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Metal-Stabilized C-Protonated Diazomethane A Methanediazonium Complex.

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with evolution of gas when heated to above its melting range
of 36-39°C in a sealed tube.
found for sp2 carbons (Table 1). For a trihydrate only 3
additional resonances are expected, whereas a mixture of three
different monohydrates should yield 15 signals. Products of
ring opening reactions cannot explain the spectrum, since they
contain only sp2 carbons and, in particular, should display a
characteristic carbonyl resonance; (8) has so far been obtained in protonated form at pH 216].
The results for (3) and (6) each show that one heteroaromatic
ring is preserved during hydrate formation. This finding is
consistent with the fact that pyridine and pyrimidine do not
form hydrates. The existence of a pteridine dihydrate under
physiological conditions as substrate of xanthine oxidase could
explain the formation of leukopterine as a degradation product
of pteridine cofactorsiIo1.
Received: January 9, 1975 [Z 181 IE]
German version: Angew. Chem. 87, 356 (1975)
CAS Registry numbers:
( 1 ) . 253-82-7; (2). 54698-98-5; (31, 254-86-4; ( 5 ) . 54698-99-6;
(6). 91-18-9: (7). 14130-90-6; ( 8 ) . 14130-91-7
[I]Applications of '3C-Resonance Spectroscopy, Part 19. This work has
been supported by the Deutsche Forschungsgemeinschaft and the Fonds
der Chemischen 1ndustrie.-Part 18 see: U . Ewers, H. Giinther,and L. Jaenicke,
Chem. Ber. 107, 3275 (1974).
[2] A. Albert and W L. F. Amarego, Advan. Heterocycl. Chem. 4, 1 (1965).
[3] D. D. Perrin, Advan. Heterocycl. Chem. 4, 43 (1965).
[4] M. J . Cho and 1. H. Pitman, J. Amer. Chem. SOC. 96, 1843 (1974);
and lit. cited therein.
[5] 7: J . Batterham, J. Chem. SOC.C 1966,999.
[6] A. Albert, 7: J . Batterham, and J . McCormack, J. Chem. SOC.B 1966,1105.
[7] I/. Ewers. H. Giinther. and L. Jaenicke, Chem. Ber. 106, 3951 (1973).
[8] U . Ewers, H. Giinther, and L. Jaenicke, Chem. Ber. in preparation.
[9] R. J . Pugmire, M. J . Robins, D. M. Grant, and R. K. Robins, J. Amer.
Chem. SOC.91, 6381 (1969).
[lo] H. Rembold, H. Metzger, and W Gutensohn, Biochim. Biophys. Acta
230, 117 (1971).
Metal-Stabilized C-Protonated Diazomethane:
A Methanediazonium Complex[']
By Wolfgang A. Herrmannp]
On reaction with simple aliphatic diazo compounds transition metal hydrides are generally converted into the corresponding alkyl derivatives, which can be explained as formal
carbene insertion into the polar metal-hydrogen bondi2-31.In
the course of investigations designed to elucidate the diazo
method leading to carbene complexes of transition metalsr41,
diazomethane has now been stabilized as an intact, subsequently protonated molecule by coordination to a metal.
Addition of an excess of diazomethane ( I ) at -85°C to
a THF solution of cyclopentadienyltricarbonyltungsten hydride (2) followed by a gradual raising of the temperature
to +25"C affords a dark red neutral compound (3) which
can be isolated by column chromatography. Compound (3)
is extremely air-sensitive in solution, and slowly decomposes
Chemisches lnstitut der Universitat
84 Regensburg 1. Universitatsstrasse 31 (Germany)
Vol. 14 (1975)
I21
I31
Complete elemental analysis and spectroscopic data show
the new complex to possess a diazomethane ligand which
has been protonated at the originally sp2-hybridized carbon
atom, and is bound to the metal via the terminal nitrogen
atom, as a characteristic structural component. While the
stretching vibrations of the two metal carbonyl groups are
observed in the IR spectrum (benzene) at 1968vs and
1886 c m - ' vs, the bands at 1635s and 1595 cm-' m are to
be assigned to the stretching vibrations of the complexed
azo functioni5*61. The 'H-NMR spectrum (60MHz; CDCl3;
external TMS) establishes the presence of the cyclopentadienyl ring (~=4.17ppm,singlet) as well as the newly formed
methyl group (T =6.37 ppm, singlet); absorption no longer
occurs in the high-field hydride region. The proposed structure
is further supported by the mass spectrum of (3) which shows,
in addition to the intense molecular peak (mle 350 for la6W),
successive elimination of CH3, N2, and the two CO groups
(70eV; direct inlet at 10°C; ion source 30--40°C).
