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Isolation and Photoisomerization of Simply Substituted Nitrile Oxides.

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191 Further details of the crystal structure investigation are available on request from the Fachinformationszentrum Energie, Physik, Mathematik
GmhH. D-75 14 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-52 153, the names of the authors, and the journal
citation.
[lo] H. H. Karsch, Chem. Ber. 110 (1977) 2213.
[ I I] Typical procedures for 4 and 8 : 1.48 g (4.25 mmol) of 1 and 0.97 g
(1.29 mL, 12.76 mmol) of PMe3 were dissolved in 7 0 m L of THF
(-78°C); the solution was then treated, via a buret, first with 286 m L
(12.76 mmol) of ethene, and then with 286 m L (12.76 mmol) of CO1.
With careful equalization of built-up pressure, the solution was slowly
warmed (6 h) to room temperature, whereupon a dark brown precipitate
separated out. This was filtered off and dried. Yield: 1.12 g; IR (KBr): V
[cm ‘I= 1580 (C=O). The dried solid was treated at -30°C with 4 m L
of 6 N methanolic HCI. After 24 hours’ stirring the solution was neutralized with NaHCO,. The volatile components were distilled off under
vacuum (2 x
bar). According to a G C analysis the distillate contained 0.93 mg ( 6 . 3 6 ~lo-’ mmol, 0.15%) of 4 and 370.84mg
(2 54 mmol, 59.76%) of 8 . The products were identified by comparison
of the M S spectra obtained after combined GC-MS with literature data
and quantitatively determined by calculation from the G C curves taking
into consideration the response factors referred to isopentyl acetate a s
internal standard. The reactions of 1 in the presence of the ligands
DMPE and DCPE in the molecular ratios given in Table 1 were carried
out analogously.
[I21 H. Hoberg, B. Apotecher, J . Organornet. Chem. 270 (1984) CIS.
1131 Ring contractions have also been observed on platinacyclopentane complexes (cf. G. €3. Young, G. M. Whitesides, J . Am. Chem. Soc. 100 (1978)
5808), tantalacyclopentane complexes (cf. S. L. McLain, J. Sancho, R. R.
Schrock, rbid. 101 (1979) 545 I), and oxanickelacyclohexanone complexes (cf. K. Sano, T. Yamamoto, A. Yamamoto, Chem. Lett. 1982.
695).
Isolation and Photoisomerization of
Simply Substituted Nitrile Oxides**
+
Hal,
Hal
--+ NH
,O,N-+O
corresponding hydroximic acid halides by HHal-elimination with based3’ has attracted renewed interest in connection with the synthesis of the antitumor reagent acivicin.[’]
Furthermore, molecules such as 2 , 5, 8, and in particular
their photoisomers, could perhaps occur in interstellar
space.[41Both aspects have prompted us to attempt the direct detection of such species.
When the fragments formed in the gas-phase pyrolysis
(600”C, lo-’ torr) of the dihaloformoximes 1 and 4 are
condensed with argon on a cold window ( T = 10 K) the
halonitrile oxides of interest, namely 2 and 5, can be detected as main products o n the basis of their typical IR
bandsl’l (Table 1). Of the five fundamental vibrations to be
expected for a linear atomic arrangement161only two are
intense enough for observation.[’] Besides these, the IR absorptions of the respective hydrogen halides and, to a
[ * ] Prof. Dr. G. Maier, DipLChem. J. H . Teles
lnstitut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-6300 Giessen (FRG)
[“*I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
Angew Chem. Int. Ed. Engl.
26 (1987) No. 2
2
3
4
5
6
A
\
,C=N
Cl
\OH
j N- C - C g N
- HCI
7
H\
C=N
/
h.v
----j
NE C-N=C=O
A
I
/
9
OH
,C=N
\
Cl
OH
10
+
- HCI
11
H
\
//-N
HO-N
=C=O
12
OH
A
I
/C=N\
Cl
+O
8
C=N
The haloformonitrile oxides 2 and 5 should, according
to Wieland,[’I be formed as intermediates upon reaction of
the mercury salt of fulminic acid (formonitrile oxide) with
chlorine and bromine to give the respective dihalofuroxanes [Eq. (a)]. The in situ generation of 2 and 5 from the
Hg(CNO),
N-C
1
cL\
By Giinther Maier* and Joaquim Henrique Teles
Hal
lesser extent, those of the corresponding haloisocyanates 3
and 6, respectively, are also observed.
