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a-Oxocarbene-Oxirene Isomerization Photolysis of [1-13C]-2-Diazo-1-phenyl-1-propanone and [2-13C]-1-Diazo-1-phenyl-2-propanone.

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tionally isomeric forms, diazene (diimine) and isodiazene (isodiimine); for the diazene two configurationally isomeric forms
are conceivable. trans- and cis-diazene.
,N="
H
.. .. H
'iN=d
H'
trans-
H\
,N=N
H'
Diazene
cis-
Isodiazene
As shown by mass spectrometric investigations, in the thermolysis of alkali-metal to~ylhydrazides[~J
according to
Tos,
lH
,N-N\
M
H
-TosM
NzHz
two constitutionally isomeric species N2H2I1] are formed
depending upon the nature of M and the pretreatment of
the tosylhydrazide: lithium, sodium, potassium, and aged
cesium tosylhydrazide lead to formation of an energy-poor,
yellow N2H2(diazene), which above ca. - 180°C mainly disproportionates into nitrogen and hydrazine; freshly prepared
cesium tosylhydrazide leads to a colorless NzH2 species (isodiazene) which is richer in energy by about 13 kcal/mol
(54 kJ/mol), readily isomerizes, and decomposes above ca.
-240°C into nitrogen, hydrogen and ammonia. Thermolysis
of rubidium tosylhydrazide affords both sorts of N2H2.
According to IR spectroscopic measurements the energypoorer diazene itself occurs in two configurationally isomeric
forms. Thus, as we have previously observed, in the thermal
decomposition of potassium tosylhydrazide mainly one NzH2
form (cis-diazene) is produced which on contact with cold surfaces transforms into the other form (trans-diazene). If the NzH2
gas is passed through a glass tube cooled with 'dry-ice' ( - 78 "C)
onto an IR window cooled with liquid nitrogen ( - 196°C)
then-according to the TR spectrum-a mixed condensate of
both isomers is obtained which, given a short cooling tube,
chiefly contains cis-diazene, and given a long cooling tube
exists mainly as trans-diazene. The temperature of the window
also plays a role: at lower temperatures the cis-diazene is
obtained, at higher temperatures the trans-diazene.
A typical IR spectrum of the NZH2 mixed condensate,
which generally contains hydrazine14' shows-besides bands
of NzH4 and two further absorptions at 2935 and 287Ocm-'
that are possibly due to hydrogen bridge vibrations-two
groups of bands which according to number and
are evidently due to vibrations of trans- and cis-diazene. The
intensity of the band for the trans isomer increases at the
expense of the absorptions of the cis isomer if a long cooling
tube (up to
and/or a relatively warm IR window[']
is used (the spectrum of a mixed condensate containing mainly
trans-diazene is illustrated in [31), and vice cersa. Should the
changes in the IR spectrum arise merely as a result of differences in molecular aggregation of a configurational isomer
then only the condensation temperature, but not the length
of the cooling tube, could influence the spectrum of the N2Hz
condensate.
I R vibration bands of solid diazene and dideuteriodiarene. The underlined
wave numbers [cm-I] are assigned to the fratis form. the remainder t o
the cis lorm.
NzH2:
N2D2:
3116. 3109. 3025, 1347. 1 3 3 . 1304
2305, 2275. 1517, 1084, 989
Our interpretation of the data is supported by investigations
on dideuteriodiazene, which on the grounds of the kinetic
isotope effect should have a lower reactivity, i.e. a higher
Angew C h i . I t i t .
Ed. E t i g l . 16 ( 1 9 7 7 ) No. 1 1
thermostability and stability towards isomerization. In fact
the thermolysis gas from lithium [Dz]-tosylhydrazide contains
astonishingly little N2D4141;also the low-temperature condensate consists of only one sort of N2Dz, even after flowing
through a longer glass tube cooled to - 78 "C: The IR spectrum
of the condensate shows only one group of relatively sharp
bands, which according to number and position correspond
to the cis form.
The two configurationally isomeric diazenes are distinguishable only on the basis of the IR spectra, but not the
UV or mass spectra. Their electronic structure ought, therefore, to be very similar (cf.1'1 and the almost identical electron
spectrum of trans and cis azomethane[']). Since no difference
in the appearance energies of the molecular and fragment
ions of the isomers can be detected mass spectrometrically
(limit of error: 1.5 kcal/mol) their energy content might
be almost equal. The observed cis-rtrans isomerization would
of course indicate that the trans-diazene is somewhat more
stable than the cis-diazene. This is consistent with calculations['], according to which isodiazene is considerably richer,
but cis-diazene only slightly richer in energy than truns-diazene.
