C–H bond activation and decarboxylation are two significant processes in organic synthesis. The combination of these processes provides a novel synthetic strategy, that is, decarboxylative C–H bond ...functionalization. Considerable attention has been focused on such an active research field. This review offers an overview of the utility of decarboxylative C–H bond functionalization in the synthesis of various organic compounds, such as styrenes, chalcones, biaryls, and heterocycles, covering most of the recent advances of the decarboxylative functionalization of Csp–H, Csp2–H, and Csp3–H bonds, as well as their scopes, limitations, practical applications, and synthetic potentials.
A rhodium(III)‐catalyzed carboxylic acid directed decarboxylative CH/CH cross‐coupling of carboxylic acids with thiophenes has been developed. With a slight adjustment of the reaction conditions ...based on the nature of the substrates, aryl carboxylic acids with a variety of substituents could serve as suitable coupling partners, and a broad variety of functional groups were tolerated. This method provides straightforward access to biaryl scaffolds with diverse substitution patterns, many of which have conventionally been synthesized through lengthy synthetic sequences. An illustrative example is the one‐step gram‐scale synthesis of a biologically active 3,5‐substituted 2‐arylthiophene by way of the current method.
Who was in control? A rhodium(III)‐catalyzed carboxylic acid directed decarboxylative CH/CH cross‐coupling of benzoic acids with thiophenes has been developed. This method provides straightforward access to biaryl scaffolds with diverse substitution patterns, many of which previously required lengthy synthetic sequences.
C3-selective formylation and acylation of free (N–H) indoles under mild conditions can be achieved by using Ru- and Fe-catalyzed oxidative coupling of free (N–H) indoles with anilines, respectively. ...Both processes are operationally simple, compatible with a variety of functional groups and generally provide the desired products in good yields. 13C-labeling experiments unambiguously established that the carbonylic carbon in the formylation products originated from methyl group of N-methyl aniline.
A long‐standing challenge in Minisci reactions is achieving the arylation of heteroarenes by oxidative decarboxylation of aromatic carboxylic acids. To address this challenge, the silver‐catalyzed ...intermolecular Minisci reaction of aromatic carboxylic acids was developed. With an inexpensive silver salt as a catalyst, this new reaction enables a variety of aromatic carboxylic acids to undergo decarboxylative coupling with electron‐deficient arenes or heteroarenes regardless of the position of the substituents on the aromatic carboxylic acid, thus eliminating the need for ortho‐substituted aromatic carboxylic acids, which were a limitation of previously reported methods.
Silver hammer: The silver‐catalyzed decarboxylative arylation of electron‐deficient (hetero)arenes has been successfully developed using aromatic carboxylic acids as arylating reagents. For most of the aromatic carboxylic acids evaluated, 5 mol % of the silver(I) salt was enough for the oxidative decarboxylation. An ortho substituent was not necessary for this decarboxylative cross‐coupling procedure.
Synthetic glucocorticoids (GCs), one of the most effective treatments for chronic inflammatory and autoimmune conditions in children, have adverse effects on the growing skeleton. GCs inhibit ...angiogenesis in growing bone, but the underlying mechanisms remain unclear. Here, we show that GC treatment in young mice induces vascular endothelial cell senescence in metaphysis of long bone, and that inhibition of endothelial cell senescence improves GC-impaired bone angiogenesis with coupled osteogenesis. We identify angiogenin (ANG), a ribonuclease with pro-angiogenic activity, secreted by osteoclasts as a key factor for protecting the neighboring vascular cells against senescence. ANG maintains the proliferative activity of endothelial cells through plexin-B2 (PLXNB2)-mediated transcription of ribosomal RNA (rRNA). GC treatment inhibits ANG production by suppressing osteoclast formation in metaphysis, resulting in impaired endothelial cell rRNA transcription and subsequent cellular senescence. These findings reveal the role of metaphyseal blood vessel senescence in mediating the action of GCs on growing skeleton and establish the ANG/PLXNB2 axis as a molecular basis for the osteoclast-vascular interplay in skeletal angiogenesis.
An efficient method involving a Pd/PCy3 catalyst in combination with a stoichiometric amount of Ag2CO3 has been established for the decarboxylative CH bond arylation of thiophenes to give ...2‐arylthiophenes (see scheme; Cy=cyclohexyl). Electron‐rich, electron‐deficient, and heterocyclic benzoic acids can be used as the arylating reagent and a broad range of substituents on the thiophene are tolerated.
