NMR chemical shifts and coupling constants of various nuclei of N,N-diethylbenzenesulfenamide,N,N-diethylbenzeneseleneamide and some related sulfur amides

The ⁷⁷Se, ¹⁵N, ¹³C and ¹H NMR parameters have been determined for N,N-diethylbenzenesulfen- and N,N-diethylbenzeneseleneamide and the ¹H¹³C coupling constants additionally for N,N-dimethylmethanesulfinamide, N,N-dimethylbenzenesulfinamide, N,N-dimethylmethanesulfonamide, N,N-dimethylbenzenesulfonamide and diphenylsulfone. The nitrogen-15 nucleus is slightly more shielded in the sulfenamide than in the seleneamide. Compared to sulfin- and sulfonamides the nitrogen nuclei of these amides are more shielded. The solvent effects on the chemical shift of both selenium-77 and nitrogen-15 nuclei are observable. The nitrogen-15 chemical shifts of sulfur and seleneamides are less sensitive to the solvents than those of carboxamides. This change in the nitrogen-15 chemical shift in sulfen- and seleneamide is the same order of magnitude, but opposite in direction compared with that in sulfon- and sulfinamides. The ¹H¹³C direct aromatic coupling constants increase along with the increasing oxidation state of sulfur in sulfur amides, being greatest in sulfonamides.     

Reaction of methyl acrylate with N,N-dimethylethanolamine in the presence of a titanium alkoxide

The kinetic features were examined for transesterifi cation of methyl acrylate with N,N-dimethylethanolamine in the presence of tetra(N,N-dimethylaminoethyl) titanate at different molar ratios of the reactants and at temperatures within 50?C80°C, as well as for side reactions of Michael addition at 95?C125°C. The major parameters governing the selectivity of the synthesis of N,N-dimethylaminoethyl acrylate were determined.     

Pd(II)-catalyzed intramolecular C–H activation/C–C cross coupling for the synthesis of carbazoles from diaryl acetamides

Pd(II)-catalyzed intramolecular C–H activation/C–C cross coupling within N,N-diphenyl-acetamides allows the efficient formation of differently substituted carbazoles. In this cross-dehydrogenative coupling, many different functional groups are tolerated and the starting material N,N-diphenyl-acetamides can be easily prepared in one step from commercially available acetanilides and iodobenzenes.     

Synthesis of oxindoles via Cu-mediated reactions between N-phenylacrylamides and ethyl 2-bromo-2-methylpropionate

A novel way of synthesizing alkylated oxindoles via Cu-mediated atom transfer radical addition reaction between N-phenylacrylamides and ethyl 2-bromo-2-methylpropionate has been described. It was found that the use of N,N,N′,N′-1,1,2,2,-tetramethylethylenediamine as ligand was important for achieving good yields. Additionally, the use of DMSO as solvent and running the reaction at 130?°C were also crucial. In some cases, the product can be further brominated when the reaction temperature was raised to 150?°C.     

Easily assembled,modular N,O-chelating ligands for Ta(V) complexation: a comparative study of ligand effects in hydroaminoalkylation with N-methylaniline and 4-methoxy-N-methylaniline

The influence of structurally related N,O-chelating ligands with additional heteroatoms (N, O, P, S) on the reactivity of in situ generated tantalum complexes for the hydroaminoalkylation of amines has been explored. Reactivity was probed by evaluating the catalytic ability of these N,O-chelating systems with N-methylaniline and 4-methoxy-N-methylaniline substrates. Enhanced reactivity is observed with amide proligands bearing an ortho-methoxyphenyl group on the nitrogen. 4-Methoxy-N-methylaniline is found to be more prone to undergo C–H functionalization via hydroaminoalkylation than N-methylaniline. The use of the related substrate 2-methoxy-N-methylaniline is not tolerated, and instead C(sp³)–O bond cleavage was observed.     

Synthesis of novel 2,2- and 1,1-linked dimeric ‘head-to-head’ N-alkoxybenzimidazoles

Synthesis of two new types of ‘head-to-head’ N,N-alkoxy bisbenzimidazoles is described. The proposed intermediate N-oxy benzimidazole from base-induced heterocyclization of N-alkylnitroanilines can be trapped with a biselectrophile (to give an N,N-linked dimer), or double heterocyclization of dimeric nitroanilines can be intercepted by electrophile trapping of both N-oxybenzimidazole termini to give C2,C2-linked dimers. These represent two regioisomeric motifs constituting new classes of benzimidazole dimers.     

