Abstract
A one-pot synthesis of several silyl bicyclic and oxatricyclic
alkenes by inter- and intramolecular Diels-Alder reactions
of 4-trimethylsilyl substituted masked o-benzoquinones
derived from the corresponding 2-methoxyphenols is described.
Key words
2-methoxyphenols - 4-silyl masked o-benzoquinones - Diels-Alder reaction - silyl bicyclo[2.2.2]octenes - silyl oxatricyclo[4.3.1.0]decenes
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General procedure
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[1]
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NMR (100 MHz), DEPT, and low and high resolution MS analyses.
12
General procedure
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a stirred mixture of a 2-methoxyphenol (2a-c, 0.5 mmol) and an alkenol (7-10,
25 mmol, 50 equiv) at 0 °C, was added DAIB (0.55 mmol,
1.1 equiv) at once and the contents were stirred for 30 min at the
same temperature [oxidations of 2-methoxyphenols in the
presence of cinnamyl alcohol (9) were carried
out at room temperature (entries 3, 7 and 11 in Table
[2]
)]. The reaction
was quenched with aq NaHCO3, extracted with ether. The
organic layer was washed with brine, dried over anhyd. MgSO4,
and concentrated. The crude residue that contains mainly MOB (11a-c to 14a-c) and excess alkenol (7-10) was heated at 80 °C for 10
h. The reaction mixture was then cooled to room temperature, the
excess alkenol was removed under reduced pressure and the residue
was subjected to silica gel column chromatography to obtain the
pure adduct (15a-c to 18a-c).
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National
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2001.
15 CCDC No.: 182122.
