scholarly journals Metal-Free Aryl Cross-Coupling Directed by Traceless Linkers

2019 ◽  
Author(s):  
Veit G. Haensch ◽  
Toni Neuwirth ◽  
Johannes Steinmetzer ◽  
Florian Kloss ◽  
Rainer Beckert ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Quantum Chemical ◽  
Singlet State ◽  
Cross Coupling ◽  
Excited Singlet ◽  
Reaction Conditions ◽  
Photochemical Process ◽  
New Approach ◽  
Metal Free ◽  
Membered Transition State

<div>The metal-free, highly selective synthesis of biaryls poses a major challenge in organic synthesis. We report the scope and mechanism of a promising new approach to (hetero)biaryls by the photochemical fusion of aryl substituents tethered to a traceless linker (photosplicing). Interrogating photosplicing with varying reaction conditions and comparison of diverse synthetic probes (40 examples, including a suite of heterocycles) showed that the reaction has a surprisingly broad scope and involves neither metals nor radicals. Quantum chemical calculations revealed that the C–C bond is formed by an intramolecular photochemical process that involves an excited singlet state and the traverse of a five-membered transition state, thus warranting consistent <i>ipso</i>‑<i>ipso</i>‑coupling fidelity. These results demonstrate that photosplicing is a unique aryl cross-coupling method in the excited state that can be applied to synthesize a broad range of biaryls. </div>

scholarly journals Metal-Free Aryl Cross-Coupling Directed by Traceless Linkers

2019 ◽  
Author(s):  
Veit G. Haensch ◽  
Toni Neuwirth ◽  
Johannes Steinmetzer ◽  
Florian Kloss ◽  
Rainer Beckert ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Quantum Chemical ◽  
Singlet State ◽  
Cross Coupling ◽  
Excited Singlet ◽  
Reaction Conditions ◽  
Photochemical Process ◽  
New Approach ◽  
Metal Free ◽  
Membered Transition State

<div>The metal-free, highly selective synthesis of biaryls poses a major challenge in organic synthesis. We report the scope and mechanism of a promising new approach to (hetero)biaryls by the photochemical fusion of aryl substituents tethered to a traceless linker (photosplicing). Interrogating photosplicing with varying reaction conditions and comparison of diverse synthetic probes (40 examples, including a suite of heterocycles) showed that the reaction has a surprisingly broad scope and involves neither metals nor radicals. Quantum chemical calculations revealed that the C–C bond is formed by an intramolecular photochemical process that involves an excited singlet state and the traverse of a five-membered transition state, thus warranting consistent <i>ipso</i>‑<i>ipso</i>‑coupling fidelity. These results demonstrate that photosplicing is a unique aryl cross-coupling method in the excited state that can be applied to synthesize a broad range of biaryls. </div>

Photophysical Properties of Conformationally Distorted Metal-Free Porphyrins. Investigation into the Deactivation Mechanisms of the Lowest Excited Singlet State

1994 ◽  
Vol 116 (16) ◽  
pp. 7363-7368 ◽  
Author(s):  
Steve Gentemann ◽  
Craig J. Medforth ◽  
Timothy P. Forsyth ◽  
Daniel J. Nurco ◽  
Kevin M. Smith ◽  
...  
Keyword(s):  
Singlet State ◽  
Photophysical Properties ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Metal Free

Experimentelle und Quantenchemische Untersuchungen der Dipolmomente von Substituierten Stilbenen im Ersten Angercgten Singulettzustand / Experimental and Quantum Chemical Investigations of Dipole Moments of Substituted Stilbens in the First Excited Singlet State

1977 ◽  
Vol 32 (5) ◽  
pp. 420-425 ◽  
Author(s):  
A. Kawski ◽  
I. Gryczyński
Keyword(s):  
Dipole Moment ◽  
Excited States ◽  
Ground State ◽  
Quantum Chemical ◽  
Singlet State ◽  
Dipole Moments ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Fluorescent State ◽  
Experimental Values

Abstract The values a/a3 (α = polarizability), the Onsager cavity radii a and the dipole moments μe of six substituted stilbens in the fluorescent state have been determined. It is shown that if the dipole moment of the lowest excited singlet state μe is parallel to the dipole moment in the ground state μg, the values of μe and a can be determined from the solvent effects. Moreover, quantum chemical investigations of the dipole moments in the ground and excited states were carried out with the Pariser-Parr-Pople method and compared with the experimental values.

