Chemistry Reference
In-Depth Information
Tab. 4.35.
Synthesis of various N,N
0
-dialkylureas 1108 [794].
Alkyl group, R
N,N
-dialkylureas
Yield (%)
O
Selectivity
(%)
PhCH
2
95
97
C
6
H
11
85
95
C
8
H
17
82
93
C
9
H
19
80
94
C
10
H
21
85
95
(R)-Ph(CH
3
)CH
75
97
PhCH
2
CH
2
78
93
65
96
H
70
97
Me
Me
Me
H
Me
precipitated by adding distilled water (150 mL). The product was isolated by Buch-
ner filtration and recrystallized from methanol.
4.3.5
Reactions with Binucleophiles
Phosgene and several of its equivalents react with 1,2-binucleophiles 1109 forming
2-oxo-five-membered heterocycles. Oxazolidin-2-ones (1110,Nu
1
NH, Nu
2
¼
¼
O),
thiazolidin-2-ones (1110,Nu
1
NH, Nu
2
S), imidazolidin-2-ones (1110,Nu
1
,
¼
¼
Nu
2
NH), and 1H-benzo[d][1,3]oxazine-2,4-diones (1110,Nu
1
COO, Nu
2
¼
¼
¼
NH) are the most important classes of reaction products.
R
1
Nu
1
H
"CO"
Source
R
1
Nu
1
O
Nu
2
R
2
Nu
2
H
R
2
1109
1110
Nu
1
= O, S, NH, COO
Nu
2
= O, S, NH
Several synthetic methods were presented in Sections 4.3.2, 4.3.3, and 4.3.4, in
which five-membered cyclic carbamates (oxazolidin-2-ones), cyclic carbonates (1,3-
dioxolan-2-ones), and cyclic ureas (imidazolidin-2-ones), respectively, were con-
structed. General reviews of the synthesis and chemistry of 2-oxazolidinones and
thiazolidin-2-ones [363, 364], reporting the reactions of N,O- and N,S-1,2-binu-
cleophilic substrates with various carbonylating agents, are available.
When the substrates 1109 are a-amino acids (1,1-binucleophiles having
Nu
1
H
COOH and Nu
2
¼
¼
NH), a special class of mixed anhydrides, 2,5-dioxo-
