Yb(OTf) 3 ‐Catalyzed Cycloaddition/[3,3]‐Rearrangement of N ‐Vinyl‐α,β‐Unsaturated Ketonitrones with Methylenecycloprop‐anes: Stereoselective Synthesis of Nine‐Membered Nitrogen Heterocycles

2019 ◽  
Vol 362 (3) ◽  
pp. 478-486 ◽  
Author(s):  
Xiao‐Pan Ma ◽  
Cai‐Mei Nong ◽  
Jie Zhao ◽  
Xiuqiang Lu ◽  
Cui Liang ◽  
...  
Keyword(s):  
Stereoselective Synthesis ◽  
Nitrogen Heterocycles

Cyclizations using Selenium Chemistry for Substituted 3-Hydroxypiperidines and 3-Hydroxypyrrolidines

2011 ◽  
Vol 64 (10) ◽  
pp. 1327 ◽  
Author(s):  
Matthew A. Cooper ◽  
A. David Ward
Keyword(s):  
Stereoselective Synthesis ◽  
Nitrogen Heterocycles ◽  
Kinetic Control ◽  
Current Interest ◽  
Reaction Conditions ◽  
Hydroxide Ion ◽  
New Methods ◽  
Electrophilic Activation ◽  
Related Compounds

The development of new methods for the stereoselective synthesis of nitrogen heterocycles is of current interest because of increasing demands for the syntheses of biologically important alkaloids and related compounds. It is shown that selenium-induced cyclization of 4-hydroxy-5-pentenylamines occurs regio- and stereo-selectively to afford cis-3-hydroxy-2-phenylselenomethylpyrrolidines, whereas 5-hydroxy-6-hexenylamines cyclize and give trans-3-hydroxy-2-phenylselenomethylpiperidines, with some compounds forming stable hydrates. In all cases cyclization proceeds regioselectively to give only the exo adducts with moderate to good diastereoselectivity. The reaction appeared to be under kinetic control as product ratios did not alter with time and the separated diastereomers did not interconvert when resubjected to the reaction conditions. These phenylseleno-substituted compounds could be transformed to diols by substitution of the corresponding selenone with a hydroxide ion. Substituted pyrrolidines and piperidines were thus afforded from unsaturated protected amines by electrophilic activation with SeII, followed by oxidation of the intermediate to SeVI and substitution with nucleophiles.

Ruthenium Porphyrin Catalyzed Intramolecular Carbenoid C−H Insertion. Stereoselective Synthesis of Cis-Disubstituted Oxygen and Nitrogen Heterocycles

2003 ◽  
Vol 5 (14) ◽  
pp. 2535-2538 ◽  
Author(s):  
Wai-Hung Cheung ◽  
Shi-Long Zheng ◽  
Wing-Yiu Yu ◽  
Guo-Chuan Zhou ◽  
Chi-Ming Che
Keyword(s):  
Stereoselective Synthesis ◽  
Nitrogen Heterocycles ◽  
Ruthenium Porphyrin

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

1997 ◽  
Vol 161 ◽  
pp. 179-187
Author(s):  
Clifford N. Matthews ◽  
Rose A. Pesce-Rodriguez ◽  
Shirley A. Liebman
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Hydrogen Cyanide ◽  
Nitrogen Heterocycles ◽  
Laboratory Studies ◽  
Heterogeneous Solids ◽  
The Many ◽  
Comet Halley ◽  
The Impact ◽  
By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

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