scholarly journals The chemical behavior of terminally tert-butylated polyolefins

2015 ◽  
Vol 11 ◽  
pp. 1246-1258
Author(s):  
Dagmar Klein ◽  
Henning Hopf ◽  
Peter G Jones ◽  
Ina Dix ◽  
Ralf Hänel
Keyword(s):  
Catalytic Hydrogenation ◽  
Spectroscopic Data ◽  
Model Compound ◽  
Saturated Hydrocarbon ◽  
Complex Mixture ◽  
Diels Alder ◽  
Equivalent Amount ◽  
Chemical Behavior ◽  
Rearrangement Product ◽  
Olefinic Carbon

The chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition to 3 and 7 yielded the dibromides 17 and 18, respectively, i.e., the oligoene system has been attacked at its terminal olefinic carbon atoms. Analogously, the higher vinylogs 19 and 20 yielded the 1,8- and 1,10-bromine adduts 23 and 24, respectively, when less than 1 equivalent of bromine was employed. Treatment of tetraene 19 with excess bromine provided tetrabromide 25. In epoxidation reactions, both with meta-chloroperbenzoic acid (MCPBA) and dimethyldioxirane (DMDO) two model oligoenes were studied: triene 7 and tetraene 19. Whereas 7 furnished the rearrangement product 31 with MCPBA, it yielded the symmetrical epoxide 32 with DMDO. Analogously, 19 was converted to mono-epoxide 33 with MCPBA and to 34 with DMDO. Diels–Alder addition of 7 with N-phenyltriazolinedione (PTAD) did not take place. Extension of the conjugated π-system to the next higher vinylog, 19, caused NPTD-addition to the symmetrical adduct 37 in good yield. Comparable results were observed on adding NPTD (equivalent amount) to pentaene 20 and hexaene 21. Using 36 in excess provided the 2:1-adduct 40 from 21 and led to a complex mixture of adducts from heptaene 22. With tetracyanoethylene (TCNE) as the dienophile, tetraolefin 19 yielded the symmetrical adduct 43, although the reaction temperature had to be increased. Pentaene 20 and hexaene 21 led to corresponding results, adducts 44 and 45 being produced in acceptable yields. With nonaene 42 and TCNE the 2:1-adduct 48 was generated according to its spectroscopic data. Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52.

Neue Phospha- und Arsa-Heterocyclen aus Cyclophosphanen bzw. -arsanen (ECF3)n (E = P, As; n = 4, 5) und 1,3-Dienen / Novel Phospha- and Arsa-Heterocycles from Cyclophosphanes or -arsanes (ECF3)n (E = P, As; n = 4, 5) and 1,3-Dienes

1995 ◽  
Vol 50 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Andreas Karst ◽  
Burkhardt Broschk ◽  
Joseph Grobe ◽  
Duc Le Van
Keyword(s):  
Spectroscopic Data ◽  
Uv Light ◽  
Diels Alder ◽  
Molar Ratio ◽  
The Novel

Reaction of the cyclotetraphosphane (PCF3)4 or of a mixture of (PCF3)4 and (PCF3)5 with 2,3-dimethyl-1,3-butadiene or isoprene at 25 °C leads to the [4 + 2]-cycloadducts of bis(trifluoromethyl) diphosphene and the phospholene derivatives 2a and 2b, respectively, in the molar ratio diphosphinine/phospholene = 1/2. The analogous reactions of the cycloarsanes (AsCF3)4,5 give the Diels/Alder compounds 4 and 5 of bis(trifluoromethyl)diarsene in 90% yield without arsolene formation. Cyclopentadiene, 1,3-cyclohexadiene and cis or trans piperylene do not react with (AsCF3)4,5, up to temperatures of 60 °C. However, the corresponding [4 + 2]-cycloadducts 6 - 8 are produced by irradiation of the reaction mixture with UV light. The novel phospholenes 2a and 2b as well as the diarsinines 4 - 8 have been characterized by spectroscopic data (MS, NMR, IR). 2a was coordinated as a phosphane ligand to the pentacarbonylchromium fragment by reaction with the photochemically generated complex Cr(CO)5 · THF to afford the new compound (3).

Exploratory synthetic investigations related to 12a-deoxypillaromycinone

2002 ◽  
Vol 80 (6) ◽  
pp. 728-738 ◽  
Author(s):  
Lan Wang ◽  
Sanath K Meegalla ◽  
Cheng-Lin Fang ◽  
Nicholas Taylor ◽  
Russell Rodrigo
Keyword(s):  
Double Bond ◽  
Catalytic Hydrogenation ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Step Procedure ◽  
Key Steps

Furfural is converted to suitably substituted AB synthon 21 for 12a-deoxypillaromycinone in 10 steps by a sequence involving the following key steps: intramolecular Diels-Alder reaction of a furan, 5-endo-trig cleavage of the oxabicyclo adducts 18, and catalytic hydrogenation of the double bond of a tetrasubstituted enone to produce 19. Enones 21a and 21b obtained by dehydrogenation of 19a and 19b, respectively, are then annulated with ethyl 2-methoxy-6-methylbenzoate in a four-step procedure to generate tetracyclic products 25 in 14 steps from furfural.