Received: August 4, 1977 [Z 815 IE]
German version: Angew. Chem. 89, 828 (1977)
CAS Registry numbers:
truns-diazene, 15626-43.4; cis-diarene, 15626-42-3; isodiazene, 28647-38-3;
Li tosylhydrazide, 38448-42-9; Na tosylhydrazide, 38448-43-0; K tosylhydraride, 38448-44-1; Cs tosylhydrazide, 63915-1 1-7; R b tosylhydrazlde, 63915-12-
Part 22 of Diimine and Its Derivatives. This work was supported by
the Deutsche Forschungsgemeinschaft.~-Part 21 : N. Wiherg. G. Fischrr,
H. Bachhuhrr,.Angew. Chem. 88. 386 (1976); Angew. Chem. Int. Ed.
Engl. 15, 385 (1976).
R . Ahiriclis, r/: Stummier. Chem. Phys. Lett. 37. 77 (1976); N . C. Baird,
R . F. Burr, Can. J. Chem. 51. 3303 (1973); G. Wiyriihr, Theor. Chim.
Acta 31, 269 (1973).
N . Wiherg, C . Fischrr, H. BuchAuher, Chem. Ber. 107, 1456 (1974).
Owing t o the high decomposibility of diazene the thermolysis gas of
alkali-metal tosylhydrazides always contains the disproportionation
product hydrazine. which can be separated from N2H2 only if the gas
mixture is passed through very long glass tubes cooled with 'dry ice'.
Considering vibration spectroscopic selection rules, 3 IR active absorptions are expected for from-diarene, 5 for cis-diazene.
Because of the decomposibility of diarene the temperature of the I R
window should not exceed - 180°C; also the cooling tube should not
be too long.
R . F . Hiittmi. C . Sterl, J. Am. Chem. Soc. 86. 745 (1964).
a-Oxocarbene-Oxirene Isomerization:
Photolysis of [1-'3C]-2-Diazo-l-phenyl-l-propanone
and [2-'3C]-l-Diazo-l-phenyl-2-propanoneC**]
By Klaus-Peter Zeller"]
The carbene-carbene rearrangement of 3-oxocarbenes via
potential antiaromatic oxirenes"' has been demonstrated on
numerous acyclic systems by carbon labeling[2]or competing
carbene reactions[3? Scheme 1 outlines the individual steps
on using the labeling technique and the Wolff rearrangement
as demonstration reactions.
p]
Priv.-Doz. Dr. K.-P. Zeller
[nstitut fur Organische Chetnie der Universitat
Auf der Morgenstelle 18, D-7400 Tiibingen 1 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft,
781
ma
00
d-C-C-R2
1
I It
0 N2
8-C-C-R2
I1 I1
(2) N2 0
(1)
hv I-N2
values are obtained from the intensities of the pronounced
[M-C02H]+ ions in the mass spectrum (m/e 105, C8H9
and m/e 106, C713CH9).In the acid obtained from (2) the
proportion of the label migrating from 0 to @ borders on
the limit of detection of the two analytical methods.
Table l . P h o t o l y s i s o f 1 . 3 ~1 0 - 2 M s o l u t i o n s o f ( / ) a n d 1 2 ) in dioxaneiwater
(13:2) at room temperature and on purging with pure nitrogen.
cr-Diazoketone
"C-Labeling
i.[nm]
Proportion of
migrated labeling
[XI [a1
lk5
R1
2)
R
8
a
c= c-0
( I ) R1=C6H5
R'=CH~
845'%, in@
>290
254
60.2
68.3
( 2 ) R'=C6H5
R~ = C H ~
60.8% in@
> 290
254
2.8
4.4
[d] Mean value of three "C-NMR and five mass spectrometric measurements; mean deviation cu. +2.
Scheme 1. The sc-oxocarbene-oxirene equilibrium as accompanying reaction
for the Wolff rearrangement.
If an 2-diazoketone labeled on 0 or @ [(I ), (2)] is used
as starting compound, a carbene-carbene rearrangement
(3)*(4)=(5)
is confirmed when the labeling is distributed
over both carbon atoms in the Wolff rearrangement product.
For closer examination of the kinetic model (Scheme 1)
both entries to the a-oxocarbene-oxirene equilibrium by photolysis of the isomers, 13C-labeleda-diazopropanones [I 'C](1) and [2-I3C]-(2) (R1=C6H5, R2=CH3) have now been
monitored.
The diazoketone (1) can be obtained from [carbonyl3C]-benzoyl chloride and excess diazoethane solution[41:
M+'=m/e 161, 84.5% 13C in 0;
IR C [cm-l]: 2075 (NN),
1570 (13CO). For the synthesis of the isomeric compound
(2), [carbonyl-13C]-ethyl acetate is first condensed with benzyl cyanide to give the nitrile (10). Hydrolysis of ( 1 0 ) with
sulfuric acid affords phenyla~etone'~],
which reacts with tosyl
azide to give the labeled diazoketone (2)L6]:M+'=rn/e 161,
IR C [cm-'1 2070 (NN), 1655 (CO).
