Chemistry Reference
In-Depth Information
Polymer networks having glycerol ether cross-links joined by polyethylene oxide
(PEO) chains, with a urethane group in the middle of each one, have been pre-
pared [271].
Transformation of commercial PEO diamines into the corresponding diisocya-
nates 386 by reaction with stoichiometric amounts of triphosgene in refluxing
dichloromethane, both in the presence and absence of triethylamine, and the sub-
sequent condensation of these bifunctional oligomers with commercial PEO triols
resulted in the aforementioned novel polymeric structures.
CH
3
CH
3
CH
3
CH
3
(CCl
3
O)
2
CO
O
O
NH
2
O
O
NCO
OCN
O
H
2
N
O
a
c
a
b
c
b
Et
3
N, CH
2
Cl
2
,40°C
CH
3
CH
3
385
386
2-Methyl-allyl-isocyanate 388 was prepared from methallylamine 387 with tri-
phosgene [266].
CH
2
CH
2
(CCl
3
O)
2
CO
NH
2
NCO
H
3
C
H
3
C
Et
3
N, CH
2
Cl
2
, 1h
387
388
Carbon dioxide and dialkyl azodicarboxylate (Mitsunobu zwitterions) as
phosgene substitutes
Primary alkylamines give high yields of isocyanates when reacted with carbon di-
oxide (CO
2
) and the Mitsunobu zwitterions generated from dialkyl azodicarboxylates
and Bu
3
P or Ph
3
P at
78
C [196, 272]. The aliphatic isocyanates prepared in this
way are listed in Table 4.18.
2 RNH
2
+ CO
2
RNHCO
2
RNH
3
RNHCO
2
H + RNH
2
389
390
391
N
H
NCOOi-Pr
RNHCO
2
H
+
i-PrOOC
N N
PPh
3
COOi-Pr
R
NCO
i-PrOOC
+ Ph
3
PO
+
(DIADH
2
)
391
392
393
394
395
5
C,
anaerobic grade CO
2
was gently bubbled through a solution of the freshly distilled
amine in dichloromethane. More CO
2
was then vigorously bubbled through the
solution for 30-60 min. In a separate flask, a stirred, cold (
General procedure for the synthesis of aliphatic isocyanates [196]:
At
10 to
20
C) solution of
PPh
3
in dichloromethane was treated with diisopropyl azodicarboxylate (DIAD)or
