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N-Imidoyl Isocyanides.

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Owing to the greater anisotropism of the g tensor, the
ESR signals of thioketyls are broader than those of the ketyls.
Coupling of the methyl protons of (1 a ) is therefore not
resolved under the given conditions. Assignment of the satellite
signals is based upon intensities and comparison with the
spectrum of the thioketyl having a natural isotopic abundance.
Only thecomponents with mI= fz/' are visible in the quadruplet due to 33Scoupling.
A positive sign is deduced for a& from variations in line
Our studies on
width in the thiocarbonyl I3C
(1 b ) yielded a sulfur coupling constant of as% +0.2mT[11;
by analogy we assume ( 1 a ) to have us>O.
Comparison of the coupling constants a& and
in
(1 a ) with those in ( 2 ) and in some substituted di-tert-butylmethyl radicals[61shows that the spin population at the thiocarbonyl C atom p; is about 0.8 to 0.9. Hence di-fert-butyl
thioketyl resembles an alkyl radical more closely than a thiyl
radical. This result confirms an INDO calculation by Ohno
et a/.[']. The measured coupling constants can be reproduced
by known or plausible 0-7t parameters[']. There is accordingly no need to postulate a pyramidal configuration for ( I ),
even
as assumed for ketyls[8"l and the tert-butyl
though this possibility cannot be entirely ruled out.
Received: July 4, 1977 [ Z 790b IE]
German version: Angew. Chern. 89, 744 (1977)
CAS Registry number:
( I a ) , 63588-77-2
Planned Dissertation by C . P . Klages, Universitit Hamburg. The pertluori has already been reported by G . A.
inated species [CF3-CS-CF,]
Russell, J . L. Grrlock, G . R . U n d e r ~ . o o dJ., Am. Chem. SOC. 94, 5209
(1 972).
C . - P . Klagra, J . h.>.s, Angew. Chem. 89, 743 (1977): Angew. Chem.
Int. Ed. Engl. 16. 725 (1977).
Generated with potassium in tetrahydrofuran: N . Hirora, S. I . Weissmun,
J . Am. Chem. SOC. X2, 4424 (1960).
Generated with potassium-sodium alloy in dimethoxyethane: G. A . Russell, G . R. Underwood, J . Phys. Chem. 72, 1074 (1968).
N . M. Atkertont Electron Spin Resonance. Wiley, New York 1973, pp.
339ff.
D. Griller. K . U . Ingold, J. Am. Chem. Soc. 96, 6715 (1974).
A . Ohno, K . Nakamura, M. Uohama. S. Oka, T Yamahe, S. Nagata,
Bull. Chem. SOC. Jpn. 48, 3718 (1975).
a) G. R. Ufwlrrwood, Mol. Phys. 22, 729 (1971); b) J . B. Lish, L. F .
Williams, 0. E . Wood, J . Am. Chem. Soc. 98, 227 (1976): P . J . Krusrc,
P . Mrukin, ihid. 98, 228 (1976); however, see also: 7: A. Claxton, E.
Plarr, M . C . R . Symons, Mol. Phys. 32, 1321 (1976): and references
cited therein.
[I]
[2]
[3]
[4]
[5]
[6]
[7]
[S]
The structures of the compounds are confirmed by their IR
spectra, which show an intense isocyanide absorption at 21 10
and2100cm-'andaC+Nabsorptionat
1632 and 1660cm-',
respectively. In the "C-NMR spectrumf2]of ( 2 a ) a signal
for the isocyanide group is observed in the expected range
at 6 = 169.3.
131
Compared to the N-acyl isocyanides, the N-imidoyl isocyanides are distinctly more stable in dilute solution; thus
( 2 ~ is) transformed into the thermodynamically more stable
imidoyl cyanide (3) only in the course of days, ( 2 b ) in several
hours. However, if the solutions are concentrated at room
temperature or reaction of the imidobromide is carried out
in boiling chloroform formation of the imidoyl cyanides (3)
Isolation of an N-imidoyl isocyanide in pure form has so
far been realized only in the case of the diphenyl derivative
( 2 a ) , which is obtained in 85 % yield in the form of yellow
crystals on low-temperature crystallization from petroleum
ether. It melts at 60°C and has a weak aromatic isonitrile
odor. It can be stored at room temperature for a few days,
and at - 20°C indefinitely. O n melting it decomposes, giving
mainly (3 a). Hydrolysis with dilute HCI leads to benzanilide
in good yields, and reaction with methanol affords mainly
N-phenylbenzimino esters.
According to mass spectral data the expected trimerization of
( 2 ) , in analogy to the N-acyl isocyanides, does not take place,
even under the most varied conditions. In contrast, in the
thermal transformation of ( 2 a ) into ( 3 a ) varying amounts
(10 to 30 %) of a by-product are observed which could be
identified by an authentic synthesis as 2,2'-diphenyl-4,4-bisquinazoline ( 5 a ) . We interpret its formation in terms of an
initial head-to-head dimerization of ( 2 a ) to give the heterocumulene ( 4 a), which by double electrocyclic ring closure and
subsequent oxidation can elude trimerizati~n[~I.
