Trimethylsilylmethylation

The phosphorus ylides of the Wittig reaction can be replaced by trimethylsilylmethyl-carbanions (Peterson reaction). These silylated carbanions add to carbonyl groups and can easily be eliminated with base to give olefins. The only by-products are volatile silanols. They are more easily removed than the phosphine oxides or phosphates of the more conventional Wittig or Homer reactions (D.J. Peterson, 1968). 

This can be circumvented by choosing alkyl groups with no P H, eg, methyl, neopentyl, trimethylsilylmethyl, phenyl and other aryl groups, and benzyl. The linear transition state for -elimination can also be made stericaHy impossible. The most successful technique for stabilization combines both principles. The pentahaptocyclopentadienyl ring anion (Cp) has six TT-electrons available to share with titanium. Biscyclopentadienyltitanium dichloride... 

Phenyl trimethylsilylmethyl sulfide 196.4, b 48 /0.04mm, 113-115 /12mm, 158.5 /52mm, d" " 0.9671, Hq 1.5380. If the sample is suspect then add H2O, wash with 10% aqueous NaOH, H2O again, dry (anhydrous CaCl2) and fractionally distil through a 2ft column packed with glass helices. [J Am Chem Soc 76 3713 1954.]... 

The transformation of an ester carbonyl group to a difluoromethylene group, which IS usually difficult to perform, can be accomplished by conversion to the thiaesier followed by treatment with diethylaminosulfur trifluoride (DAST). A vanety of ester types react efficiently, although the reaction fails with lactones. Remarkably, trimethylsilylmethyl esters carry through the proeedure with the silyl group intact [13] (equation 17). 

Another triflate ester that recently has found growing application in organic synthesis is commercially available trimethylsilylmethyl trifluoromethanesul fonate. This powerful alkylating reagent can be used for the synthesis of various methylides by an alkylation-desilylation sequence A representative example is the generation and subsequent trapping by 1,3-dipolar cycloaddition of indolium methanides from the corresponding indole derivatives and trimethylsilylmethyl trifluoromethanesulfonate [108] (equation 54)... 

Dioxolanes, 312 4-Bromomethyl-1,3-dioxolane, 322 4-(3-Butenyl)-1,3-dioxolane, 323 4-Phenyl-1,3-dioxolane, 323 4-(4-Methoxyphenyl)-1,3-dioxolane, 324 4-(2-Nitrophenyl)-1,3-dioxolane, 324 4-Trimethylsilylmethyl-1,3-dioxolane, 324... 

These methylenecyclopentane annulations may also be applied to conjugated dienones, e.g., 4-methyl-4-[2-(trimethylsilylmethyl)-2-propeny[]-3-vinyl-2-cyclohexenones43 44. Again, fluoride ion was used successfully to generate either octahydro-5//-inden-5-ones or hexahydro-2( 1H (-pentalenones. 

To a solution of trimethylsilylmethyl lithium (from chloromethyltrimethyl-silane (15.8mmoI) and lithium dispersion (196mmol)) in ether (30ml) was added cyclohexane carboxaldehyde (14.2 mmol) at ambient temperature, with stirring. After a further 10min at ambient temperature, the solution... 

Trimethylsilyhex-l-yne, 46 Trimcthylsilylmethyl cyclohexyl ketone, 78-9 Trimethylsilylmethyl lithium, 64,78,79... 

A number of trimethylsilylmethyl and related complexes have been converted into others by standard ligand displacement procedures from... 

Heating of bis(trimethylsilylmethyl)sulfoxide 1166 generates HMDSO 7 and, via 1167, the reactive intermediate thioformaldehyde-S-methyhde 1168, which can be trapped in situ, e.g. by N-methylmaleimide, to give 81% of the l,3-dipolar cycloaddition product 1169 [14] (Scheme 8.3). Further analogous 1,3-dipolar cycloadditions with acetylenes are discussed elsewhere [15]. 

Pyrrolidines have been prepared by 1,3-dipolar cycloaddition of N-(benzyli-dene)trimethylsilylamine/TMSOf 20 and methyl acrylate, N-methylmaleimide, or dimethyl maleate [35]. More recently, methyl trans-3-cyanociruiamate 1479 was reacted with N-benzyl-N-(trimethylsilylmethyl)aminomethyl methyl ether 1480 and trifluoroacetic acid in CH2CI2 at 0°C and 24°C to afford, via 1481, the pyrrolidine derivative 1482 in high yield and MeOSiMe3 13a [35a] (Scheme 9.20). Several... 

Trimethylsilylmethyl Grignard or lithium reagents 1606 add to ketones such as cyclohexanone to give, via the intermediates 1607, the olefins 1608, often in high yields (Scheme 10.5). 

Dialkyl zinc compounds form phosphine complexes of formula RZnP(SiMe3)2 on addition of one equivalent of bis(trimethylsilyl)phosphine. Solution and solid-state studies showed that the complexes are dimeric or trimeric in solution or the solid state. Bis(trimethylsilyl)phosphido-methylzinc crystallizes as a trimeric molecule with a Zn3P3 core in the twist-boat conformation. Bis(trimethylsilyl)phosphido- -butylzinc, shows a similar central Zn3P3 fragment. The sterically more demanding trimethylsilylmethyl substituent forms a dimeric species of bis(trimethylsilyl) phosphido-trimethylsilylmethylzinc. Solution studies of bis(trimethylsilyl)phosphido- .vo-propyl-zinc demonstrate a temperature-dependent equilibrium of the dimeric and trimeric species and the crystalline state contains a 1 1 mixture of these two oligomers. A monomeric bis(trimethyl-silyl)phosphido-tris(trimethylsilyl)methylzinc has also been synthesized.313... 

Synthesis and Characterization. Tris(trimethylsilylpropyl)tin fluoride (PTF) and tris(trimethylsilylmethyl)tin fluoride (MTF) were synthesized according to scheme A (Figure 1) while scheme B (Figure 1) was followed in the synthesis of dibutyl-(trimethylsilylpropyl)tin fluoride (BTF). MTF has been reported in the literature (6) however, it was synthesized to compare its solution properties with the other two novel compounds. The steps involved in these syntheses were straight-forward and thus need no elaboration. In the synthesis of BTF, the unsymmetrical triorganotin fluoride, bromination of tetraorganotin compound resulted... 

It bums spontaneously in air and reacts violently with water, as does the congener, bis(trimethylsilylmethyl)aluminimn bromide. 

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