Processus primaire de la photolyse et de la photo-oxydation de l'o-phényl-phénol

1980 ◽  
Vol 58 (21) ◽  
pp. 2230-2235 ◽  
Author(s):  
Louise-Marie Coulangeon ◽  
Gilles Perbet ◽  
Pierre Boule ◽  
Jacques Lemaire
Keyword(s):  
Quantum Yield ◽  
Singlet State ◽  
Excited Singlet State ◽  
Quantum Yields ◽  
Oxygen Effect ◽  
Dual Fluorescence ◽  
Excited Singlet ◽  
Photochemical Process ◽  
Phenoxy Radicals ◽  
Effect Of Oxygen

The dual fluorescence observed in aqueous solution of o-phenyl-phenol is attributed to a deprotonation equilibrium in the excited singlet state. The effect of oxygen on the primary photochemical process of formation of phenoxy radicals can be explained in a parallel study of the variations of fluorescence and photo-oxidation quantum yields of this phenolic compound at different pH. It is shown that photoionisation occurs only from the excited singlet state of the phenolate form. Oxygen inhibits recombination of the solvated electron and phenoxy radical. Increase of quantum yield for the disappearance of irradiated o-phenyl-phenol in degased solution also is observed in the presence of electron scavengers like Cd2+ or NO3− ions. Even when the phenoxy radicals are not able to react with oxygen, quantum yield for the disappearance of the phenolic compounds is higher in an aerated than in a degassed solution; the oxygen effect on the primary photochemical step may explain this difference.

scholarly journals Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1806 ◽  
Author(s):  
Matteo Lanzi ◽  
Gianpiero Cera
Keyword(s):  
Transition Metals ◽  
Organic Synthesis ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Reaction Conditions ◽  
Efficient Catalyst ◽  
Widespread Application ◽  
Promising Alternative ◽  
Cross Coupling Reactions ◽  
Benign Nature

3d transition metals-catalyzed C–H bond functionalizations represent nowadays an important tool in organic synthesis, appearing as the most promising alternative to cross-coupling reactions. Among 3d transition metals, iron found widespread application due to its availability and benign nature, and it was established as an efficient catalyst in organic synthesis. In this context, the use of ortho-orientating directing groups (DGs) turned out to be necessary for promoting selective iron-catalyzed C–H functionalization reactions. Very recently, triazoles DGs were demonstrated to be more than an excellent alternative to the commonly employed 8-aminoquinoline (AQ) DG, as a result of their modular synthesis as well as the mild reaction conditions applied for their removal. In addition, their tunable geometry and electronics allowed for new unprecedented reactivities in iron-catalyzed C–H activation methodologies that will be summarized within this review.

scholarly journals N-Iodosuccinimide as a Precatalyst for Direct Cross-Coupling of Alcohols with C-Nucleophiles under Solvent-Free Reaction Conditions

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 850
Author(s):  
Njomza Ajvazi ◽  
Stojan Stavber
Keyword(s):  
Large Scale ◽  
Bond Formation ◽  
Cross Coupling ◽  
Solvent Free ◽  
Reaction Conditions ◽  
Benzyl Alcohols ◽  
Metal Free ◽  
Direct Cross ◽  
Synthetic Routes ◽  
Solvent Free Reaction

C–C bond formation is one of the most important implements in synthetic organic chemistry. In pursuit of effective synthetic routes functioning under greener pathways to achieve direct C–C bond formation, we report N-iodosuccinimide (NIS) as the most effective precatalyst among the N-halosuccinimides (NXSs) for the direct cross-coupling of benzyl alcohols with C-nucleophiles under solvent-free reaction conditions (SFRC). The protocol is metal-free, and air- and water-tolerant, providing a large-scale synthesis with almost quantitative yields.

