A facile synthesis of novel 9-substituted 2,3,4,9-tetrahydro-1H-xanthen-1-ones

A strategically new approach to 9-substituted 2,3,4,9-tetrahydro-1H-xanthen-1-ones is described. The protocol includes TMG promoted, conjugate addition of cyclohexane-1,3-diones to 3-(diethoxyphosphoryl)coumarins and a domino transesterification-cyclodehydration reaction of the adducts obtained. Modification of the tetrahydroxanthenone at position 9 is reported for the first time.     

Microwave-assisted synthesis of 3-formyl substituted imidazo[1,2-a]pyridines

An efficient, metal-free method for the synthesis of 3-formyl imidazo[1,2-a]pyridines is reported. The method utilises commercially available substrates and features a broad substrate scope. The intermediate enamine was isolated and a plausible reaction mechanism proposed.     

Assessment of chemical elements in cosmetics' eyeshadows by X‐ray fluorescence and International Nomenclature of Cosmetic Ingredients characterization

Energy dispersive X‐ray fluorescence (EDXRF) technique, as a qualitative and quantitative analysis, was used for inorganic chemical elements determination (K, S, Cl, Al, Si, Ca, Ti, Mn, Fe, Pb, Zn, Rb, and Bi) in eyeshadows for safe human use. International Nomenclature of Cosmetic Ingredients standardized nomenclature was used for labels investigation to obtain data on legal regularity. Data of 23 samples were clustered by similarity, measuring relative concentrations of detected chemical elements. Calculating the correlation among such values, a similarity matrix was used to generate a dendrogram. Pb was found in samples silver color S12E and copper color S22I above permissible limits (20 μg/g). Same composition was reported for the pink (S01A), black (S02A), and brown (S03A) samples, but the same chemical elements were not detected by EDXRF in them. The best correlation was found between samples S08D and S23 J (0.961). The least correlation was 0.0012 between S01A and S12E. The clustering analysis showed 7 groups of similar samples according to EDXRF data. Relations among 6 eyeshadows' colors and chemical compositions were discovered by using decision trees, where the most determinant elements were Mn, S, Cl, Ca, and Fe, in this order. Commercial regularization and International Nomenclature of Cosmetic Ingredients standardization of eyeshadows in Brazil are not fully complied by the manufacturers of the investigated brands.     

Calculation for an Oriented Eutectic Interface of Constant Curvature

Calculation of interface shape for oriented eutectic growth has been proposed for regular structure formation. The constant interface curvature has been applied in the analysis. The obtained function contains some physical factors which affects the formation of concave-convex interface. The proposed approach has been related to the theory of completely coupled growth.     

Minimum undercooling condition as a particular case of the criterion of minimum entropy production

The attempt to compare the diffusional-thermal model based on the criterion of minimum entropy production to diffusional one based on the condition of minimum undercooling has been presented for regular eutectic growth. Finally, the general relationship describing lamellar structure formation is to be reduced to another one proposed by Jackson and Hunt's theory. This reduction has been in great part obtained. However, it remain some equivalent terms, which are not identical. It is probably produced by some imperfections of Jackson and Hunt's model, as well as any other adversities, e.g., some different assumptions in both compared models. The reduction of the criterion of minimum entropy production to the condition of minimum undercooling has also been suggested.     

CO2-catalyzed/promoted transformation of organic functional groups

Carbon dioxide is a cheap, non-toxic, abundant chemical and has been widely utilized in organic syntheses. Many new strategies have been developed using CO₂ as a C1 building block and highly utilizable chemicals have been synthesized out of it. On the other hand, CO₂-catalyzed or promoted reactions can also be important from an environmental and scientific point of view. These reactions avoid toxic chemicals, expensive catalysts and often occur under mild reaction conditions. In this review, we would like to draw a summary about organic functional group transformation reactions that are promoted or catalyzed by CO₂.