h.v
jO+N-C-CEN-+O*
- 2HCl
OH
14
13
O+N-C-N=C=O
15
The structures of 2 and 5 fotlow also from the fact that
these compounds are smoothly converted into the haloisocyanates upon irradiation in the matrix (A = 254 nm,
10 min),’*I as shown by a comparison with the spectra of
authentic samples[’] of 3 and 6. Vacuum pyrolysis of chlorocyanoformoxime 7 at 400°C leads to formation of cyanogen mono-N-oxide 8, which can be isolated as the only
product besides HCI in the argon matrix.‘lo1f n the case of
a linear structure, seven bands should occur in the IR; five
were observed (Table 1). Irradiation in the matrix
(A = 254 nm, t = 20 min) affords cyanogen isocyanate 91”1
and C,O.[’*] Gas-phase pyrolysis of chloroglyoxime 10
analogously afforded the nitrile oxide 11. Its constitution
follows, once again, from the IR spectrum (Table I): irradiation of 11 in the matrix at 10 K affords the isocyanate
12 (IR bands at 3638, 2276, 1646, and 9 7 6 c m - ’ ) within
2 min.
Table 1. IR spectra [Ar matrices, 10 K, V [cm-’1 (relative intensity)] of the
nitrile oxides 2, 5 , 8, and 11.
v,(CNO)
v,,(CNO)
2v,(CNO)
1326.3 (100)
2261.7 (21) [a]
2281.4 (31)
2643.5 (11)
1305.6 (100)
2252.5 (19) [a]
2271 3 (34)
2602.1 (10)
1445 (25)
2356 (100)
1453 (34)
2301 (100)
[a1 Splitting due to matrix effects. [b] Additional bands: 407 (2). 717 (I), 2192
(9). [c] Additional bands: 423 (30), 425 (63). 914 (28), 940 (21), 989 ( 5 3 , 1241
(I I), 1258 (30), 1346 (9), 3621 (83).
0 VCH Verlagsgesellschuji mbH, D-6940 Weinheim, 1987
0570-0833/87/0202-0155 $ 02.50/0
155
Survey: C. Grundmann, P. Griinanger: The Nitrile Oxides, Springer,
New York 1971.
Review: G. Winnewisser, E. Herbst, Top. Curr. Chem., in press. The list
of detected interstellar molecules includes, inter aha, HCI and isocyanic
acid HNCO.
Aromatic nitrile oxides show two intense bands at ca. 2330 and 1370
cm-’: [3], p. 24ff.
D. Poppinger, L. Radom, J. A. Pople, J. Am. Chem. SOC.99 (1977) 7806;
D. Poppinger, L. Radom, ibid. 100 (1978) 3674.
M N D O calculations [M. J. D. Dewar, W. Thiel, J. Am. Chem. Sac. 99
(1977) 48991 gave the following absorption values for the most intense
IR bands [cm-’1 (relative intensities): 2 : 2674 (IOO), 1766 (70); 5 : 2654
(IOO), 1751 (46); 8 : 2695 (IOO), 2535 (15), 1824(27).
Irradiation of fulminic acid HCNO in the matrix leads, in the same unusual reaction, to isocyanic acid. V. E. Bondybey, J. H. English, C. W.
Mathews, R. J. Contolini, J . Mol Spectrosc. 92 (1982) 431.
E. Nachbaur, W. Gottardi, Monatsh. Chem. 97(1966) 115; W. Gottardi,
ibid. 103 (1972) 1150.
For the in situ preparation of 8 and 11 and their application in 1,3dipolar cycloadditions cf. C. Grundmann, H.-D. Frommeld, J . Org.
Chem. 31 (1966) 4235; M. Christl, R. Huisgen, Tetrahedron Lett. 1968.
5209.
E. Mayer, Monatsh. Chem. 101 (1970) 834.
M. E. Jacox, D. E. Milligan, N. G. Moll, W. E. Thompson, J . Chem.
Phys. 43 (1965) 3734.
C. Crundmann, V. Mini, J. M. Dean, H.-D. Frommeld, Justus Liebigs
Ann. Chem. 687(1965) 191.
