Intramolecular cyclization of <Emphasis Type="Italic">N</Emphasis>-propargyl anilines: a new synthetic entry into highly substituted indoles

Indole derivatives are an important class of heterocycle found in a large number of natural products and synthetic pharmaceuticals. Given the low cost and easy availability of N-propargyl anilines, synthesis of indole cores from these versatile structural motifs has attracted a lot of attention in the past decade. In this review, we summarize the most representative and interesting reports on this rapidly advancing area, with special emphasis on mechanistic aspects of the reactions.     

Chloropicrin sensor based on the pristine BN nanocones: DFT studies

Structural Chemistry - We investigated the chloropicrin adsorption on the BN nanocones using DFT calculations. We selected two kinds of BN nanocones with 180? disclination angle entailing BN-N...     

The Regiospecific Synthesis of Some New 3,5‐Disubstituted Isoxazoles

The compounds with isoxazole moiety have many pharmacological, biological and industrial applications, specifically their antiviral activity. In this research work, seven new compounds of 3,5‐disubstituted isoxazoles were synthesized. Propargyl alcohol ( 1 ) reacted with benzoyl chloride to give propargylphenylcarboxylate ( 2 ). Then, the aldehydes ( 3a‐3g ) were converted to the related oximes ( 4a‐4g ) and nitrileoxides in situ by NaOCl, consequently. Reaction of compound 2 with nitrileoxides in a [3+2] cycloaddition reaction gave regiospecifically isoxazoles ( 5a‐5g ). ¹H NMR, ¹³C NMR, FT‐IR, and elemental analyses confirmed the structure of the synthesized compounds.     

A novel multicomponent reaction between amino acids,aromatic aldehydes and p-toluenesulfonylmethyl isocyanide: an efficient and green one-pot synthesis using nanosilica

The novel diastereomeric sulfonylamide derivatives 4a–h were synthesized by multi-component reactions between (l)-α-amino acids, 1, aromatic aldehydes, 2 and p-toluenesulfonylmethyl isocyanide, 3 in water/methanol using nanosilica as a catalyst. The one-pot green reactions were carried out at room temperature with a quantitative yield in water/methanol. The yield of the reactions and products was determined and discussed. The reusablity of the catalyst is discussed.     

Hammett constants and NMR shifts of α-acyloxy carboxamide derivatives

Geometrical structures, Hammett constants, ¹H and ¹³C chemical shift values, molecular electrostatic potential maps, and several thermodynamic parameters of α-acyloxy carboxamide derivatives (4a–o) were calculated using HF and DFT/B3LYP methods with 6-31G(d) basis set. The optimized structures were compared with analogous compound. The ¹H and ¹³C NMR shielding tensors were computed with the Gauge-Independent Atomic Orbital (GIAO) method. Comparison of the experimental ¹H and ¹³C NMR chemical shifts of 4a–o molecules with the theoretical data indicates good agreement.     

Geographical variation in residence and risk of multiple nonmelanoma skin cancers in US women and men

Residence in high ultraviolet (UV) locations is associated with increased risk for incident nonmelanoma skin cancer (NMSC). However, the effect of geographic location on multiple NMSC development has not been well studied. We evaluated the association between state of residence at birth, age 15 and 30 and risk of multiple NMSCs among 80275 women and men. After adjusting for age, gender, hair color, number of sunburns, tanning ability, family history of melanoma and nevus count, the cumulative relative risks (RRs) of developing ≥1 NMSC for those consistently residing in medium- and high-UV index states were 1.20 (95% CI 1.14-1.27) and 1.42 (95% CI 1.32-1.53) respectively. We found that compared to individuals with one lifetime NMSC, the multivariate cumulative RRs of developing ≥2 NMSCs for those who stayed in medium- and high-UV index states at all three timepoints were 1.09 (95% CI 1.00-1.19) and 1.15 (95% CI 1.02-1.30) respectively. These results cannot account for migration during the interval period and seasonal changes in residence; further, as BCC is the predominant NMSC, the results may be BCC-driven. In conclusion, we found that consistent residence in medium- or high-UVR locations was significantly associated an incremental risk of ≥2 NMSCs later in life.     

Heteroatom effects in XC5H5C Arduengo-type carbenes (X = CH,N, P,and As) in singlet and triplet states

Internal energy difference, ΔE _s-t; enthalpy difference, ΔH _s-t; Gibbs free energy difference, ΔG _s-t, between the singlet (s) and triplet states (t) of XC₅H₅C, 1X (X = CH, N, P, and As) were computed at B3LYP/6-311++G** and MP2/6-311++G**//B3LYP/6-311++G** levels of theory. The ΔG _s-t between the singlet and triplet states of 1 _X were changed in the order: 1 _P > 1 _As > 1 _N .     

A novel nanomagnetic solid acid catalyst for the synthesis of new functionalized bis-coumarin derivatives under microwave irradiations in green conditions

In this study, a novel, green, environmentally friendly and magnetically heterogeneous catalyst based on the immobilization of sulfosalicylic acid onto Fe₃O₄ nanoparticles (Fe₃O₄@sulfosalicylic acid MNPs) is reported. The bis-coumarin analogs were synthesized in high yield using the reaction of 1 equivalent of aryl aldehydes with 2 equivalents of 4-hydroxycoumarin in water under microwave irradiation conditions. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, dynamic light scattering, vibrating sample magnetometry, Fourier transform infrared spectroscopy, UV–visible absorption, and Brunauer-Emmett-Teller (BET) techniques confirmed the successful synthesis of the catalyst. The main attractive characteristics of the presented green protocol are very short reaction times (10–15 min), excellent yields, and the avoidance of hazardous or toxic reagent and solvents. Thermal durability, easy separation, and high reusability are important advantages of the new catalyst in comparison to other catalysts.