60.8 % 13C in 0;
Consequently, the Wolff rearrangement product formed
from (1) does not predominantly orginate from the primarily
generated a-oxocarbene (3) but from the isomeric a-oxocarbene ( 5 ) formed by oxygen migration. On the other hand,
in the photolysis of (2) the oxygen atom largely remains on
the original carbon atom 0.
This finding points to a complicated dependence of the
carbene-carbene rearrangement of a-oxocarbenes on the partial steps k l to k6. The preferred formation of ( 7 ) [and subsequently of (9)], irrespective of whether the a-oxocarbene-oxirene equilibrium proceeds via ( 1 ) + ( 3 ) or ( 2 ) + ( 5 ) , is
explained in part by the pronounced migration ability of the
methyl group (R2) compared to the phenyl group (R') in
the photochemical Wolff rearrangement['", 'I. The drastic difference in the proportion of migrated oxygen, however, is
only understandable if it is also assumed that the equilibrium
(3)+(4)$(5)
is strongly shifted towards ( 5 ) .
I f k l and k2 are summed to k 1 3 , 4 1 5and
, k4 ad k2 to kf5,+(3,
a kinetic evaluation from the 254 nm photolysis[8] yields the
ratio kf3,,i5,/k5=2.5 and ki5,,,3,/k6=0.!6 (cf. Scheme 1).
Thence for the carbenes ( 3 ) and ( 5 ) we have the following
proportions for rearrangement with and without oxygen shift:
28
yy
Rearrangement without
oxygen shift
-86.1
%
oxygen shift
Received: August 9, 1977 [Z 814 IE]
German version: Angew. Chem. 89, 827 (1977)
12)
Photolysis of ( I ) and (2) in aqueous dioxane leads to
3C-labeled 2-phenylpropionic acid (8) and ( 9 ) , respectively,
(R' =C6H5, Rz=CH3) in which the distribution of 13C over
the carboxy group and the tertiary C atom can be determined
from the 3C-NMR spectrum and the mass spectrometric
fragmentation.
The PFT 13C-NMR spectrum of unlabeled 2-phenylpropionic acid contains signals at 6 (rel. TMS)=180.8 (C02H),
139.7, 128.6, 127.5 (Car),45.3 (CH) and 17.9 (CH3). The spectrum of the acid obtained from ( I ) shows that ca. 60%
(irradiation with Pyrex-filtered radiation from a Hanovia 450
watt medium-pressure lamp) or 68 "/, (mercury low-pressure
The same
burner) of the label has migrated from @ to 0.
782
CAS Registry numbers:
( I ) (unlabeled), 31164-01-9; [l-'3C]-(1), 63904-55-2; ( 2 ) (unlabeled), 389335-4; [2-"C]-(2), 63904-56-3; [carb~nyl-'~C]-benzoylchloride, 52947-05-4;
diazoethane, 1 I 1 7-96-0; [carbonylbL3C]-ethyl acetate, 3424-59-7; benzyl
cyanide, 140-29-4; tosyl azide. 941-55-9
[I]
[2]
[3]
[4]
[5]
161
[7]
[8]
Review: a) H.M e i e r , K . - P . Zeller, Angew. Chem. 87, 52 (1975); Angew.
Chem. Int. Ed. Engl. 14, 32 (1975); b) C. Weiitrup, Top. Curr. Chem. 62,
173 (1976).
J . Fenuick, G. Frater, K . Oqi. 0. P . Srruusz, J. Am. Chem. Soc. 95,
124 (1973); K:P. Z e / l r r , H . M r i e r , H . K o b h o r ~ E, . Muller, Chem. Ber.
105, 1875 (1972); K.-P. Zeller, Tetrahedron Lett. 1977, 707.
S . A . M a t h , P . G. Summes, J. Chem. Soc. Perkin Trans. I I 1972, 2623.
A. L. Wilds, A. L. Merrder, J. Org. Chem. 13. 763 (1948).
P. L. Juliun, J . J . Olioer, Org. Synth. Collect. Vol. 11, 391 (1943).
M . Regit-, Chem. Ber. 98, I210 (1965).
R . Muller, Diplomarbeit. Universitit Tubingen 1977.
It is assumed that ( 3 ) and ( 5 ) are in real equilibrium.
Anyew. Chem. l i l t . Ed.
Eiigl.
16 ( 1 9 7 7 ) N o . I 1
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oxocarbene, propanone, photolysis, oxirene, 13c, phenyl, isomerization, diaz
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