One-pot synthesis of aliphatic and aromatic 2H-indazolo[2,1-b]phthalazine-triones catalyzed by N-halosulfonamides under solvent-free conditions

N, N, N′, N′-Tetrabromobenzene-1,3-disulfonamide and poly(N-bromo-N-ethylbenzene-1,3-disulfonamide) were used as efficient catalysts for the one-pot synthesis of aliphatic and aromatic 2H-indazolo[2,1-b]phthalazine-triones in excellent yields from aldehydes, phthalhydrazide, and dimedone at 80-100 °C under solvent-free conditions.     

Carbon-13 NMR study of some acetylenic amines,the N-oxides and their rearrangement products

Carbon-13 NMR chemical shifts of some N, N-dialkyl-4-acetoxybut-2-ynylamines and their corresponding N-oxides have been analysed. These N-oxides undergo thermal rearrangement to O-allenyl hydroxylamine for which the ¹³C NMR spectral assignments were also carried out. The effect of N-oxidation on the chemical shifts is calculated.     

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.     

Preparation of chiral bipyridine bis-N-oxides by oxidative dimerization of chiral pyridine N-oxides

The direct preparation of chiral 2,2′-bipyridine bis-N-oxides has been developed. The method involves two stages, first, the deprotonation of substituted chiral pyridine N-oxides and second, the oxidative dimerization of the resulting 2-lithiopyridine N-oxides. Optimization of the reaction conditions led to the selection of LiTMP in THF for the deprotonation and molecular iodine as the oxidant. The corresponding 2-iodopyridine N-oxide is invariably formed as a by-product. A series of 11 chiral pyridine N-oxides was prepared that bear substituents at the C(2) and C(5) positions. Oxidative dimerization of these mono-N-oxides proceeded in 33–77% yield. In all cases, the dimerization was highly diastereoselective for the formation of the P-configuration of the chiral axis.     

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.     

New N-acylamino acids and derivatives from renewable fatty acids: gelation of hydrocarbons and thermal properties

This work reports the synthesis of new fatty N-acylamino acids and N-acylamino esters from the C16:0, C18:0, C18:1, and C18:1(OH) fatty acid families and demonstrates the activity of these compounds as organogel agents. Compounds were heated and dissolved in various solvents (n-hexane, toluene, and gasoline). Only saturated C16:0 and C18:0 derived from alanine were able to form gels in toluene, and saturated C16:0 derived from phenylalanine showed gelation in n-hexane. This is the first evidence that fatty N-acylamino esters and N-acylamino acid derivatives of l-serine and fatty acids C16:0, C18:0, and C18:1 are able to form gels with hexane. This observation confirms the importance of the hydroxyl group in the segment derivative of l-serine in forming good gels.     

Convenient preparation of dichloromethyl alkyl ethers

Dichloromethyl alkyl ethers have been synthesized from alkyl formates (C1–C4) and oxalyl chloride in the presence of catalytic amount of N-methylformanilide. N,N-Dimethylformamide is not suitable for the reaction. The method has the advantages of simple experimental procedure, which is applicable to large scale synthesis, without use of harmful reagents.     

Étude de la complexation des lanthanides trivalents par les six isomères de l'acide diaminocyclohexane-tétraacétique : Partie 3. Relation entre les Constantes d'Acidité et la Structure Moleculaire des Chélatants

(Study of the complexation of trivalent lanthanides by the six isomers of diaminocyclohexanetetraacetic acid. Part 3. Relationship between the acidity constants and the molecular structure of the ligands.)Potentiometric measurements of the acidity constants of the six isomers of diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA) are reported for an ionic strength of 1 mol l^?1 (KCl) at 25°C. The values of the two constants K_a3 and K_a4 are correlated with the maximum N—N distance for each ligand. Ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) and some homologous ligands, including specially synthesized, 1,8-diaminooctane-N,N,N′,N′-tetraacetic acid and 1,10-diaminodecane-N,N,N′,N′-tetraacetic acid, are studied under the same conditions. It is proved that there is a relationship between the molecular structure and the affinity for protons.     