Attempts to
transform P-styryl isocyanides into 2,2'-bisisoquinolines in the
same way have so far failed.
N-Imidoyl Isocyanides [**I
By Gerhard Hope and Bernd Lungel*]
Successful preparation of the first N-acyl isocyanides from
carboxylic acid iodides and silver cyanide[ raised the question
whether structurally related isocyanides could be prepared
according to the same principle.
We have found that the N-phenylimidoyl bromides (1 a )
and ( 1 b ) undergo rapid reaction with silver cyanide in CHCl3
to give the imidoyl isocyanides ( 2 a ) and ( 2 b ) , respectively.
-.
~
[*] Priv.-Doz. Dr. G Hone, Dip].-Chem. B. Lange
lnstitut fur Organische Chemie der Tecbnischen Universitit
Strasse des 17. Juni 135. D-1000 Berlin 12 (Germany)
[**] Reactions of Organic Halogen Compounds with Silver Cyanide, Part
4. This work was supported by the Deutsche Forschungsgemeinschaft.Part
3 : [I].
AngeK Chem. Int. Ed Enyl. 16 (1977) No. 10
Experimental
Synthesis of ( 2 a ) : 1.34 g (5.15 mmol) N-phenylbenzimidoyl
bromide is added to a solution of AgC"'] (1.7 g, 12.7mmol)
in anhydrous CHzCIz (20ml). After 10 minutes' stirring at
20°C the silver salt is filtered off and the filtrate evaporated
down at 0"C/0. 1 torr. The orange-red residue is extracted several times with petroleum ether. O n cooling the concentrated
petroleum extract from 0°C to ca. -60"C, 0.90g (85 %) ( 2 a )
crystallized out, m.p. 60°C.
Synthesis of ( 5 a ) : A solution of AgCN (1.34g, 10mmol)
and N-phenylbenzimidoyl bromide (1.04 g, 4.0 mmol) in anhydrous benzene (25 ml) is heated under reflux for 4 h. The silver
salts are separated by filtration and washed several times with
hot benzene. The combined filtrates are concentrated and
727
then treated with petroleum ether. This affords 0.26g (32 %)
( 5 a ) , m.p. 293-294°C. 0.31 g (38%) ( 3 a ) can be obtained
from the petroleum ether solution by distillation.
Received: July 4. 1977 [Z 789 IE]
German version: Angew. Chem. 89, 742 (1977)
CAS Registry numbers:
( 1 u), 40168-06-7; (1 b ) , 63588-82-9; ( 2 a ) . 63588-83-0; (Zb), 63588-84-1;
( 3 a ) , 4686-14-0; ( 5 a), 60538-88-7; AgCN, 506-64-9
G. Hojle, B. Lunge. Angew. Chem. 89, 272 (1977); Angew. Chem. Int.
Ed. Engl. 16, 262 (1977).
Bruker W H 270 at 67.88 MHz in CDCI, at 30°C; 13C enrichment in
theisocyanidegroup90%,; halfwidthofsignal l 0 H z a t 6 = 169.3. Oncooling, a coalescence of this signal a t ca. - 10°C is followed at - 50°C by its
replacement by two new signals of comparable intensity at 6=146.3
and 157.2, which can be assigned t o the E- and Z-isomers. Unusual,
however, is that both signals are shifted t o higher field. The possibility
that we observed the dimer ( 4 a ) , likely to be present in the equilibrium,
is ruled out by the low-temperature IR spectrum.
This thermolability casts doubt upon the isolation [4] of N-alkylformimidoyl isocyanides in admixture with the corresponding cyanides. The IR
and "C-NMR data [4] (2120 cm-' and Sac= 157.7, resp.) suggest that
these compounds are actually alkyl isocyanides originating from basecatalyzed H C N elimination from the N-alkylformimidoyl cyanides.
J . H . Boyer, J . Kooi, J. Chem. SOC.Perkin I. 1975, 1743; J . H. Boyer,
J . Dunn, J . Kooi, J . Am. Chem. SOC.98, 1099 (1976).
A cyanide-catalyzed dimerization of ( 2 a ) by way of a 2-phenylquinazoline can be ruled out since added 2-(m-tolyl)quinazoline i s neither
consumed nor incorporated in ( Z a ) .
[l]
[2]
[3]
[4]
[S]
N-Acyl-N-arylsulfonyldiazenes ; Detection and Use in
the Synthesis of Amides
By Hansjurgen Golz, Bernd Glatz, Georges Haas, Gunter
Helmchen, and Hans Muxfeldt (deceased)[*]
While N,N'-diacyldiazenes are in many cases stable and
readily accessible, to our knowledge the N,N'-disulfonyl- and
N-acyl-N'-sulfonyldiazenes (excepting azobissulfates) have so
far not been reported'']. Owing to the pronounced nucleofugal
character of the sulfonylazo group['] these compounds ought
to represent an interesting new class of acylating agents.