Catalytic oxidative C-H bond functionalization reactions that proceed without requiring stoichiometric amounts of external oxidants or pre-functionalized oxidizing reagents could maximize the atom- ...and step-economy in chemical syntheses. However, such a transformation remains elusive. Here, we report that a photo-driven catalytic process enables decarboxylative C-H trifluoromethylation of (hetero)arenes with trifluoroacetic acid as a trifluoromethyl source in good yields in the presence of an external oxidant in far lower than stoichiometric amounts (for example, 0.2 equivalents of Na
S
O
) using Rh-modified TiO
nanoparticles as a photocatalyst, in which H
release is an important driving force for the reaction. Our findings not only provide an approach to accessing valuable decarboxylative C-H trifluoromethylations via activation of abundant but inert trifluoroacetic acid towards oxidative decarboxylation and trifluoromethyl radical formation, but also demonstrate that a photo-driven catalytic process is a promising way to achieve external oxidant-free C-H functionalization reactions.
In this work, the pyrolysis behavior of plastic waste—TV plastic shell—was investigated, based on thermogravimetric analysis and using a combination of model-fitting and model-free methods. The ...possible reaction mechanism and kinetic compensation effects were also examined. Thermogravimetric analysis indicated that the decomposition of plastic waste in a helium atmosphere can be divided into three stages: the minor loss stage (20–300°C), the major loss stage (300–500°C) and the stable loss stage (500–1000°C). The corresponding weight loss at three different heating rates of 15, 25 and 35 K/min were determined to be 2.80–3.02%, 94.45–95.11% and 0.04–0.16%, respectively. The activation energy (Ea) and correlation coefficient (R2) profiles revealed that the kinetic parameters calculated using the Friedman and Kissinger–Akahira–Sunose method displayed a similar trend. The values from the Flynn–Wall–Ozawa and Starink methods were comparable, although the former gave higher R2 values. The Eα values gradually decreased from 269.75 kJ/mol to 184.18 kJ/mol as the degree of conversion (α) increased from 0.1 to 0.8. Beyond this range, the Eα slightly increased to 211.31 kJ/mol. The model-fitting method of Coats–Redfern was used to predict the possible reaction mechanism, for which the first-order model resulted in higher R2 values than and comparable Eα values to those obtained from the Flynn–Wall–Ozawa method. The pre-exponential factors (lnA) were calculated based on the F1 reaction model and the Flynn–Wall–Ozawa method, and fell in the range 59.34–48.05. The study of the kinetic compensation effect confirmed that a compensation effect existed between Ea and lnA during the plastic waste pyrolysis.
Acid to acid: A general method has been developed for the synthesis of biaryl compounds through a decarboxylative cross‐coupling reaction between two different (hetero)aryl carboxylic acids (see ...scheme). The use of a PdII/PCy3 catalyst enables the cross‐coupling reaction of electronically different or electronically similar aryl carboxylic acids. This method is compatible with substrates having nitro, cyano, fluoro, chloro, bromo, trifluoromethyl, and methoxy substituents.
Modular and regio-/stereoselective syntheses of all-carbon tetrasubstituted olefins from simple alkene materials remain a challenging project. Here, we demonstrate that a remote-carbonyl-directed ...palladium-catalyzed Heck/isomerization/C(sp
)-H arylation sequence enables unactivated 1,1-disubstituted alkenes to undergo stereoselective terminal diarylation with aryl iodides, thus offering a concise approach to construct stereodefined tetrasubstituted olefins in generally good yields under mild conditions; diverse carbonyl groups are allowed to act as directing groups, and various aryl groups can be introduced at the desired position simply by changing aryl iodides. The stereocontrol of the protocol stems from the compatibility between the E/Z isomerization and the alkenyl C(sp
)-H arylation, where the vicinal group-directed C(sp
)-H arylation of the Z-type intermediate product thermodynamically drives the reversible E to Z isomerization. Besides, the carbonyl group not only promotes the Pd-catalyzed sequential transformations of unactivated alkenes by weak coordination, but also avoids byproducts caused by other possible β-H elimination.
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