Allenyl silane

Triphenylsilanol is one of several products obtained in the thermally induced decarbonylation of Ph3SiC02H (129). Acylsilanes react readily with aqueous base for example, Ph3SiC(0)Ph affords Ph3SiOH and PhC(0)H when treated with aqueous sodium hydroxide solution (130). Similarly, hydrolysis of the allenyl silane 22 leads to the formation of 23 via the acylsilane 24 [Eq. (24)] (131). (For further examples of acylsilane chemistry, see Refs. 132-134.)... 

The acid portion of 1 was assembled by enantio-and diastereocontrolled addition of Z-crotyl borane to the aldehyde 8, following the Brown protocol. Hydroboration and oxidation led to 9, which was condensed with the allenyl silane 10 to give 11 with high diastereocontrol. Conversion of the alcohol to the iodide followed by three-carbon homologation by the Myers procedure then led to 1, which was cyclized with > 10 1 regio- and diasterocontrol to give 12. Ozonolysis and methylenation of the less hindered ketone then delivered 3. 

The /3-lactone was formed by the cyclization of a 3-hydroxycarboxylic acid with sulfonyl chloride. An alternative synthesis attempted to control all stereochemical relationships in the molecule using the properties of silyl moieties attached to substrates and reagents <20040BC1051>. Stereoselective reactions of this type included the use of silyl groups in enolate alkylations, hydroboration of allylsilanes, and an anti Se2 reaction of an allenyl silane with an aldehyde and ry -silylcupration of an acetylene. The /3-lactone was again formed by the standard sulfonyl chloride cyclization method. 

Propargyltrimethylsilanes give allenyl derivatives on reaction with -acyliminium precursors. - On the other hand, application of allenyl-silanes or -stannanes provides access to propargyl-substituted lactams. All reactions proceed with high regio- and stereo-selectivity (equations 54 and 55). 4-Allenyl-azetidinones can be cyclized to A -carbapenem systems, mediated by Ag or Pd salts. - The reactions of ethoxylactams with allenylsilanes can be modified in such a way that bicyclic systems are obtained in one step (equation 56). ... 

Homopropargylic alcohols are available by reaction of carbonyl compounds with allenyl silanes.105 Full details of this chemistry include preparations of variously substituted allenysilanes together with methods for their reaction using TiCl4. The same compounds are available in optically active form by use of chiral allenylboronic esters.106 This method is rather similar to the chemistry outlined in Scheme 27 for the preparation of homoallylic alcohols. A third method for the preparation of homoallylic... 

Figure 7.10 (a) Resonance description of the interaction in allenyl silanes, (b) Comparison of allenyl... 

Masse, C. E., Panek, J. S. (1995). Diastereoselective Reactions of Chiral Allyl and Allenyl Silanes with Activated C X.pi.-Bonds. Chemical Reviews, 95(5), 1293-1316. 

Allenyl-silanes are known to react with electron-deficient olefins to give cyclopentenes and this reaction has now been extended... 

Trifluoromethyl)allyltrimethylsilane results frwith aldehydes and ketones gives trifluoromethyl-ated alcohols and silyl ethers. Synthesis of allyl and allenyl-silanes is stereospecific from hydroalumination or hydroboration of... 

Reactions of similar organoalkynyl/allenyl silanes containing various metals with carbonyl compounds to give propargylic products have been reported. " Conjugate addition of allenyl stan-nanes to Q , -unsaturated carbonyl compounds to give propargylic products can be effected in the presence of titanium(IV) chloride. ... 

Purification allenes (la), (lb), and (Ic) are purified by distillation at reduced pressure or by column chromatography. Allene (Id) is distilled at atmospheric pressure. The allenyl-silanes obtained by the Vermeer method typically contain up to 7-8% of the trialkylsilyl-l-butyne isomer produced by Sn2 reaction. This mixture can be used directly in most subsequent reactions without further purification. If desired, however, the alkynyl contaminant can be selectively removed by treatment of the mixture with silver(I) nitrate in (10 1) methanol-water at room temperature for one hour. 1-Methyl-l-(trimethylsilyl)-allene is obtained in 79% yield after pentane extraction and distillation. 

Masse CE, Panek JC. Diastereoselective reactions of chiral allyl and allenyl silanes with activated C=X TT-bonds. Chem. Rev. 1995 95 1293-1316. 

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