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In the manuscript, the application of β,γ‐unsaturated ketones as precursors of electron‐rich dienophiles in the organocatalytic, aromative inverse‐electron‐demand hetero‐Diels‐Alder cycloaddition is described. The reaction leads to the formation of biologically relevant benzofuran derivatives bearing additional tetrahydropyridine ring. The reaction is fully site‐selective and occurs preferentially at the distal double bond of the dienolate intermediate. Given the absolute configuration assignment a step‐wise mechanism has been proposed and the formation of aromatic benzofuran ring indicated as the driving force of the cascade.magnified image

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In this article, we report the crystallization of struvite in sodium metasilicate gel by single diffusion gel growth technique. The obtained crystals have a very rich morphology displaying 18 faces. In this study, the habit and morphology of the obtained struvite crystals are analyzed. The crystals were examined and identified as pure struvite by single X-ray diffraction (XRD). The orthorhombic polar noncentrosymmetric space group Pmn21 was identified. The structure of the crystal was determined at a temperature of 90 K. Our research indicates a lack of polymorphism, resulting from the temperature lowering to 90 K, which has not been previously reported. The determined unit cell parameters are as follows a = 6.9650(2) Å, b = 6.1165(2) Å, c = 11.2056(3) Å. The structure of struvite is presented here with a residual factor R1 = 1.2% at 0.80 Å resolution. We also present thermoanalytical study of struvite using thermal analysis techniques such as thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA).

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Abstract:The Candida antarctica lipase (CAL-B)-catalyzed acetylation of racemic 2-hydroxy-phenylphosphine oxide, performed in diethyl ether, led to kinetic resolution with an unusually high enantioselectivity (E = 3000). The CAL-B-mediated desymmetrization of prochiral bis(2-hydroxymethylphenyl)methylphosphine oxide gave, via its enantioselective monoacetylation, the corresponding monoacetate in 80% yield and with ee > 98%. The latter transformation allowed us to efficiently transform the prochiral substrate into the enantiomerically pure product in one single step. In both cases the stereogenic or prostereogenic phosphorus atom and the reacting hydroxy oxygen are distant from each other by four bonds. The absolute configurations of all the products were determined by a chemical correlation and X-ray analysis. The products will be used as enantiopure substrates in the preparation of a variety of chiral organophosphorus ligands/catalysts for asymmetric synthesis.

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