- Stereospecific Hydrogenolysis of Lactones: Application to the Total Syntheses of (R)-ar-Himachalene and (R)-Curcumene
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A straightforward strategy for the syntheses of curcumene and ar-himachalene is reported. Synthetic highlights include a catalytic and asymmetric vinylogous Mukaiyama reaction and a stereospecific hydrogenolysis of a tertiary benzylic center using Pd/C or Ni/Raney catalysts. Notably, using Ni/Raney, the stereoselectivity outcome (inversion vs retention) of the hydrogenolysis depends on the tertiary benzylic alcohol substitution.
- Spielmann, Kim,De Figueiredo, Renata Marcia,Campagne, Jean-Marc
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- Synthesis of (R)-curcumene and (R)-xanthorrizol based on 1,2-aryl migration via phenonium ion
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Solvolysis reaction of methyl (4S,5S)-4-(4′-methoxyphenyl)-5- tosyloxy-2(E)-hexenoate 5 in water-saturated MeNO2 gave the 1,2-migration product, (4S,5S)-5-hydroxy-4-(4′-methoxyphenyl)-2-(E)- hexenoate 6 (55% yield), which was converted to methyl (R)-(4′- methylphenyl)hexanoate 11 in 25% overall yield (5 steps). Treatment of (R)-11 with MeLi gave tertiary alcohol congener 12, which was subjected to dehydration to afford (R)-(-)-curcumene 1. An introduction of hydroxyl group at meta-position of the aromatic ring in (R)-11 was achieved based on consecutive treatment [1) selective iodination, 2) conversion of aryl iodide to aryl boronate, 3) conversion of aryl boronate to phenol]. Thus obtained phenol (R)-16 was treated with MeLi to give tertiary alcohol congener 17, which was subjected to dehydration to afford (R)-(-)-xanthorrizol 2.
- Ehara, Takeru,Tanikawa, Shin,Ono, Machiko,Akita, Hiroyuki
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p. 1361 - 1364
(2008/03/11)
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