Synthesis of Cyclopropylpyrrolidines via Reaction ofN-Allyl-N-propargylamides with a Molybdenum Carbene Complex. Effect of Substituents and Reaction Conditions

1996 ◽  
Vol 61 (7) ◽  
pp. 2268-2272 ◽  
Author(s):  
Daniel F. Harvey ◽  
Dina M. Sigano
Keyword(s):  
Reaction Conditions ◽  
Complex Effect ◽  
Carbene Complex ◽  
Effect Of Substituents

scholarly journals Influence of the Substituents on the Opening of Silylepoxy Alcohols: 5-exo-Cyclization towards Tetrahydrofurans vs. Unexpected Side Reaction Leading to Tetrahydropyrans

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7386
Author(s):  
Carlos Díez-Poza ◽  
Asunción Barbero
Keyword(s):  
Ring Opening ◽  
Side Reaction ◽  
Structural Factors ◽  
Reaction Conditions ◽  
Effect Of Substituents ◽  
Different Types ◽  
Acid Catalyzed ◽  
Epoxy Alcohols

The regioselective ring opening of epoxy alcohols is an effective method for the synthesis of different types of oxacycles. The 5-exo opening being preferred vs. the 6-endo mode, according to Baldwin rules, the use of silyl-substituted oxiranes has been reported as a possible method to favor the 6-endo cyclization. However, there is a need for a detailed study on the different factors (structural factors, catalyst nature or conditions) that influence this process. In this paper, the acid-catalyzed cyclization of epoxysilyl alcohols was studied, focusing on the effect of substituents and reaction conditions on the outcome of the process. Two types of heterocycles (tetrahydrofurans or tetrahydropyrans) were selectively obtained depending on the structure of the initial epoxysilyl alcohol. Interestingly, cyclization of hindered epoxysilyl alcohols mainly proceeds through an unexpected side reaction, which implies a previous isomerization to an aldehyde. A mechanistic proposal for the formation of the different products is presented.

Effect of substituents on molybdenum triiodide complexes bearing PNP-type pincer ligands toward catalytic nitrogen fixation

2019 ◽  
Vol 48 (10) ◽  
pp. 3182-3186 ◽  
Author(s):  
Takayuki Itabashi ◽  
Ikki Mori ◽  
Kazuya Arashiba ◽  
Aya Eizawa ◽  
Kazunari Nakajima ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pincer Ligands ◽  
Ammonia Production ◽  
Reaction Conditions ◽  
Effect Of Substituents

Molybdenum triiodide complexes bearing phenyl and ferrocenyl substituted PNP-type pincer ligands acted as more effective catalysts toward ammonia production under ambient reaction conditions.

Übergangsmetall-Carben-Komplexe, CXXXI. Umsetzung von [(CO)5WCNEt2]BF4 mit anionischen Organylverbindungen von Elementen der V. Hauptgruppe/ Transition Metal Carbene Complexes, CXXXI. Reaction of [(CO)sWCNEt2]BF4 with Anionic Organyl Compounds of Group V Elements

1983 ◽  
Vol 38 (5) ◽  
pp. 582-586 ◽  
Author(s):  
Ernst Otto Fischer ◽  
Rudolf Reitmeier
Keyword(s):  
Transition Metal ◽  
Nucleophilic Addition ◽  
Spectroscopic Data ◽  
The Novel ◽  
Reaction Conditions ◽  
Group V ◽  
Carbene Complexes ◽  
Carbene Complex ◽  
Reductive Dimerization ◽  
New Compounds

AbstractThe cationic carbyne complex [(CO)5WCNEt2]BF4 (1) reacts with potassiumdiphenylamide, KNPh2, with nucleophilic addition of the amide anion to give (CO)5W[C(NEt2)NPh2] (2). The corresponding reactions with KPPh2, KPEt2, KPMePh, NaSbPh2 and NaBiPh2 yield the complex [(CO)5W(CNEt2)]2 (3), which is formed by reductive dimerization of two carbyne fragments. In case of KPMePh the carbene complexes (CO)5W[C(NEt2)PMePh (4) and trans-(MePhPH)(CO)4W[C(NEt2)PMePh] (5) are also obtained. On warming in solution 5 spontaneously rearranges to the novel cyclic carbene complex (6). Reaction conditions, properties and spectroscopic data of the new compounds are reported.

Substituent effects of the cycloaddition reaction of 7-substituted 5H-benzocycloheptenes with singlet oxygen and the chemistry of the benzocycloheptene endoperoxides

2005 ◽  
Vol 83 (3) ◽  
pp. 227-235 ◽  
Author(s):  
Murat Güney ◽  
Zeynep Çelik Ceylan ◽  
Arif Daştan ◽  
Metin Balci
Keyword(s):  
Reaction Mechanism ◽  
Singlet Oxygen ◽  
Electronic Effect ◽  
Cycloaddition Reaction ◽  
Substituent Effects ◽  
Reaction Conditions ◽  
Effect Of Substituents

The cycloaddition reaction of 7-substituted 5H-benzocycloheptenes with singlet oxygen and the chemistry of the obtained endoperoxides were investigated. Reaction of carboethoxy-substituted endoperoxide with NEt3 gave a mixture of products; hydroxyketone, diketone, and carboethoxy-substituted keto–enol tautomers, whereas the reaction of methyl-substituted endoperoxide only formed a diketone under the same reaction conditions. Thermolysis, thiourea, and CoTPP reactions of the endoperoxides were also studied. The reaction mechanism and electronic effect of substituents were discussed.Key words: benzocycloheptene, photooxygenation, endoperoxides, rearrangement, CoTPP.

Undecagold labeling of tRNA

1991 ◽  
Vol 49 ◽  
pp. 44-45
Author(s):  
James F. Hainfeld ◽  
Kyra M. Alford ◽  
Mathias Sprinzl ◽  
Valsan Mandiyan ◽  
Santa J. Tumminia ◽  
...  
Keyword(s):  
High Resolution ◽  
Transmission Electron Micrograph ◽  
Anticodon Loop ◽  
Electron Micrograph ◽  
Reaction Conditions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

Dimensionally-Controlled Hydrothermal Tm3+-doped Oxidic Nanocrystals and Their Photoluminescence Properties

2010 ◽  
Vol 1247 ◽  
Author(s):  
Rocío Calderón-Villajos ◽  
Carlos Zaldo ◽  
Concepción Cascales
Keyword(s):  
Single Crystals ◽  
Fluorescence Lifetimes ◽  
Photoluminescence Properties ◽  
Reaction Conditions ◽  
Hydrothermal Processes ◽  
Bulk Single Crystals ◽  
Template Free ◽  
Reaction Media

AbstractControlled reaction conditions in simple, template-free hydrothermal processes yield Tm-Lu2O3 and Tm-GdVO4 nanocrystals with well-defined specific morphologies and sizes. In both oxide families, nanocrystals prepared at pH 7 reaction media exhibit photoluminescence in ∼1.95 μm similar to bulk single crystals. For the lowest Tm3+ concentration (0.2 % mol) in GdVO4 measured 3H4 and 3F4 fluorescence lifetimes τ are very near to τrad.

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

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