Chemistry Reference
In-Depth Information
Typical procedure. 2-Iodo-4-nitrobenzonitrile 1469 [1116]:
A mixture of the carbox-
amide 1468 (5.5 g, 18.8 mmol) and thionyl chloride (35 mL) was refluxed for 3 h
under argon and then concentrated under reduced pressure. The residue was pu-
rified by flash chromatography (20% EtOAc in hexane) to give 4.12 g (80%) of 2-
iodo-4-nitrobenzonitrile 1469 as cream-colored crystals; mp 154-155.5
C (EtOAc/
hexane, 1:4).
4-Ethynyl-4H-pyran-3,5-dicarbonitrile 1472 has been prepared in 95% yield from
the dicarbaldoxime 1471 by dehydration with thionyl chloride [1117].
SOCl
2
HON=HC
CH=NOH
NC
CN
0°C, 1 h
O
O
95 %
1472
1471
Typical procedure. 4-Ethynyl-4H-pyran-3,5-dicarbonitrile 1472 [1117]:
Dicarbaldoxime
1471 (0.38 g, 2 mmol) was reacted under stirring with thionyl chloride (excess) at
0
C for 1 h. After evaporating the excess thionyl chloride in vacuo, the residue
was sublimed at 80
C/1 Torr to give 0.30 g (95%) of 1472 as colorless needles; mp
91
C.
The solvent-free thionyl chloride method has also been applied in the synthesis
of o-azidobenzonitriles, which are employed in photoinduced ring-expansions to
form 3-cyano- and 7-cyano-3H-azepin-2(1H)-ones [1118].
p-Toluenesulfonyl chloride (tosyl chloride)
p-Tosyl chloride is used as a dehydration agent in preparing a cyano group from an
amide to form the dienophile in a Diels-Alder reaction forming cyano norborna-
dienes, which can be reversibly converted into quadrocyclanes, affording a cycle in
solar-energy storage [1119].
Ph
Ph
TsCl
CN
Ph
CONH
2
CN
hv
Ph
Ph
cat.
Ph
reflux
2.5 h
CO
2
Et
CO
2
Et
CO
2
Et
- E(therm.)
88 %
1475
1473
1474
Typical procedure. 1,4-Dimethyl-5,6-diphenyl-3-propionylbicyclo[2.2.1]hepta-2,5-diene-2-
carbonitrile 1474 [1119]:
A solution of the amide 1473 (104.8 mg, 0.28 mmol) and
p-tosyl chloride (119.8 mg, 0.63 mmol) in absolute pyridine (2 mL) was refluxed for
2.5 h. The mixture was then poured onto ice, acidified with 10% aq. HCl, and ex-
tracted with diethyl ether. The combined extracts were washed with 10% HCl and
brine, dried, and concentrated to dryness. Chromatography on silica gel eluting
