Electrochemical fluorination of N,N-dimethylperfluoroacylamides

The electrochemical fluorination (ECF) of N,N-dimethylperfluoroacylamides gives the corresponding perfluoro-N,N-dimethylacylamides in low yield. With increase of the number of carbon atoms in the perfluoroacyl radical the yield of the required perfluoro-N,N-dimethylacylamides is slightly increased.     

Synthesis and aromatic nucleophilic N-N, N-S and N-O exchange reactions of N,N-dimethyl-2-trifluoroacetyl-1-naphthylamine

We succeeded in the synthesis of N,N-dimethyl-2-trifluoroacetyl-1-naphthylamine (10) by the regioselective deacylation of N,N-dimethyl-2,4-bis(trifluoroacetyl)-1-naphthylamine with trifluoroacetic acid and water. The aromatic nucleophilic substitutions of 10 with various amines, thiols and alcohols proceeded cleanly to give the corresponding N-N, N-S and N-O exchanged products in moderate to excellent yields.     

CuI/N,N-dimethylglycine-catalyzed synthesis of N-aryloxazolidinones from aryl bromides

CuI/N,N-dimethylglycine catalyzed coupling of aryl bromides with substituted oxazolidinones took place at 120 °C in DMF, affording the corresponding N-arylation products with good to excellent yields. A number of functional groups, such as ketone, nitrile, nitro, methoxy, and hydroxyl were tolerated under these conditions, thereby allowing diversity synthesis of N-aryloxazolidinones.     

Synthesis of B-trisubstituted borazines via the rhodium-catalyzed hydroboration of alkenes with N,N′,N″-trimethyl or N,N′,N″-triethylborazine

Hydroboration of terminal and internal alkenes with N,N′,N″-trimethyl- and N,N′,N″-triethylborazine was carried out at 50 °C in the presence of a rhodium(I) catalyst. Addition of dppb or DPEphos (1 equiv.) to RhH(CO)(PPh₃)₃ gave the best catalyst for hydroboration of ethylene at 50 °C, resulting in a quantitative yield of B,B′,B″-triethyl-N,N′,N″-trimethylborazine. On the other hand, a complex prepared from (t-Bu)₃P (4 equiv.) and [Rh(coe)₂Cl]₂ gave the best yield for hydroboration of terminal or internal alkenes.     

Pyridinium N-heteroarylaminides: synthesis of N-heteroarylpolyamines

The synthesis of a set of new N-heteroarylpolyamines is reported. A multiple and regioselective alkylation on the exo nitrogen of pyridinium N-(heteroaryl)aminides with several polybromo compounds, followed by a clean N-N bond reduction of the corresponding pyridinium salts, provides an easy and general method to obtain the title compounds.     

Coordination steric effect of N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl-2-pyrrolidone on the assembly of coordination polymers

Three coordination polymers 1, 2 and 3 have been synthesized in DMF (N,N-dimethylformamide), DMA (N,N-dimethylacetamide) and NMP (N-methyl-2-pyrrolidone), respectively. In 1, DMF solvent molecule coordinates to zinc ion as an ancillary ligand, and 1D chain structure is obtained. 2 and 3 are isostructural, in which solvent molecules, DMA and NMP, do not coordinate to zinc ions, and 1D double stranded chain structures are formed. The coordination steric hindrance of the solvents is suggested as the decisive factor of the assemblies. Crystallography and thermoanalysis reveal that 2 and 3 are more stable and also include more guest solvent molecules than 1.     

Ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides

A ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides was found to afford corresponding amides in good to high yields. A simple RuCl₃/Zn-Cu/alcohol system, without the addition of any other ligands, exhibited a high catalytic activity, and therefore the present reaction does not require a stoichiometric amount of metals or metal complexes as reductants. When β-substituted-α,β-unsaturated N-methoxyamides were employed as substrates, concurrent hydrogenation of the olefin moiety proceeded slowly with deprotection of the methoxy group. In the reduction of N-hydroxyamides, the alcoholic solvent was found to function as a hydrogen donor.     

