100312-73-0Relevant academic research and scientific papers
Stereoselective synthesis of (Z)- and (E)-allylic silanes by copper- mediated substitution reactions of allylic carbamates with grignard reagents
Smitrovich, Jacqueline H.,Woerpel
, p. 1601 - 1614 (2007/10/03)
Both (Z)- and (E)-allylic silanes were prepared with high stereoselectivity by the copper-mediated substitution of allylic carbamates by organometallic reagents. The reaction of alkylmagnesium reagents with (E)- allylic carbamates provides (Z)-allylic silanes, whereas both alkylmagnesium and alkyllithium reagents react with (Z)-allylic carbamates to afford (E)- allylic silanes. Because Grignard reagents are often more facile to prepare than alkyllithium species, these reagents are the optimal nucleophiles for the synthesis of both (Z)- and (E)-allylic silanes. This method also allows readily available nonracemic allylic carbamates to be converted to chiral, nonracemic (Z)- and (E)-allylic silanes with high stereoselectivity.
A Regioselective and Stereospecific Synthesis of Allylsilanes from Secondary Allylic Alcohol Derivatives
Fleming, Ian,Higgins, Dick,Lawrence, Nicholas J.,Thomas, Andrew P.
, p. 3331 - 3350 (2007/10/02)
Primary and secondary allylic acetates and benzoates react with the dimethyl(phenyl)silyl-cuprate reagent to give allylsilanes, provided that the THF in which the cuprate is prepared is diluted with ether before addition of the allylic ester.The reaction is reasonably regioselective in some cases: (i) when the allylic system is more-substituted at one end than the other, as in the reactions 4->5 and 9->10; (ii) when the steric hindrance at one end is neopentyl-like, as in the reactions 15->16; and (iii) when the disubstituted double bond has the Z configuration, as in th e reactions Z-19->E-21 or, better, because the silyl group is becoming attached to the less-sterically hindered end of the allylic system, Z-20->E-22.The regioselectivity is better if a phenyl carbamate is used in place of the ester, and a three-step protocol assembling the mixed cuprate on the leaving group is used, as in the reactions 23->24 and E- or Z-29->E-21, or, best of all, because the silyl group is again becoming attached to the less-sterically hindered end of the allylic system, E- or Z-30->E-22.This sequence works well to move the silyl group onto the more substituted end of an allyl system, but only when the move is from a secondary allylic carbamate to a tertiary allylsilane, as in the reaction 38->39.Allyl(trimethyl)silanes can be made using alkyl- or aryl-cuprates on trimethylsilyl-containing allylic esters and carbamates, as in the reactions 40->41, and 43->44.The reaction of the silyl-cuprate with allylic esters and the three-step sequence with the allylic carbamates are stereochemically complementary, the former being stereospecifically anti and the latter stereospecifically syn.Homochiral allylsilanes can be ma de by these methods with high levels of stereospecificity, as shown by the synthesis of the allylsilanes 54, 58 and 59.
A Regiocontrolled and Stereocontrolled Synthesis of Allylsilanes from β-Silyl Enolates
Fleming, Ian,Gil, Salvador,Sarkar, Achintya K.,Schmidlin, Tibur
, p. 3351 - 3362 (2007/10/02)
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.
THE SILYL-CUPRATION AND STANNYL-CUPRATION OF ALLENES
Fleming, Ian,Rowley, Michael,Cuadrado, Purificacion,Gonzalez-Nogal, Ana M.,Pulido, Francisco J.
, p. 413 - 424 (2007/10/02)
The stoichiometric silyl-cupration of allene 7, followed directly by treating the intermediate cuprate with a proton, with a range of carbon electrophiles, and with chlorine gives the vinylsilanes 8-13.Alternatively, when iodine is the electrophile, the product is the vinyl iodide 16.This can then be metallated and treated with a proton or a range of carbon electrophiles to give the allylsilanes 18-21.More-substituted allenes also undergo silyl-cupration followed by protonation, phenylallenes giving vinylsilanes, and alkylallenes giving, on the whole, allylsilanes.Stoichiometric stannyl-cupration of allenes takes place, with similar but less reliable regiocontrol to that of the corresponding silyl-cupration.
The Syntheses of Allylsilanes and Vinylsilanes by Silyl-cupration of Allenes
Fleming, Ian,Pulido, Francisco J.
, p. 1010 - 1011 (2007/10/02)
Allenes react with silyl-cuprate reagents to give either allylsilanes or vinylsilanes, depending upon the substituents on the allene.
