scholarly journals Photo-induced tandem cyclization of 3-iodoflavones with electron rich five-membered heteroarenes

RSC Advances ◽  
2017 ◽  
Vol 7 (68) ◽  
pp. 43206-43211 ◽  
Author(s):  
Qian Yang ◽  
Rui Wang ◽  
Jie Han ◽  
Chenchen Li ◽  
Tao Wang ◽  
...  
Keyword(s):  
Reaction Conditions ◽  
Vinyl Radicals ◽  
Broad Variety ◽  
Tandem Cyclization

Vinyl radicals were generated from 3-iodoflavones and occurred tandem cyclizations to synthesis a broad variety of novel polycyclic xanthone frameworks in good yields under mild and environmentally reaction conditions.

scholarly journals Astrochemistry and Astrobiology: Materials Sciencein Wonderland?

2019 ◽  
Vol 20 (17) ◽  
pp. 4079 ◽  
Author(s):  
Marco d'Ischia ◽  
Paola Manini ◽  
Marco Moracci ◽  
Raffaele Saladino ◽  
Vincent Ball ◽  
...  
Keyword(s):  
Material Design ◽  
Reaction Pathways ◽  
Mineral Surfaces ◽  
Thermal Transformations ◽  
Reaction Conditions ◽  
Organic Systems ◽  
Polycyclic Aromatic ◽  
Broad Variety ◽  
The Origin Of Life ◽  
Complex Organic

Astrochemistry and astrobiology, the fascinating disciplines that strive to unravel the origin of life, have opened unprecedented and unpredicted vistas into exotic compounds as well as extreme or complex reaction conditions of potential relevance for a broad variety of applications. Representative, and so far little explored sources of inspiration include complex organic systems, such as polycyclic aromatic hydrocarbons (PAHs) and their derivatives; hydrogen cyanide (HCN) and formamide (HCONH2) oligomers and polymers, like aminomalononitrile (AMN)-derived species; and exotic processes, such as solid-state photoreactions on mineral surfaces, phosphorylation by minerals, cold ice irradiation and proton bombardment, and thermal transformations in fumaroles. In addition, meteorites and minerals like forsterite, which dominate dust chemistry in the interstellar medium, may open new avenues for the discovery of innovative catalytic processes and unconventional methodologies. The aim of this review was to offer concise and inspiring, rather than comprehensive, examples of astrochemistry-related materials and systems that may be of relevance in areas such as surface functionalization, nanostructures, and hybrid material design, and for innovative technological solutions. The potential of computational methods to predict new properties from spectroscopic data and to assess plausible reaction pathways on both kinetic and thermodynamic grounds has also been highlighted.

Photoinduced Proton Transfer Reactions for Mild O-H Functionalization Reactions of Unreactive Alcohols

2019 ◽  
Author(s):  
Sripati Jana ◽  
Zhen Yang ◽  
Fang Li ◽  
Claire Empel ◽  
Junming Ho ◽  
...  
Keyword(s):  
Photochemical Reaction ◽  
Transfer Reactions ◽  
Mechanistic Studies ◽  
Acid Base ◽  
Reaction Conditions ◽  
Proton Transfer Reactions ◽  
Photoinduced Proton Transfer ◽  
Broad Variety ◽  
Stoichiometric Reaction ◽  
Fluorinated Ethers

Hexafluoroisopropanol is typically considered as an unreactive solvent and not as a reagent in organic synthesis. Herein, we report on a mild and efficient photochemical reaction of aryl diazoacetates with hexafluoroisopropanol that enables, under stoichiometric reaction conditions, the synthesis of fluorinated ethers in excellent yield. We support these findings with mechanistic studies, which indicate a preorganization of hexafluoroisopropanol and the diazoalkane as an unreactive Lewis Acid-Base adduct. Only upon photoexcitation, this adduct undergoes a protonation-substitution reaction to the reaction product. We conclude with investigations on the applicability of this photochemical transformation and could show that a broad variety of acidic alcohols can be subjected to this transformation and thus demonstrate the feasibility of this concept in O-H functionalization reactions (52 examples, up to 98% yield).

Photoinduced Proton Transfer Reactions for Mild O-H Functionalization Reactions of Unreactive Alcohols

2019 ◽  
Author(s):  
Sripati Jana ◽  
Zhen Yang ◽  
Fang Li ◽  
Claire Empel ◽  
Junming Ho ◽  
...  
Keyword(s):  
Photochemical Reaction ◽  
Transfer Reactions ◽  
Mechanistic Studies ◽  
Acid Base ◽  
Reaction Conditions ◽  
Proton Transfer Reactions ◽  
Photoinduced Proton Transfer ◽  
Broad Variety ◽  
Stoichiometric Reaction ◽  
Fluorinated Ethers

Hexafluoroisopropanol is typically considered as an unreactive solvent and not as a reagent in organic synthesis. Herein, we report on a mild and efficient photochemical reaction of aryl diazoacetates with hexafluoroisopropanol that enables, under stoichiometric reaction conditions, the synthesis of fluorinated ethers in excellent yield. We support these findings with mechanistic studies, which indicate a preorganization of hexafluoroisopropanol and the diazoalkane as an unreactive Lewis Acid-Base adduct. Only upon photoexcitation, this adduct undergoes a protonation-substitution reaction to the reaction product. We conclude with investigations on the applicability of this photochemical transformation and could show that a broad variety of acidic alcohols can be subjected to this transformation and thus demonstrate the feasibility of this concept in O-H functionalization reactions (52 examples, up to 98% yield).

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>

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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