Fluorsilylsubstituierte N,N- und N,O-bis(trimethylsilyl)-hydroxylamine

Fluoro- und aminofluoro-silanes react with the lithium salt of N,O-bis(trimethylsilyl)hydroxylamine under LiF elimination and substitution. Alkyl- and amino-fluorosilanes give O-fluorosilyl-N,N-bis(trimethylsilyl)hydroxylamines, arylfluorosilanes give N-fluorosilyl-N,O-bis(trimethylsilyl)hydroxylamines. By the further reaction of O-difluorosilyl-N,N-bis(trimethylsilyl)hydroxylamine with the lithiated hydroxylamine, O,O′-fluoromethylsilyldi[N,N-bis(trimethylsilyl)hydroxylamine] is formed. On heating N-difluorophenylsilyl-N,O-bis(trimethylsilyl)hydroxylamine di[fluorophenylsilyl(methyl)amino]pentamethylsiloxane is formed by methyl group migration. The NMR and mass spectra of the compounds are reported.     

Catalytic photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine and carbon dioxide

Photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine (TMB) in MeCN under bubbling of CO₂ proceeded with high catalytic efficiency, giving 3,3-diphenylacrylic acid (DPA) and 3-hydroxy-3,3-diphenylpropionic acid (20). The turnover number (TON=(DPA+20)/TMB) reached 17. Similarly, 1-phenyl-1-cyclohexene yielded cis-2-acetamido-2-phenylcyclohexanecarboxylic acid with TON 5.9. As compared with related N,N-dimethylaniline derivatives, TMB is more resistant to photodecomposition, has the much larger absorbance in the S₀→S₁ transition, and has the lower quenching efficiency by CO₂. Probably these factors are partly responsible for the high TON observed for TMB.     

Highly selective isomerization of N-allylamides and N-allylamines

A highly selective rhodium and ruthenium catalyzed transformation of N-allylamines and N-allylamides to the corresponding 1-propenyl derivatives is described. Strong E-selectivity in the isomerization of allylamines was observed. The first catalytic system containing a transition metal complex for Z-selective isomerization of allylamides is presented. An application of siliceous mesoporous cellular foams for effective removal of the catalyst from the post-reaction mixture is described.     

N-Polyfluoroethyl and N-2-chlorodifluorovinyl derivatives of azoles

Reactions of tetrafluoroethylene, chlorotrifluoroethylene and 1,2-dichlorodifluoroethylene with N-potassium salts of imidazole, 2-methylbenzimidazole, 3,5-dimethylpyrazole, 1,2,4-triazole, and benzotriazole lead to the formation of the corresponding N-(1,1,2,2-tetrafluoroethyl), N-(2-chloro-1,1,2-trifluoroethyl), and N-(2-chloro-1,2-difluorovinyl) azoles. Treatment of N-(2-chloro-1,2-difluorovinyl) and N-(2-chloro-1,1,2-trifluoroethyl) derivatives of azoles with tetramethylammonium fluoride is a useful synthetic method for the preparation of heterocycles with 1,2,2,2-tetrafluoroethyl group attached to nitrogen.     

Single-step conversion of N-benzyl, N-trityl and N-diphenylmethyl amines to t-butyl carbamates using polymethylhydrosiloxane

t-Butyl carbamates were obtained efficiently in high yields from the corresponding N-benzyl, N-trityl and N-diphenylmethyl precursors in a single-step reductive transformation employing polymethylhydrosiloxane and di-t-butyl dicarbonate under Pd(OH)₂/C catalysis.     

Synthesis of N,N-dialkylaminobenzonitriles and halo-(N,N-dialkyl)benzamidines by reaction of halobenzonitriles with lithium amides

3- and 4-N,N-Dialkylaminobenzonitriles and 4-chloro-(N,N-dialkyl)benzamidines were isolated by reacting 4-chlorobenzonitrile with hindered lithium amides under thermodynamic (0 °C) and kinetic control conditions (−78 °C), respectively. As previously reported, a benzyne mechanism seems to be confirmed since N,N-dialkylaminobenzonitriles are formed. Only benzamidines were isolated in fair to high yields at both 0 °C and −78 °C with non-hindered lithium amides. Exploitation and mechanistic rationale of the reaction of different halobenzonitriles are also reported.     

