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Isomers of the Elemental Composition CN2O.

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dried in vacuo with toluene twice to remove any remaining solvent and water. The
dried resin was weighed and used in the screening procedure. The resin-supported
ligand (0.02 mmol) was placed in a dried test tube with a rubber septum under an
argon atmosphere. Ti(OiPr), (0.1 M in toluene, 200 pL, 0.02 mmol) was added and
allowed to stand for 1 h. Subsequently, cyclohexene oxide ( 1 . 0 ~
in toluene, 200 pL,
0.2 mmol) and TMSCN ( 1 . 0 ~In toluene 200 pL, 0.2 mmol) were added, and the
reaction was gently agitated for 20 h (4 “C). The reaction was quenched by addition
of Et,O ( I .O mL), and the solution forced through a silica gel plug with additional
Et,O (1.0 mL). Reaction selectivity was determined by GLC analysis (BETADEX 120 chiral column).
Received: March 5, 1997 [Z10201IE]
German version: Angen,. Chem. 1997, 109, 1781-1785
Isomers of the Elemental Composition CN,O
Giinther Maier,* Hans Peter Reisenauer,
Jiirgen Eckwert, Matthias Naumann, and
Michael De Marco
In our search for the still unknown molecule C2OZ,[l1we
irradiated cyanogen di-N-oxide (1) in solid argon at 10 K with
light of wavelength 254 nm. Nitrosyl cyanide (3) was formed,
probably by loss of CO from the rearrangement product 2.[’,31
OeNEC-CZN+O
-
Keywords: asymmetric catalysis epoxides
catalysis peptides * solid-phase synthesis
heterogeneous
[l] B. M. Cole, K. D. Shimizu, C. A. Krueger, J. P. A. Harrity, M. L. Snapper,
A. H. Hoveyda, Angen. Chem. 1996,108, 1776-1779; Angew. Chem. Int. Ed.
Engl. 1996, 35, 1668-1671.
[2] Recent advances in the application of combmatorial techniques in the discovery of chiral catalysts: a) F M. Menger, A. V. Eliseev, V. A. Migulin, J. Org.
Chem. 1995. 60. 6666-6667; b) G. Lin, J. A. Ellman, ibid. 1995, 60, 77127713: c) S. R Gilbertson, X. Wang, Tetrahedron Lett. 1996, 37, 6475-6478;
d) K. Burgess, H. Lim, A. M. Porte, G. Sulikowski, Angew. Chem. 1996, 108,
192-194; Angelic Chem. Inr. Ed. Engl. 19%,35, 220-222.
[3] F. Balkenhohl, C. von dem Bussche-Hunnefeld, A. Lansky, C. Zechel, Angew
Chem. 1996, /OH, 2436-2487; Angen. Chem. Int. Ed. Engl. 1996, 35, 22882337
[4] a ) H. Nitta, D. Yu, M. Kudo, A. Mori, S . Inoue, J. Am. Chem. Soc. 1992, f 14,
7969~7975, and references therein; b) M. Hayashi, Y. Miyamoto, T Inoue, N
Ogunt, J Org. Chrm. 1993, 58, 1515-1522.
[5] Although the synthesis of all peptide combinations is straightforward, we are
currently limited in our ability to evaluate efticiently every possible ligand for
asymmetric induction. Studies aimed at developing strategies that address this
issue are under way.
[61 C. T. Dooley, R A Houghten, Life Sciences 1993, 52, 1509-1517.
Our initial efforts towards carrying out ligand screening on a solid support
were unsuccessful [l]
R. Noyori, A.svmmetric Cotalysrs in Orgunic Chemrstry, Wiley, New York,
1994, pp. 346- 364.
Although levels of selectivity on solid and in solution phases may correlate,
they may not he reliable. This is particularly an issue if selectivites on solid
phases are low (for example less than 15% ee). In such instances ranking of
various catalyst systems in order of their effectiveness becomes increasingly
dubious. since differences in selectivity are small.
