Photochemical reactions of diazodihydronaphthalenones in cyclic ethers

Article abstract of DOI:10.1039/b106968n

Photolysis of 4-diazonaphthalen-1(4H)-one (1a), 2-methyl-4-diazonaphthalen-1(4H)-one (1b) and 4-diazo-2-nitronaphthalen-1(4H)-one (1c) in neat THF and 1,4-dioxane produced a variety of products depending on the 2-substituent and the solvent. While 1a and

Full text of DOI:10.1039/b106968n

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Photochemical reactions of diazodihydronaphthalenones† in cyclic
ethers
Wei Zhang, Xiangfeng Shao, Li Yang, Zhong-Li Liu* and Yuan L. Chow‡
2
National Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou,
Gansu 730000, China. E-mail: liuzl@lzu.edu.cn; Fax: ϩ86-931-8625657
Received (in Cambridge, UK) 31st July 2001, Accepted 26th February 2002
First published as an Advance Article on the web 19th March 2002
Photolysis of 4-diazonaphthalen-1(4H )-one (1a), 2-methyl-4-diazonaphthalen-1(4H )-one (1b) and 4-diazo-
2-nitronaphthalen-1(4H )-one (1c) in neat THF and 1,4-dioxane produced a variety of products depending on the
2-substituent and the solvent. While 1a and 1c produced predominantly insoluble copolymers in both solvents, 1b
produced, besides small amounts of copolymers, a novel polyether bridged naphthalene, 2,3:11,12-bis(2-methyl-
1,4-naphthylene)-18-crown-6 (2b), 1,4-dioxa-3Ј-methyl-4Ј-oxo-1Ј,4Ј-dihydronaphthalene-1Ј-spiro-5-cycloheptane
(3b), 2-methyl-4-(1,4-dioxan-2-yl)naphthol (4b) and 2-methylnaphthol (5b) in dioxane, and 3Ј-methyl-4Ј-oxo-
1Ј,4Ј-dihydronaphthalene-1Ј-spiro-2-pyrane (3bЈ), 2-methyl-4-(tetrahydrofuran-2-yl)naphthol (4bЈ) and 5b in
THF. Compound 2b is characterised by X-ray crystallography.
Introduction
Compounds where an oxo group is replaced by a diazo group in
arenoquinones are convenient precursors of conjugated keto-
carbenes which are active intermediates and can react readily
with alkanes, alcohols, olefins and cyclic ethers interchange-
ably as carbenes, biradicals and/or zwitterions.1–10 Earlier works
on photolysis of 4-diazocyclohexa-2,5-dien-1-one in cyclic
(1)
Photolysis of 1b in dioxane produced a novel 2 : 2 polyether
bridged naphthalene, 2,3:11,12-bis(2-methyl-1,4-naphthylene)-
18-crown-6 (2b), 1,4-dioxa-3Ј-methyl-4Ј-oxo-1Ј,4Ј-dihydro-
naphthalene-1Ј-spiro-5-cycloheptane (3b), 2-methyl-4-(1,4-di-
oxan-2-yl)naphthol (4b) and 2-methylnaphthol (5b) [eqn. (2)].
ethers reported exclusive formation of 1 : 1 copolymers of the
ketocarbene with the solvent,6,7 while thermal decomposition
of 3,5-di-tert-butyl-4-diazocyclohexa-2,5-dien-1-one in cyclic
ethers at high temperatures was reported to give 1 : 1 spirocyclic
compounds in good yields.8 On the other hand, thermal
decomposition of 2,6-diphenyl-4-diazocyclohexa-2,5-dien-1-
one in dioxane produced a 1 : 1 cyclic polyether compound,4
and photolysis of cyano-substituted 2-diazoazulen-4(2H )-one
in tetrahydrofuran, tetrahydropyran and dioxane produced
1 : 2, 1 : 3 and 1 : 4 polyether-bridged azulenes.9,10 These diver-
sity of activities motivated us to explore the reaction of diazo-
dihydronaphthalenones in cyclic ethers. Here we report the
photolysis of 4-diazonaphthalen-1(4H )-one (1a), 2-methyl-4-
diazonaphthalen-1(4H )-one (1b) and 2-nitro-4-diazonaphth-
alen-1(4H )-one (1c) in neat THF and dioxane.
Results
(2)
Photolysis of 1 in anhydrous THF or dioxane with a 250 watt
high pressure mercury lamp in a Pyrex bottle (λ > 300 nm)
under an argon atmosphere produced a diversity of products
depending on the substituent and the solvent. Compound 1a
produced exclusively insoluble polymers which adhered to the
wall of the bottle in both solvents. Similar to the reaction
of 4-diazocyclohexa-2,5-dien-1-one reported previously,6,7 the
polymers should be the 1 : 1 copolymers (CPs) of the corre-
sponding ketocarbene with the solvents [eqn. (1)].
† These compounds are often referred to as naphthoquinone diazides in
the literature.
‡ Visiting Professor from Simon Fraser University, Burnaby, British
Columbia, Canada.
DOI: 10.1039/b106968n
J. Chem. Soc., Perkin Trans. 2, 2002, 1029–1032
This journal is © The Royal Society of Chemistry 2002
1029

