Ruthenium-catalyzed nitrogen-directed ortho CH borylation of aromatic imines with pinacolborane

An efficient ruthenium catalyst system for the direct ortho CH borylation of aromatic imines is described. The reaction of tert-butyl-1-arylmethanimines with pinacolborane in the presence of Ru(cod)(cot), followed by hydrolysis, to afford the ortho-formyl-substituted arylboronates. The borylation was achieved with complete mono-selectivity.     

Phosphinate selective hosts and importance of CH hydrogen bonding for affinity modulation toward anion guests

Even though phosphinate and its analogs are very important guests in nature, the artificial receptors which are capable of selective recognition of phosphinate are rare. Here, we report a series of acetate and phosphinate selective hosts (1, 2 and 3) which utilize amide NH and aliphatic CH groups as hydrogen bonding donors. In this series of receptors, even though the amide NH hydrogen bonding element was found to be the most significant, by varying the polarity of CH group, the magnitude of recognition could be modulated considerably. The affinities of host 3 against all the tested anion guests showed significantly higher affinities compared with those of hosts 1 and 2, and this could be attributed to the difference of CH group polarities among the receptors 1, 2 and 3. C_α-H hydrogen in host 3 is the most highly polarized by the charged pyridinium group. Therefore, it is the strongest host in this series of hosts. From the experiments shown here, we demonstrated the importance of CH hydrogen bonding element as a decisive modulating moiety for anionic recognition.     

Base-promoted nucleophilic fluoroarenes substitution of CF bonds

With the use of KOH/DMSO as the superbase medium, the nucleophilic fluoroarene substitution for CF bonds is presented. The transformation proceeds smoothly with the use of fluoroarenes bearing not only electron-withdrawing group, but also electron-donating group and a variety of nucleophiles such as alcohols, phenols, amines, amides and nitrogen-heterocyclic compounds. The double nucleophilic substitution using ortho-difluoroarenes and nucleophiles bearing ortho-dinucleophilic groups results in the formation of 2,3-dihydro-1,4-benzodioxins, dibenzo[b,e][1,4]dioxins and 10H-phenoxazines in moderate to good yields.     

Rhodium-catalyzed NH-indole-directed ortho CH coupling of 2-arylindoles with diazo compounds via metal carbene migratory insertion

A high regioselective rhodium-catalyzed ortho CH coupling of 2-arylindoles with diazo compounds via NH-indole-directed CH bond activation has been developed. The catalytic reaction features mild reaction conditions, broad substrate scope and good functional group tolerability.     

Rh(III)-catalyzed, 1,2,3-triazole-assisted directed CH coupling with diazo diphosphonates

A mild and efficient procedure was developed for the [Cp1Rh(III)]-catalyzed, 1,2,3-triazole directed CH coupling with diazomethylene-diphosphonates. This protocol provided a step- and atom-economical protocol for CC bond formation and led to structurally diverse 2-(1,2,3-triazol-2-yl)benzyl diphosphonates in good to excellent yields.     

One-pot Sonogashira coupling,hydroamination of alkyne and intramolecular CH arylation reactions toward the synthesis of indole-fused benzosultams

A one-pot Sonogashira coupling, hydroamination of alkyne and CH arylation reactions for the synthesis of indole-fused benzosultams are described. This method allows access to a variety of indole-fused seven membered benzosultams in good to excellent yields. The free indolyl nitrogen containing indole-fused benzosultams are also prepared by this method. The structures of the synthesized compounds are confirmed by single crystal XRD studies.     

Synthesis of functionalized benzothiadiazine 1,1-dioxide derivatives via intramolecular CH activation reactions of trichloroacetamidine and benzenesulfonyl chloride

The synthesis of functionalized benzothiadiazine 1,1-dioxide derivatives was achieved through a novel three-component intramolecular CH activation reaction of trichloroacetonitrile, benzenesulfonyl chloride, and various primary amines. This reaction was performed in the presence of catalytic copper(I) and l-proline as the ligand in tetrahydrofuran at room temperature.     

