Acidcatalyzedopeningofan

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Unformatted text preview: nylethanol
is
first
reacted
 with
p‐toluenesulfonyl
chloride
followed
by
reaction
with
potassium
acetate.
 Synthesis
of
Ethers
 (1)
Ethers
by
Intermolecular
Dehydration
of
Alcohol:

Primary
alcohols
can
dehydrate
to
 ethers.

This
reaction
occurs
at
lower
temperature
than
the
competing
dehydration
to
 an

alkene.

This
method
generally
does
not
work
with
secondary
or
tertiary
alcohols
 because
elimination
dominates.
 The
reaction
proceeds
by
an
SN2
mechanism:
 (2)
Williamson
Ether
Synthesis:
This
is
a
good
route
for
synthesis
of
unsymmetrical
ethers.
 The
alkyl
halide
(or
alkyl
sulfonate)
should
be
primary
to
avoid
an
E2
reaction.

 Substitution
is
favored
over
elimination
at
lower
temperatures.
 (3)
Synthesis
of
Ethers
by
Alkoxymercuration‐Demercuration:
An
alcohol
is
the
 nucleophile
(instead
of
the
water
nucleophile
used
in
the
analogous
reaction
to
form
 alcohols
from
alkenes).
 (4)
tert‐Butyl
Ethers
by
Alkylation
of
Alcohols:
Protecting
Groups:
This
method
is
used
to
 protect
primary
alcohols.

The
protecting
group
is
removed
using
dilute
acid.
 (5)
Silyl
Ether
Protecting
Groups:
Silyl
ethers
are
widely
used
protecting
groups
for
 alcohols.

The
tert‐butyl
dimethysilyl
(TBDMS)
ether
is
a
common
protecting
group.

The
 protecting
group
is
introduced
by
reaction
of
the
alcohol
with
the
appropriate
 chlorosilane

in
the
presence
of
an
aromatic
amine
base
such
as
imidazole
or
pyridine.


 The
silyl
ether
protecting
group
is
easily
removed
by
treatment
with
fluoride
ion
(e.g.
 from
tetrabutyl
ammonium
fluoride).
 In
Class
Problem:
 Outline
the
syn...
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This note was uploaded on 06/19/2009 for the course CHEM 2311 taught by Professor Tyson during the Fall '07 term at Georgia Institute of Technology.

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