Chemistry Reference
In-Depth Information
Chlorosulfonyl isocyanate
Chlorosulfonyl isocyanate, Cl
O, is an effective dehydrating agent for
the preparation of various aryl- and alkyl-nitriles from the corresponding amides
and aldoximes in yields of 74-87% and 75-86%, respectively [1128].
x
SO
2
x
N
y
C
y
General procedure. Nitriles from aldoximes [1128]: To a magnetically stirred solution
of the aldoxime (10 mmol) and dry triethylamine (20 mmol) in dry dichloro-
methane (10 mL), a solution of chlorosulfonyl isocyanate (15 mmol) in dichloro-
methane (10 mL) is added at 0
C. The reaction mixture is stirred for 8 h at room
temperature and then poured into water (caution!). The dichloromethane layer is
separated and the aqueous layer is extracted with dichloromethane (3
25 mL).
The organic layers are combined, washed with water, and dried over anhydrous
sodium sulfate. Evaporation of the solvent gives the nitriles, which are purified by
distillation or recrystallization.
General procedure. Nitriles from amides [1128]:
The procedure used for the dehy-
dration of amides is the same as that described above, except that the reaction
mixture is refluxed for 1 h after stirring for 8 h at room temperature. It is then
cooled and worked-up as described above.
Methyl carboxysulfamoyl triethylammonium hydroxide inner salt (Burgess reagent)
The Burgess reagent 1488 can be viewed as an advancement of the chlorosulfonyl
isocyanate method (see above). It is tailored to provide the required selectivity and
reactivity for dehydration reactions. It can be widely applied as a dehydration agent
for a great variety of structures, including those with several additional functions,
to generate cyanides (e.g. 1489-1492) from amides in good yields of 82-92%
under mild conditions and with a rather simple work-up [1129]. Moreover, the
Burgess reagent is chlorine-free.