An initial analysis of various solvents (toluene, CH,CI,, T H E Et,O, and
MeCN) indicated that the most selective and reproducible results were obtained in toluene.
C Bolm in Adiunced Asj.mmetric Synthesis (Ed.: G. R. Stephenson), Blackie
Academic and Professional, London, 1996, pp. 9-26.
The predicted nonlinear effect, based on the model in which homo- and heterodimers of the catalyst are present but dissociate at different rates to give the
active monomeric catalyst, is calculated with Equation (a). (ee,,,[%] =
ee,,isd = [ee,., x
( K x e e , J / [ K x eel,,+ 1 x (I00 - eel,,)]
O=C=N-CEN+O
2
1
When an ArF laser (2 = 193 nm) was used, a new species with a
strong IR absorption at 1837 cm-’ was generated instead of 3.
Since the position of this band could be reasonable for C202,[41
we attempted to determine its origin. A more precise study of the
photochemistry of 3 in an argon matrix at 15 K showed that the
above-mentioned absorption is not due to C,O, but to isonitrosyl cyanide (5). To the best of our knowledge this isomer of 3 is
the first “organic” isonitrosyl compound.151
Four ways of linking an NO group and a CN moiety are
conceivable: not only 3, which was synthesized in 1971,[61but
also nitrosyl isocyanide (4), isonitrosyl cyanide (5), and isonitrosyl isocyanide (6) are minima on the C N 2 0 energy hypersurfaceL7].Their relative energies and structural data, calculated
with the density functional theory (DFT) method BLYP/631 1+G*18’in the Gaussian 94 package of programs,191are given
in Scheme 1. This DFT method was chosen because MP2 cal-
E I kcal rno1-I
A
-
49.2
O=N.
7
.C--N
- 34.1 N---O--N=C
6
- 31.1 N U C E N 5
(2)
- 15.9 - N 4 <
4
- 0
3
W - C r N
‘a
3
entiomeric excess of the product with optically pure ligand, ee,,,rh] =
enantiomeric excess of the ligand, K = ratio ofthe initial rates ofoptically pure
versus racemic ligands ( K = 3 in this case)): K. Mikami, M. Terrada, Tetrahedron 1992, 48, 5671 -5680
A. Akelah. D. C. Sherrington, Chem. Rev. 1981,8f, 557-587.
All reaction products i n Table 3 were fully characterized by ’H, I3C NMR, and
IR spectrometry, high-resolution mass spectroscopy, or combustion analysis.
The effect of the glycine at AA3 was originally not appreciated and therefore
went unnoted [ l ]
FMOC-Gly-PAC resin (PerSeptive Biosystems; FMOC = 9-fluorenylmethyloxycarbonyl) may also be used to obtain similar results.
N 179.5’
I 189
5
6
(I 172)
1.179
N-C
-
(I151)
1.16
* N-0
7
Scheme 1. Calculated relative energies and geometries (BLYP/6- 31 1 +GI) of the
CN,O isomers 3-6and the radical pair 7(distances in A). All CN,O isomers possess
C, symmetry. Experimental data are given in parentheses [6b, 1 I ]
[*] Prof. Dr. G. Maier, Dr. H. P. Reisenauer, Dr. J. Eckwert,
Dip].-Chem. M. Naumann, DipLChem. M. De Marco
Institut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-35392 Giessen (Germany)
Fax: Int. code +(641)99-34309
Angew. Chem. Int Ed Engl. 1997, 36, No. 16
0 WILEY-VCH Verlag GmhH, D-69451 Weinheim, 1997
0570-0833/97/3616-1707 $17 50+ 5010
1707
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culations give less accurate results, especially for NO' and
CN'.[''I According to the energy scheme, 4 should be even
more easily accessible than 5. Indeed, this species can also be
generated and identified by matrix spectroscopy if 3 is irradiated with light of wavelengths greater than 570 nm instead of
193 nm.
