Catalytic decomposition of 5-diazo-2,2-dimethyl-1,3-dioxane-4,6-dione and its analogs

Full text of DOI:10.1134/S1070428006110273

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2006, Vol. 42, No. 11, pp. 1741−1744.  Pleiades Publishing, Inc. 2006.
Original Russian Text  V.V. Shevchenko, A.A. Shakhmin, V.A. Nikolaev, 2006, published in Zhurnal Organicheskoi Khimii, 2006, Vol. 42,
No. 11, pp. 1749−1752.
SHORT
COMMUNICATIONS
Catalytic Decomposition
of 5-Diazo-2,2-dimethyl-1,3-dioxane-4,6-dione and ItsAnalogs
V. V. Shevchenko, A.A. Shakhmin, and V.A. Nikolaev
St. Petersburg State University, St. Petersburg, 198504 Russia
e-mail: vnikola@VN6646.spb.edu
Received July 12, 2006
DOI: 10.1134/S1070428006110273
Insertion of carbenoids into X–H bonds of various
substrates (X = N, O, P, S etc.) becomes now a standard
procedure of preparative organic synthesis [1]. The
carbenoids generation in these reactions is performed as
a rule by catalytic decomposition of diazo compounds with
variable valence metals at room temperature; the reaction
proceeds with high yields and a good chemoselectivity.
Quite a number of examples of this reaction is known in
the series of hydroxy group containing organic compounds
(X = O) at the use of rhodium, copper catalysts, boron
trifluoride etherate etc. [1].
dioxanedione (IIa) whose formation was presumed to
occur at the photolysis of the diazo compound Ia [2]. We
believed that one of the most efficient procedures for the
synthesis of this methoxy ether was the catalytic
decomposition of easily available diazo compound Ia with
dirhodium tetraacetate in the presence of methanol. We
report here on the results of investigation of catalytic
reactions with diazodioxanedione Ia and also with its
acyclic and carbocyclic analogs, dimethyl diazomalonate
(Ib) and diazodimedone (Ic).
The initial attempt to carry out the catalytic decomposi-
tion of diazo compound Ia under standard conditions of
insertion into X–H bond, namely, with the help of
dirhodium tetraacetate Rh2(OAc)4 in a mixed CH2Cl2–
MeOH at 20°C [1], were unsuccessful. Diazodioxane-
dione Ia proved to be quite stable under these conditions
and did not suffer any notable decomposition even on
adding into the reaction mixture of 3–5-fold excess of
rhodium catalyst. Variation of different parameters of the
process (catalyst, solvent) at 18–20°C did not visibly
accelerate the catalytic reaction, and only at heating the
reaction mixture to 80°C (in benzene–ethanol solution)
the catalytic decomposition by dirhodium tetraacetate
occurred with a considerable rate.
In the study of photochemical transformations of 5-di-
azo-2,2-dimethyl-1,3-dioxane-4,6-dione (Ia) and its
analogs it was necessary to synthesize 5-methoxy-
O
O
O
O
O
O
_
а d
OMe
N2
H
O
O
IIa
Ia
Et
H
O
O
O
O
O
O
HO
OEt
EtOH
_ Me2CO
e
OEt
_N2
It however turned out that occurred not only elimina-
tion of the nitrogen of the initial diazo compound Ia but
also the opening of the dioxane ring, and as a result we
isolated in 40% yield only 2-ethoxymalonic acid monoethyl
ester (III). Since the 1,3-dioxane derivatives relatively
easily undergo the cleavage of the heterocyclic system
in the presence of acidic catalysts or on silica gel [3], it is
H
O
EtO
III, 40%
IIb
(a) Rh2(OAc)4–CH2Cl2 (20°C), (b) Rh2(OAc)4–benzene
(20°C), (c) Cu(CF3SO3)2–CH2Cl2 (20°C), (d) BF3· Et2O–
CH2Cl2 (20°C), (e) Rh2(OAc)4–benzene (80°C).
1741

