Reactions of tris(amino)phosphines with arylsulfonyl azides: product dependency on tris(amino)phosphine structure

The Staudinger reaction of N(CH2CH2NR)3P [R = Me (1), Pr (2)] with 1 equiv of N3SO2C6H4Me-4 gave the ionic phosphazides [N(CH2CH2NR)3PN][SO2C6H4Me-4] [R = Me (3), R = Pr (5a)], and the same reaction of 2 with N3SO2C6H2Me3-2,4,6 gave the corresponding aryl sulfinite 5b. On the other hand, the reaction of 1 with 0.5 equiv of N3SO2Ar (Ar = C6H4Me-4) furnished the novel ionic phosphazide [[N(CH2CH2NMe)3P]2(mu-N3)][SO2Ar] (6). Data that shed light on the mechanistic pathway leading to 3 were obtained by low temperature 31P NMR spectroscopy. A crystal and molecular structure analysis of the phosphazide sulfonate [N(CH2CH2NMe)3PN3][SO3C6H4Me-4] (4), obtained by atmospheric oxidation of 3, indicated an ionic structure, the cationic part of which is stabilized by a transannular P-N bond. A crystal and molecular structure analysis of 6 also indicated an ionic structure in which the cation features two untransannulated N(CH2CH2NMe)3P cages bridged by an azido group in an eta 1: mu: eta 1 fashion. The reaction of P(NMe2)3 with N3SO2Ar (Ar = C6H4Me-4) in a 1:0.5 molar ratio furnished [[(Me2N)3P]2(mu-N3)][SO2-Ar] (11) in quantitative yield. On the other hand, the same reaction involving a 1:1 molar ratio of P(NMe2)3 and N3SO2Ar produced a mixture of 11, [(Me2N)3PN3][SO2Ar] (12), and the iminophosphorane (Me2N)3P=NSO2Ar (10). In contrast, the bicyclic tris(amino)phosphines MeC(CH2NMe)3P (7) and O=P(CH2NMe)3P (8) reacted with N3SO2-Ar (Ar = C6H4Me-4) to give the iminophosphorane MeC(CH2NMe)3P=NSO2Ar (14) (structured by X-ray means) and O=P(CH2NMe)3P=NSO2Ar (16) via the intermediate phosphazides MeC(CH2NMe)3PN3SO2Ar (13) and O=P(CH2NMe)3PN3SO2Ar (15), respectively. The variety of products obtained from the reactions of arylsulfonyl azides with proazaphosphatranes (1 and 2), acyclic P(NMe2)3, bicyclic tris(amino)phosphines 7 and 8 are rationalized in terms of steric and basicity variations among the phosphorus reagents.     

Vanadium(III) chloride as an effective catalyst for the Pechmann reaction

Good yields of substituted coumarins were obtained by a synthetic method involving the Pechmann reaction using vanadium(III)chloride (VCl₃) reagent to effect this condensation under solvent-free conditions. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 197–200, February, 2006.     

Synthesis,Characterization, and Antimicrobial Activity of a Series of 2-(5-Phenyl-1,3,4-oxadiazol-2-yl)-N-[(1-aryl-1H-1,2,3-triazol-4-yl)methyl]anilines Using Click Chemistry

Russian Journal of General Chemistry - series of new triazolyl derived 1,3,4-oxadiazoles 7a–7l is synthesized with high yields by coppercatalyzed alkyne–azide cycloaddition reaction...     

Facile and Green Syntheses of 2-(N-Methylindole-3-carbonyl)-3-(N-methylpyrrol-2-yl)acrylonitriles and a Study of Their Antimicrobial Activities

Facile and green syntheses of substituted-2-(N-methylindole-3-carbonyl)-3-(N-methyl pyrrol-2-yl) acrylonitriles 6a–d are being reported. L-Proline has been utilized as an efficient and ecofriendly catalyst in aqueous medium for Knoevenagel condensation of pyrrole-2-carboxyaldehyde (1) and its N-methyl derivative (2) with the active methylene compounds 3-cyanoacetylindoles 3a–d at room temperature to afford substituted-2-(1H-indole-3-carbonyl)-3-(1H-pyrrol-2-yl)acrylonitriles 4a–d and substituted-2-(1H-indole-3-carbonyl)-3-(N-methylpyrrol-2-yl) acrylonitriles 5a–d respectively. Subsequently these products were treated with dimethyl sulfate (DMS) in polythylene glycol (PEG)–600 as an efficient and green solvent to afford the corresponding substituted-2-(N-methylindole-3-carbonyl)-3-(N-methylpyrrol-2-yl)acrylonitriles 6a–d. The antibacterial and antifungal activities of 4a–d, 5a–d, and 6a–d have been studied.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Expeditious Pechmann Condensation by Using Biodegradable Cellulose Sulfuric Acid as a Solid Acid Catalyst

