115884-63-4Relevant academic research and scientific papers
Copper(I)-catalyzed regio- and chemoselective single and double addition of nucleophilic silicon to propargylic chlorides and phosphates
Hazra, Chinmoy K.,Oestreich, Martin
, p. 4010 - 4013 (2012/10/08)
Copper(I)-catalyzed propargylic substitution of linear precursors with (Me2PhSi)2Zn predominantly yields the γ isomer independent of the propargylic leaving group. The thus formed allenylic silane reacts regioselectively with another equivalent of (Me2PhSi) 2Zn, yielding a bifunctional building block with allylic and vinylic silicon groups. The reaction rates of both steps are well-balanced for chloride (γ:α ≥ 99:1) where the propargylic displacement occurs quantitatively prior to the addition step. Substitutions of α-branched propargylic phosphates are also reported.
Copper(I)-catalyzed regioselective propargylic substitution involving Si-B bond activation
Vyas, Devendra J.,Hazra, Chinmoy K.,Oestreich, Martin
, p. 4462 - 4465 (2011/10/08)
The silicon nucleophile generated by copper(I)-catalyzed Si-B bond activation allows several γ-selective propargylic substitutions. The regioselectivity (γ:α ratio) is strongly dependent on the propargylic leaving group. Chloride is superior to oxygen leaving groups in linear substrates (γ:α > 99:1), and it is only the phosphate group that also shows promising regiocontrol (γ:α = 90:10). That leaving group produces superb γ-selectivity (γ:α > 99:1) in α-branched propargylic systems, and enantioenriched substrates react with excellent central-to-axial chirality transfer.
Accurate determinations of the extent to which the SE2′ reactions of allyl-, allenyl- and propargylsilanes are stereospecifically anti
Buckle, Michael J.C.,Fleming, Ian,Gil, Salvador,Pang, Kah Ling Christine
, p. 749 - 769 (2007/10/03)
The allylsilanes, (R)-E- and (R)-Z-4-trimethylsilylpent-2-ene 16, were prepared in essentially an enantiomerically and geometrically pure state (er >99.95 : 0.05, E : Z and Z : E >99.95 : 0.05) by, successively, conjugate addition of lithium dimethylcuprate to N-[(E)-3′-trimethylsilylpropenoyl]-(7S)-10, 10-dimethyl-4-aza-5-thiatricyclo[5.2.1.03,7]-decane 5,5-dioxide, to give N-[(E)-(3′ R)-3′-trimethylsilylbutanoyl]-(7S)-10, 10-dimethyl-4-aza-5-thiatricyclo[5.2.1.03,7]decane 5,5-dioxide 13, removal of the chiral auxiliary with bromomagnesium benzyloxide, aldol reaction with acetaldehyde, and decarboxylative elimination, to give either the Z- or E-isomer. Both the E- and Z-allylsilanes 16 reacted with the adamantyl cation to give mixtures of E- and Z-4-adamantylpent-2-enes 17. The E-allylsilane gave the E- and Z-products in a ratio of 40 : 60, and the Z-allylsilane gave the E- and Z-products in a ratio of 99.8 : 0.02. The enantiomer ratio was >99 : 1 for the reaction of the E-allylsilane giving the Z-product, 90 : 10 for the E-allylsilane giving the E-product, and 95 : 5 for the Z-allylsilane giving the E-product, showing that the reactions were stereospecific to a high degree, but not always quite completely so. The allenylsilane, 2-trimethylsilylpenta-2,3-diene 29, was prepared enantiomerically highly enriched (er 99 : 1) by copper-catalysed reaction of methylmagnesium chloride with (S)-4-trimethylsilylbut-3-yn-2-yl camphor-10-sulfonate 28. The allenylsilane 29 reacted with the adamantyl cation to give (S)-4-adamantylpent-2-yne (S)-30 with the same level of enantiomeric purity, showing that the reaction was, as accurately as can be measured, completely stereospecific. The allenylsilane 29 also reacted with isobutanal in the presence of titanium tetrachloride to give 2,4-dimethylhept-5-yn-3-ol as a mixture of diastereoisomers, syn 31 and anti 32, in a ratio of 95 : 5, with the major diastereoisomer present as a mixture of enantiomers (4R,5R) : (4S,5S) in a ratio of 99 : 1, showing that the reaction was, as accurately as can be measured, completely stereospecific in the anti sense. The corresponding propargylsilane, 4-trimethylsilylpent-2-yne 37, reacted with the adamantyl cation to give dienes assigned the structures 2,3-diadamantyl-1,3-pentadiene 42 and 2,4-diadamantyl-1,3-pentadiene 43, and reacted with isobutanal in the presence of titanium tetrachloride to give 2-(1-hydroxy-2-methylpropyl)-3-trimethylsilylpenta-1,3-dienes 45 and 2,4-dimethyl-5-trimethylsilylhept-5-en-3-one 46. The enantiomerically enriched propargylsilane (R)-1,3-bis(trimethylsilyyl)but-1-yne 62 (er >99.7 : 0.3) was prepared from the sultam 13, by removal of the chiral auxiliary with lithium ethoxide, reduction of the ethyl ester to give (R)-3-trimethylsilylbutanal 60, enol triflate formation, β-elimination and C-silylation. The propargylsilane 62 reacted with 2,4-dinitrobenzaldehyde in the presence of titanium tetrachloride to give the allenes, 1-(2,4-dinitrophenyl)-2-trimethylsilylpenta-2,3-dienols 63-66, as two diastereoisomers in a ratio of 2 : 1, each of which was a pair of enantiomers in a ratio of approximately 3 : 1, showing that there was considerable loss of stereospecificity, but that what there was in the anti sense. A similar reaction with isobutanal gave a similar set of four allenes, 2-methyl-4-trimethylsilylhepta-4,5-dien-3-ol 73-76, but with a negligible degree of stereospecificity.
Generation of allenic samarium complexes from propargylic ethers and (C5Me5)2Sm(thf)2, and their electrophilic trapping
Makioka,Makioka, Yoshikazu,Koyama,Koyama, Koji,Nishiyama,Nishiyama, Tetsushi,Takaki,Takaki, Ken,Taniguchi,Taniguchi, Yuki,Fujiwara,Fujiwara, Yuzo
, p. 6283 - 6286 (2007/10/02)
Allenic samarium complexes are readily generated in high yields by the reaction of propargylic benzyl ethers with (C5Me5)2Sm(thf)2. Electrophilic trapping of the complexes derived from the secondary and tertiary ethers with cyclohexanone and dimethylphenylsilyl chloride gives the corresponding propargylic products selectively, whereas α-allenic alcohols are predominantly obtained in the reaction of the complexes, generated from the primary ethers, with cyclohexanone.
Synthesis of Allenylsilanes from Propargyl Carbamates
Fleming, Ian,Takaki, Ken,Thomas, Andrew P.
, p. 2269 - 2274 (2007/10/02)
Pent-3-yn-2-yl acetate (1) reacts with dimethyl(phenyl)silyl cuprate reagent to give a mixture of allenylsilane and propargylsilane.The corresponding N-phenylcarbamate (4) gives only the allenylsilane.Four other examples of this regioselective reaction are reported.The stereochemistry is largely syn.
