Chemistry Reference
In-Depth Information
H
(4-NO
2
C
6
H
4
)
2
CO
O
NO
R
R'NH
2
/CH
2
Cl
2
717
R
NN
R'
RNH
2
O
CH
2
Cl
2
, rt, 2 h
rt, 4 h
NO
2
HH
718
(44 -78 %)
719
(50 -96 %)
716
R = alkyl, cycloalkyl, aryl
R' = alkyl, cycloalkyl
The second step is considerably slower than the first and requires a longer reaction
time of ca. 4 h. By reacting 717 with an excess of amine (1:2 ratio), symmetrical
ureas are formed directly in high yield (50-95%).
General procedure. 4-Nitrophenyl N-alkylcarbamates [503]:
To a stirred solution of
bis(4-nitrophenyl) carbonate 717 (for a preparation of 717, see Section 4.3.3 ''Car-
bonates'') (3.04 g, 10 mmol) in dichloromethane (50 mL), a solution of the amine
(10 mmol) in dichloromethane (10 mL) was added dropwise. Following the ad-
dition, the mixture was allowed to stand for 2 h. The orange-yellow mixture was
then washed with 10% aq. NaHCO
3
(4
30 mL) and brine (30 mL). The solution
was dried with anhydrous MgSO
4
, filtered, and the solvent was evaporated under
reduced pressure. The crystalline residue was recrystallized from iPrOH, MeOH,
or Et
2
O.
o-(4-Nitrophenylene) carbonate, NPC
o-(4-Nitrophenylene) carbonate, NPC (5-nitrobenz-1,3-dioxol-2-one) 721, has been
reported as an activated ester of carbonic acid [504]. Addition of one equivalent of
aniline in benzene led to a single adduct in 78% yield following overnight stirring
at room temperature.
OH
OH
O
COCl
2
O
+
O
O
2
N
O
O
2
N
O
2
N
OH
O
u
720
721
722
O
Nu
O
O
2
N
OH
Nu = PhNH, Et
2
N,
cyclo
-C
6
H
11
NH
723
