Critical examination of the 1H NMR spectra of aryl epoxides

The proton chemical shift of several derivatives of styrene oxides have been obtained in different solvents in order to check the relative importance of different contributions to the shielding of oxirane protons. It seems likely that ‘ring current’ and electrostatic effects can explain differences within the several compounds examined. An investigation of the conformational requirements of the phenyl group in these systems shows that the preferred conformation present in styrene oxide is also likely to be maintained in other compounds, where groups cis and trans to the phenyl ring are present. A discussion of the possibility of employing ‘ring currents,’ obtained both in the Johnson and Bovey scheme and with an SCF treatment for conformational analysis is given and it seems that this contribution, when considered alone, can only give very approximate information regarding the geometrical pattern of the molecule.     

Complete 1H and 13C NMR assignment for aryl diisoprenes

The characterization of four aryl diisoprenes was carried out by 1D‐ and 2D‐NMR methods, which permitted the assignment of the signals of all protons and all carbon atoms. Copyright © 2003 John Wiley & Sons, Ltd.     

A new synthesis of aryl substituted quinazolin-4(1H)-ones

Treatment of a variety of substituted 2-aminobenzonitriles with formic acid under strong acid catalysis provides the corresponding quinazolin-4(1H)-ones in good yield. A potential reaction pathway is described.     

Metal-free synthesis of aryl esters by coupling aryl carboxylic acids and aryl boronic acids

A facile synthesis of aryl esters is developed by coupling aryl carboxylic acids and aryl boronic acids in the presence of PhI(OAc)₂ and carbonyl diimidazole. A wide range of functional groups were tolerant to the metal-free reaction condition that led to the desired products in good yields.     

Dilithium aryl cyanocuprates from butyl aryl tellurides

Butyl aryl tellurides reacted with dilithium dimethyl cyanocuprate and with dilithium methyl(2-thienyl)cyanocuprate to give the corresponding dilithium aryl cyanocuprates, which were captured with enones leading to 4-aryl ketones in good yields.     

Substituent effect on the 1H NMR Spectra of trans aryl methyl oxiranes and arylpropenes

The ¹H NMR spectra of 1-aryl-2-methyl oxiranes substituted in the phenyl ring and of the corresponding vinyl derivatives have been analysed. The substituent effect on oxiran protons seems mostly polar in character, as shown by correlations with substituent constants, solvent effects and the fact that perturbation decreases with increasing distance from the substituent. The comparison with the corresponding vinyl derivatives, in which conjugation effects are present, confirms this point. The results also seem to exclude the possibility of substituents causing significant changes on the preferred conformation of the phenyl ring. Ring current contributions on oxirane protons, evaluated by SCF procedure, show that their change with substituents is very small and does not represent a significant part of the change of proton chemical shift with substituents.     

N‐Arylation of N‐H heterocycles with aryl bromides and aryl iodides using cui and kf/Al2O3

Copper‐catalyzed system for N‐arylation of N‐H group in heterocycles such as indole, pyrrole and carbazole with aryl iodides and aryl bromides using potassium fluoride supported on alumina as a base is described. This is a simple and efficient method for the coupling of aryl iodides and bromides with N‐H heterocycles. Different functionalized iodo and bromo arenes were coupled with N‐H heterocycles using this system.     

Photolysis of aryl bromides and aryl chlorides in benzene

Conclusions As a result of photolysis of aromatic bromo- and chlorohydrocarbons in benzene solution, products of replacement of the halogen atoms by a phenyl group were obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 456–457, February, 1967.     

Electron impact induced migrations of aryl groups in substituted 4(3H)-quinazolinones

Electron impact mass spectra of 2-diphenylmethyl-3-aryl-4(3H)-quinazolinones display ions arising from migrations of different aryl groups in the molecular and [M? H]⁺ ions. The most abundant ion due to rearrangement, [C₁₃H₉NO]^+˙, is formed by migration of a phenyl from the benzhydryl group onto N-1 and subsequent cleavage of the heterocyclic ring. Other rearrangements involve initial migration of the N-3 aryl group to the benzylic carbon. The mechanisms of migrations were elucidated by means of deuterium and ¹⁵N labelling and are supported by metastable spectra.     

