79594-11-9Relevant academic research and scientific papers
Synthesis of (S)-imperanene by using allylic substitution
Takashima, Yuji,Kobayashi, Yuichi
scheme or table, p. 5920 - 5926 (2009/12/26)
(Chemical Equation Presented) Synthesis of (S)-imperanene (1) was studied by using copper-assisted allylic substitution of ArCH=CHCH(L)CH2Ar (L: leaving group) and (i-PrO)Me2SiCH2MgCl. Preliminary substitution between PhCH=CHCH(L)Me (L = AcO, PivO, MeOCO2, (2-Py)CO2) and Bu copper reagents derived from BuMgX (X = Br, Cl) and CuBr·Me2S or CuCl in 1:1-40:1 ratios suggested acetate 28 as the best substrate. To prepare 28, kinetic resolution of racemic (E)-TMSCH=CHCH(OH)CH2Ar2 (Ar2 = (p-TBSO)(m-MeO)C6H3) carried out by using the asymmetric epoxidation with (-)-DIPT afforded the corresponding epoxy alcohol and (S)-allylic alcohol. After separation by chromatography, these products were converted to (S,E)-Bu3SnCH=CHCH(OH)CH2Ar2, which upon palladium-catalyzed coupling with Ar2-I followed by acetylation gave 28 (95-98% ee). Substitution of 28 with (i-PrO)Me 2SiCH2MgCl and CuBr·Me2S in a 4:1 ratio at 0°C proceeded cleanly to produce 29 with 100% inversion in 92% yield. Finally, Tamao oxidation furnished 1.
Alkylation of Allylic Derivatives. 11. Copper(I)-Catalyzed Cross Coupling of Allylic Carboxylates with Grignard Reagents
Tseng, Chung Chyi,Paisley, Steven D.,Goering, Harlan L.
, p. 2884 - 2891 (2007/10/02)
Reactions of allylic carboxylates with Grignard reagents containing catalytic amounts (1-10 mol percent) of cuprous salts give high yields of cross-coupled products.With alkyl Grignard reagents, regiochemistry can be controlled by choice of cuprous salt.With cuprous halides, little regiospecificity is observed.There is a small excess of γ-coupling in unbiased systems such as 5-methyl-2-cyclohexenyl (1), 2-cyclohexenyl (3), and β-phenylallyl (5) carboxylates.With CuCN, complete regiospecificity (exclusive γ-coupling) is observed with all alkyl Grignard reagents in unbiased systems, and with n-butylmagnesium halide >97percent γ-coupling results with α-methyl-γ-phenylallyl pivalate (7-OPiv) which is biased in favour of coupling at the α-position.In sharp contrast to alkyl Grignard reagents, phenyl and vinyl Grignard reagents containing CuCN show no regiospecificity.
Alkylation of Allylic Derivatives. 3. The Regiochemistry of Alkylation of the Isomeric trans-α,γ-Methylphenylallyl Acetates with Lithium Dialkyleuprates
Goering, Harlan N.,Seitz, Earl P.,Tseng, Chung Chyi
, p. 5304 - 5308 (2007/10/02)
Alkylation of the isomeric trans-α,γ-methylphenylallyl acetates (1-OAc and 2-OAc) with lithium dimethylcuprate or di-n-butylcuprate is regioselective but not regiospecific.Both isomers give essentially the same product mixture which contains 95percent of the trans conjugated alkylation product (3).The starting acetates do not rearrange under the conditions for these reactions.These results show that the isomeric acetate give the same product-forming intermediate(s).Presumably the key intermediate that is common to the two isomers is a ?-allyl copper(III).