Theabove reaction which entails a lowering of the coordination number of the central metal is the first example of CO
substitution effected by diazomethane, even though it is associated with a 1,4-hydrogen shift"]. The ligand CH3N2 which
corresponds to the highly unstable methanediazonium ion
assumes the function of a neutral three-electron donor in
the complex.
Procedure:
All operations are carried out with rigorous exclusion of
oxygen and moisture (N2atmosphere).-A precooled (- 35 "C)
approximately 0.25 M ethanol-free solution of ( 1 ) (10mmol)
in diethyl etherca1is added dropwise to a magnetically stirred
solution of (2)IZ1(1.67g, Smmol) in THF (100rnl) at -85°C
in a thermostated darkened Schlenk flask (programmed cryostat LAUDA K 120W). After 1 h at -85°C the mixture is
warmed to room temperature over 12 h and stirring continued
to complete the reaction (12 h). Chromatography of the concentrated crude product at +lO°C over silica gel 60 (Merck
7734; I = 80, 0 = 1.8cm) with benzene permits elution of a
rapidly migrating yellow zone whose residue affords the methyl
derivativeC5H5W(CO)3CH3121(26mg,
1.5 %)on high vacuum
sublimation at 55°C. A second red zone is concentrated and
rechromatographed under the same conditions. The complex
(3) initially obtained as a red oil yields fine crystals on reprecipitation (diethyl etherin-pentane; OOC) and is analytically pure
after recrystallization from diethyl etherin-pentane (1 :2) at
- 100°C and several hours' drying in high vacuum (0°C).
Yield 1.08g (62%).
Received: January 24, 1975 [Z 192 IE]
German version: Angew. Chem. 87, 358 (1975)
CAS Registry numbers:
( I ) . 334-88-3; ( 2 ) , 12128-26-6; ( 3 ) . 54774-68-9
[l] Complex Chemistry of Reactive Organic Compounds, Part 7.--Part
6: W A. Herrmann, J. Organometal. Chem. 84, C 2 5 (1975).
[2] E. 0. Fischer, W Hafner, and H. 0. Stahl, Z. Anorg. Allg. Chem. 282,
[*] Dr. W. A. Herrmann
Angew. Chem. internat. Edit.
dHg
Ill
1 No. 5
47 (1955).
355
M . F. Lappert and J . S . Poland, Advan. Organometal. Chem. 9, 397
(1970);literature cited therein.
W A. Herrmann, Angew. Chem. 86, 556 (1974);Angew. Chem. internat.
Edit. 13, 599 (1974);Chem. Ber. 108, 486 (1975).
R . B. King and M . B. Bisnette, J. Amer. Chem. SOC.86, 5694 (1964);
Inorg. Chem. 5, 300 (1966).
M . F. Lappert and J . S . Poland, Chem. Commun. 1969, 1061.
The behavior of higher diazoalkanes towards ( 2 ) clearly shows the
initial reaction step to be CO substitution. The transient diazo complexes
CsH5W(C0)2(HXNz=CRR') can undergo either intramolecular or intermolecular stabilization with participation of the hydride ligand (W A.
Herrmann and H. Biersack, to be published).
7: J . DeBoer and H. J. Backer, Rec. Trav. Chim. Pays-Bas 73, 229
(1954).
Selective Oxidation of the Methyl Group of p-Cresols
by Base-Catalyzed Oxygenation
C(CH3)3>OCH3>CH3>H>Br (Table 1). The use of an
excess of base is essential for this selective oxidation; oxidation
of the benzene ring increases with decreasing amount of butoxide. The failure of 3,5-di-tert-butyl-l-methyl-4-oxo-2,5-cyclohexadienyl hydroperoxide (3) [formed from the p-cresol (1 a )
by oxygenation in aqueous alkaline solution] to give the
p-hydroxybenzaldehyde ( 2 a ) on treatment with potassium
tert-butoxide in DMFI31 indicates that the reaction does not
proceed via a hydroperoxide.
