Chemistry Reference
In-Depth Information
Finally, indole ring formation is via condensation of the amino and keto functions. This is analogous to
imine formation, as seen in part (a), but dehydration produces the aromatic pyrrole ring rather than an imine.
Alternatively, one could write imine formation followed by tautomerism to the aromatic enamine.
H
CO
2
Et
− H
+
, + H
+
− H
2
O
CO
2
Et
CO
2
Et
OH
CO
2
Et
O
H
2
O
H
H
NH
2
Problem 16.24 (level 2; chapters 11 and 7)
(a) Treatment of 2-methylpyridine with benzaldehyde under basic conditions gives the compound stilbazole.
Give a mechanism for the reaction and predict the product formed when 2,3-dimethylpyridine is reacted with
benzaldehyde under the same conditions.
PhCHO
NaOMe
MeOH
N
N
CH
3
stilbazole
(b) What product would you expect to obtain if 2-chloropyridine was treated with sodium methoxide in methanol?
What product would be obtained upon similar treatment of 3,4-dichoropyridine?
(c) Give mechanisms to account for the following two reactions:
CO
2
Et
CO
2
Et
PhL
i
EtBr
CH
3
CH
3
CO
2
Et
N
N
N
NaOEt
EtOH
N
CO
2
Et
CH
3
(d) Treating indole with the unsaturated ketone shown (mesityl oxide) under acid conditions gives a carbazole
derivative. Formulate a rational mechanism for the transformation, which proceeds through an indolenium
cation intermediate (not isolated).
CH
3
O
CH
3
CH
3
H
3
C
H
3
C
H
3
C
CH
3
O
O
H
+
H
3
C
EtOH/H
2
O
N
N
N
Me
Me
Me
not isolated