N--O--C3N
2126 (25.0)
13C: 2079
1469 (100.0) [b]
13C: 1468
I5N: 1443
'*O: 1430
748 (31.0)
1JC: 738
573 (29.0)
13C: 567
212 (10.0)
199 (8.0)
2163.0 (60.2)
13C: 2113.4
1498.5 (100.0)
I3C: 1497.3
15N: 1472.5
" 0 : 1460.2
809.5 (64.8)
13C: 798.6
576.1 (26.6)
13C: 5709
A
CN str
v2
A
NO str
vj
A
ip
s4
A
ONC str
vb
A
A
oop
ip
cm-I
O=N-N=C
I
i
400
I
l
500
I
I
600
CN str
1944 (9.0)
13C: 1913
Gcxp/ cm-'
1997.5 (26.1) [b]
1967.1 (33.1)
[1978.5]
1945.9
1681.0 (100.0)
1677.2
723.4 (21.7)
723.4
261.0 (40.5)
259.0
+
+
Table 3. Calculated vibratlonal spectrum of 5 (BLYP/6-311 +G*) and experimentally observed IR absorptions (Ar matrix, 1 5 K ; relatlve intensities are given in
parentheses).
Type [a1
~,,,,d/cm-
iexD/
cm-'
2079 (1.3)
" C : 2034
1939 (100.0) [b]
13C: 1939
"N: 1904
" 0 : 1888
469 (1 3 )
13C: 466
243 (4.2)
11 1 (0.05)
92 (0.05)
2086.0 (0.6)
"C: 2043.5
1836.9 (100.0)
"C: 1836.9
I5N: 1804.9
" 0 : 1789.2
488.4 (1.2)
"C: 482.5
v,
A
C N str
v2
A
NO str
sj
A
ip
I
700
linm +
CO str
oop
ip
v5
A
Combination bands and overtones (probable assignment): 3650.7 (2v,), 2313 0
( V 2 + va)
sq
Figure 1. Experimental UV spectra of the two new isomers 5 (a) and 4 (b) as well
as the starting material 3 (c) in an Ar matrix at 15 K .
pound 3 is the preferred isomer at excitation with light of wavelength 1= 254 or 405 nm, 4 at 1> 570 nm, and 5 at I = 185 or
193 nm. No IR bands attributable to the fourth isomer 6 were
detected.
For the planar molecules 3,4, and 5 (C,symmetry), six IR-active fundamental vibrations of varying intensity are expected
(Tables 1-3). According to the calculation 4 should exhibit four
0 WILEY-VCH
a,,,,,/c1n-
NO str
A
3
T
out-of-plane
[a] See footnote [a] of ydbk 1. [b] Anharmonic resonance of sI with the combination mode (s, v4). The hand position of the fundamental tone (in parentheses) was
determined from the resulting bands and their relative intensities [c] Absolute
intensity 823 kmmol-'.
4
C
OzN-CEN
A
i',
Type [a1
+
3.03
i
=
Table 2. Calculated vibrational spectrum of 4 (BLYP/6-311 +G*) and experimentally observed IR absorptions (Ar matrix, 18 K ; relative intensities are given in
parentheses).
s2
b
1708
?exJ
"C:
1795 (100.0) [c]
I3C: 1786
"C:
ip
650 (11.0)
v,
A
"C: 649
"C:
N N str
284 (19.0)
v4
A
1%:
282
"C:
ip
163 (0.4)
s5
A
Vb
A
oop
31 (0.0)
Combination bands and overtones (probable assignment): 3312.2 (Zv,), 2415.1
(s2
Vj), 974.4 (v,
v4), 539.8 (2v,)
a
I
v,,I,d/cm-
[a] str = stretching vibration; ip = in-plane bending vibration; oop
bending vibration. [b] Absolute intensity 141 kmmol-'.
