Cross with allyl silane

PEG-grafted polystyrene is also well suited for reactions with highly reactive orga-nometallic reagents, provided that the support has been dried. PEG-containing polymers are generally more difficult to dry than pure polystyrene. Cross-linked PEG is stable towards Lewis acids, and can be used for SnCl4-mediated allylations of aldehydes with allyl silanes [21],... 

Taking advantage of the slow hydrogenation of carbon-carbon double bonds at room temperature in the presence of platinum dioxide, it was possible to perform the ruthenium-catalyzed cross coupling reaction of electron-deficient olefins such as conjugated enones and acrylic derivatives with allyl silanes in the presence of Pt(>2 under hydrogen (Scheme 46) [99]. Prolonged... 

Bis[(dimethylisopropoxysilyl)methyl]zinc (74) has proven to be a valuable reagent in the nickel-catalysed cross-coupling reactions with alkenylsulfoximines, giving allylic silanes with complete retention of configuration. An X-ray crystal structure determination of 74 showed this compound to exist in the solid state as a coordination polymer (Figure 41). In 74, in addition to the two covalent Zn—C bonds [Zn—C(l) 1.953(7)... 

Symmetrical (equation 22a) and unsymmetrical 1,4-diketones (equations 22b and 22c) are obtained in good yield with the vanadium(V) alkoxo derivatives VO(OR)Cl2 (R = Et,, -Pr)65 xfjg same reagent induces cross coupling between allyl silanes and silyl enolates to y,5-unsaturated ketones. Noteworthy is the fact that only traces of the homocoupled 1,4-diketones and 1,5-hexadienes are produced. 

In many complex syntheses, good yields can be obtained by combining a sterically hindered olefin with a readily available cross partner, and allyl silanes have proven to be very valuable cross partners in such processes [36]. 

Mechanistic implications of a general cross-metathesis of vinylsilicon with allyl-substituted heteroorganic compounds have been studied in detail for the reaction with allyl alkyl ethers [13]. The detailed NMR study of the stoichiometric reaction of Grubbs catalyst with allyl-n-butyl ether has provided information on individual steps of the catalytic cycle. A general mechanism of the cross-metathesis of vinyltri(alkoxy, siloxy)silanes (as well as octavinylsilsesquioxane) with 3-heteroatom-containing 1-alkenes in the presence of ruthenium carbene is shown in Scheme 5. 

We sought to examine the enzymatic dioxygenation of aryl silanes using a number of different aromatic dioxygenases in order to determine if such transformations were possible and to define the substrate-specificity profile. We were also motivated by the rich chemistry of silicon-based materials, which includes the hydrosilylation of alkenes and ketones, the addition of electrophiles to vinyl and allyl silanes, and palladium catalyzed cross-coupling of vinyl silanes with aryl halides (13). As a result, silyl functional cw-diols have potential as chiral intermediates for drug development, as polymer precursors/modifiers and as elements in non-linear optical materials. 

Homoallyl bromide 314, prepared from readily available non-racemic ester 313, was converted to the Grignard reagent, which reacted with non-racemic epoxide, derived from D-maUc acid, to afford the alcohol 305. Ozonolysis of the alkene gave a ketone, which was converted into enol tri-flate 316. Ni-catalyzed cross coupling with trimethylsilylmethyl magnesium chloride afforded the allyl silane, which was converted into the allyl stan-nane 317. The asymmetric allylation of 313 with 317 provided 304 with a ration of 8.5 1. Methyl etherification and oxidative cleavage of exo-methylene... 

Negishi-type cross-coupling of the title conpound with alkenyl bromides, to form allyl silanes, can be achieved in the presence of a palladium catalyst (eq 2). ... 

Scheme 3-67. Palladium-catalyzed cross-coupling of vinylstannanes with allylic acetate prepared by the reaction of trimethyl(pyridyl)silane with acrolein.

The cross-linking rate of EPR by radiation comes close to that of polypropylene. EPDM terpolymers exhibit an enhanced cross-linking rate, and it increases with the diene content. However, not only the cross-linking rate, but also a greater yield of scissions results from the addition of the third monomer. Cross-linking of EPR can be promoted by the addition of a variety of additives, particularly by those that were found effective in polypropylene. Tetravinyl silane, chlorobenzene, nitrous oxide, allyl acrylate, neopentyl chloride, and N-phenyl maleimide were reported to promote the process. 

Resin-bound (4-acyloxy-2-buten-l-yl)silanes, which can be prepared from resin-bound allylsilanes and allyl esters by cross-metathesis, react with dilute TFA to yield free carboxylic acids (Figure 3.7 [75]). However, the scope of this strategy remains to be explored. Similarly, esters of polystyrene-bound (2-hydroxyethyl)silanes readily undergo acidolysis and have been used as acid-labile linkers (Figure 3.7 [76]). 

Taylor reported kinetically controlled cross metathesis of homoallylic alcohols and allyl trimethyl silane with (4a) gave products with high E-olefin selectivity and good yields via a five-membered chelate intermediate (equation 20). ... 

Summary Two catalytic reactions, i.e. silylative coupling (mms-silylation) (SC) catalyzed by complexes containing or generating Ru-H and/or Ru-Si bonds (I, II, V, VI) and cross-metathesis (CM) catalyzed by mthenium-carbene (i.e. 1st and 2nd generation mthenium Grubbs catalyst (ID, IV)) of vinyl and allyl-substituted hetero(N,S,B)organic compounds with conunercially available vinyltrisubstituted silanes, siloxanes, and silsesquioxane have been overviewed. They provide a universal route toward the synthesis of well-defined molecular compounds with vinylsilicon functionality. 

On the other hand, our recent study on the highly efficient cross-metathesis of vinyltrialkoxy-and vinyltrisiloxy-silanes with various olefins, for example, with styrene [12] allyl eth [13] and esters [14] as well as octavinylsilsesquioxane [IS] with several olefins have opened a new opportunity for the use of alkene-cross-metathesis in the synthesis of unsaturated organosilicon compounds (see also Refs. [5] and [6]). In this p r new examples of the two reactions involving hetero(N,S,B)organic olefins have been overviewed. 

A second example is found in the photoaddition of allylic or benzylic silanes to iminium salts reported by Mariano and his co-woikers. - PET reactions of allylic or benzylic silanes with iminium salts generate two kinds of neutral radicals, allyl or benzyl radicals and a-amino radicals. The C-C bond-forming reaction between two different radicals occurs by cross coupling (Scheme 4). 

Recently, Shibata and co-workers found that aryl(trimethoxy)silanes were also applicable to the Pd-catalyzed cross-coupling reaction with aryl bromides (Scheme 14). A similar procedure using phenyl-, vinyl- and allyl(trialkoxy)silanes was also reported by Mowery and DeShong. ... 

On the other hand, although well-defined or in-situ initiated metallacarbenes are inactive for selfmetathesis of vinyl-substituted silanes and siloxanes, we revealed recently a high catalytic activity of Grubbs catalyst in cross-metathesis of vinyltrialkoxysilanes and vinyltrisiloxanes with styrene, 1-alkenes and selected allyl ethers and other derivatives [10-12]. 

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