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Chapter 11 405
Copyright © 2017 Pearson Education, Inc.
A
cannot be
directly
synthesized by a Heck reaction. A Heck reaction couples a vinylic halide and an
alkene, so the product contains at least two double bonds. However,
A
can be made by a Heck reaction
followed by reduction of the double bonds.
Pd/C H
2
+
Br
PdL
2
(CH
3
CH
2
)
3
N
b.
The starting materials for the synthesis of
A
are shown above. Those for the synthesis of
B
are shown
here.
Br
+
B
43.
2-pentene
CH
3
CH CHCH
2
CH
3
CH
A
=
3
CH
CH
B
=
3
CH
2
CH
A
=
a piece containing two carbons
B
=
a piece containing three carbons
The two pieces can be put together in four different ways.
A
¬
A
B
¬
B
A
¬
B
B
¬
A
Two of the four pieces (
A—B
and
B—A
) represent 2-pentene. Therefore, the maximum yield of 2-pentene
is 50%.
44.
Bombykol can be prepared using a Suzuki reaction. First make the organoboron compound. Draw the
vinylic bromide so that you can see what product will be obtained from the coupling reaction.
OH
(RO)
2
B
OH
OH
H B(OR)
2
Br
PdL
2
HO
−