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Synthesis of (−)‐Erythrodiene and (+)‐7‐Epispirojatamol via Intramolecular Pd‐Catalyzed Allylzincation
Author(s) -
Oppolzer Wolfgang,
Flachsmann Felix
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010228)84:2<416::aid-hlca416>3.0.co;2-k
Subject(s) - chemistry , intramolecular force , transmetalation , olefin fiber , diastereomer , catalysis , methyl ketone , ketone , stereochemistry , medicinal chemistry , organic chemistry
Two spirobicyclic sesquiterpenoids, (−)‐erythrodiene ( 1 ) and (+)‐7‐epispirojatamol ( 30 ), were synthesized in enantiomerically pure form via an intramolecular allylzincation process. The allylzinc species were formed in the presence of Et 2 Zn via transmetallation of a catalytically generated allylpalladium intermediate. Several Pd catalysts were tested for this transformation, and [Pd(OAc) 2 ]/Bu 3 P (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.