Gold catalysed Suzuki-Miyaura coupling of arenediazonium o-benzenedisulfonimides

Arenediazonium o-benzenedisulfonimides have been used as efficient electrophilic partners in Au(I) catalysed Suzuki coupling reactions. The synthetic protocol is general, easy and produced either biaryls or heteroaryl arenes in good yields (51 positive examples, average yield 80%). o-Benzenedisulfonimide was recovered at the end of the reactions and was reused to prepare the starting salts for further reactions. Mechanistic insights suggest that the o-benzenedisulfonimide anion act as an electron transfer agent and promotes a catalytic cycle which does not require the presence of photocatalysts or external oxidants.     

Arenediazonium o-benzenedisulfonimides as efficient reagents for Heck-type arylation reactions

Arenediazonium o-benzenedisulfonimides can be used as new and efficient reagents for Heck-type arylation reactions of some common substrates containing C-C multiple bonds, namely ethyl acrylate, acrylic acid, acroleyne, styrene and cyclopentene. The reactions were carried out in an organic solvent, in the presence of Pd(OAc)₂ as pre-catalyst, and gave rise to arylated products, for example, ethyl cinnamates, cinnamic acids, cinnamic aldehydes and stilbenes, possessing an (E)-configuration, and 1-arylcyclopentenes, in good to excellent yields. It is noteworthy that all the reactions led to the recovery, in greater than 80% yield, of o-benzenedisulfonimide, recyclable for the preparation of other diazonium salts.     

Approaches to pseudoindene : Products derived from the carbenes benzocyclobuten-1-ylcarbene, 2-methylbenzocyclobutenylidene and o-styrylcarbene

The title carbenes, which in principle can all serve as precursors to the reactive hydrocarbon pseudoindene, have been generated by the photolysis of the sodium salts of the tosylhydrazones of (a) benzocyclobutene-1-carboxaldehyde, (b) 2-methylbenzocyclobutenone and (c) o-formylstyrene. Indene was formed in reactions (a) and (c): in the former case deuterium labelling experiments suggest a ring expansion mechanism rather than a pseudoindene intermediate. In the latter case deuterium labelling and trapping experiments implicate a symmetrical isoindene intermediate, which can arise either via pseudoindene, or via direct electrocyclic ring closure of o-styrylcarbene.     

Water‐Promoted Ring‐Opening Reactions of N‐Substituted Saccharins and Phthalimides by Amines

The reactions of N‐substituted saccharins and phthalimides with amines were promoted by water. Various o‐sulfamoyl benzamides and N,N′‐disubstituted phthalamides were prepared in moderate to good yields. These reactions have prominent advantages, such as short reaction time, less by‐products and simple isolation of the products. Water can probably stabilize the reaction intermediates and facilitate precipitation of the ring‐opening products. When steric hindrance arose, hydrolytic compounds, either free acid or salts of the acids, were obtained. Possible reason for the formation of amine salts of o‐sulfamoyl benzoic acids was proposed.     

Azonia polycyclic quinones,o-diazo-oxides and related products

4α-Azoniaanthracene-5,6- and 5,8-dione salts have been prepared by nitric acid oxidation of their respective diols, and are shown to function as either an electrophilic dienophile or a diene component in Diels-Alder-type reactions. Several azonia o-quinones have been treated with tosylhydrazine in methanol saturated with hydrogen chloride to give unusually stable o-diazo-oxides. A four-step dehydroxylation procedure is detailed for the conversion of .5,6-dihydroxy-4α-azonia-anthracene salts to new 5-hydroxy-4α-azoniaanthracene salts.     

A kinetic template effect in the metal ion-catalysed formation of arylphosphonium salts

Tertiary phosphines react with $\text{o}$-halobenzaldimines and $\text{o}$-bromodiarylazo compounds, under mild conditions in the presence of a metal ion catalyst, with displacement of the halogen to form the related arylphosphonium salts. The corresponding $\text{o}$-haloaryl compounds do not undergo these reactions.     

Phosphatriptycene

Phosphatriptycene (1) is prepared by cyclizing 9-(o-chlorophenyl)-9,10-dihydrophosphaanthracene (6) with an excess of lithium diisopropylamide in ether. Its structure is confirmed by its ¹³C-NMR spectrum. In nucleophilic reactions 1 is less reactive than triphenylphosphine. The nature of the bonding in quaternary phosphonium salts of 1 is discussed.     