Rhodium(III)-catalyzed CH amination of 2-arylquinazolin-4(3H)-one with N-alkyl-O-benzoyl-hydroxylamines

N-benzoate alkylamines were used as the aminating agents, a efficient Rh-catalyzed ortho CH amination of 2-arylquinazolin-4(3H)-one has been reported. The reactions exhibit high efficient and good functional group tolerance. Exclusive 2,6-bis-aminated product and good to excellent yields were obtained under mild reaction conditions.     

Site selective [bmIm]OH catalyzed CC bond functionalization under green conditions

Effective methodology that activates selectively either end of a carbon–carbon triple bond requires key challenge of differentiating between the multitude of CC bonds present in complex organic molecule. The synthetic strategy exploited the electronic biases within the substrate and successfully achieved site–selective [bmIm]OH catalyzed CC bond functionalization under mild reaction conditions. This resulted in C-2-selective addition of phenacyl bromide on p-substituted phenyl acetylene and C-1 selective addition on the o-substituted phenyl acetylene leading to CC bond formation. The reaction proceeded smoothly with excellent yield under ambient conditions. This report demonstrates the progress on the catalytic activity of recyclable [bmIm]OH for selective CC bond formation.     

Terminal C(sp3)H alkylation of internal alkenes via Ni/H-catalyzed isomerization

An efficient nickel-catalyzed reductive relay cross-coupling of internal alkenes with alkyl (or aryl) halides has been developed. This method has demonstrated broad substrate scope, mild reaction conditions and excellent terminal-selectivity. Moreover, this efficient strategy could be applied to the terminal-selective alkylation of isomeric mixtures of internal alkenes.     

Formal carbene insertion into CO double bond: A facile approach to the synthesis of 2H-chromenes

A formal carbene insertion into CO double bonds of 2-hydroxycinnamaldehydes catalyzed by Rh₂(esp)₂ with Na₂CO₃ as additive has been disclosed by using aryldiazoacetates as carbene precursors. 2H-chromenes with a quaternary carbon at C-2 position were readily obtained from simple starting materials in good yields with excellent diastereoselectivity under mild reaction conditions in one pot. The reaction mechanism was investigated and proposed as the formation of epoxide intermediate from Rh(II)-associated carbene and (E)-2-hydroxycinnamaldehyde and followed by a cascade epoxide ring-opening procedure in which the (E)-intermediate was converted into the (Z)-intermediate to give (Z)-products.     

Synthesis of 2-(2-oxoindolin-3-ylidene)-2-arylacetonitriles through transition metal-free C(sp2)CN bond construction

An efficient method for the construction of C(sp²)CN bonds directly from C(sp²-H) cyanation of 3-arylideneindolin-2-ones with benzoyl cyanide under transition metal-free condition is described. Various 2-(2-oxoindolin-3-ylidene)-2-arylacetonitriles were efficiently synthesized using air as an oxidant under mild conditions. This protocol has excellent functional group tolerance and can be easily scaled up with good efficiency. This reaction successfully offers an alternative to structurally diverse alkenyl nitriles.     

Synthesis of novel dithiocarbamates and xanthates using dialkyl azodicarboxylates: SN bond formation

A one?pot three?component route for the synthesis of a novel category of dithiocarbamates or xanthates is developed by a reaction of in-situ generated dithiocarbamic acids or xanthates with dialkyl azodicarboxylates under mild and catalyst-free conditions. The reaction is characterized by a wide scope, high efficiency and straightforward isolation protocol. The synthetic utility of the dithiocarbamates and xanthates was demonstrated on the preparation of symmetrical and unsymmetrical thioureas, isothiocyanates, and thiocarbamates.     

