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2005
Multi-membered O,S-heterocycles
R 0691
Preparation of Methoxy-Substituted Optically Active 7-Alkoxycarbonylcyclohepand Their Acid-Promoted Rearrangements. — Four optically active cy33- 186 tatrienes
cloheptatriene derivatives like (II) are prepared by the pentanediol-tethered Buechner
reaction of (I), (V), and (VII) with a rhodium(II)-catalyst. This reaction proceeds not
only with high stereoselectivity but the tether also controls the regioselectivity in a good
to high degree. Only optically active compound (IIb) is stable to silica gel and its purification is performed without problems. The sensitivity of the products towards acids
results in isomerization through prototropic reaction or aromatization. Treatment of
isomerized product (III) with a Lewis acid causes a rearrangement via the norcaradiene
tautomer which is known for varied Buechner products, although most examples are
promoted by a Broensted acid. — (SUGIMURA*, T.; KAGAWA, M.; OHUCHI, N.;
HAGIYA, K.; OKUYAMA, T.; Bull. Chem. Soc. Jpn. 78 (2005) 4, 671-676; Dep.
Mater. Sci., Fac. Sci., Himeji Inst. Technol., Himeji, Hyogo 678-12, Japan; Eng.) —
H. Hoennerscheid
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