Control of polymorphism by crystallization of N,N-diisopropylcarbamoylisatin

N,N-Diisopropylcarbamoylisatin showed polymorphism and was crystallized into two different space groups, chiral P2₁2₁2₁ and racemic P2₁/c from the solvent; the polymorphism could be controlled by crystallization from the melt using the difference of melting points.     

Synthesis and reactivity of N-aryl substituted N-heterocyclic silylenes

The synthesis of two N-aryl substituted 2-silaimidazolidenes 9a, b by metal-reduction of the appropriate silicon(IV) heterocycles is reported. Structural as well as spectroscopic data obtained for the N-aryl substituted N-heterocyclic silylenes (NHSi) are very close to those obtained previously for their N-alkyl substituted counterparts. NHSis 9a, b are used as starting materials for the synthesis of a series of dichalcogenadisiletanes 19-24 and for of a mono silylene tungsten complex 29. The reactivity studies revealed only marginally differences between the N-aryl substituted NHSis 9a, b and previously described N-alkyl substituted silylenes.     

Lithiation of 2-(chloroaryl)-2-aryl-1,3-dioxolanes with butyllithium activated by N,N,N′,N″,N″-pentamethyldiethylenetriamine

Intramolecular competition of variously substituted phenyl rings of benzophenone ketals in lithiation reactions proved to be a useful tool to study both ortho-directing ability and long-range effects of the substituents. The regioselectivities observed in the reaction of benzophenone ketals having one or two chloro substituents in one of the aryl rings with butyllithium complexed to N,N,N′,N″,N″-pentamethyldiethylenetriamine demonstrate the significance of both ortho- and meta-acidifying effect of the chloro substituents. The lithio species thus generated were carboxylated resulting in new polysubstituted benzoic acids.     

Sialylation reactions with N,N-dibenzylthiosialoside donor

A new sialyl donor, N,N-dibenzyl-protected p-toluenethiosialoside, was synthesized and its sialylation reaction was investigated. This reaction proceeded in a preactivation manner and preferred to provide β-anomeric coupling products. The β-selectivity was rationalized based on the assumption that N,N-dibenzylamino group could serve as an oriented group to activate the hydroxyl group of acceptor from β-face.     

Photophysical properties and photoreduction of N-acetyl- and N-benzoylphthalimides

The photophysical properties and photoreduction of N-acetylphthalimide (AcP) and N-benzoylphthalimide (BzP), N-3,4,5-trimethoxybenzoylphthalimide (trimethoxyBzP) and N-4-nitrobenzoylphthalimide (nitroBzP) were studied by steady-state and transient techniques. Radicals and their precursor triplet states were detected by flash photolysis. The triplet state properties of AcP and BzP were characterized. In contrast, no triplet absorption was observed with ns-detection for trimethoxyBzP and nitroBzP. Specific products are formed upon electron transfer from triethylamine to the photoexcited acylphthalimides. In addition, H-atom transfer from 2-propanol or other alcohols to the triplet state takes place. The properties of several radical intermediates involved in photoreduction of the acylphthalimides as well as some structure-function relationships are described.     

Enantioselective aldol reactions of trichlorosilyl enol ethers catalyzed by chiral N,N-dioxides and monodentate N-oxides

Chiral N,N^′-dioxides and monodentate N-oxides were employed as catalysts in catalytic, enantioselective aldol reactions of trichlorosilyl enol ethers. The reactions of acyclic enol ethers using N,N^′-dioxides resulted in the anti-adducts from (E)-enol ethers and the syn-adducts from (Z)-enol ethers. The reactions of cyclic (E)-enol ethers using N,N^′-dioxides gave the anti-adducts, whereas monodentate N-oxides predominantly gave the syn-adducts.