Nickel(0)/N-heterocyclic carbene complexes catalysed arylation of aromatic diamines

Nickel complexes of N-heterocyclic carbenes were examined for effecting C–N coupling reactions between aromatic diamines and aryl chlorides of varying electron density. The Ni(0) · 2IPr (IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) complex associated to t-BuONa allowed N,N′-diarylation at 100 °C in 1,4-dioxane with excellent yields. Selective monoarylation of diamines could be performed in THF at 65 °C.     

The molecular structure of the N-chloroimine product of rearrangement of N,N-dichloroperfluoroaniline: A study by gas-phase electron diffraction

A gas-phase electron-diffraction study of the product of rearrangement of N,N-dichloro-perfluoroaniline has assisted in establishing it to be the N-chloroimine, I, rather than the azepine, II. The molecule is found to be planar apart from atoms Cl13 and F14. The detailed dimensions shown in Fig. 2 were obtained by least-squares refinements in which several structural constraints were applied to reduce the total number of independent parameters. Of particular interest is the evidence for overcrowding around the CN bond: ∠N7C1C2 = 128°, ∠C18N7C1 = 126°, ∠N7C1C6 = 118° ; the distance C18 β F9 is 2.73 Å.     

The Antifungal Action Mode of N-Phenacyldibromobenzimidazoles

Our study aimed to characterise the action mode of N-phenacyldibromobenzimidazoles against C. albicans and C. neoformans. Firstly, we selected the non-cytotoxic most active benzimidazoles based on the structure–activity relationships showing that the group of 5,6-dibromobenzimidazole derivatives are less active against C. albicans vs. 4,6-dibromobenzimidazole analogues (5e–f and 5h). The substitution of chlorine atoms to the benzene ring of the N-phenacyl substituent extended the anti-C. albicans action (5e with 2,4-Cl₂ or 5f with 3,4-Cl₂). The excellent results for N-phenacyldibromobenzimidazole 5h against the C. albicans reference and clinical isolate showed IC₅₀ = 8 µg/mL and %I = 100 ± 3, respectively. Compound 5h was fungicidal against the C. neoformans isolate. Compound 5h at 160–4 µg/mL caused irreversible damage of the fungal cell membrane and accidental cell death (ACD). We reported on chitinolytic activity of 5h, in accordance with the patterns observed for the following substrates: 4-nitrophenyl-N-acetyl-β-d-glucosaminide and 4-nitrophenyl-β-d-N,N′,N″-triacetylchitothiose. Derivative 5h at 16 µg/mL: (1) it affected cell wall by inducing β-d-glucanase, (2) it caused morphological distortions and (3) osmotic instability in the C. albicans biofilm-treated. Compound 5h exerted Candida-dependent inhibition of virulence factors.     

Synthesis of the C6–C18 bis-tetrahydrofuran fragment of the proposed structure of iriomoteolide-2a via stepwise double SN2 cyclization reactions

The C6–C18 bis-tetrahydrofuran (bis-THF) fragment of the proposed structure of iriomoteolide-2a has been synthesized via stepwise double intramolecular S_N2-type etherifications. The C11 and C16 stereogenic centers could be secured in the forms of propargyl alcohols by asymmetric transfer hydrogenation of the corresponding propargyl ketones. The C9–C12 THF ring was first constructed via a tandem asymmetric dihydroxylation (AD)–S_N2 sequence while the C13–C16 THF ring was later installed via an intramolecular S_N2 reaction of a chiral propargyl mesylate. During the latter THF ring formation, epimerization at the propargylic carbon was not observed. Since the initially proposed (9R,11S,12R) configuration of iriomoteolide-2a has recently been revised to (9S,11R,12S), the established synthesis of the C6–C18 bis-THF fragment could be easily amended by using the opposite enantiomers of the chiral ligands for AD and asymmetric transfer hydrogenation.     

An efficient, mild, and selective Ullmann-type N-arylation of indoles catalyzed by copper(I) complex

A wide range of N-arylated indoles are selectively synthesized through intermolecular C(aryl)-N bond formation from the corresponding aryl iodides and indoles through Ullmann-type coupling reactions in the presence of a catalytic amount of easily available N,N,N′,N′-tetramethyl-BINAM-CuI complex under very mild reaction conditions.     

A Journey from June 2018 to October 2021 with N,N-Dimethylformamide and N,N-Dimethylacetamide as Reactants

A rich array of reactions occur using N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc) as reactants, these two amides being able to deliver their own H, C, N, and O atoms for the synthesis of a variety of compounds. This account highlights the literature published since June 2018, completing previous reviews by the author.