Ene-silanes

Bi s (tri methyl si lyloxy )cyclobut-l-ene Silane, (1 -cyclobuten-1,2-ylenedioxy)bis[trimethyl- Silane, [1-cyclobutene-1,2-diylbis(oxy)]bis[trimethy1- (17082-61-0), 65, 17 Boron trifluoride etherate Ethyl ether, compd. with boron fluoride (BFj) (1 1) Ethane, 1,1 -oxybis-, compd. with trifluoroborane (1 1) (109-63-7), 65, 17... 

Bis(trimethylsilyloxy)cyclobut-l-ene Silane, (1-cyclobuten-l,2-ylenedioxy)bis[trimethyl- (8) Silane, [1-cyclobutene-l,2-diylb1s(oxy)]bis[trimethyl- (10) (17082-61-0)... 

Formation of allylic alcohols from ketones with [l,2]-transposition of the oxygen function can be achieved via ene-silanes (38) (Scheme 14) ° the dye-sensitized oxygenation in regiospecific across silicion, possibly an ene reaction. The less substituted ene-silane is obtained from unsymmetrical ketones,... 

Another interesting innovation is that developed by the Malaysian Rubber Producers Research Association. In this case the coupling agent is first joined to a natural rubber molecule involving an ene molecular reaction. The complex group added contains a silane portion which subsequently couples to filler particles when these are mixed into the rubber. 

Nowadays silenes are well-known intermediates. A number of studies have been carried out to obtain more complex molecules having Si=C double bonds. Thus, an attempt has been made to generate and stabilize in a matrix 1,1-dimethyl-l-silabuta-l,3-diene [125], which can be formed as a primary product of pyrolysis of diallyldimethylsilane [126] (Korolev et al., 1985). However, when thermolysis was carried out at 750-800°C the absorptions of only two stable molecules, propene and 1,1-dimethylsilacyclobut-2-ene [127], were observed in the matrix IR spectra of the reaction products. At temperatures above 800°C both silane [126] and silacyclobutene [127] gave low-molecular hydrocarbons, methane, acetylene, ethylene and methylacetylene. A comparison of relative intensities of the IR... 

A mixture of exo- and endo-isomers of 5-methylbicylo[2.2.1]hept-2-ene is hydrogenated with the aid of five equivalents of triethylsilane and 13.1 equivalents of trifluoroacetic acid to produce a 45% yield of < <7o-2-methylbicylo[2.2.1] heptane (Eq. 71). The same product is formed in 37% yield after only five minutes. The remainder of the reaction products is a mixture of three isomeric secondary exo-methylbicylo[2.2.1]heptyl trifluoroacetates that remains inert to the reaction conditions. Use of triethylsilane-l-d gives the endo-2-methylbicylo-[2.2.1]heptane product with an exo-deuterium at the tertiary carbon position shared with the methyl group. This result reflects the nature of the internal carbocation rearrangements that precede capture by the silane.230... 

However, most asymmetric 1,3-dipolar cycloaddition reactions of nitrile oxides with alkenes are carried out without Lewis acids as catalysts using either chiral alkenes or chiral auxiliary compounds (with achiral alkenes). Diverse chiral alkenes are in use, such as camphor-derived chiral N-acryloylhydrazide (195), C2-symmetric l,3-diacryloyl-2,2-dimethyl-4,5-diphenylimidazolidine, chiral 3-acryloyl-2,2-dimethyl-4-phenyloxazolidine (196, 197), sugar-based ethenyl ethers (198), acrylic esters (199, 200), C-bonded vinyl-substituted sugar (201), chirally modified vinylboronic ester derived from D-( + )-mannitol (202), (l/ )-menthyl vinyl ether (203), chiral derivatives of vinylacetic acid (204), ( )-l-ethoxy-3-fluoroalkyl-3-hydroxy-4-(4-methylphenylsulfinyl)but-1 -enes (205), enantiopure Y-oxygenated-a,P-unsaturated phenyl sulfones (206), chiral (a-oxyallyl)silanes (207), and (S )-but-3-ene-1,2-diol derivatives (208). As a chiral auxiliary, diisopropyl (i ,i )-tartrate (209, 210) has been very popular. 