General procedure:
Oxygen is passed through a solution of a substituted p-cresol
( I ) (2 mmol)in DMF (20ml) containing potassium tert-butoxide (20 mmol) at room temperature. After acidification of the
reaction mixture and extraction with ether the aldehydes (2)
areisolated by TLC and identified by comparison with authentic material (IR and NMR).
By Akira Nishinaga, Toshio Itahara, and Teruo Matsuura"]
Oxidation of simple alkylarenes to arenecarboxylic acids
by base-catalyzed oxygenation in diphenyl sulfoxide['l or hexamethylphosphoramide (HMPA)"] is well known. In contrast,
little work has been done on side-chain oxidation of alkylphenols because the benzene ring is normally attacked under
the reaction conditions. Thus oxygenation of alkylphenols
in HMPAjpotassium tert-butoxide affords 4-hydroxy-5,6epoxy-2-cyclohexenonederivatives quantitativelyl31. We have
now found that if a large excess of potassium tert-butoxide
is used in dimethylformamide (DMF) the methyl group of
substituted p-cresols ( I ) is exclusively oxygenated, affording
CH3
CHO
0
Table 1. Formation of p-hydrexybenzaldehydes (2) by base-catalyzed oxygenation of p-cresols ( I ) at room temperature
with potassium tert-butoxide as base.
R'
a
C(CHd3
R2
C(CHdn
Solvent
[a1
Reaction
time [h]
DMF
DEF
DMAc
DMSO
HMPA
tBuOH
DMSO-HNEtl
(15: 1)
DMSO-HNEt2
(2:1)
DMSO-NEt3
12
Conversion
[%I
Yield
[%I
15
15
15
15
15
24
24
24
(15:2)
b
C
d
e
f
CH3
CHI
CHiO
Br
H
CH3
H
H
Br
H
HMPA-HNEtz
(15:2)
DMF
DMF
DMF
DMF
DMF
24
48
48
48
48
48
[a] DMF = dimethylformamide, DEF =diethylformamide, DMAc = N,N-dimethylacetamide, DMSO =dimethyl sulfoxide, Bu= butyl, Et =ethyl. Values in parentheses: vjv.
[b] Yield of isolated aldehyde.
derivatives.
[c] Accompanying 4-hydroxy-5,6-epoxy-2-cyclohexenone
[d] Yield determined by TLC analysis (Shimazu Co. Ltd. TLC scanner CS-900).
[el Yield determined by NMR spectroscopy.
the corresponding p-hydroxybenzaldehydes (2) in excellent
yield (Table 1).
No oxidation of the o-methyl group was observed for 2,4,6trimethylphenol (I b), 2Pxylenol ( I c), and o-cresol. m-Cresols did not react. The reactivity of the p-methyl group depends
upon the o-substituent and decreases in the order
[*I
Dr. A. Nishinaga, T. Itahara, and T. Matsuura
Department of Synthetic Chemistry, Faculty of Engineering
Kyoto University, Kyoto (Japan)
356
Received: January 27,1975 [Z 190 IE]
German version: Angew. Chem. 87.386 (1975)
CAS Registry numbers:
( l a ) , 128-37-0;( l b ) , 521-60-6;( l e ) . 105-67-9:( I d ) , 93-51-6;
( l e ) , 2432-14-6;(If), 106-44-5
[l] 7: J . Wallace, A. Schriesheim, and N . Jacobson, J. Org. Chem. 29, 2907
( 1964).
[2] J . E. Hofmann, A. Schriesheim, and D. D. Rosenfeld, J. Amer. Chem.
SOC.87, 2523 (1965).
[3] A. Nishinaga, 7: Itahara, and T Matsuura, Chem. Lett. 1974, 667.
Angew. Chem. internat. Edit. 1 Vol. 14 ( 1 975) J No. 5
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