Isomers 3, 4, and 5 are probably linked to each other by the
radical pair 7.However, this intermediate could not be detected,
presumably because it is trapped in the matrix cage and
undergoes immediate recombination. In any case, all three isomers can be interconverted photochemically; the relative ratios
of the components were determined by the different UV/Vis
absorptions (3: Figure lc, 4: Figure Ib, 5: Figure la). Com-
300
Type [dl
v1
s5
5
01
Table 1. Calculated vibrational spectrum of 3 (BLYP/6-311+ G*) and experimentally observed IR absorptions (Ar matrix, 15 K ; relative intensities are given in
parentheses)
Verlag CrnbH, D-69451 Weinheim, 1997
S6
A
A
[a] See footnote [a] of Table I . [b] Absolute intensity 632 kmrnol-'
bands in the accessible spectral range (C > 220 cm- '). Three
of these-namely, the N-N stretching vibration at 261.0 cm-',
a bending mode at 723.4cm-', and the N - 0 stretching
vibration at 1681.0 cm-' (Figure 2b)-are readily assigned by
0570-0833/97/3616-1708 $17.50+.80/0
Angew Chem. Int. Ed. Engl. 1997, 36, No. 16
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comparison with the theoretical predictions. Instead of a single
absorption for the C-N stretching mode (v,) we observe a pair
of bands at 1997.5 and 1967.1 cm-', which arise from anharmonic resonance with the combination mode v z + v4. This interpretation was unequivocally confirmed by a '3C-labeling experiment. Due to the resulting band shifts, the accidental
degeneracy of the fundamental and combination modes is removed, and only the band for the I3C-N stretch appears at
1945.9 cm-'.
2 9
a
v2
I
I
I
5
N-0-CZN
"1
x40
b
O=N-N=C
4
t
A
v4
v3
I
0a
C
I
O=N-CrN
2000
-
to00
:500
3
500
c /cm-'
Figure 2. Experimental IR spectra of the two new isomers 5 (a) and 4 (b) as well as
the starting material 3 (c) in an Ar matrix at 15 K.
The analysis of the IR spectrum of 5 (Figure 2a) is less problematic. The most intense band by far is that due to N - 0
stretching (v,) at 1836.9 cm-', the first overtone of which appears at 3650.7 cm-'. The C-N stretching vibration gives rise
to a weak absorption at 2086.0 cm-'; the equally weak band at
485.4 cm- ' is due to a bending mode. We have not yet been able
to definitively assign an experimental absorption to the C - 0
stretching transition, which should occur at the lower end of the
accessible spectral range.
Two further computational results worth mentioning are the
long N - N bond in 4 (1.72 A; typical N-N single bonds are
1.4 A) and the long 0 - C bond in 5 (2.21 A; typical C - 0 single
bonds are 1.4-1.5 A).
It must be assumed that the conversion of 3 into an isonitrosyl
isomer is not unique, but may also occur with other nitrosyl
species. This is supported by the corresponding rearrangement
in nitrosyl
'I
Received: January 23, 1997 [Z10027IE]
German version: Angew,. Chem. 1997, 109, 1785-1787
Keywords: ab initio calculations * isomerizations . matrix isolation
- photochemistry
*
radicals
Angew. Chrm. In8 Ed. Engi. 1997, 36, N o . 16
[l] G. Maier, H. P. Reisenauer, B. Rother, J. Eckwert, Liebig.\ Ann. 1996, 303306, and references therein.
[21 G. Maier, J. H. Teles, Angew. Chem. 1987, 99, 152-153; Angrit-. Chem. Int. Ed.
Engl 1987,26,155-156.
[3] G. Maier, M. Naumann, H. P. Reisenauer, J. Eckwert, A n g w Chem. I%,
108, 1800-1801; Anget. Chem. Int. Ed. Engl. 1996,35, 1696.1697.
[4] Review: J. A. Berson, D. M. Birney, W. P. Dailey, 111, J. F. Liebman in Molecular StrucrureandEnergetics, Vol. 6(Eds.: J. F. Liebman, A. Greenberg), VCH,
New York, 1988, pp. 391 -441.