Convenient one-step synthesis of 4-unsubstituted 2-amino-4H-chromene-2-carbonitriles and 5-unsubstituted 5H-chromeno[2,3-b]pyridine-3-carbonitriles from quaternary ammonium salts

We have reported DBU catalyzed synthesis of 4-unsubstituted 2-amino-4H-chromene-2-carbonitriles in water under reflux. The attractive features of this process are mild reaction conditions, short reaction times, easy isolation of products and good yields. 5H-chromeno[2,3-b]pyridine-3-carbonitriles were obtained by refluxing excess of malononitrile and quaternary ammonium salts in ethanol in the presence of NaOH as catalyst. The mechanisms of these reactions are believed to involve the formation of the o-quinone methide intermediate.     

Ga(OTf)3-promoted condensation reactions for 1,5-benzodiazepines and 1,5-benzothiazepines

Condensation reactions of o-phenylenediamine and two equivalents of acetophenone under gallium(III) triflate catalysis produce biaryl-substituted 1,5-benzodiazepines. Similar reactions of o-phenylenediamine or o-aminothiophenol and o-hydroxy chalcones lead to formation of functionalized 1,5-benzodiazepines and 1,5-benzothiazepines in good to excellent yields. The ortho-hydoxy group of chalcones is crucial for this unprecedented condensation process.     

Preparation and oxidative coupling of bis[o-(hydrosilyl)phenyl]cuprates and bis[o-(fluorosilyl)phenyl]cuprates

Bis[o-(hydrosilyl)phenyl]cuprates and bis[o-(fluorosilyl)phenyl]cuprates were prepared by reacting [o-(hydrosilyl)phenyl]lithiums and [o-(fluorosilyl)phenyl]lithiums, respectively, with copper salts, such as CuCN and Cu(OPiv)₂. The phenylcuprates underwent oxidative coupling to afford 2,2′-bis(hydrosilyl)biphenyls and 2,2′-bis(fluorosilyl)biphenyls.     

Efficient method for the synthesis of diphosphine ligands with a heteroaryl-aryl bridge

A new efficient method for the synthesis of heteroaryl-aryl diphosphine ligands by direct double metallation of heteroaryl-aryls followed by phosphorylation of the resulting o,o′-dilithium salts is described. A number of new C₁-symmetric diphosphine ligands based on 3-arylheteroaryls, X-heteroaryls (X=N), and diphosphine ligands with a heterocyclic bridge with o-tolyl as the aryl fragment have been synthesized.     

Carbonyl complexes of molybdenum and tungsten with sulfur donors: V. Reactions of carbonyl complexes of molybdenum(0) with uninegative (X,Y)-donor ligands (X,Y = S,N, O)

The reactions of the zerovalent carbonyl complexes Mo(CO)₆ and Mo(CO)₄(bipy) with a series of uninegative bidentate (X,Y)-donor ligands (X,Y = xanthates, dithiocarbamates, o-aminophenoxide, o-aminothiophenoxide, 2-picolinate and thioacetate) lead to new anionic tetracarbonyl complex anions [Mo⁰(X,Y)(CO)₄]^?. These anions, which can be isolated as their tetraphenylphosphonium salts, contain the (X,Y)-ligand as a bidentate group. In the case of (X,Y) = monothioacetate the decarbonylated species [PPh₄][Mo^II(TA)₃] is formed. The reacions of the new complexes with allyl bromide and methyl iodide are described.     

Screening of intramolecular hydrogen bonds in monosalts of diols and IR continuum

Solutions of salts of the diols o-xylidenedicarbinol, o-xylidenetetraethyldicarbinol and o-xylidenetetrahexyldicarbinol were studied by IR and NMR spectroscopy. Within this series the IR continuum caused by intramolecular OH…O^? ? ^?O…HO bonds vanishes, a band at 1950 cm^?1 being observed. Thus occurence of the continuum requires interaction of the hydrogen bonds with great proton polarizability with their solvent environments.     

Arsenorgano-Verbindungen : XXII. Zur synthese der 1,3-benzazarsoline

o-Aminophenylarsine is prepared by reduction of o-nitrophenylarsonic acid. Metallation and subsequent treatment with alkyl halides give the secondary o-aminophenylarsines. o-Aminophenylarsines react with aldehydes, ketones and ketoesters forming derivates of the 1,3-benzazarsoline. Exceptions are redox reactions between o-aminophenylarsine and aldehydes. The properties of the compounds are described in more detail.     

The suitability of various calcium electrodes based on metal salts of di-(n-octylphenyl)phosphoric acid and some derivatives for the measurement of calcium in sea water

The calcium salts of di-(n-octylphenyl)-phosphoric acid, di-(p-n-octyl-o-nitrophenyl)-phosphoric acid and di-(p-n-octyl-o-bromophenyl)-phosphoric acid have been investigated as calcium sensors in membrane electrodes. The electrodes have been used for potentiometric titrations of calcium in sea water. The effect of varying the membrane solvent and the chelate metal has been studied.     