E. A. Dorko, L. Buelow, J . Chem. Phys. 62 (1975) 1869.
D. E. Milligan, M. E. Jacox, J . Chem. Phys. 40 (1964) 2461.
A. Rauk, P. F. Alewood, Can. J . Chem. SS (1977) 1498.
As expected, flash vacuum pyrolysis of dichloroglyoxime 13 leads to smooth formation of the well-known
cyanogen di-N-oxide 14, which is stable up to -45”C.1131
A special feature of this series is that photoexcitation of 14
(1= 254 nm) does not lead to the isocyanate 15, but to nitrosyl cyanide 18.Il4]This photoreaction is to be seen in
h.v
2
+ co
j CI-N
16
h . v
8
+ N-C-N
+ CO
17
h.v
14 j O = N - C E N
+ CO
18
context with the observation that the bands of chloronitrene 16”51also appear in the IR spectrum after prolonged irradiation of the nitrile oxide 2 in argon at 10 K
and that not only the photostable isocyanate 9 but also
C,O is obtained upon photochemical excitation of 8. This
reaction is probably best explained in terms of the formation of cyanonitrene 17 (detectable on using light of wavelength 229 nm), from which nitrogen is split off. The
atomic carbon formed thereby is finally trapped by the carbon monoxide that is still present in the argon cage (the
intensity of the CO band decreases upon prolonged irradiation).
The “breakaways” in the photochemically-induced nitrite oxide-isocyanate rearrangement can be accounted for
in terms of a theoretically justifiable mechanism[6,’61if one
assumes that the nitrile oxides 19 are converted via the oxazirenes 20 into the acylnitrenes 21.The latter can subsequently rearrange to the isocyanates 23 or be cleaved in a
second photo-step to give nitrene 22 and carbon monoxide. Since it has been confirmed experimentally, at least in
the case of R = C N , that the carbon monoxide does not originate from the isocyanate, a process 23-22 is also not
very likely in the case of other residues R.
+
h . v
R-C=N+O
19
20
R-E
22
21
+ CO
R-N=C=O
23
Summary: Simple nitrile oxides are readily accessible by
gas-phase pyrolysis of the corresponding hydroximic acid
halides. We are confident that this method will prove advantageous in the preparative use of simply substituted nitrile oxides.
Received: October 30, 1986;
supplemented: November 24, 1986 [ Z 1973 IE]
German version: Angew. Chem. 99 (1987) 152
[I] H. Wieland, Ber. Dtsch. Chem. Ges. 42 (1909) 4192.
[2] J. E. Baldwin, C. Hoskins, L. Kruse, J . Chem. Soc Chem. Commun.
1976. 795: A. A. Hagedorn, 8. J. Miller, J. 0. Nagy, Tetrahedron Lett. 21
(1980) 229; P. A. Wade, M. K. Pillay, S. M. Singh, ibid. 23 (1982) 4563;
R. V. Stevens, R. P. Polniaszek, Tetrahedron 39 (1983) 743.
156
0 VCH VerlagsgesellschaJi mbH. 0-6940 Weinherm. 1987
’H,*H-COSY and
ZH,2H,’3C-RELAYNMR Experiments
for the Analysis of Deuteriated Compounds**
By Detlef Moskau and Harald Giinther*
The homonuclear shift correlation technique (COSY“‘])
introduced by Jeener””’ and Ernst et al.[”] is one of the
most important 2D-NMR spectroscopic methods. The
cross peaks occurring between anisochronous nuclei are
due to scalar spin-spin coupling, which generally leads to
characteristic line splittings in a one-dimensional spectrum. COSY-NMR spectra therefore afford immediate
structural information and are indispensable, in particular,
for the detection of connectivities in complicated N M R
spectra.
An attractive aspect of the COSY-NMR experiment is
that cross peaks can even be obtained when the coupling
between two nuclei is not resolved in a one-dimensional
spectrum because of line broadening.”] 5uch situations are
encountered with quadrupolar nuclei whose lines are usually strongly broadened by fast relaxation, so that line splittings due to homonuclear spin-spin couplings are not observed.I3] Consequently, line assignments in the 1D-NMR
spectrum are rendered difficult or impossible. Although
even the COSY-NMR experiment is not unproblematical
for such nuclei because of the dependence of the crosspeak intensities on the magnitude of the scalar coupling
and the relaxation time Tpl, successful 11B,’1B-,[51
”V,
51V-)61 and 6Li,6Li-correlation experimentd’l show that
COSY-NMR spectroscopy is possible with quadrupolar
nuclei and is most useful for the elucidation of structures.
We now report on the COSY- and RELAY-NMR spec[*] Prof. Dr H. Giinther, DiplLChem. I) Mockau
FB 8, OC I 1 der Universitat-Cesamthochschule
Postfach 10 1240, D-5900 Siegen (FRG)
[**I
This work was supported by the Minister fur Wissenschaft und Forschung des Landes Nordrhein-Westfalen.
0570-0833/87/0202-01S6 $. 02.50/0
Angew. Chem. Inf. Ed Engl. 26 (1987) No 2
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