SHEVCHENKO et al.
1742
18–20°C formed mainly products of reaction between
the intermediate Rh(II)-carbenoid and dichloromethane
(Va, 65%), (Vb, 6%), and the yield of the target product
of insertion into O–H bond VIa was only 10%.
presumable that initially at 80°C the catalytic decomposi-
tion occurs of diazo compound Ia yielding a product of
insertion into O–H bond, ethoxyether IIb, which then
under the reaction conditions is converted into 2-ethoxy-
malonate III along the above scheme.
On decomposition of diazodimedone (Ic) in neat
CH3OH the reaction provided mainly dimeric adduct VII
(82%) alongside a small amount of 2-methoxycyclo-
hexanone (VIa) (9%). The catalytic decomposition of
diazodimedone (Ic) in benzene at 80°C in the presence
of ethanol gave rise to the expected product of insertion
into O–H bond VIb but in a moderate preparative yield
(40%).
Hence the catalytic decomposition of diazodioxane-
dione Ia in the presence of alcohols (MeOH, EtOH) failed
to provide under standard conditions common products
II of intermediate carbenoid insertion into the O–H bond
of alcohols.
For the sake of comparison we also studied the
catalytic reactions of acyclic and carbocylic analogs of
diazodioxanedione Ia, dimethyl diazomalonate (Ib) and
diazodimedone (Ic). It turned out that the reaction of
dimethyl diazomalonate (Ib) took the usual route [1], and
on its decomposition in the presence of CH3OH was
Structure of compounds III–VII obtained was con-
firmed by spectral data reported in the experimental
section.
The appearance in the reaction mixture of 2-chloro-
dimedone (Va) and 3-chloromethoxy derivative Vb is due
O
O
O
O
Rh2(OAc)4,
MeOH, 20oC
_
MeO
OMe
MeO
OMe
_N2
O
O
O
N2
O
+
CH2Cl
Cl
Me
H
CH2Cl2
_RhLn
Ib
_
RhLn
+
O
O
O
1.2 ~H
MeO
H
OMe
А
B
OMe
O
IV, 70%
CH2Cl2
Vа
Cl
obtained in good yield (70%) the expected product of
insertion into O–H bond, dimethyl 2-methoxymalonate
(IV).
O
O
The catalytic decomposition of diazodimedone (Ic)
occurred in different ways and depended on the alcohol
concentration in solution and on reaction temperature. In
dilute methanol solution in CH2Cl2 (~1:20 by volume) at
CH2Cl
Cl
Vb
O
O
O
Rh2(OAc)4,
apparently to the reaction of the intermediate dioxo-
carbenoid A with dichloromethane following, for example,
the below scheme and proceeding through a chloronium
ylide B, homolytic rupture of the C–Cl bond in this ylide
and subsequent reactions of arising radicals.
CH2Cl2, ROH
Cl
N2
_N2
O
O
Ic
Vа
OCH2Cl
The alternative route of transformation of halo-
genonium ylide B cannot be excluded: [1,4]-σ-shift of
CH2Cl group with formation of enol ether Vb and product
of its further hydrolysis Va.
O
O
OMe
Cl
+
+
OMe ;
(OEt)
2
O
The formation of bisadduct VII obviously originated
from the oxidative dimerization of the primary product of
O
O
Vb
VIа, VIb
VII
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 42 No. 11 2006