We have now been able to demonstrate the existence of
a compound of type ( 2 ) , uiz. N-benzoyl-N'-tosyldiazene ( 2 a )
(cf. Scheme 1 and Table 1). Oxidation of the hydrazide ( I a )
with lead tetraacetate in the presence of cyclopentadiene at
-78°C leads to formation of the cycloadduct (3)[31in 33 %
yield, and on addition of boron trifluoride ether in 53%
yieldr41(cf. experimental procedure). In order to estimate the
lifetime of ( 2 a ) the temperature and the interval of time
between completion of oxidation and addition of cyclopentadiene were varied. Oxidation at - 50°C and addition of cyclopentadiene after 30 minutes leads to 40 % (3), whereas oxidation at -30°C and addition of cyclopentadiene after 10
minutes leads to only traces of (3). Consequently, at temperatures below ca. -50°C ( 2 a ) is sufficiently stable for its isolation.
Table 1. Carboxamides ( 4 ) and sulfinamides ( 6 ) prepared (see experimental)
from hydrazides ( I ) and benzylamine (R3=CH2C6H5)by oxidation with
lead tetraacetate.
Reactant
R'
R'
T
["CI
Products
yield [ %]
-60
( 4 a ) >98
25
-60
25
-80
(4a)
-50
25
-60
25
(4b)
(46)
(4c)
(412)
(4c)
(4c)
(4c)
75
77
51
>98
89
28
92
9
-
5
(6a)
(6b) 2
(66) 12
~
(6b) 9
( 6 6 ) 42
(6c) 5
( 6 c ) 76
N-Acyl-N'-arylsulfonyldiazenes (2) can acylate amines.
Thus, oxidation of the hydrazides ( I a)-( 1 e ) with lead tetraacetate in the presence of benzylamine below -60°C leads
to the carboxamides (4)15] in good yields, together with small
amounts of the sulfinamides (6) (cf. Table 1 and experimental
procedure). The amount of ( 6 ) can reach significant proportions if the reaction is carried out at room temperature. It
follows from our present studies and from numerous other
data[61that the ratio ( 6 ) / ( 4 ) increases with increasing temperature and increasing bulkiness of R' and R2.Electronic effects
have comparatively little influence in this respectL6?
The results can be interpreted in terms of Scheme 1. The
diazenes ( 2 ) stable at -60°C react cleanly with amines to
give carboxamides; however, at higher temperatures competing elimination of nitrogen leads to the mixed anhydrides
( 5 ) . These are preferentially attacked at the sulfur atom by
arnines1'1. This is confirmed by predominant formation of
the sulfinamide ( 6 e ) from ( I e ) at room temperature; in
this instance the situation is especially sterically unfavorable
for attack at the sulfur atom.
Experimental
[**I
2-Benzoyl-3-tos~l-2,3-diaza-S-norbornene
(3): A solution of
lead tetraacetate (4.0 mmol) in dichloromethane (25 ml) is
added dropwise during I h at -78°C to a solution of ( 1 a )
(880mg, 3.03 mmol),cyclopentadiene(30.3mmol), and boron trifluorideether(1.54mmol)in THF/acetonitrile (1/1)(SO ml). After
a further 4 h at -78°C the solution is allowed to warm over
a period of ca. 20 h to room temperature. The crude product
obtained after treatment with ether, extraction with sodium
hydrogen carbonate solution, drying (sodium sulfate) and
removal of organic phase by evaporation is chromatographed
on 300g silica gel (chloroform/acetone 95/5, 15 ml fractions).
Fractions 64 to 80 yielded 564mg (53 %) ( 3 ) , colorless crystals,
m. p. 148-1 49 "C, after recrystallization from ethyl acetate/
hexane.
Carboxamides ( 4 ) : A solution of lead tetraacetate (1 mmol)
in dichloromethane (10ml) is added dropwise during 20min
to a solution of hydrazide ( I ) (1 mmol) and benzylamine
(Smmol) in T H F (for temperature see Table 1). After 2 h
728
Angew. Chem. Jnt. Ed. Engl. 16 (1977) N o . 10
[*] Dr. H. Golz, Dr. B. Glatz, Dr. G. Helmchen ['I, Prof. Dr. H. Muxfeldt
['I
(deceased)
Institut fur Organische Chemie, Biochemie und lsotopenforschung der
Universitat
Pfaffenwaldring 55, D-7000 Stuttgart 80 (Germany)
Dr. G. Haas ["'I
Ciba-Geigy AG
CH-4000 Basel (Switzerland)
Author to whom correspondence should be addressed
Formerly at Cornell University, Ithaca, N. Y.
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