Convenient preparation of a β-O-4-type lignin model trimer via KOH-catalyzed hydroxymethylation and a new protection method

Holzforschung ◽  
2013 ◽  
Vol 67 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Maarit Lahtinen ◽  
Anssi Haikarainen ◽  
Jussi Sipilä
Keyword(s):  
Model Compound ◽  
Catalytic Amount ◽  
Side Chain ◽  
Hydroxyl Groups ◽  
Chemical Behavior ◽  
Model Compounds ◽  
Protection Method ◽  
Convenient Synthesis ◽  
Lignin Model ◽  
Convenient Preparation

Abstract Lignin, as the second most abundant biopolymer on earth, is one of the targets for plant biorefinery studies. Its complex chemical behavior is frequently studied by dimeric, trimeric, etc. model compounds, preferably with a β-O-4-type structure. In the present study, a convenient synthesis of a β-O-4-type trimeric model compound possessing a free syringylic hydroxyl has been investigated. Two key modifications were in focus: (1) Protection of the aliphatic hydroxyl groups of the starting phenolic dimer prior to the SN2 displacement reaction before introducing the syringylic moiety with 2,2-dimethoxypropane. (2) The hydroxymethylation step to introduce the full side chain moiety. When this reaction was performed in dioxane/water in the presence of a catalytic amount of KOH instead of K2CO3, the formation of a side product via dehydration was markedly reduced. In addition, a convenient method for introducing an α,β-epoxide structure in acetophenone is recommended.

The regioselectivity of the formation of dihydro- and tetrahydrocarbazoles by the Fischer indole synthesis

1982 ◽  
Vol 60 (4) ◽  
pp. 419-424 ◽  
Author(s):  
G. W. Bryan Reed ◽  
Peter T. W. Cheng ◽  
Stewart McLean
Keyword(s):  
Sulfuric Acid ◽  
Significant Variation ◽  
Complex Mixture ◽  
Mechanistic Explanation ◽  
Transformation Products ◽  
Diels Alder ◽  
Fischer Indole Synthesis ◽  
Indole Synthesis

The cyclohexanone 3 and the cyclohexenone 13 have been prepared, converted to their phenylhydrazones, and subjected to the Fischer indole synthesis under conditions ranging from 7% to 60% sulfuric acid in methanol. The tetrahydrocarbazoles 4 and 5 were isolated in a 2:1 ratio in the sequence starting from 3 and no significant variation in the ratio was observed through the range of conditions used. In the sequence starting with 13, the dihydrocarbazoles 14 and 15 were isolated in a 1:1 ratio when 7% or 15% sulfuric acid was used; when more concentrated acid was used, normal Fischer products were not obtained but some transformation products were isolated from the complex mixture of products obtained. The observed regioselectivity of these reactions is not predicted from mechanistic considerations, and no mechanistic explanation for the results is apparent. As part of the proof of structure of 4 and 14, their N-benzyl derivatives were prepared from 1-benzyl-2-vinylindole by Diels–Alder reactions.

The Nakada Synthesis of (-)-FR182877

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Complex Mixture ◽  
Alder Reaction ◽  
Single Step ◽  
Diels Alder ◽  
Allylic Alcohol ◽  
Allylic Alcohols ◽  
Weinreb Amide ◽  
Diels Alder Reaction ◽  
Reaction Matrix ◽  
Stereogenic Centers

