silicon and phosphine

This paper describes the recent advances in the syntheses of organophosphines by forming several types of phosphorus-carbon bonds via activation of the phosphorus-silicon bond of silylphosphines. In this account, the activation methods are classified into three types: nucleophile-induced activations, reactions with Lewis acid-activated electrophiles, and transition metal catalyzed reactions. Nucleophile-induced activations of silylphosphines, especially by a fluoride, generated a reactive phosphide equivalent for selective formation of a P-C bond. Silylphosphines also reacted selectively with Lewis acid-activated electrophiles. The Lewis acid mediated/catalyzed additions and substitutions, to form sp3-carbon-phosphorus bonds including an asymmetric reaction, are described. Several important types of transition metal catalyzed reactions of silylphosphines are also mentioned in this account. Selective formation of a P-C bond is achieved through these activations to produce a variety of functional organophosphines including optically active ones.

Topics: Catalysis; Phosphines; Phosphorus; Silicon

Chiral phosphine oxides successfully catalyze asymmetric cross-aldol reactions of various carbonyl compounds in a highly enantioselective manner. The phosphine oxide catalysts coordinate to chlorosilanes to form chiral hypervalent silicon complexes in situ, which activate both aldol donors and acceptors, thus realizing cross-aldol reactions between a ketone and an aldehyde, between two aldehydes, between two ketones, and of 2,6-diketones. The use of phosphine oxide catalysis can be further extended to achieve the first catalytic enantioselective double aldol reactions, realizing one-pot stereoselective construction of up to four stereogenic centers.

Topics: Aldehydes; Catalysis; Cyclization; Ketones; Oxides; Phosphines; Silicon; Stereoisomerism

By using a phosphine oxide-catalyzed enantioselective double aldol reaction, we achieved the concise construction of C2 -symmetric 1,9-diarylnonanoids, enabling the synthesis of (-)-ericanone from p-hydroxybenzaldehyde in 6 steps with 65 % overall yield. The enantioselective double aldol reaction is useful for establishing C2 -symmetric 1,9-diaryl-3,7-dihydroxy-5-nonanones with a single operation. Furthermore, the use of o-nosyl-protected p-hydroxybenzaldehyde and a 4,4'-disubstituted BINAP dioxide catalyst dramatically improved the reactivity and selectivity in the double aldol reaction, enabling the total synthesis of (-)-ericanone with high yield and with excellent enantiopurity.

Topics: Aldehydes; Benzaldehydes; Catalysis; Hydrocarbons, Aromatic; Naphthalenes; Oxides; Phosphines; Silicon; Stereoisomerism

Structural characterization and electrical measurements of silicon nanowires (SiNWs) synthesized by Au catalyzed vapor-liquid-solid growth using silane and axially doped in situ with phosphine are reported. We demonstrate that highly n-doped SiNWs can be grown without structural defects and high selectivity and find that addition of the dopant reduces the growth rate by less than 8% irrespective of the radius. This indicates that also the dopant incorporation is radius-independent. On the basis of electrical measurements on individual wires, contact resistivities as low as 1.2 x 10(-7) omega cm(-2) were extracted. Resistivity measurements reveal a reproducible donor incorporation of up to 1.5 x 1020 cm-3 using a gas phase ratios of Si/P = 1.5 x 10(-2). Higher dopant gas concentrations did not lead to an increase of the doping concentration beyond 1.5 x10(20) cm(-3).

Topics: Crystallization; Macromolecular Substances; Materials Testing; Molecular Conformation; Nanotechnology; Nanotubes; Particle Size; Phosphines; Semiconductors; Silicon; Surface Properties

This Communication describes a highly efficient phosphine-catalyzed [2+3]-cycloaddition reaction using alpha-trimethylsilyl-substituted aryl allenones and electron deficient olefins; both good yields and good asymmetric induction were obtained.

Topics: Alkenes; Catalysis; Cyclization; Electrons; Molecular Structure; Phosphines; Silicon

Topics: Arsenicals; Iron; Phosphines; Phosphorus; Phosphorus, Dietary; Silicon