Ru3(CO)12-catalyzed dehydrogenative SiN coupling of indoles with hydrosilanes without additive

An efficient Ru₃(CO)₁₂-catalyzed dehydrogenative SiN coupling reaction of indoles, pyrrole, and carbazole with hydrosilanes is reported. The reaction does not need any external additive. This catalytic reaction has a wide substrate range, excellent functional group tolerance, and high to excellent reaction efficiency. Gram-scale synthesis demonstrates the practicability of this synthetic method.     

nBu4NI-catalyzed CC bond formation to construct 2-carbonyl-1,4-diketones under mild conditions

An nBu₄NI-catalyzed oxidative cross-dehydrogenative-coupling of β-dicarbonyl compounds with acetone under mild reaction conditions is described. This methodology provides a straightforward pathway to synthesize 2-carbonyl-1,4-diketones and features a simple system, low reaction temperature, and environmental friendliness.     

Iron-catalyzed cross-dehydrogenative CN coupling of thiohydantoins with various amines

A novel iron-catalyzed CN bond construction method for the hetero-cross-dehydrogenative coupling (CDC) of diverse thiohydantoins with amines utilizing TBHP as the oxidant was developed. This sp³ CH amination at the carbons alpha to carbonyl groups of thiohydantoin tolerates the presence of a wide range of functional groups and provides the corresponding N-substituted amines in moderate to good yields. Various substrate scopes and optimum reaction conditions leads inside in organic synthesis.     

Ligation state of nickel during CO bond activation with monodentate phosphines

The oxidative addition of phenolic electrophiles at Ni(0) in the presence of monodentate phosphine ligands was studied with both dispersion-free and dispersion-containing DFT methods. With the popular bulky ligand PCy₃, consideration of dispersion has a striking effect on the predicted ligation state of nickel during oxidative addition of aryl sulfamates. Dispersion-containing methods such as M06L indicate a clear preference for a bis-phosphine ligated transition state (TS), while dispersion free methods like B3LYP strongly favor a mono-phosphine ligated TS. This discrepancy in predicted ligation state is also found with small phosphines (PMe₃) in combination with some aryl electrophiles (carbamates, acetates, pivalates, chlorides), but a bis-PMe₃-ligated TS is predicted regardless of dispersion for other electrophiles (sulfamates, mesylates, tosylates). DFT calculations that include dispersion also offer a possible explanation for the observed poor efficacy of P^tBu₃ as a ligand in Ni-catalyzed cross-coupling reactions.     

Facile CH arylation using catalytically active terminal sulfurs of 2 dimensional molybdenum disulfide

The first methodology of CH arylation of heteroarene via 2D transition metal dichalcogenides that have catalytically active edge functional groups was described. The terminal sulfur groups could effectively catalyze a formation of an azo-linked intermediate with aryl diazonium salts, leading to produce heteroarenes with good yields. This novel methodology using bulk 2D transition metal dichalcogenides that have catalytically active edge functional groups can apply for various reactions to achieve CC bond formation in the fields of heterogeneous catalysis that is easily separable, highly reusable, and inexpensive method.     

Visible-light-induced photocatalytic difluoroalkylation of 3-substituted benzo[d]isoxazoles via direct and regioselective CH functionalization

The difluoroalkylation of unactivated benzo[d]isoxazoles with ethyl difluorobromoacetate by visible-light photoredox catalysis via direct and regioselective CH functionalization has been efficiently achieved under mild reaction conditions. The difluoroalkylated adducts could be readily converted to a variety of corresponding CF₂-containing heterocycles, demonstrating the synthetic utility of the present approach.     

Visible light mediated aerobic photocatalytic activation of CH bond by riboflavin tetraacetate and N-hydroxysuccinimide

A green and highly efficient cooperative photocatalytic system which consists of riboflavin tetraacetate (RFT), N-hydroxysuccinimide (NHS) and FeCl₃·6H₂O has been developed for CH bond oxygenation with visible light under mild reaction conditions. Compared to the previous procedures about CH bond activation by using flavins as photocatalyst, we use cheap ferric chloride and NHS instead of expensive scandium triflate or biomimetic non-heme iron complex, further expand the substrate scopes. In addition, a possible radical mechanism for the CH bond oxygenation in this photocatalytic system is proposed.