Silane hydroxy

Cleavage of Si—C bonds (12,243-245). This oxidation can be used to convert vinylsilanes in three steps to syn- or anti-1,2-diols. Thus Grignard reagents cleave epoxides of vinylsilanes selectively to (3-hydroxy silanes, which can be oxidized with retention of configuration to 1,2-diols. When applied to an (E)-vinylsilane, the sequence results in the syn-l,2-diol the an -l,2-diol is obtained from a (Z)-vinylsilane by the same reactions. 

H1 CH3O3C—Sl-CgHg 35 10 10 Bis- 3-(bzw. 4J-nitro-phenyl]-tert.-butyl-hydroxy-silan 65 (4 1) 2... 

Enamines. In the presence of alumina (Woelm 200 neutral) cw-a,p-epoxy-silanes can be opened by pyrrolidine or morpholine to give a-amino-p-hydroxy-silanes, from which the pure as-enamine can be obtained by KH-induced syn p-elimination (equation I). The isomeric trans-a,p-epoxysilane is inert to this ring... 

Use of chromic acid-based oxidation reagents often results in silicon-carbon bond cleavage (Scheme 13)5, although such an oxidation has been used to produce a-cyclopropyl acyl silanes (vide infra, Section III.E)85. In an interesting development, this handicap of ready silicon-carbon bond cleavage during oxidation of a-hydroxy silanes has been cleverly utilized in an acyl silane synthesis by incorporation of two silicon moieties in the substrate (Scheme 14). 

Further addition of the Grignard reagent can take place to give -hydroxy silanes with high diastereoselectivity (Scheme 103)12,165. The hydroxy silanes can of course undergo subsequent stereocontrolled acid or base catalysed elimination of trialkylsilanol to give alkenes. 

The Peterson Reaction allows the preparation of alkenes from a-silylcarbanions. The intermediate p-hydroxy silane may be isolated, and the elimination step - the Peterson Elimination - can be performed later. As the outcome of acid or base-induced elimination is different, the Peterson Olefination offers the possibility of improving the yield of the desired alkene stereoisomer by careful separation of the two diastereomeric p-hydroxy silanes and subsequently performing two different eliminations. 

ETHER-KETONES acetals + vinyl ethers 10-64 of hydroxy-silanes ... 

Alternatively, some conclusions can be derived from the relative reactivities of car-banions. For example, DePuy and colleagues made use of a clever method involving reactions of silanes with hydroxide ion to deduce acidities of such weak acids as alkanes and ethylene. The silane reacts with hydroxide ion to form a pentacoordinate anion that ejects a carbanion held as a complex with the hydroxy silane rapid proton transfer gives the stable silanoxide ion and the carbon acid (equation 5). 

Diastereomerically enriched P-hydroxy silanes are also accessible from a,P-epoxy silanes and reaction of these with organocuprate reagents. The epoxy silanes are synthesized by epoxidation of (E)- or (Z)-vinylsilanes with m-chloroperbenzoic acid. The required (Z)- and ( )-vinylsilanes can be obtained by hydroboration-protonolysis of 1-trimethylsilyl-l-alkynes or by hydrosilylation of 1-alkynes, respectively. 

The rearrangement regularly takes place with retention of configuration at the carbon atom to which the silyl group is attached, and it is compatible with ketone and ester groups. In the case of p-hydroxy-silanes, no Peterson-type elimination occurs. Some representative reactions are shown in Scheme 31. 

In addition to the examples in Table 1, the Peterson methylenation has been used in several interesting natural product syntheses, as the examples in equation (2M6) indicate. Danishefsky and coworkers used the Peterson reaction in an approach to mitomycins (4 equation 2). This application demonstrated the use of unique elimination conditions. The hydroxy silane intermediate was stable to direct Peterson elimination. Therefore, the removal of the silyl protecting group and the elimination of the silyloxy group were carried out with DDQ in quantitative yield. 

Allylstannanes can be used instead of the germanium reagents, and the reaction can be performed in micellar systems." The reaction with acylsilanes provides a-hydroxy-silanes. ... 

Reaction of the -hydroxy selenides with phosphorus triiodide or A. A -carbonyl-diimidazole leads to elimination of both the hydroxy and selanyl moieties, and, as with the / -hydroxy silanes, to formation of alkylidenecyclopropanes (see Section 5.2.2.7.3.). 

Table 16. Alkylidenecyclopropanes by Elimination of j8-Hydroxy Silanes (Peterson Olefination)...

Heterocycle openings. a,p-Epoxy silanes fiimish P-hydroxy silanes due to the attack of cuprate reagents at the a-carbon. The regioselectivity for the reaction of methyl ( J-4,5-epoxypent-2-enoate with arylcopper is dependent on the presence or absence of BF,. The S 2 pathway giving the a-aryl esters becomes significant with the added Lewis acid. The Sf 2 products are observed in the reaction of epoxy vinyl sulfoxides with... 

There is a silicon version of the Wittig reaction, known as the Peterson reac-tion. Reaction of an aldehyde or ketone with an a-silyl carbanion forms a -hydroxy silane, from which elimination of trialkylsilanol, RsSiOH, provides... 

Trimethylsilylstyrenes are formed by reaction of alka-nesulfonyl chlorides with TMSCHN2 in the presence of triethyl-amine (eq 13). TMSC(Li)N2 reacts with carbonyl compounds to give a-diazo- -hydroxy silanes which readily decompose to give O, /3-epoxy silanes (eq 14). However, benzophenone gives diphenylacetylene under similar reaction conditions (eq 15). ... 

This reaction was first reported by Peterson in 1968. It is a two-step synthesis of olefin involving the addition of an a-silyl carbanion to a carbonyl compound to form y3-silyl alcohol (or /3-hydroxy silane) and the elimination of silol. Therefore, this reaction is generally known as the Peterson olefination. In addition, this reaction is also referred to as the Peterson reaction " and Peterson elimination. Occasionally, the Peterson olefination is also called the Peterson alkenation or Peterson alkenylation. ... 

FUms on these materials can be formed if adhesion promoters are used. With adhesion promoters it is possible to deposit films of conducting polymers on insulators, semiconductors with highly polished surfaces, and corrosive metals. An adhesion promoter consists of an adhesion group, e.g., chloro- or hydroxy silane groups, phosphonic acid groups, which can bond to the surface of the soUd, spacer group, and a monomer molecule as a head group. 

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