Electrophilic fluorination of aryl tin and aryl mercury derivatives

Cleavage of aryl-tin and aryl-mercury derivatives with CF₃OF occurs particularly readily and the mercury derivatives give the corresponding arylfluorine compounds in especially high yield.     

Acid-mediated aryl migration reaction of C-3 aryl substituted pyrrolidinoindolines

Aryl migration reactions of C-3 aryl substituted pyrrolidinoindoline compounds to provide highly conjugated C-2 aryl indole compounds have been discovered. The developed reactions have a wide substrate scope and proceed in high yield under simple acidic conditions. A unique cationic cyclopropane intermediate as the transition state is proposed.     

Nickel-catalyzed amination of aryl phosphates through cleaving aryl C-O bonds

The amination of triaryl phosphates was achieved using a Ni(II)-(σ-Aryl) complex/NHC catalyst system in dioxane at 110 °C in the presence of NaH as base. Electron-neutral, -rich, and -deficient triaryl phosphates were coupled with a wider range of amine partners including cyclic and acyclic secondary amines, aliphatic primary amines, and anilines in good to excellent yields.     

Palladium-catalyzed N-arylation of sulfoximines with aryl bromides and aryl iodides

Various N-arylated sulfoximines have been synthesized in high yield by a direct approach which is based on a palladium-catalyzed cross-coupling strategy. Aryl bromides of variable substitution pattern were found to be the most effective coupling partners, whereas aryl iodides showed a nonpredictable behavior requiring lithium or silver salts as additives to ensure product formation in acceptable yields. Coupling of (S)-2-(2'-bromophenyl)-4-tert-butyloxazoline with enantiomerically pure (-)-(RS)-S-methyl-S-phenylsulfoximine afforded the corresponding product in good yield as a single diastereomer, showing that the palladium-catalyzed arylation proceeds in a stereospecific manner. The reaction with dibromobenzenes yielded the monosulfonimidoyl arenes in all cases, suggesting that the introduction of the sulfonimidoyl moiety deactivates the arene, thus preventing a second coupling step.     

Preparation and synthetic applications of aryl tetraflates (ArOSO2CF2CF2H)

We have recently developed an improved synthetic route to 1,1,2,2-tetrafluoroethanesulfonic acid (HCF2CF2SO3H, TFESA) and explored the applications of this newly available superacid in catalysis. Low volatility, ease of handling, and a convenient 1H NMR handle make this acid an attractive alternative to triflic acid. TFESA can also be converted to several of its derivatives: anhydride, sulfonyl chloride, and sulfonyl fluoride, which provide a good entry point for the synthesis of aryl sulfonates. We prepared several aryl esters of 1,1,2,2-tetrafluoroethanesulfonic acid (aryl tetraflates) and showed that they can be used in a number of palladium-catalyzed coupling reactions (Suzuki, Heck, and Buchwald-Hartwig couplings). While the reactivity of tetraflates lies between that of triflates and chlorides, tetraflates appear to be more thermally stable. Additionally, the presence of a hydrogen atom in the tetraflate group facilitates monitoring of reactions and characterization of derivatives.     

Interaction of N-(aryl)picolinamides with iridium. N–H and C–H bond activations

Reaction of N-(4-R-phenyl)picolinamide (R = OCH₃, CH₃, H, Cl and NO₂) with [Ir(PPh₃)₃Cl] in refluxing ethanol in the presence of a base (NEt₃) affords two yellow complexes (1-R and 2-R). The 1-R complexes contain an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphines, a chloride and a hydride. The 2-R complexes contain an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphines and two hydrides. Similar reaction of N-(naphthyl)picolinamide with [Ir(PPh₃)₃Cl] affords two organometallic complexes, 3 and 4. In complex 3 the amide ligand is coordinated to the metal center, via C–H activation of the naphthyl ring at the 8-position, as a dianionic tridentate N,N,C donor, along with two triphenylphosphines and one chloride. Complex 4 is similar to complex 3, except a hydride is bonded to iridium instead of the chloride. Structures of the 1-OCH₃, 2-Cl and 4 complexes have been determined by X-ray crystallography. All the complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ir^III–Ir^IV oxidation within 0.50–1.16 V vs. SCE and a reduction of the coordinated amide ligand within −1.02 to −1.25 V vs. SCE.