Trimethyl 2- -2-propenyl silane

Chelation control has been invoked to explain the stereoselectivity of the reaction between 2-methoxycyclohexanone and trimethyl(2-propenyl)silane promoted by titanium(IV) chloride59, and has been observed for addition of allylsilanes to a-amidoaldehydes60, although the stereoselectivity is very dependent upon the amount of Lewis acid used and the structure of the substrate, particularly when the Lewis acid can bind to more than one site61. 

On treatment with trimethyl(2-propenyl)silane and titanium(IV) chloride, chiral methyl fi-formylcarboxylates give di- and tetra-substituted y-lactones with moderate to good stereoselectivity. Participation of seven-membered ring chelates was suggested65. 

Trimethyl(l-phenyl-2-propenyl)silane of high enantiomeric excess has also been prepared by asymmetric cross coupling, and reacts with aldehydes to give optically active products in the presence of titanium(IV) chloride. The stereoselectivity of these reactions is consistent with the antiperiplanar process previously outlined75. 

Very few optically active cyanohydrins, derived from ketones, are described in the literature. High diastcrcosclectivity is observed for the substrate-controlled addition of hydrocyanic acid to 17-oxosteroids27 and for the addition of trimethyl(2-propenyl)silane to optically active acyl cyanides28. The enantioselective hydrolysis of racemic ketone cyanohydrin esters with yeast cells of Pichia miso occurs with only moderate chemical yields20. 

More recently, the Lewis acid promoted asymmetric 1,4-addition of trimethyl(2-propenyl)silane to chiral a,/ -unsaturated /V-acylamides has been published33. Lewis acid mediated reactions of trimethyl(2-propenyl)silanes with a,/I-unsatu rated AT-acyloxazolidinones or iV-enoylsultams show high chemical yield with good diastereomeric excess. The absolute configuration of the new asymmetric center is controlled by the nature of the Lewis acid used. 

Radical Allylation Reactions. Trimethyl 2-[(tributylstannyl) methyl]-2-propenyl silane reacts with organic halides under photochemical conditions (irradiation with a medium pressure mercury lamp through a pyrex filter) at temperatures below 20 °C to give various allylsilanes (eq 7). The ease of the reaction was found to be halide dependent with those affording more electrophilic radicals generally behaving most effectively. 

New protocols for the catalytic asymmetric monoallylation of aldehydes using the title reagent continue to be developed. For example, it has been shown (eq 10) that a range of aromatic and aliphatic aldehydes engage, in the presence of 5 mol % [(/ )-BlNOL]-Ti [OCH(CF3)2]2, in an enantioselective addition reaction with trimethyl 2-[(tributylstannyl)methyl]-2-propenyl -silane to give the expected addition products in >90% ee and 54—94% chemical yield. ... 

Trimethyl 2-[(tributylstannyl)methyl]-2-propenyl silane, 731 C2iH2iClSi... 

Dichlorodiethoxytitanium Titanium, dichlorodiethoxy-, (8,9) (3582-00-1) 2-Trimethylsiloxybutadiene Silane, trimethyl[(l-methylene-2-propenyl)oxy]-, (9) (38053-91-7)... 

Difluoroallyl)trimethylsilane Silane, (3,3-difluoro-2-propenyl)trimethyl-(9) (40207-81-6)... 

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