Tandem Catalysis: Alcohol Oxidation and C?C Bond Formation via C?H Bond Activation

A tandem process involving oxidation of a benzylic alcohol functionality followed by hydroarylation is described. These two atom‐economic sequences are very convenient to access functionalized aromatic ketones, using simple ruthenium trichloride as catalyst precursor. Moreover they appear to be highly compatible, tolerant, and selective toward various functional groups, and the ease of the protocol should make it very convenient for synthetic purposes.     

Iron‐Catalyzed C?C Bond Cleavage and C?N Bond Formation

A novel approach for C N bond formation was developed by iron‐catalyzed C C bond cleavage. Anilines and sulfonamides reacted smoothly with 2‐substituted 1,3‐diphenylpropane‐1,3‐diones to afford N‐alkylation products, in which the 1,3‐dicarbonyl group acts as a leaving group in the presence of an iron catalyst. The reversible C C bond cleavage plays a driving force to give the thermodynamically stable products. The method is complementary to the previous methods for C N bond formation.     

Building Functionality through Sequential C?B and C?F Bond Formation

α′‐Fluoro β‐boryl ketones can be efficiently synthesised from a sequential organocatalytic β‐boration pathway and consecutive electrophilic fluorination reaction in an acidic medium. Alternatively, the regioisomers of α‐fluoro β‐boryl ketones can be diastereoselectively obtained from Cu(I)‐mediated β‐boration followed by in situ fluorination of the boron enolate. Enantioenriched mixtures of the major anti‐diastereomer of vicinal C B and C F bonds are found in the presence of the chiral ligand QuinoxP*.     

Zinc‐Catalyzed Organic Synthesis: C?C,C?N,C?O Bond Formation Reactions

Zinc is the 24^th most abundant element in the Earth’s crust. Since the discovery of pure zinc metal in the 18^th century, the main application of zinc metal is as materials. Because zinc salts are abundant, cheap, non‐toxic, and exhibit environmentally benign properties, organic chemists have been interested in using zinc salts as catalysts in organic synthesis during the last three decades. Within this review, we have summarized the progress on applications of zinc salts in organic reactions. Our the target is to emphasize the special properties of zinc catalysts, and further promote the interest of organic chemists.     

Recent Developments in Enzymatic Asymmetric C?C Bond Formation

Some of the recent developments in enzymatic asymmetric C C bond formation are described in this review. The close relationship of biocatalysis and biosynthesis is highlighted with a special emphasis on diversity and biogenesis. One focus of this review is the creation of tetrasubstituted carbon stereocenters. Members of the supposedly well‐known aldolase and hydroxynitrile lyase enzyme families possess the ability to catalyze the formation of tertiary alcohols. In the case of aldolases, this can occur through intramolecular cyclization or intermolecular asymmetric C C bond formation. Thiamine diphosphate‐dependent YerE has been identified as a potent catalyst for the acyloin condensation with ketones as acceptor substrates. C₁ transformations such as methylation or carboxylation are catalyzed in an asymmetric manner by enzymes from different classes, for example S‐adenosylmethionine‐dependent (radical) enzymes or NADPH‐dependent oxidoreductases. Insights from biosynthetic and mechanistic studies of enzymatic reactions proceeding via radical intermediates give valuable hints towards possible applications in biocatalysis. Still, the oxygen sensitivity of many of these biocatalysts poses a considerable challenge for practical applications.     

Direct Trifluoromethylation of the C?H Bond

Trifluoromethylation meets C H activation: after transition metal‐catalyzed trifluoromethylation became more and more popular, trifluoromethylation via C H activation is now emerging as the latest attraction. Several pioneering examples and their mechanisms are discussed in this review.     

Chemische Synthese des Dodecanucleotids dpT?T?T?T?T?T?C?A?T?C?A?T

Chemical Synthesis of the Dodecanucle otide dpT T T T T T C A T C A T For studies on the specifity of enzymes, the dodecanucleotide dpT T T T T T C A T C A T was required. Its chemical synthesis is reported starting with the mononucleotides dpT, dpC and dpA.     

Chemische Synthese des Dodecanucleotids dC?A?C?A?A?G?C?T?T?G?T?G

Chemical Synthesis of the Dodeecanuceleotide. dC A C A A G C T T G T G For studies of some sequence dependent structural factors the self-complementary dodecanucleotide dC A C A A G C T T G T G was required. Its chemical synthesis is reported according to the diester approach starting with the monomers dC, dpA, dpG, dpC and dpT.     

Expedient Synthesis of Functionalized Triarylmethanols through Tandem Formation of Geminal C?C and C?O Bonds

The rearrangement/oxidation of N,N‐disubstituted anilines and the formal dehydrogenative cross‐coupling of diarylmethanols with aniline derivatives have been developed for the preparation of symmetric and unsymmetric functionalized triarylmethanols. Both reactions proceed smoothly in trifluoroacetic acid in the presence of an inexpensive oxidant (manganese dioxide or potassium persulfate) and a catalytic amount of palladium diacetate to give a range of functionalized triarylmethanols in moderate to good yields and with extremely high regioselectivity. The two unprecedented reactions involve tandem formation of geminal C C and C O bonds, and they are synthetically useful, atom‐efficient, and operationally simple.     