METHYL 3-NITROACRYLATE REACTION WITH 2-(2-NITROETHENYL)FURAN
1743
insertion into O–H bond VIa under the conditions of the
catalytic process. Analogous reaction was formerly
observed with 2-ethoxydimedone (VIb) in the course of
catalytic decomposition of diazodimedone (Ic) on a copper
Cu(II)-catalyst in the presence of ethanol [4].
we obtained in the order of elution the following
substances: 0.034 g (10%) of 2-methoxy-3-hydroxy-5,5-
dimethyl-2-cyclohexen-1-one (VIa), 0.027 g (6%) of 2-
chloro-3-(chloromethoxy)-5,5-dimethyl-2-cyclohexen-1-
one (Vb), 0.227 g (65%) of 2-chloro-5,5-dimethyl-1,3-
cyclohexandione (Va).
It may be stated in conclusion that unlike acyclic Ib
and carbocyclic Ic analogs diazodioxane Ia in reaction
of catalytic decomposition is relatively stable and at
ambient temperature does not give products of insertion
into O–H bond characteristic of other diazocarbonyl
compounds. On raising the temperature of the catalytic
process the 1,3-dioxane ring suffers opening, and the
initially formed products of insertion into O–H bond
undergo further transformations.
3-Hydroxy-5, 5-dimethyl-2-methoxy-2-
1
cyclohexen-1-one (VIa). H NMR spectrum, δ, ppm:
1.16 s (6H, 2CH3), 2.52 br.s (2H, CH2), 3.02 br.s (2H,
CH2), 3.85 (3H, OCH3), 5.92 br.s (1H, OH). 13C NMR
spectrum, δ, ppm: 27.9 (CH3), 32.7 (C5), 44.2 (C4), 47.8
(C6), 53.0 (OCH3), 161.6 (C2), 178.0 (C3), 193.1 (C1).
Mass spectrum, m/z (Irel, %): 170 (4) [M]+, 143 (100),
115 (20), 108 (8), 101 (16), 97 (22), 83 (83). Found, %: C
63.45; H 8.18. C9H14O3. Calculated, %: C 63.51; H 8.29.
Catalytic decomposition of diazodioxanedione Ia
by dirhodium tetraacetate in benzene at 80°C in
the presence of EtOH. To a suspension of 17 mg
(0.04 mmol) of Rh2(OAc)4 in 1.2 ml (20 mmol) of ethanol
and 1 ml of benzene was added a solution of 0.340 g
(2 mmol) of diazo compound Ia in 3 ml of benzene, and
the mixture was boiled for 3 days. During chromato-
graphic separation of the reaction mixture were isolated
in the order of elution diazo compound Ia, yield 0.087 g
(26%) and 2-ethoxy-malonic acid monoethyl ester (III)),
yield 0.141 g (40%) (calculated on reacted diazodi-
oxanedione).
5,5-Dimethyl-2-chloro-3-(chloromethoxy)-2-
1
cyclohexen-1-one (Vb). H NMR spectrum, δ, ppm:
1.16 s (6H, 2 CH3), 2.44 s (2H, CH2), 2.69 s (2H, CH2),
5.83 s (2H, OCH2Cl). 13C NMR spectrum, δ, ppm: 28.6
(CH3), 32.8 (C5), 40.0 (C4), 51.0 (C6), 74.9 (OCH2),
115.9 (C2), 165.4 (C3), 191.3 (C1). Mass spectrum, m/z
(Irel, %): 226 (1) [M + 4]+, 224 (20) [M + 2]+, 222 (26)
[M]+, 194 (22), 174 (27), 166 (50), 136 (26), 118 (100).
Found, %: C 48.33; H 5.51. C9H12Cl2O2. Calculated, %:
C 48.45; H 5.42.
5,5-Dimethyl-2-chloro-1,3-cyclohexanedione
1
2,3-Diethoxy-3-oxopropionic acid (III). H NMR
1
(Va), mp 158–160°C [7]. H NMR spectrum, δ, ppm:
spectrum, δ, ppm: 1.30 t (3H, CH3, J 6.5 Hz), 1.32 t (3H,
CH3, J 6.6 Hz), 3.70 q (2H, CH2, J1 6.6, J2 1.4 Hz),
4.30 q (2H, CH2, J 6.5 Hz), 4.55 s (1H, CH), 9.5 br.s
(1H, OH) [5].
1.11 s (6H, 2 CH3), 2.47 s (4H, CH2), 5.95 br.s (1H).
Mass spectrum, m/z (Irel, %): 176 (10) [M + 2]+, 174
(30) [M]+, 159 (12), 146 (11), 120 (32), 118 (100).
Catalytic decomposition of diazodimedone (Ic in
methanol. To a suspension of 26 mg (0.06 mmol) of
Rh2(OAc)4 in 2 ml (50 mmol) of methanol was added
dropwise a solution of 0.332 g (2 mmol) of diazodiketone
Ic in 2 ml of methanol, and the reaction mixture was
stirred for 48 h at 18–20°C. After chromatographic
separation of the mixture on silica gel we obtained in the
order of elution the following substances: 0.031 g (9%)
of 2-methoxy-3-hydroxy-5,5-dimethyl-2- cyclohexen-1-
one (VIa) and 0.277 g (82%) of bis(1-methoxy-4,4-
dimethyl-2,6-cyclohexanedione) (VII).
Catalytic decomposition of dimethyl diazo-
malonate (Ib). To a mixture of 0.16 ml (4 mmol) of
CH3OH, 1 ml of of dichloromethane, and 26 mg
(0.09 mmol) of Rh2(OAc)4 was added dropwise a solu-
tion of 0.474 g (3 mmol) of diazoester Ib in 3 ml of
dichloromethane, and the reaction mixture was stirred
for 48 h at 18–20°C. After chromatographic separation
followed by microdistillation of the main fraction we
obtained 0.341 g (70%) of 2-methoxymalonate IV,
bp 75–80°C (1–2 mm Hg) [6].
Catalytic decomposition of diazodimedone (Ic)
by dirhodium tetraacetate in the presence of
CH3OH in CH2Cl2 solution. To a suspension of 17 mg
(0.04 mmol) of Rh2(OAc)4 in 0.16 ml (4 mmol) of
methanol and 1 ml of dichloromethane was added
dropwise a solution of 0.332 g (2 mmol) of diazo compound
Ic, and the mixture was stirred for 2 h at 18–20°C. After
chromatographic separation of the mixture on silica gel
Bis(4,4-dimethyl-1-methoxy-2,6-cyclohexan-
1
dione) (VII). H NMR spectrum, δ, ppm: 1.10 s (12H,
4CH3), 2.35 s (8H, 4 CH2), 3.74 (6H, 2OCH3). 13C NMR
spectrum, δ, ppm: 28.3 (4CH3), 31.7 (C5), 47.8 (C4,6),
50.5 (OCH3), 81.9 (C2), 193.2 (C1,3). Mass spectrum,
m/z (Irel,%): 338 (20) [M]+, 185 (27), 170 (100), 154 (27),
143 (40), 124 (30). Found, %: C 63.96; H 7.68. C18H26O6.
Calculated, %: C 63.89; H 7.74.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 42 No. 11 2006

SHEVCHENKO et al.
1744
Catalytic decomposition of diazodimedone (Ic)
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 42 No. 11 2006