Novel Bicyclic P,S-Heterocycles via Stereoselective hetero-Diels-Alder Reactions of Thiochalcones with 1-Phenyl-4H-phosphinin-4-one 1-Oxide.

Thiochalcones undergo cycloaddition reactions in THF solution at 60 °C with the synthetically unexplored 1-phenyl-4H-phosphinin-4-one 1-oxide in a highly regio- and stereoselective manner, yielding hitherto unknown bicyclic P,S-heterocycles containing fused thiopyran and phosphinine rings. The stereochemical structures of two of the obtained (4+2)-cycloadducts were unambiguously assigned by means of the X-ray single-crystal analysis. Based on these assignments, a concerted mechanism of the hetero-Diels-Alder reaction via the preferred endo approach of the heterodiene from the less hindered P=O side of the phosphininone molecule is postulated to explain the established rac-(4RS,8SR,9SR,10SR)-configured (4+2)-cycloadducts isolated as major products.

Cori Ester as the Ligand for Monovalent Cations.

Gerty T. and Carl F. Cori discovered, during research on the metabolism of sugars in organisms, the important role of the phosphate ester of a simple sugar. Glucose molecules are released from glycogen-the glucose stored in the liver-in the presence of phosphates and enter the blood as α-D-glucose-1-phosphate (Glc-1PH2). Currently, the crystal structure of three phosphates, Glc-1PNa2·3.5·H2O, Glc-1PK2·2H2O, and Glc-1PHK, is known. Research has shown that reactions of Glc-1PH2 with carbonates produce new complexes with ammonium ions [Glc-1P(NH4)2·3H2O] and mixed complexes: potassium-sodium and ammonium-sodium [Glc-1P(X)1.5Na0.5·4H2O; X = K or NH4]. The crystallization of dicationic complexes has been carried out in aqueous systems containing equimolar amounts of cations (1:1; X-Na). It was found that the first fractions of crystalline complexes always had cations in the ratio 3/2:1/2. The second batch of crystals obtained from the remaining mother liquid consisted either of the previously studied Na+, K+ or NH4+ complexes, or it was a new sodium hydrate-Glc-1PNa2·5·H2O. The isolated ammonium-potassium complex shows an isomorphic cation substitution and a completely unique composition: Glc-1PH(NH4)xK1-x (x = 0.67). The Glc-1P2- ligand has chelating fragments and/or bridging atoms, and complexes containing one type of cation show different modes of coordinating oxygen atoms with cations. However, in the case of the potassium-sodium and ammonium-sodium structures, high structural similarities are observed. The 1D and 2D NMR spectra showed that the conformation of Glc-1P2- is rigid in solution as in the solid state, where only rotations of the phosphate group around the C-O-P bonds are observed.

Thermal Characterization of Crosslinked Polymeric Microspheres Bearing Thiol Groups Studied by TG/FTIR/DSC under Non-Oxidative Conditions.

This paper presents the thermal behavior of polymer microspheres based on glycidyl methacrylate (GMA) and crosslinking agents benzene-1,4-diylbis(2-methylprop-2-enoate) (1,4DMB) and trimethylolpropane trimethacrylate (TRIM) before and after functionalization with thioglycolic acid (TGA). The thermal stability of the polymers was determined using thermogravimetric analysis and differential scanning calorimetry under non-oxidizing conditions. The evolved gases were detected by FTIR and NMR spectroscopy, and the chemical structure of solid residues after preheating was assessed by FTIR/ATR spectroscopy. The post-functionalized microspheres showed higher thermal stability (within 270-290 °C) than the initial copolymers (within 240-250 °C). In this paper, examples of decomposition patterns of polymer microspheres before and after functionalization are presented. The decomposition of the initial microspheres starts with the emission of GMA monomers, acrolein, carbon dioxide, and the formation of unsaturated bonds in the solid residue. In the case of functionalized microspheres, degradation involves the transesterification of ester groups with the -SH groups, resulting in the emission of carbonyl sulfide, acrolein and carbon dioxide. Furthermore, lactone groups are created in the solid residue. The degradation of the functionalized copolymers is a complex process due to their crosslinked structure, rendering the identification of all the degradation products unattainable.