Regioselective Cleavage of Unstrained C?C Bond and C?H Bond: Palladium–Copper Catalyzed Deacetophenonylative Arylation of Coumarin Derivatives

A C_α C_β bond activation of the carbonyl group in unstrained ketones catalyzed cooperatively by palladium and copper(II) with the departure of the acetophenone has been developed, and the subsequent coupling with a variety of aromatics via the formal C H activation similar to the Friedel–Crafts reaction affords the skeleton‐reconstructed coumarin derivatives with high regioselectivity.     

Flow Metal‐Free Ar?C Bond Formation via Photogenerated Phenyl Cations

A convenient photochemical flow protocol for the formation of aryl‐carbon bonds via photogenerated phenyl cations has been developed. A wide range of phenylated products, including biaryls, allylarenes, 2‐arylacetals and benzyl γ‐lactones, was smoothly synthesized in satisfactory yields under metal‐free conditions. The adoption of a flow reactor often allowed us to adopt higher concentrations of substrates and shorter irradiation times compared to those usually employed in batch systems.

     

An Efficient Synthesis of Polysubstituted Pyridines via C?H Oxidation and C?S Cleavage of Dimethyl Sulfoxide

An expedient cleavage of the C S bond of dimethyl sulfoxide (DMSO) has been developed for the preparation of substituted pyridines from ketones. In this transformation, the co‐product formic acid was formed from ammonium formate, which acted as an important catalyst for the reaction. Notably, this transformation exhibited a broad substrate scope towards a wide variety of different ketones to give the corresponding substituted pyridines in high yields. Mechanistic studies suggested that dimethyl sulfoxide delivered a methylene fragment, which was subsequently captured in situ to give a pyridine.

     

Palladium‐Catalyzed Oxidative Intramolecular C?C Bond Formation via Double sp2 C?H Activation between the 2‐Position of Imidazoles and a Benzene Ring

Oxidative intramolecular C C bond formation via double sp² C H activation between the 2‐position of imidazoles and a benzene ring catalyzed by palladium(II) has been developed, which provides an atom‐economical, concise and efficient methodology to synthesize imidazole‐ or benzimidazole‐fused isoquinoline polyheteroaromatic compounds.     

Arene C?H Bond Functionalization Coupling with Cyclization of Allenes

Under the catalysis of a rhodium(III) complex, the cyclization of 2,3‐allenols was most probably initiated with the C H bond functionalization of N‐methoxybenzamides using the tetramethylcyclopentadiene anion (C₅Me₄⁻) as ligand, affording differently substituted 2,5‐dihydrofuran derivatives. Highly efficient axial‐to‐central chirality transfer has been observed.     

Carbon Nitride‐Catalyzed Photoredox C?C Bond Formation with N‐Aryltetrahydroisoquinolines

In this communication we describe the oxidative C C bond formation of tertiary amines with various nucleophiles under very mild and environmental friendly conditions by using mesoporous graphitic carbon nitride (mpg‐C₃N₄) semiconductor as a heterogeneous, metal‐free photosensitizer in combination with visible light and oxygen as the terminal oxidation agent. This system can be further combined with proline‐organocatalysis to achieve oxidative tandem photocatalysis, demonstrating a rich cascade of chemical possibilities of the current photosynthesis system.     

Copper(II) Acetate/Oxygen‐Mediated Nucleophilic Addition and Intramolecular C?H Activation/C?N or C?C Bond Formation: One‐Pot Synthesis of Benzimidazoles or Quinazolines

Diarylcarbodiimides or benzylphenylcarbodiimides are converted to 1,2‐disubstituted benzimidazoles or 1,2‐disustituted quinazolines via addition/intramolecular C H bond activation/C‐N or C C bond forming reaction using copper(II) acetate/oxygen [Cu(OAc)₂/O₂] as the oxidant at 100 °C in one‐pot cascade procedure.     

Calculation of the Detonation Properties of C?H?N?O explosives

On the basis of the steady state model of detonation, using Becker-Kistiakowsky-Wilson equation of state for gaseous products of detonation and Cowan-Fickett equation of state for solid carbon, algorithm and computer program for the calculation of the detonation properties of C H N O type explosives are developed. The program has been tested by the comparison of the calculated data with experimental ones for some high explosives being of different densities and compositions. The calculated data have also been compared with data obtained by program FOR-TRAN BK W. Both comparisons gave satisfactory agreement.     

C?C Hydrolases for Biocatalysis

Although C C bond hydrolases are distributed widely in Nature, they has as yet have received only limited attention in the area of biocatalysis compared to their counterpart the C‐heteroatom hydrolases, such as lipases and proteases. However, the substrate range of C C hydrolases, and their non‐dependence on cofactors, suggest that these enzymes may have considerable potential for applications in synthesis. In addition, hydrolases such as the β‐diketone hydrolase from Rhodococcus (OCH) are known, that catalyse the formation of interesting chiral intermediates. Further enzymes, such as kynureninase and a meta‐cleavage product hydrolase (MhpC), are able to catalyse carbon‐carbon bond formation, suggesting wider applications in biocatalysis than previously envisaged. In this review, the distribution, catalytic characteristics and applications of C C hydrolases are described, with a view to assessing their potentialfor use in biocatalytic processes in the future.