209. Synthesis of (-)-Erythrodiene and (+)-7-Epispirojatamol via Intramolecular Pd-Catalyzed Allylzincation
     Oppolzer, W.; Flachsmann, F.
     Helv. Chim. Acta 2001, 84, 416-430

Two spirobicyclic sesquiterpenoids, (−)-erythrodiene (1) and (+)-7-epispirojatamol (30), were synthesized in enantiomerically pure form viaan intramolecular allylzincation process. The allylzinc species were formed in the presence of Et₂Zn via transmetallation of a catalytically generated allylpalladium intermediate. Several Pd catalysts were tested for this transformation, and [Pd(OAc)₂]/Bu₃P (1?equiv.) was found to be, by far, the most effective. Whereas the preparation of 1 involved allylzincation of a tethered terminal olefin, 30 was formed via a novel intramolecular allyl zincation of a methyl ketone. Both reactions showed the same stereochemical preference, yielding the spirobicyclic products in 95 : 5 and 4 : 1 diastereoisomer ratios, respectively.

DOI : 10.1002/1522-2675(20010228)84:2<416::AID-HLCA416>3.0.CO;2-K 

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