Chemistry Reference
In-Depth Information
H
Trt-HN
Trt-HN
Pr
i
N=C=NPr
i
S
S
S
O
1685
O
N
HO
2
C
N
H
dioxane
H
2
O, 3:2
rt, 2 h
O
O
CO
2
-Bn
CO
2
K
CO
2
-Bn
67 %
1686
1687
penicillin V
1684
O
O
O
N
N
N
NH
R
R
R
+
O
Y
R´
H
O
O
O
1688
H
1691
N
NH
NH
NH
R´
Y
H
1690
DCC
1689
1693
1692
Y = NH, NR´´, O
1688:
carboxylic acid
1690:
alcohol
1691:
ester
amino acid
amine
amide
peptide acid
amino acid ester
peptide ester
peptide ester
Reviews on the synthesis and chemistry of carbodiimides are given in [1248-
1250]. Carbodiimides are mainly synthesized in one of three ways: from ureas or
thioureas, from isocyanates, or from isocyanides. Several reagents have been em-
ployed in carbodiimide synthesis: phosgene [1252, 1253], dimethylphosgenimi-
nium chloride [1254], triphosgene [561, 562], phosphorus pentoxide [1255], phos-
phoryl chloride [1256], triphenylphosphine dibromide [758, 1257-1261],
triphenylphosphine/tetrahalomethanes [1262, 1263], iminophosphoranes [1264-
1277], Mitsunobu reagent [1278, 1279], p-tosyl chloride [1280, 1281], and CDC
[1137]; oxidative additions have also been used [1282-1284].
4.5.3.1
Phosgene and Equivalents
Phosgene
In a new and e
cient synthesis of guanosine, 1-alkoxycarbonyl-3-arylmethylcarbo-
diimides serve as essential reagents. They can be synthesized in excellent yields
from thioureas using phosgene [1252]. 1-Ethoxycarbonyl-3-benzylcarbodiimide
1695 has been prepared quantitatively from the corresponding thiourea 1694
within 1 h at 80
C.
