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Representative
Procedure for the Synthesis of
N
-Alkylureas; 1-Phenethylurea (2f)
A
stirred solution of 2-phenethylamine (2.3 mL, 18 mmol) in 1 N HCl
(18 mL) and H2O (9 mL) was treated with KOCN (7.3 g,
90 mmol) and then the mixture was irradiated to 80 ˚C for
1 h in a sealed tube (CEM designed 10-mL pressure-rated reaction
vial) in a self-tuning single mode CEM Discover Focused synthesizer.
The mixture was chilled rapidly to r.t., by passing compressed
air through the microwave cavity for 3 min. After the cooling to
r.t., the precipitate formed was filtered, and washed with hexane
and Et2O. The crude urea was dissolved in MeOH, the residue was
filtered off. The desired 1-phenethylurea (2f)
was isolated, by evaporating the solvent under reduced pressure, in
a pure form and in high yield (2.3 g, 73%) as a crystalline white
solid; mp 114-115 ˚C [lit.¹6 115 ˚C]. ¹H
NMR (300 MHz, CDCl3): δ = 2.64 (q, J = 6.6 Hz, 2 H), 3.17 (q, J = 6.4 Hz, 2 H), 5.43 (br s,
2 H), 5.94 (br s, 1 H), 7.23 (m, 5 H).
¹³C
NMR (75 MHz, DMSO): δ = 36.2, 40.8, 125.9, 128.3, 128.6,
139.8, 158.1. MS: m/z = 164 [M+].
Anal. Calcd for C9H12N2O: C, 65.83;
H, 7.37; N, 17.06. Found: C, 65.78; H, 7.32; N, 16.98.
Representative Procedure for the Synthesis of
N
-Aryl-ureas;
1-
o
-Tolylurea
(2k): A stirred solution of o-toluidine (1.9
mL, 18 mmol) and AcOH (1.7 mL, 30 mmol) in H2O (27 mL)
was treated with KOCN (7.3 g, 90 mmol) and then was irradiated to
80 ˚C for 1 h in a sealed tube (CEM designed 10-mL pressure-rated
reaction vial) in a self-tuning single mode CEM Discover Focused
synthesizer. The mixture was chilled rapidly to r.t., by passing
compressed air through the microwave cavity for 3 min. After the
cooling to r.t., the precipitate formed was filtered, and washed
with hexane and Et2O. The crude urea was dissolved in
MeOH, and the residue was filtered off. The desired 1-o-tolylurea (2k)
was isolated by evaporating the solvent under reduced pressure in
a pure form and in high yield (2.4 g, 88%) as a white solid; mp
186-188 ˚C (lit.¹7 191 ˚C). ¹H
NMR (300 MHz, DMSO): δ = 2.18 (s, 3 H), 6.03 (br
s, 2 H), 6.86 (m, 1 H), 7.09 (m, 2 H), 7.72 (br s, 1 H), 7.77 (d, J = 8.1 Hz, 1 H). ¹³C
NMR (75 MHz, DMSO): δ = 17.4, 120.4, 121.5, 125.5,
126.6, 129.5, 137.7, 155.7. MS: m/z = 150 [M+].
Anal. Calcd for C8H10N2O: C, 63.98;
H, 6.71; N, 18.65. Found: C, 63.76; H, 6.65; N, 18.66.
Representative Procedure for the Synthesis of
N
-Carbamoyl
l
-Amino
Acids;
N
-Carbamoyl-
l
-phenyl-alanine
(2q): A stirred solution of l-phenylalanine
(3.0 g, 18 mmol) in H2O (27 mL) was treated with KOCN
(7.3 g, 90 mmol) and then was irradiated to 80 ˚C for 1
h in a sealed tube (CEM designed 10-mL pressure-rated reaction vial)
in a self-tuning single mode CEM Discover Focused synthesizer. The
mixture was chilled rapidly to r.t., by passing compressed air through
the microwave cavity for 3 min. After the cooling to r.t., the mixture
was acidified to pH 2 with 6 N HCl. The obtained solid was filtered
and washed with cold H2O (3 × 5 mL) and dried
under vacuum to yield the N-carbamoyl-l-phenyl alanine (2q)
in a pure form and in high yield (3.4 g, 90%) as a white
solid; mp 192-194 ˚C (lit.¹8 191-192 ˚C); [α]²0
D +38.7
(c = 1, MeOH).¹8 ¹H
NMR (300 MHz, DMSO): δ = 2.90 (m, 2 H), 4.32 (m,
1 H), 5.62 (br s, 2 H), 6.16 (br d, J = 8.4
Hz, 1 Η), 7.22 (m, 5 H).¹8 ¹³C NMR
(75 MHz, DMSO): δ = 37.6, 53.7, 126.3, 128.2,
129.2, 137.5, 158.1, 173.9.¹8 MS: m/z = 208 [M+].¹8 Anal.
Calcd for C10H12N2O3:
C, 57.68; H, 5.81; N, 13.45. Found: C, 57.71; H, 5.79; N, 13.44.
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McGee JJ.
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1963,
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2123