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The ring opening by the cleavage of the C(sp$^3$)–O bond of 2-hydroxybutyrolactone with (ethylthio)trimethylsilane was effectively catalysed by indium triiodide. Screening the reaction conditions allowed optimizing the ring opening. The effect of the nucleophile/catalyst ratio on the reaction efficiency has also been demonstrated. After optimization, 2-hydroxy-4-(ethylthio)butyric acid was isolated with an excellent yield (85%), thus making this method useful for the preparation of methionine analogues.

The BH3‐mediated reduction of P‐stereogenic hydroxyalkylphosphine oxides was investigated by Density Functional Theory calculations. By combining theoretical approaches with experimental observations, we explored two mechanisms that account for its stereospecificity, implying an inversion of the configuration at the phosphorus atom. One mechanism proceeds through a cyclic intermediate in which the coordination of borane to the oxygen atoms lowers the BH3.THF‐attack barrier. However, the free energy barrier for this combined process is too high for a reaction feasible at room temperature. The calculations rather support a second mechanism that proceeds through from the same cyclic intermediate and the in‐situ formation of BH4− as reducing agent. [ABSTRACT FROM AUTHOR]

The racemization mechanism of tert‐butylphenylphosphido‐borane is investigated experimentally and theoretically. Based on this converging approach, it is shown, first, that several phosphido‐borane molecular species coexist at the time of the reaction and, second, that one particular of both initially assumed reactive routes most significantly contribute to the overall racemization process. From our converging modeling and experimental measurement, it comes out that the most probable species to be here encountered is a phosphido‐borane‐Li (THF)2 neutral solvate, whose P‐stereogenic center monomolecular inversion through a Y‐shaped transition structure (ΔrG°≠: 81 kJ mol−1) brings the largest contribution to the racemization process. [ABSTRACT FROM AUTHOR]

Metal-phosphinito-phosphinous acid complexes are interesting catalysts exhibiting unique reactivities. In this account, we intend to provide a clear overview of palladium- and platinum-phosphinito-phosphinous acid complexes, their preparation from secondary phosphine oxides, and their applications in catalysis. They have been mainly used to develop [2+1] cycloadditions to afford methylenecyclopropane derivatives using norbornenes and various alkynes as partners. As a function of the catalyst, the reaction conditions, or the nature of the reagents, different synthetic transformations have been observed: [2+1] cycloadditions, giving rise to either alkylidenecyclopropanes or vinylidenecyclopropanes; tandem [2+1]/[3+2] cycloadditions, and so forth. The mechanisms of these reactions have been studied to rationalize the different reactivities observed. [ABSTRACT FROM AUTHOR]

A series of [RuCl2(η6-p-cymene)] complexes bearing phosphinous acid (PA) ligands have been straightforwardly prepared from the dimer [RuCl2(p-cymene)]2 and secondary phosphine oxides (SPOs) and fully characterized. The steric parameter quantification of PAs, other L ligands and η6-p-cymene allowed a better comprehension of the coordination chemistry of these types of complexes and explained the absence of coordination in the case of bulky SPOs such as Ad2P(O)H. These complexes were tested in the C–H activation/functionalization of 2-phenylpyridine and a good activity was obtained at 80 °C for the complex exhibiting the highest steric bulk. A study on halide effects, either on the ruthenium complex or for the aryl halide partner, has also been carried out showing drastic differences. Further investigations on halide effects were performed notably by using a cationic ruthenacycle which was found to be an intermediate for the reaction. In order to rationalize the role played by the phosphinous acid, a mechanism involving a concerted metallation deprotonation favored by a phosphinito species has been proposed. [ABSTRACT FROM AUTHOR]

Access to hydroxy-functionalized P-chiral phosphine-boranes has become an important field in the synthesis of P-stereogenic compounds used as ligands in asymmetric catalysis. A family of optically pure α and β-hydroxyalkyl tertiary phosphine-boranes has been prepared by using a three-step procedure from readily accessible enantiopure adamantylphosphinate, obtained by semi-preparative HPLC on multigram scale. Firstly, a two-step one-pot transformation affords the enantiopure hydroxyalkyl tertiary phosphine oxides in good yields and enantioselectivities. The third step, BH3-mediated reduction, allows the formation of the desired phosphine-boranes with excellent stereospecifity. The mechanistic study of this reduction provides new evidence to elucidate the crucial role of the pendant hydroxy group and the subsequent activation of the PO bond by the boron atom. [ABSTRACT FROM AUTHOR]

Access to hydroxy-functionalized P-chiral phosphine-boranes has become an important field in the synthesis of P-stereogenic compounds used as ligands in asymmetric catalysis. A family of optically pure α and β-hydroxyalkyl tertiary phosphine-boranes has been prepared by using a three-step procedure from readily accessible enantiopure adamantylphosphinate, obtained by semi-preparative HPLC on multigram scale. Firstly, a two-step one-pot transformation affords the enantiopure hydroxyalkyl tertiary phosphine oxides in good yields and enantioselectivities. The third step, BH3 -mediated reduction, allows the formation of the desired phosphine-boranes with excellent stereospecifity. The mechanistic study of this reduction provides new evidence to elucidate the crucial role of the pendant hydroxy group and the subsequent activation of the P=O bond by the boron atom., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)