Transition-Metal-Free Synthesis of Thiosulfonates through Radical Coupling Reaction

Synlett ◽  
2018 ◽  
Vol 29 (15) ◽  
pp. 2076-2080 ◽  
Author(s):  
Wen-Ting Wei ◽  
Zhiyong Guo ◽  
Guodong Zhou ◽  
Xu-Dong Xu ◽  
Gan-Ping Chen
Keyword(s):  
Transition Metal ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Coupling Process ◽  
Metal Free ◽  
Radical Coupling ◽  
Radical Coupling Reaction ◽  
High Yields

An efficient and practical transition-metal-free radical ­coupling reaction of sulfonyl hydrazides mediated by NIS/K2S2O8 has been developed to afford a variety of biological activity thiosulfonates in moderate to excellent yields. Compared to a known approach for the synthesis of thiosulfonates from sulfonyl hydrazides, this strategy features high yields, mild reaction conditions, and broad substrate scope. The mechanistic studies revealed that the procedure undergoes via a radical cross-coupling process for the construction of S–S bonds.

An oxidative cross-coupling reaction of 4-hydroxydithiocoumarin and amines/thiols using a combination of I2 and TBHP: access to lead molecules for biomedical applications

2018 ◽  
Vol 54 (12) ◽  
pp. 1513-1516 ◽  
Author(s):  
Karuna Mahato ◽  
Neha Arora ◽  
Prasanta Ray Bagdi ◽  
Radhakrishna Gattu ◽  
Siddhartha Sankar Ghosh ◽  
...  
Keyword(s):  
Biomedical Applications ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Environmentally Benign ◽  
Reaction Conditions ◽  
Metal Free ◽  
Cross Coupling Reaction

Environmentally benign mild reaction conditions for the construction of new S–N/S–C/S–S bonds under metal free conditions.

Metal-free, oxidative decarboxylation of aryldifluoroacetic acid with formation of ArS-CF2 bond

2021 ◽  
Author(s):  
Yifang Zhang ◽  
Qian Wang ◽  
Yi Peng ◽  
haiying Gong ◽  
Hua Chen ◽  
...  
Keyword(s):  
Cross Coupling ◽  
Oxidative Decarboxylation ◽  
Reaction Conditions ◽  
Metal Free

A metal-free, oxidative decarboxylative reaction of aryldifluoroactetic acids with diaryl disulfides or thiols under mild reaction conditions has been develpoed. This protocol provides an efficient and straightforward radical cross-coupling access...

scholarly journals Catalyst Controlled Regiodivergent C-H Alkynylation of Thiophenes

2020 ◽  
Author(s):  
Arup Mondal ◽  
Manuel van Gemmeren
Keyword(s):  
Natural Products ◽  
Organic Synthesis ◽  
Late Stage ◽  
Cross Coupling ◽  
Bioactive Molecules ◽  
Reaction Conditions ◽  
Common Procedure ◽  
Broad Scope ◽  
Palladium Catalyzed

Alkynes are highly attractive motifs in organic synthesis due to their presence in natural products and bioactive molecules as well as their versatility in a plethora of subsequent transformations. A common procedure to insert alkynes into hetero(arenes), such as the thiophenes studied herein, consists of a halogenation followed by a Sonogashira cross-coupling. The regioselectivity of this approach depends entirely on the halogenation step. Similarly, direct alkynylations of thiophenes have been described that follow the same regioselectivity patterns. Herein we report the development of a palladium catalyzed C–H activation/alkynylation of thiophenes. The method is applicable to a broad range of thiophene substrates. For 3-substituted substrates where controlling the regioselectivity between the C2 and C5 position is particularly challenging, two sets of reaction conditions enable a regiodivergent reaction, giving access to each regioisomer selectively. Both protocols use the thiophene as limiting reagent and show a broad scope, rendering our method suitable for late-stage modification.

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