Isokinetic correlation analysis of the series of electrophilic substitution reactions ofo-substituted phenylmercurials

Isokinetic relationships of the series of electrophilic substitution reactions ofo-substituted phenylmercurials are studied, and the results show, for the first time, that isokinetic correlation analysis can reveal the dominant factor in the system of the reactions. The analysis of S_E2 ofo-substituted phenylmercuric chlorides indicates that the steric effect ofo-substituents is the predominant factor when I₂ is used as electrophilic agent, however, the electronic effect ofo-substituents would become the predominant factor when HCl is used as the electrophilic agent. In S_E1 ofo-substituted phenylmercuric chlorides, the results of the analysis display that the predominant factor is the field effects ofo-substituents. The determination of predominant factors in those reactions would provide further scientific basis for those reaction mechanisms.     

Synthesis of sterically hindered benzoquinone methacrylates

Sterically hindered p- and o-benzoquinone methacrylates, viz., 2,5-di(tert-butyl)-3,6-di-oxocyclohexa-1,4-dienyl methacrylate and 2,5-di(tert-butyl)-3,4-dioxocyclohexa-1,5-dienyl methacrylate, were synthesized by O-acylation of the lithium and tetrabutylammonium salts of 3,6-di(tert-butyl)-2-hydroxy-p-benzoquinone with methacryloyl chloride. The influence of the nature of cation and solvent on regioselectivity of the acylation was studied. The o-benzoquinone derivative obtained can serve as a paramagnetic ligand in metal complexes.     

Simultaneous detection of ascorbate and uric acid using a selectively catalytic surface

The direct and selective detection of ascorbate at conventional carbon or metal electrodes is difficult due to its large overpotential and fouling by oxidation products. Electrode modification by electrochemical reduction of diazonium salts of different aryl derivatives is useful for catalytic, analytical and biotechnological applications. A monolayer of o-aminophenol (o-AP) was grafted on a glassy carbon electrode (GCE) via the electrochemical reduction of its in situ prepared diazonium salts in aqueous solution. The o-aminophenol confined surface was characterized by cyclic voltammetry. The grafted film demonstrated an excellent electrocatalytic activity towards the oxidation of ascorbate in phosphate buffer of pH 7.0 shifting the overpotential from +462 to +263 mV versus Ag/AgCl. Cyclic voltammetry and d.c. amperometric measurements were carried out for the quantitative determination of ascorbate and uric acid. The catalytic oxidation peak current was linearly dependent on the ascorbate concentration and a linear calibration curve was obtained using d.c. amperometry in the range of 2-20 μM of ascorbate with a correlation coefficient 0.9998, and limit of detection 0.3 μM. The effect of H₂O₂ on the electrocatalytic oxidation of ascorbate at o-aminophenol modified GC electrode has been studied, the half-life time and rate constant was estimated as 270 s, and 2.57 × 10⁻³ s⁻¹, respectively. The catalytically selective electrode was applied to the simultaneous detection of ascorbate and uric acid, and used for their determination in real urine samples. This o-AP/GCE showed high stability with time, and was used as a simple and precise amperometric sensor for the selective determination of ascorbate.     

Reactions of epoxides derived from internal perfluoroolefins with o-phenylenediamine and 2-aminophenol

The reactions of epoxy derivatives of internal perfluoroolefins with o-phenylenediamine and 2-aminophenol in dioxane gave 23–67% of the corresponding 2,3-bis(perfluoroalkyl)quinoxalines and 2,3-bis(perfluoroalkyl)-2H-1,4-benzoxazin-2-ols, respectively. When N,N-dimethylacetamide was used as a solvent, the main reaction pathway was anionic isomerization of epoxides into ketones which were then converted into 2-perfluoroalkylbenzimidazoles (in the reactions with o-phenylenediamine) or 2-hydroxy-N-perfluoroalkanoylanilines (in the reactions with 2-aminophenol). The reaction of 3,4-epoxydodecafluorohexane with 2-aminophenol in N,N-dimethylacetamide was accompanied by unusual cyclization to afford 2-pentafluoropropanoyl-2-pentafluoroethyl-1,3-benzoxazolidine.     

Iron-catalyzed cascade reaction of ynone with o-aminoaryl compounds: a Michael addition-cyclization approach to 3-carbonyl quinolines

An efficient iron-catalyzed cascade Michael addition-cyclization of o-aminoaryl compounds including o-aminoaryl aldehydes, o-aminoaryl ketones, and o-aminobenzyl alcohols with ynones for the synthesis of 3-carbonyl quinolines is reported. The reactions proceed to afford 3-carbonyl quinoline derivatives with or without substituent at the C-4 position in good to high yields using Iron(III) chloride hexahydrate as the catalyst in the air.