Reduction using trichlorosilane

Preparation of Phosphines by Reduction.- A procedure for the reduction of phosphine oxides using trichlorosilane in inert... 

Cationic palladium complex 121 reductively coupled enynes (Eq. 20) using trichlorosilane as the stoichiometric reductant [71]. This combination of catalyst and silane afforded silylated methylenecyclopentanes such as 122 in good yield from enynes such as 123. Attempts to develop an enantioselective version of this reaction were not successful [71]. When enediyne 124 was cyclized in the presence of trichlorosilane, the reaction favored enyne cycli-zation 126 by a 3 1 ratio over diyne cyclization to 125 (Eq. 21). In contrast, when the more electron-rich dichloromethylsilane was used as the reductant, diyne cyclization product 125 was preferred in a ratio of 4 1 [71]. Selectivities of up to 10 1 for enyne cyclization were observed, depending on the substrate employed [72],... 

Pu and co-workers incorporated atropisomeric binaphthols in polymer matrixes constituted of binaphthyl units, the macromolecular chiral ligands obtained being successfully used in numerous enantioselective metal-catalyzed reactions,97-99 such as asymmetric addition of dialkylzinc reagents to aldehydes.99 Recently, they also synthesized a stereoregular polymeric BINAP ligand by a Suzuki coupling of the (R)-BINAP oxide, followed by a reduction with trichlorosilane (Figure 10).100... 

Next, a few examples of asymmetric reductions with trichlorosilane are presented. An asymmetric reduction of ketones and imines was reported by Matsumura and coworkers by using trichlorosilane as reductant and A-formyl pyrrolidine derivative 36 as ligand (Scheme 28) [101, 102]. 

Reductive Silylation of Amides Using Trichlorosilane/Tertiary Amine Mixture... 

The postulation of SiCl3 can also accommodate the equally useful, clean, selective reductions by trichlorosilane (bp 33°C) and also the formation of C—C and Si—C bonds by reaction of SiHCl3 with CCI4, RX, RCOC1, and other halogen compounds in the presence of amines. In these cases the hypothetical SiCl3 could be generated by the reaction... 

Copolymerization of two different dichlorosilanes can also be achieved by the reduction using a sacrificial anode [177,178]. It is interesting that copolymerization of sila-functional dichlorosilanes with simple dichlorosilanes took place smoothly to provide an elegant route to functionalized polysilanes [178]. As to the synthesis of sila-functional polysilanes, the electrochemical reduction of perfluoroalkyl-substituted trichlorosilane to give perfluoroalkyl-substituted polysilane is interesting [179]. 

Reduction of trichlorosilane is the most used industrial method. It takes place at around 1,100°C. It is inexpensive and the precursor is available in large quantities. 

Triarylphosphines with formyl or acetyl groups substituted into the aromatic rings can be prepared by a Grignard reaction using ethylene keta derivatives. The resulting phosphines (1) are treated with toluene-p-sulphonic acid. The acetyl derivatives may also be prepared by oxidation of the ethyl derivatives (2) followed by reduction with trichlorosilane. ... 

The postulation of SiCl3 can also accommodate the equally useful, clean, selective reductions by trichlorosilane (b.p. 33°) and also the formation of... 

Preparation of Phosphines by Reduction. - The reduction of phosphine oxides in the final stage of phosphine synthesis remains a common strategy, with silane reagents often being used. Trichlorosilane has found application in the synthesis of the axially chiral systems (83), 73 (84), 7 (85), 75 the chiral... 

The reduction of dichlorosilanes or chloroalkyl chlorosilanes stimulates the formation of linear chains, whereas the same reaction using trichlorosilanes or similar compounds may support cross-linked products. Cross-linking can also be obtained by the use of vinyl silanes [33-35] or Si-H-modified compounds. A silylation reaction occurs at higher temperatures, also leading to branched products. 

Although the reduction of imines has been widely explored, as described above, the reduction of carbonyl groups has been less studied until now. Specifically, the reduction of ketones is more limited due to the low reactivity shown by these compounds. In this field, the pioneering works using trichlorosilane as reducing agent and a chiral Lewis base were reported by Matsumura and co-workers in 1999,... 

Miscellaneous Reactions. DTBP has been used as a hydrosi-lylation catalyst, even though catalysis by transition metal complexes have largely replaced the radical methods. DTBP has also been used as an oxidant for silanes. Other applications of DTBP include its use as an initiator for radical mediated deoxygenation of alcohols via the corresponding chloroformate or acetate ester (eq 20). It has also been used as an initiator for the reduction of lactones and esters to ethers using trichlorosilane. In a rare example of a nonradical reaction, DTBP has been used in conjunction with titanium(IV) chloride for the formation of chlorohydrin from alkenes (eq 21). ... 

Iwasaki F, Onomura O, Mishima K, Kanematsu T, Maki T, Matsumura Y. First chemo- and stereoselective reduction of imines using trichlorosilane activated with /V-formylpyrroli-dine derivatives. Tetrahedron Lett. 2001 42 2525-2527. 

The [24-24-2] cycloaddition was also used to synthesize biaryl diphosphines (Scheme 2.56) [107]. A double [2- -2- -2] cycloaddition of l,4-bis(diphenylphosphino)buta-l,3-diyne 2.162 to diyne 2.161 in the presence of cationic Rh(I) and Ag/binap as a catalyst afforded biaryl diphosphine oxides 2.163 in high yield and with excellent enantioselectivity. Reduction with trichlorosilane/phosphite led to the corresponding... 

A well-defined iron hydride complex FeH(CO)(NO)(Ph3P)2 is highly active as a catalyst for selective hydrosilylation of internal alkynes to vinylsilanes. Depending on the silane employed, either E- or Z-selective hydrosilylation products are formed in excellent yields and good to excellent stereoselectivities. The stereochemical course of this transformation is dependent on the steric demand of the substituents on the silane. " A new 0 family of Lewis-basic 2-pyridyloxazolines catalyses the enantioselective reduction of prochiral aromatic ketones and ketimines using trichlorosilane. 1-Isoquinolyloxazoline (20) derivative was identified as the most efficient catalyst of the series capable of delivering high enantioselectivities in the reduction of both ketones (up to 94% ee) and ketimines (up to 89% (p)... 

The hydride donor ability of Hantzsch ester 4a has been experimentally determined to be slightly higher than that of N-benzylnicotinamide, both being comparable to the borane-triethylamine complex [17]. Together with trichlorosilane [18], Hantzsch esters 4 are the reagents of choice to effect asynunetric reductions using chiral organocatalysts. 

The next step is the hydrogen reduction of the trichlorosilane (Reaction 2 above). The end product is a poly crystalline silicon rod up to 200 mm in diameter and several meters in length. The resulting EGS material is extremely pure with less than 2 ppm of carbon and only a few ppb of boron and residual donors. The Czochralski pulling technique is used to prepare large single crystals of silicon, which are subsequently sliced into wafers for use in electronic devices.1 1... 

More recently, P-cored derivative (116) was prepared from a straightforward combination of a Heck coupling, to afford an intermediate functionalised stil-bene phosphine oxide (114),a Horner-Wittig reaction yielding the phosphine oxide (115), and finally trichlorosilane reduction (Scheme 31) [89]. Using similar strategies, both the valence isoelectronic N- (117) and C- (118) cored dendrimers have been prepared (Scheme 31). 

---