Phosphine oxides reactions with silanes

Several of the procedures discussed in the sulfoxide section describe the successful extension of the method to the reduction of selenoxides, - - and there is little doubt that many of the other procedures cited earlier could be used likewise. Sakaki and Oae used triphenylphosphine selenide and similar se-lenides to reduce selenoxides to selenides in 79-93% yield (equation 19). Using a chiral phosphine selenide, these workers showed that the phosphine oxide formed had suffered predominant inversion, with a stereospecificity of over 80%. Detty has reported the application of the silane PhSeSiMes (12) to the reduction of selenoxides and telluroxides. The reactions are rapid and proceed essentially quantitatively, even in the presence of a hydroxy or carbonyl group. 

As mentioned earlier, reductive elimination reactions are commonly observed processes that involve M-Si bond cleavage. Usually the transition-metal reductive elimination product is trapped by an added reagent such as a silane (equation 63)204, a germane (equation 64)205, a phosphine (equation 65)167 or hydrogen (equation 66, dppe = Ph2PCH2CH2PPh2)206. The latter reaction with hydrogen probably proceeds via initial oxidative addition of H2 to form a Pt(IV) intermediate. In the case of chiral complex ds-(SX-)-[(l-Naph)PhMeSi]PtH(PPh3)2, elimination of the silane upon addi-... 

Nonflammable gas supports the combustion of many compounds, including carbon, sulfur, and phosphorus. Nitrous oxide decomposes explosively at high temperatures. It forms explosive mixtures with hydrogen, ammonia, silane, and phosphine. Reactions with hydrazine and alkali-metal hydrides produce flame. It is a strong oxidizer at elevated temperatures, at about 300°C (572°F), when its dissociation begins. 

Metals in a finely divided state bum spontaneously in chlorine. Solid metals (nonpow-dered form) bum spontaneously at elevated temperatures. Metal carbides react with chlorine with incandescence. Metal hydrides bum spontaneously in chlorine. Diborane explodes with chlorine at ordinary temperature silane, phosphine, arsine, or stibine produce a flame. The latter compounds react explosively with chlorine at elevated temperatures. Metal sulfides, silicides, nitrides, phosphides, and oxides bum in chlorine. Phosphorus undergoes a highly exothermic reaction with chlorine. White phosphorus explodes with liquid chlorine white phosphorus and finely divided red phosphorus bum spontaneously in chlorine gas with a pale green light (NFPA 1997). 

Reaction of PPFA with the racemic secondary phosphine 146 furnished 147 as a 1 1 diastereomeric mixture, which could be separated by column chromatography. Each individual diastereomer of 147 finally afforded P3Chir in good yields after simultaneous reduction/boronation of the phosphine oxide and deprotection of the borane groups. Direct reduction of 147 with silanes epimerised the stereogenic phosphorus atom. 

With respect to the catalytic Wittig reaction discussed above, draw a mechanism for the reduction of the phosphine oxide R3PO by the silane Ph2SiH2. 

In 2007, Ishihara and co-workers first reported that simple alkali metal phe-noxides were effective catalysts for the aldol reaction of ketones and trimethyl silane enolates in the presence of phosphine oxides, especially bidentate 1,2-(0=PPh2)2C4H4 (Scheme 21). With 10 mol% each of alkali metal phenox-ides and phosphine oxides in this aldol reaction, PhONa showed the best... 

A subsequent Pd-catalyzed coupling reaction with diphenylphosphine oxide produces mainly the monophosphorylated product. Reduction of the phosphine oxide with silane followed by hydrolysis of the ester group produces a hydroxy phosphine. The final condensation with (S)-binaphthophosphorchloridite affords (R,S)-BINAPHOS. In the same way, enantiomeric (S,R)-BINAPHOS was prepared. Both were the first in a series of chiral ligands used in target-oriented... 

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