[5] The reaction of F atoms with NO leads to both possible isomers, ONF and the
"inorganic" isonitrosyl compound NOF. The latter yields the thermodynamically more stable nitrosyl isomer upon irradiation in a matrix at 8 K: R. R.
Smardzewski, W. B. Fox, J Chem Soc. Chem. Commun. 1974, 241 -242; J.
Chem. Phys 1974,60,2104-2110.
[6] a) P. Horsewood, G. W. Kirby, J. Chem. Suc. Chem. Cummrm. 1971, 11391140; b) R. Dickinson, G. W. Kirby, J. G. Sweeny, J. K. Tyler, rbid. 1973.
241-242; c) E. A. Dorko, L. Buelow, J. Chem. Phys. 1975,62, 1869-1872.
[7] a) A. A. Korkin, P. von R. Schleyer, R. J. Boyd, Chem. P h p Lett. 1994,227,
312-320: b) B. G. Gowenlock, L. Radom, Ausr J Chrm 1978, 31, 23492353.
[8] Review: L. J. Bartolotti. U. Flurchick, Rev. Comput. Chem. 1996, 7, 187 -216.
[9] Gaussian 94, revision B.1: M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W.
Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A.Petersson,
J. A. Montgomery, K. Raghavdchari, M. A. Alaham, V. G. Zakrzewski,
J. V.Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M.
Challacombe, C. Y Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres,
E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J.
Derees, J. Baker, .I.
P. Stewart, M. Head-Gordon, C. Gonzalez, J. A. Pople.
Gaussian Inc., Pittsburgh, PA, USA, 1995.
[lo] a) B. G. Johnson, P. M. W. Gill, J. A. Pople, J. Chem. Pliys. 1993, 98, 56125626; b) own calculations with the Gaussian 94 program MP2/6-311 + G*.
[I 11 G. Herzberg, Specrra of Diatomic Molecules, Van Nostrand, Princeton, 1950
5
isomerizes to NOCl ( N - 0
[12] ONCl ( N - 0 stretching vibration: 3 ~ 1 8 0 cm-')
stretching vibration' i = 1842 cm-') upon irradiation at i = 193 nm. The reverse reaction is initiated with light of wavelength i.2310 nm M. De Marco,
Diplomarbeit, Unwersitiit Giessen, Germany, 19%.
2,3-Dihydrothiazol-2-ylidene
Gunther Maier,* Jorg Endres, and
Hans Peter Reisenauer
Dedicated to Professor Peter Welzel
on the occasion of his 60th birthday
There are two main approaches for investigating species that
are not isolable under normal conditions : increasing their kinetic stability by introducing sterically demanding substituents and
utilizing matrix-isolation techniques. The first method was successfully applied to nucleophilic carbenes by Arduengo
et al.['"*'"] However, it later turned out that, at least for the
imidazolylidenes, steric hindrance is of secondary importance.['b] The second method, which should be suitable for detecting unsubstituted parent compounds and allows a comparison of the experimental data with quantum-chemical
calculations, was not employed for this class of compounds until
now.
2,3-Dihydrothiazol-2-ylidene(2) was selected as the target
molecule for several reasons. This ring system exemplifies the
nucleophilic carbene, since, as Breslow showed almost 40 years
ago,['] it is the structural element that is responsible for the
activity of vitamin B, .[31 Additionally, the catalytic activity of
the thiazolium salt/2 system is of technical interest.[41During the
recent renaissance of nucleophilic carbenesI5] 2,3-dihydro[*] Prof. Dr. G. Maier, DipLChem. J. Endres, Dr. H. P. Reisenauer
Institut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-35392 Giessen (Germany)
Fax: Int. code +(641)99-34309
0 WILEY-VCH Verlag GmbH, D-69451 Weinhelm, 1997
0570-0833/97/3616-1709S 17.50+.50,0
1709
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