- Manganese-Catalyzed Silylmagnesiation of Acetylenes and 1,3-Dienes
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The treatment of 4-benzyloxy-1-butyne with PhMe2SiMgMe in the presence of a catalytic amount of MnCl2 gave a monosilylated product, (E)-PhCH2OCH2CH2CH=CHSiMe2Ph, selectively after an aqueou
- Tang, Jun,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 245 - 251
(2007/10/03)
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- A Regioselective and Stereospecific Synthesis of Allylsilanes from Secondary Allylic Alcohol Derivatives
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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.
- Fleming, Ian,Higgins, Dick,Lawrence, Nicholas J.,Thomas, Andrew P.
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p. 3331 - 3350
(2007/10/02)
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- THE SILYL-CUPRATION AND STANNYL-CUPRATION OF ALLENES
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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.
- Fleming, Ian,Rowley, Michael,Cuadrado, Purificacion,Gonzalez-Nogal, Ana M.,Pulido, Francisco J.
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p. 413 - 424
(2007/10/02)
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- ORGANIC SYNTHESIS WITH REAGENTS DERIVED FROM 3R3SiMgMe AND MnCl2
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Synthetically useful reactions mediated by reagents derived from 3 equiv. of R3SiMgMe and MnCl2 are disclosed. (1) The manganese species reacted with terminal acetylenes to give 1,2-disilylated 1-alkenes.Mono- and bis(trimethylsilyl)acetylenes gave tri- a
- Fugami, Keigo,Hibino, Jun-ichi,Nakatsukasa, Shigeki,Matsubara, Seijiro,Oshima, Koichiro,et al.
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p. 4277 - 4292
(2007/10/02)
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- The Syntheses of Allylsilanes and Vinylsilanes by Silyl-cupration of Allenes
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Allenes react with silyl-cuprate reagents to give either allylsilanes or vinylsilanes, depending upon the substituents on the allene.
- Fleming, Ian,Pulido, Francisco J.
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p. 1010 - 1011
(2007/10/02)
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- SILYLMANGANATION OF 1,3-DIENES. A FACILE SYNTHESIS OF FUNCTIONALIZED VINYLSILANES
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Treatment of 1,3-dienes with (R3Si)3 MnMgMe provides silylated allylmanganese compounds which add to carbonyl moiety with high regioselectivity.
- Fugami, Keigo,Nakatsukasa, Shigeki,Oshima, Koichiro,Utimoto, Kiitiro,Nozaki, Hitosi
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p. 869 - 870
(2007/10/02)
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