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New Preparation of Isocyanides.

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Equimolar amounts of the components react in boiling tetrachloroethane within about 8 h. When the solvent is distilled off
there remains a paste-like residue which is extracted with boiling
benzene. The product then crystallizes and can be recrystallized
from nitromethane; yield ca. 50%.
Tabie. Chemical shifts S"P x
appear upfieId from H,PO,.)
X
(3)
c1
(3)
(3)
BPh,
c10,
(3)
(3)
SbF,
SbCI,
(2)
NHi
lo6of octaphenyltetraphosphorus
M.p. ("C)
339-340
(338-345 [21)
202-204
303-305
285-290
308-313
(2)
mcn,
(2)
N(CH3h
Experiments with formamides deuterated at the nitrogen showed that the proton OE the chloroform comes exclusively from
the N-H bond.
nitride oxide derivatives. (Positive values signify that the signals
PZ+P8
P4+P6
Sol L e n t
-25.7
-1i.5
CH,CI,
-25.4
-25.7
-25.0
-27.6
-11.6
-11.3
-10.4
-13.1
CH,CI,
CH2C12
CHINO,
C2H2C14
P'
-15.2
-19.5
77-83
171-175
130-136
bodiimides from urea[,], phosphorylates the formamide at the
oxygen. Chloroform is first liberated and then HCI.
-22.5
P'
-10.4
- 9.1
- 6.5
P8
P6
-1.0
+0.2
+o.z
i1.3
+2.0
CH,CI,
The NMR signals of (3) (Table) are assigned to the two halves
of the ring on the basis of the following comparison of the
31P shifts:
Y=
S
Y=R,P-N=R,P-Y@
Y =R,P-O-R,P=Y
-35.614]
-79.3[61
Ph3P + CC1,
New Preparation of Isocyyanides['l[* *I
Isocyanides can be obtained by elimination of water from monosubstituted formamides. According to Ugi and
phosphorus oxide trichloride has proved to be a most effective dehydrating agent for this reaction. It reacts rapidly in the presence
of pyridine or potassium tert-butoxide to give good yields in
some cases (25 to 95%).
In conjunction with our studies on the ternary system phosphane/CC14/ammonia derivatives we have now found that isocyanides (I) are formed very readily by the joint action of triphenylphosphane, CCI,, and triethylamine on monosubstituted
aliphatic and aromatic formamides:
(1)
General procedure:
Equimolar amounts of monosubstituted formamide, carbon tetrachloride, triethylamine, and triphenylphosphane (20 % excess) are dissolved in 1,2-dichloroethane, dichloromethane, or
chloroform (0.1 mole in 100 ml of solvent) and heated to 60°C
for 2.5 h. The solvent is distilled offat slightly reduced pressure
and the residue is extracted five times with light petroleum. The
residue left on removal of the light petroleum is then fractionated.
Received: December 9, 1970 [ Z 321 I€]
German version: Angew. Chem. 83.143 (1971)
[*] Prof. Dr. R. Appel, DipLChem. R.Kleinstuck.
and DipLChem. K.-D. Ziehn
Anorganisch-ChemischesInstitut der Universitat
53 Bonn, Meckenheimer Allee 168 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft.
[ I ] Studies on the joint action of phosphines and carbon tetrachloride
on ammonia derivatives, Part 3. - Part 2: ref. 131.
[2] I. Ugi and R. Meyr, Chem. Ber. 93,239 (1960).
[3] R. Appel, R. Kiejnstuck, and K. D. Zjehn, Chem Ber., in press.
[4] R. Appel, R. KkinsrJck, and K. D. Zjebn, Chem. Ber., in press.
Stereoelectronically Controlled Reductive Ring
Cleavage of cis-1,2-Divinylcyclobutanes
0 0
R-NPC: + Ph3PO + HCC13 + [(C,Hs),NH] C1
By Hansjorg Hey[*]
(1)
Use of a 20% excess of triphenylphosphane gives an approximately 90% yield of isocyanide.
I
Solvent
R
1
n-C4Hq
C,Hs
C6Hs-CH2
CH,C12
C IC H,CH2CI
HCCI,
I
B.p.("Cltorr)
119/760
54112
90-92110
1 1
Reduction of cis-1,2-divinylcyclobutane(I a ) [ ' ] , which is readily
accessible via acatalytic reaction, with alkali metals in liquid am-
(%I
Light petroleum
(bp.,"C)
90
91
89
35-50
60-95
60-95
Yield
The elimination of water proceeds stepwise. A n adduct is formed initially from the phosphane and CCI, which, as in the corand carresponding synthesis of nitriles from carboxa~nides[~]
132
OCH-NH-R
P
[Ph,P-O-CH=NR]
0
CIO + HCC1,
By Rolf Appel, Roland Meinstuck, and Klaus-Dieter Ziehnp]
(b)
(c)
[Ph,PC1]CCl3
N%
-12.7i5] -11.5 (3),P4+P6
-33.1[71 -25.7 (3), P2+Ps
Received: October 26,1970 [Z 3llaIEl
German version: Angew. Chem. 83,142 (1971)
(a)
-
0
In the case of (2) the assignment is based on the expectedly
relatively low shielding of the amino-substituted Pz atom, which
decreases further on methylation, and its competition with the
shielding of P4, which is characteristic for PNP systems[4].
(1)
CH,CI2
CH,CI,
monia results in ring cleavage to give cis,trans-2,6-octadiene
(2a)in 69% yield. The trans,transisomer is formed in only 5.7%
yield and the cis,cis isomer in 4.6% yieid.
Angew. Chem. internat. Edit. i Vol. 10 (1971) i No. 2
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