A facile synthesis of coumarins was performed in excellent yields via Pechmann condensation by using different type of phenols and ethylacetoacetates under solvent–free media using both conventional method and microwave irradiation in short reaction times is described. The reaction workup is very simple, and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions.     

Synthesis,Structure, Luminescent and Intramolecular Proton Transfer in Some Imidazole Derivatives

A group of novel 2-aryl imidazole derivatives were synthesized and characterized by NMR spectra, X-ray, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazoles (dmip and dmtip) have been studied using emission spectroscopy and it was detected that the two distinct ground state rotamers of I and II are responsible for the normal and the tautomer emission respectively. In hydrocarbon solvent, the tautomer emission predominates over the normal emission for both dmip and dmtip. This reveal that rotamer II is responsible for the tautomer emission and it is stabler than rotamer I which causes the normal emission. In alcoholic solvent like ethanol, a dramatic enhancement of normal emission is observed which was due to increased solvation, the more polar rotamer I become stabler than rotamer II. In dioxane—water mixtures it is observed that the addition of water inhibits the ESIPT process due to the formation of the intermolecular hydrogen bonding involving water. DFT calculations on energy, dipole moment, charge distribution of the rotamers in the ground and excited states of the imidazole derivatives were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state.     

Parameter-uniform numerical methods for singularly perturbed mixed boundary value problems using grid equidistribution

In this paper, we present the analysis of an upwind scheme for obtaining the solution of a convection-diffusion two-point boundary value problem with Robin boundary conditions. The solution is obtained on a suitable nonuniform mesh which is formed by equidistributing the arc-length monitor function. It is shown that the discrete solution obtained by the upwind scheme converges uniformly with respect to the perturbation parameter. Numerical results are presented that demonstrate the sharpness of the theoretical estimates.     

Spectral Investigations on Ho3+ Doped Mixed Alkali Chloroborate Glasses

The optical absorption and emission spectra of two different Ho³⁺ doped mixed alkali chloroborate glasses have been studied in the ultraviolet-visible near-infrared regions. Various spectroscopic parameters like Racah (E¹, E², and E³), spin orbit (ξ_4f), and configuration interaction (α) parameters have been calculated. From the measured spectral intensities of the various absorption bands of Ho³⁺ ion, the Judd–Ofelt intensity parameters (Ω₂, Ω₄, and Ω₆) have been evaluated and covalency was studied as a function of x in the glass matrices. Using these parameters, radiative transition probabilities, radiative lifetimes, branching ratios, and integrated absorption cross-sections have been calculated and reported for certain excited states of Ho³⁺ ion. From the emission spectra, stimulated emission cross-sections are determined for the emission transitions, ⁵F₄, ⁵S₂?→?⁵I₈, and ⁵F₅?→?⁵I₈ in these two mixed alkali chloroborate glasses. An attempt has been made to throw some light on the environment of Ho³⁺ ions in these glass systems by studying the variation in various spectroscopic parameters.     

Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14H-dibenzo[a.j]xanthenes under conventional heating and microwave irradiation

A simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a.j]xanthenes is described through a one-pot condensation of β-naphthol with aryl aldehydes in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.     

An efficient conversion of berberine into a rhoeadine via an indenobenzazepine

Treatment of ketoaziridine $\text{4}$ with aqueous formaldehyde gives the unusual bridged indenobenzazepine derivative $\text{6}$ whose reduction uith sodium cyanoborohydride produces trans ketol $\text{8}$. In the presence of hydrochloric acid, $\text{8}$ undergoes irreversible conversion to the more stable cis ketol $\text{10}$. Periodate oxidation of $\text{8}$ supplies γ-laotone $\text{11}$. NaBH₄ reduction of $\text{11}$ followed by acid treatment affords δ-lactone $\text{12}$ which upon reduction and O-methylation furnishes cis rhoeadine analog $\text{14}$.