Scheme 14.38. Ring-closing metathesis of [2,2-bis(phenylthio)ethyl]dimethyl-(l-phenylbut-3-enyloxy)-silane (89) and subsequent oxidation to (Z)-5-phenylpent-2-ene-l, 5-diol (90).

The chemical modification of fullerenes has received considerable attention in the last decade in order to achieve new applications to material sciences [27]. Fuller-ene-bonded polysilane derivatives might be expected to show high conductivity since Ceo-doped polysilane is found to be a good photoconductor [28]. Therefore, a variety of silylated derivatives have been obtained to date, although the available methods are limited to the photoinduced addition of various silanes to Ceo-... 

The cross-conjugated trienes have potential in many different types of diversification strategies. For example, the triene clearly lends itself to inter- and intramolecular Diels-Alder reactions. Incorporation of the hydroxymethyl group on the tether allows attachment of functionality suitable for reactions subsequent to the Alder-ene reactions. As depicted in Scheme 8.5, propargyl tosylamides A, alkynyl silanes B, acrylate esters C, and propargyl ethers D can all be readily prepared from 39... 

Note The buta-1,3-diene is exclusively incorporated by 1,4-addition which cannot be reflected in the source-based name. The strueture-based name (see [5]) is [deea(but-2-ene-1,4-diyl)]methyl[pentadeea(but-2-ene-1,4-diyl)][poly(2-phenylethylene)]silane... 

Irradiation of a mixture of 2,3-dicyano-5,6-dimethylpyrazine 85 and allylic silanes leads to the formation of 2,8-diazatricyclo[3.2.1]oct-2-enes 86 via [2-I-2] photocyclization followed by rearrangement (Equation 12)... 

Selectivity for the formation of 207 is dramatically improved by use of either a stronger base, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) instead of EtsN (0.1 molar equiv. of DBU is sufficient for selective formation of 205), or a bulkier silane, such as Bu Me2SiH. The spiro-typc /3-lactones 207, 208, and 209 are also obtained in good... 

Mikami has carried out a number of investigations aimed at elucidating mechanistic aspects of this Si-atom transfer process. In particular, when the aldol addition reaction was conducted with a 1 1 mixture of enoxysilanes 60 and 62, differentiated by the nature of the 0-alkyl and 0-silyl moieties, only the adducts of intramolecular silyl-group transfer 63 and 64 are obtained (Scheme 8B2.6). This observation in addition to results obtained with substituted enol silanes have led Mikami to postulate a silatropic ene-like mechanism involving a cyclic, closed transition-state structure organized around the silyl group (Scheme 8B2.6). 

It has also been shown that the Sakurai-Hosomi reaction of methallylsilanes with glyoxylates is catalyzed by the BINOL-Ti complex (1) to give the products, surprisingly, in an allylic silane (ene product) form with high enantioselecdvity (Scheme 8C.22) [53],... 

It is well known that thermal decomposition of allyl-substituted silanes proceeds by retro-ene reaction with formation of transient species having a Si=C bond, such as silaben-zene, silatoluene and dimethylsilaethylene4b e. The kinetic data on the gas-phase pyrolysis of a similar allyloxysilane derivative, (l,l-dimethylallyloxy)dimethylsilane (16), and the results on thermolysis of allyloxydimethylsilane (17) in a flow system both indicate the participation of an intermediate silanone, (CH3)2Si=0 (10), as shown in Scheme 523. 

Lewis acid-mediated addition of (phenylthio)trimethylsilane to acryloyl silane takes place to give l,3-bis(phenylthio)-l-trimethylsilylprop-l-ene (18). This compound may be deprotonated with t-butyl lithium at the /J-position and alkylated to give a range... 

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