Zeo-click synthesis: Cu-zeolite-catalyzed one-pot two-step synthesis of triazoles from halides and related compounds

Cu^I-zeolites proved to be an efficient heterogeneous catalyst for the one-pot two-step synthesis of triazoles from halides or tosylates, sodium azide, and alkynes. The step and atom economies of this cascade reaction as well as water used as solvent and catalyst recycling make such synthesis a trully green process. With selected substrates, the peculiar roles of Cu^I-zeolites as catalysts were highlighted.     

Efficient enantioselective reduction of ketones with Daucus carota root

A novel and efficient reduction of various prochiral ketones such as acetopehones, alpha-azido aryl ketones, beta-ketoesters, and aliphatic acyclic and cyclic ketones to the corresponding optically acive secondary alcohols with moderate to excellent chemical yield was achieved by using Daucus carota, root plant cells under extremely mild and environmentally benign conditions in aqueous medium, has been described. Many of these optically active alcohols are the potential chiral building blocks for the synthesis of pharmaceutically important molecules and asymmetric chiral ligands. Hence, this biocatalytic approach is found to be the most suitable for the preparation of a wide range of chiral alcohols and gave inspiration for the development of a new biotechnological process.     

Temperature-modulated selective C(sp3)–H or C(sp2)–H arylation through palladium catalysis

Transition metal-catalysed C–H bond functionalisations have been extensively developed in organic and medicinal chemistry. Among these catalytic approaches, the selective activation of C(sp³)–H and C(sp²)–H bonds is particularly appealing for its remarkable synthetic versatility, yet it remains highly challenging. Herein, we demonstrate the first example of temperature-dependent selective C–H functionalisation of unactivated C(sp³)–H or C(sp²)–H bonds at remote positions through palladium catalysis using 7-pyridyl-pyrazolo[1,5-a]pyrimidine as a new directing group. At 120 °C, C(sp³)–H arylation was triggered by the chelation of a rare [6,5]-fused palladacycle, whereas at 140 °C, C(sp²)–H arylation proceeded instead through the formation of a 16-membered tetramer containing four 7-pyridyl-pyrazolo[1,5-a]pyrimidine–palladium chelation units. The subsequent mechanistic study revealed that both C–H activations shared a common 6-membered palladacycle intermediate, which was then directly transformed to either the [6,5]-fused palladacycle for C(sp³)–H activation at 120 °C or the tetramer for C(sp²)–H arylation at 140 °C with catalytic amounts of Pd(OAc)₂ and AcOH. Raising the temperature from 120 °C to 140 °C can also convert the [6,5]-fused palladacycle to the tetramer with the above-mentioned catalysts, hence completing the C(sp²)–H arylation ultimately.

Unprecedented 16-membered tetramer or [6,5]-fused palladacycle, mutually shadowboxing-like transformed from the shared common intermediate, accomplishes the Pd-catalysed temperature-dependent selective arylation of C(sp²)–H or C(sp³)–H.     

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.     

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.