rearrangement and provides direct access to bicyclo[2.2.2]octanones by a new route that compliments the traditional cyclohexadiene cycloaddition approach. Key words: magnesium chelate, Lewis acid, taxanes, Diels–Alder, sigmatropic rearrangement, oxy-Cope, ring-closing metathesis, bicyclo[2.2.2]octanone.

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