- Reaction of acylsilanes with potassium cyanide: Brook rearrangement under phase-transfer catalytic conditions
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The reactions of acylsilanes with KCN under liquid-liquid phase-transfer catalytic conditions proceeded smoothly via the Brook rearrangement to produce O-silylated cyanohydrin derivatives in excellent yields. We also found that α-cyano carbanions generate
- Takeda, Kei,Ohnishi, Yuji
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p. 4169 - 4172
(2007/10/03)
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- The Highly Regioselective Carbonylation of Vinylsilanes
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The hydroesterification of vinylsilanes, catalyzed by transition-metal complexes, afforded both β-silyl esters 2 and α-silyl esters 3 in high yield.The Pd(II) complex-catalyzed reaction showed high β-regioselectivity, whereas the Co2(CO)8-catalyzed reaction showed high α-regioselectivity.Vinylsilanes which bore trialkyl-, diphenylmethyl-, dimethylethoxy-, trimethoxy-, diphenylfluoro-, and difluorophenylsilyl groups were regioselectively, and in some cases regiospecifically, hydroesterified.Pd(II) complexes were also shown to be effective catalysts of the hydrocarboxylation of vinylsilanes.Hydrocarboxylation was β-regiospecific and gave excellent yields of β-silyl carboxylic acids.Reasonable mechanisms for the reactions are described.
- Takeuchi, Ryo,Ishii, Naomi,Sugiura, Masaharu,Sato, Nobuhiro
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p. 4189 - 4194
(2007/10/02)
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- A Regiocontrolled and Stereocontrolled Synthesis of Allylsilanes from β-Silyl Enolates
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The α-lithiated diphenylphosphine oxides 3 react with methyl iodide to give the phosphine oxides 4 and 5 in a ratio 3-4:1.The corresponding reaction with aldehydes gives all four diastereomeric alcohols 7-10, which are not suitable for the synthesis of allylsilanes by a Wittig-Horner reaction.The β-dimethyl(phenyl)silyl enolates 13-15 and 25-28 react with aldehydes to give aldol products with high diastereoselectivity.The benzyl and allyl ester groups can be cleaved from these aldols to give the acids 16-18 and 29-32.The acids, in turn, can be induced to undergo dec arboxylative elimination stereospecifically either in a syn or an anti sense to give the allylsilanes 19, 20, 23, 24, 33, 34 and 39-41.A similar series of reactions can be carried out with the β-trimethylsilyl enolates 45 and 46 giving the allylsilanes 49, 50, 53 and 54.
- Fleming, Ian,Gil, Salvador,Sarkar, Achintya K.,Schmidlin, Tibur
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p. 3351 - 3362
(2007/10/02)
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- Asymmetric synthesis of α-methylene-γ-butyrolactones fused to carbocyclic rings via the Hosomi reaction of chiral allylsilanes
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Optically active α-methylene-γ-butyrolactones fused to five or six-membered carbocyclic ring were synthesized in 64-92% enantiomeric excess using the intramolecular Hosomi reaction of ω-formylated β-(chiral)alkoxycarbonylallylsilanes.
- Nishitani, Kiyoshi,Yamakawa, Koji
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p. 387 - 390
(2007/10/02)
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- Cyclic Olefins by Anodic Oxidation of β-(Trimethylsilyl)carboxylic Acids. - β-(Trimethylsilyl)acrylic Acid Derivatives as Acetylene Equivalents in Diels-Alder Reactions
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Trimethylsilyl-substituted dienophiles 1, 2, and 4 react with dienes 6-14 in 66-100percent yields to give β-trimethylsilyl-substituted carboxylic acids 15-25, some of which are hydrogenated to 26-31.These are decarboxylated-desilylated to cyclic olefins 35-47 by Non-Kolbe electrolysis in 45-91percent yields.The dienophiles 1, 2, and 4 are thus suitable acetylene equivalents for Diels-Alder reactions.
- Hermeling, Dieter,Schaefer, Hans J.
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p. 1151 - 1158
(2007/10/02)
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- SILYL- AND GERMYL-CYCLOPROPANONES
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1.The reactions of silylcyclopropanones with compounds containing a mobile hydrogen atom and also with alkoxy, dialkylamino, and dialkoxyphosphinooxy derivatives of Group IVB elements give adducts at the carbonyl group of the cyclopropanone, and, when heated, these undergo isomerization with opening of the three-membered ring exclusively at the C1-C2 bond and with the formation of β-heteroelement-substituted propionic derivatives. 2.Acetic acid and bis(trifluoroacetic) anhydride in reaction with (trimethylsilyl)cyclopropanone form relatively stable products of addition at the carbonyl group. 3.Bromine and iodotrimethylsilane react with silylcyclopropanones with breakage of the C2-C3 bond of the cyclopropanone ring and give the corresponding O- and C-isomeric derivatives of α-silylated ketones containing halogen atoms in the molecule. 4.The reactions of silyl- and germyl-cyclopropanones with diazomethane and with azido-silanes and -germanes can provide a method of synthesis of heteroelement-substituted (Si, Ge) cyclobutanones and β-lactams.
- Zaitseva, G. S.,Krylova, G. S.,Perelygina, O. P.,Baukov, Yu. I.,Lutsenko, I. F.
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p. 1935 - 1947
(2007/10/02)
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- β-Silylcarbonyl Compounds as Masked Enones
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β-Trimethylsilylketones and lactones can be brominated (3)->(4) and desilylbrominated (4)->(5) specifically to place a double bond between the carbonyl group and the β-carbon atom to which the silicon had originally been bound.The silyl group therefore is a base- and acid stable group masking the α,β-unsaturation of enones.Several α-methylene-ketones and -lactones have been prepared in this way.With ketones, the bromination step seems always to introduce bromine mainly or exclusively at the α-position on that side of the ketone on which the β-silyl group is placed, regardless of whether it is more or the less substituted α-position.
- Fleming, Ian,Goldhill, Jon
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p. 1493 - 1498
(2007/10/02)
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