Chemistry Reference
In-Depth Information
CN
AcO
1511
Typical procedure. 3-Acetyloleanolic nitrile 1511 [1142]: 3-Acetyloleanolic amide (497
mg, 1.0 mmol), benzyl triethylammonium chloride (PTC; 250 mg), and 40% aq.
NaOH were refluxed under stirring in chloroform for 20 min. Work-up gave 471
mg (98.5%) of 3-acetyloleanolic nitrile 1511 as needles, mp 299-300
C (methanol),
[a]
19
D
46).
The above method has been investigated in more detail, e.g. with regard to the
influence of ultrasound on the reaction of benzamide to give benzonitrile. It was
shown that a combination of PTC and ultrasound could reduce the reaction time
by a factor of six compared to the reaction performed without ultrasound; yields
were about 80% [1143].
¼þ
83
:
40 (c
¼
0
:
Silver oxide (Ag
2
O) and iodoethane
Aryl carboxamides can be converted to the respective nitriles by treatment with
silver oxide (Ag
2
O) and iodoethane in benzene under non-acidic conditions in
good yields of 50-93% [1144].
General procedure. Nitriles from carboxamides [1144]:
A solution of the carboxamide
(5 mmol) in dry benzene (50 mL), containing silver oxide (1.8 g, 7.7 mmol) and
powdered 4
˚
molecular sieves (5.0 g) was stirred in the dark at 25
C for 12 h. Io-
doethane (0.86 g, 0.44 mL, 5.5 mmol) was then added, and the mixture was heated
to reflux under argon for 17 h. The cooled solution was then filtered (Celite) and
the filtrate was concentrated under reduced pressure. Purification was accom-
plished by chromatography on silica gel, eluting with hexane and ethyl acetate in
varying proportions.
Dibutyltin oxide
A versatile method for the conversion of aromatic and aliphatic primary amides to
nitriles, using dibutyltin oxide as a catalytic neutral dehydrating agent, has been
applied in various cases. The reaction temperature is about 110
C, the reaction
time is 12-18 h, and product yields are 70-95% [1145]. A reaction mechanism has
been proposed.
General procedure. Nitriles 1379 from amides 1377 [1145]:
A mixture of the amide
(2.0 mmol) and dibutyltin oxide (0.186 g, 0.373 mmol) was stirred in refluxing an-
hydrous toluene (5 mL) for a period of 12-18 h until the amide had been con-
sumed (TLC analysis). The mixture was then concentrated in vacuo and the resi-
due was purified by column chromatography (EtOAc/hexane, 1:9, v/v) to afford