Resolution of P-Sterogenic 1-Phenylphosphin-2-en-4-one 1-Oxide into Two Enantiomers by (R,R)-TADDOL and Conformational Diversity of the Phosphinenone Ring and TADDOL in the Crystal State.

The resolution of racemic 1-phenylphosphin-2-en-4-one 1-oxide (2), was achieved through the fractional crystallization of its diastereomeric complexes with (4R,5R)-(-)-2,2-dimethyl -α,α,α',α'-tetraphenyl-dioxolan-4,5-dimethanol (R,R-TADDOL) followed by the liberation of the individual enantiomers of 2 by flash chromatography on silica gel columns. The resolution process furnished the two enantiomers of 2 of 99.1 and 99.9% e.e. at isolated yields of 62 and 59% (counted for the single enantiomer), respectively. The absolute configurations of the two enantiomers were established by means of X-ray crystallography of their diastereomerically pure complexes, i.e., (R)-2•R,R)-TADDOL and (S)-2•(R,R)-TADDOL. The structural analysis revealed that in the (R)-2•(R,R)-TADDOL complex, the P-phenyl substituent occupied a pseudoequatorial position, whereas in (S)-2•(R,R)-TADDOL, it appeared in both the pseudoequatorial and the pseudoaxial positions in four symmetrically independent molecules. Concurrent conformational changes of the TADDOL molecules were best described by the observed changes of a pseudo-torsional CO...OC angle that could be considered as a possible measure of TADDOL conformation in its receptor-ligand complexes. The structural analysis of the (R,R)-TADDOL molecule revealed that efficiency of this compound for use as an effective resolving factor comes from its ability to flexibly fit its structure to both enantiomers of a ligand molecule, producing a rare case of resolution for both pure enantiomers with one chiral separating agent. The resolved (R)-2 was used to assign the absolute configuration of a recently described (-)-1-phenylphosphin-2-en-4-one 1-sulfide by chemical correlation. In addition, an attempted stereoretentive reduction of (R)-2 by PhSiH3 at 60 °C revealed an unexpectedly low barrier for P-inversion in 1-phenylphosphin-2-en-4-one.

Desymmetrization Approach to the Synthesis of Optically Active P-Stereogenic Phosphin-2-en-4-ones.

Two synthetic protocols for the conversion of 1-phenylphosphinan-4-ones to novel P-stereogenic 1-phenylphosphin-2-en-4-ones by enantioselective deprotonation followed by oxidation and by asymmetric organocatalytic halogenation accompanied by elimination have been developed. These two-step one-pot transformations provide convenient access to optically active 1-phenylphosphin-2-en-4-one 1-sulfide and 1-phenylphosphin-2-en-4-one 1-oxide of 96 and 55% enantiomeric purities, respectively.

[4 + 2] Cycloaddition of Vinylphosphine Oxides to α-Oxy- o-xylylene as a route to Phosphorylated Naphthyl and Biaryl Scaffolds.

α-Oxy- o-xylylene, a highly reactive diene readily accessible from benzocyclobutenol, undergoes Diels-Alder reaction with vinylphosphine oxides, yielding the corresponding 2-phosphorylated 1-hydroxy-1,2,3,4-tetrahydronaphthalenes in excellent yields. Use of unsubstituted and trans-2-aryl-substituted vinylphosphine oxides leads to cycloadducts with complete regioselectivity and with cis/trans selectivity up to 19:1 in the most favorable case. In the case of P-stereogenic trans-2-aryl-substituted vinylphosphine oxides, a virtually complete chirality transfer from P to C can be achieved. Dehydration and aromatization of the obtained cycloadducts bearing the resolved P-stereogenic phosphinoyl groups can be carried out to afford the valuable P-stereogenic and axially chiral phosphorylated 1,2'-binaphthyl ring system. Cases of restricted rotation around Csp3-Csp2 single bond in some tetrahydronaphthalene cycloadducts have also been revealed.