1174917-10-2Relevant academic research and scientific papers
Synthesis of (S)-imperanene by using allylic substitution
Takashima, Yuji,Kobayashi, Yuichi
experimental part, 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.