The Streptomyces metabolite (-)-FR182877 3 binds to and stabilizes microtubules, showing the same potency of anticancer activity as Taxol (paclitaxel). Masahisa Nakada of Waseda University assembled (Angew. Chem. Int. Ed. 2009, 48, 2580) the hexacyclic ring system of 3 by the tandem intramolecular Diels-Alder–intramolecular hetero Diels-Alder cyclization of 1, generating seven new stereogenic centers in a single step. The construction of the pentaene substrate 1 started with the known aldehyde 4, prepared by homologation of commercial ethyl 3-methyl-4-oxocrotonate. Addition of the propionyl oxazolidine anion 5 proceeded with high diastereocontrol, to give 6. The acyl oxazolidinone was not an efficient acylating agent, so it was converted to the Weinreb amide. Protection and deprotection then delivered the allylic acetate 7. The key step in the pentaene assembly was the carefully optimized Negishi-Wipf methylation of 8, followed by Pd-mediated coupling of the alkenyl organometallic so generated with the allylic acetate, to give 9. Condensation of the derived keto phosphonate 11 with the known aldehyde 12 then delivered the enone 13. The Nakada group has worked extensively on the intramolecular Diels-Alder reaction of substrates such as 1. They have shown that protected anti diols such as 1 cyclize with substantial diastereocontrol and in the desired sense. In contrast, cyclizations of protected syn diols proceed with poor diastereocontrol. The enone 13 was therefore reduced to the anti diol and protected, leading to 14 . Oxidation of 14 at room temperature led to a complex mixture, but slow oxidation at elevated temperature delivered 2 . Although the yield of 2 was not much better than if the reactions were carried out sequentially, first the intramolecular Diels-Alder cyclization, then the intramolecular hetero Diels-Alder cyclization, with the cascade protocol pure 2 was more readily separated from the reaction matrix. With 2 in hand, there was still the challenge of assembling the seven-membered ring. Cyclization was effected with an intramolecular Heck protocol. The two diastereomers of the allylic alcohol 15 cyclized with comparable efficiency. Ir-catalyzed alkene migration then converted the allylic alcohols to a mixture of ketones, which was equilibrated to give the more stable diasteromer.

Synthesis, Experimental and Theoretical Study on the Structure of Some Semicarbazides with Potential Antibacterial Activity

2011 ◽  
Vol 66 (5) ◽  
pp. 505-511 ◽  
Author(s):  
Monika Pitucha ◽  
Zbigniew Karczmarzyk ◽  
Urszula Kosikowska ◽  
Anna Malm
Keyword(s):  
Antibacterial Activity ◽  
Gas Phase ◽  
Elemental Analysis ◽  
Active Compound ◽  
Spectroscopic Data ◽  
Model Compound ◽  
Tautomeric Form ◽  
Theoretical Study ◽  
Tautomeric Equilibrium ◽  
New Compounds

A series of 1,4-disubstituted semicarbazide and 4,4’-bis[1-substituted semicarbazide]diphenylmethane derivatives were synthesized to explore their antibacterial activity. New compounds were characterized by elemental analysis and spectroscopic data. In order to find the tautomeric equilibrium for the molecules energy calculations for each possible tautomeric form of model compound 2, and for the most antibacterially active compound 7 in the investigated series, were calculated for the gas phase at the RHF/SCF/6-31G** level of theory

Determination of the Complete Set of Iron Normal Modes in the Heme Model Compound FeIII(OEP)Cl from Nuclear Resonance Vibrational Spectroscopic Data

2003 ◽  
Vol 107 (40) ◽  
pp. 11170-11177 ◽  
Author(s):  
Timo E. Budarz ◽  
E. W. Prohofsky ◽  
Stephen M. Durbin ◽  
Theodore Sjodin ◽  
J. Timothy Sage ◽  
...  
Keyword(s):  
Spectroscopic Data ◽  
Model Compound ◽  
Normal Modes ◽  
Nuclear Resonance ◽  
Complete Set

scholarly journals Renewable Cyclopentanol From Catalytic Hydrogenation-Rearrangement of Biomass Furfural Over Ruthenium-Molybdenum Bimetallic Catalysts

2020 ◽  
Vol 8 ◽  
Author(s):  
Shihang Meng ◽  
Yujing Weng ◽  
Xiaolong Wang ◽  
Hongxing Yin ◽  
Zhenfei Wang ◽  
...  
Keyword(s):  
Catalytic Hydrogenation ◽  
Selective Hydrogenation ◽  
Bimetallic Catalysts ◽  
Bimetallic Catalyst ◽  
Catalytic Performance ◽  
Fine Chemicals ◽  
Product Selectivity ◽  
Rearrangement Product ◽  
Hydrogenation Activity ◽  
Rearrangement Reaction

Biomass furfural-like compounds are chemicals that cannot be extracted from fossil materials, through which a large number of fine chemicals and fuel additives can be opened up, but one big efficiency problem during the transformation is the accumulation of oligomers. Here, we propose a novel and efficient Ru-Mo bimetallic catalyst for selective hydrogenation-rearrangement of furfural-like compounds. The result showed that an unprecedented rearrangement product selectivity of 89.1% to cyclopentanol was achieved under an optimized reaction condition over a 1%Ru−2.5%Mo/CNT catalyst reduced at 600°C. Subsequent characterization suggested that the catalyst presented with weak acidity and strong hydrogenation activity for the reaction, which not only ensures the smooth hydrogenation-rearrangement reaction but also inhibits the accumulation of furan polymers. These findings provide a convenient strategy to tune the catalytic performance of Mo-based catalysts by controlling the reduction and carburization conditions, which appear to be versatile for the rearrangement of furans and similar compounds.

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