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Table 1 Photolysis of diazodihydronaphthalenones in THF and
Photolysis of 1b in THF produced similar spirocyclic com-
pounds 3Ј-methyl-4Ј-oxo-1Ј,4Ј-dihydronaphthalene-1Ј-spiro-2-
pyrane (3bЈ), 2-methyl-4-(tetrahydrofuran-2-yl)naphthol (4bЈ)
and 5b, but no polyether-bridged 2-methylnaphthalene (2b ana-
logues) was obtained [eqn. (3)]. Structures of these compounds
dioxane
Substrate
Solvent
Product and isolated yield (%)
1a
1a
1b
1b
1c
1c
Dioxane
THF
Dioxane
THF
Dioxane
THF
CP-1 (85)
CP-2 (90)
CP-3 (14)
CP-4 (35)
CP-5 (80)
CP-6 (85)
2b (30), 3b (22), 4b (7), 5b (15)
3bЈ (32), 4bЈ (8), 5b (14)
5c (7)
5c (5)
Discussion
(3)
It is well-known that the thermal or photolytic decomposition
of diazo-ketones (1) produces doubly conjugated transient
ketocarbenes that can react interchangeably as singlet carbene
(6 and/or 7), triplet carbene (8), zwitterion (9) and/or biradical
(10) (Scheme 1).1–5 A number of such diazo-ketones have been
were characterized by spectroscopic data including 2D NMR,
and in the case of 2b, also confirmed by single crystal X-ray
analysis (Fig. 1). As shown in the figure, 2b possesses a sym-
Scheme 1
photolysed in argon matrices to generate the matrix isolated
ketocarbenes that have been characterized by IR, EPR and UV
spectroscopy.11–14 It was concluded that the energy of the
triplet ground state of the conjugated ketocarbene is lower than
that of the singlet ground state, but the energy gap between
the triplet and singlet states is very small, especially for the
σ,p-triplet state (8) and the p2-singlet state (7).1,2,10,15 There-
fore, both triplet and singlet reactions can take place and the
reactivity is significantly influenced by the structure of the sub-
strate, and in some cases singlet reactions are dominant.3–5,10
Ether formation from alcohols,1–5 ylide formation with pyr-
idine16 and stereospecific cyclopropanation of olefins5 are
commonly attributed to the singlet state reaction, while the
reaction with oxygen,1–2 hydrogen atom abstraction2–5,10 and
nonstereospecific cyclopropanation of olefins2 are believed to
be characteristic reactions of the carbenes in their triplet states.
In the present case formation of polymers from the photol-
ysis of 1 is similar to the photolysis of diazocyclohexadien-
one and 4-diazo-2,6-dimethylcyclohexa-2,5-dien-1-one in THF
which gave exclusively 1 : 1 copolymers.6,7 The reaction may be
rationalized by a zwitterion reaction as shown in Scheme 2. The
relatively polar solvent cyclic ether stabilizes the zwitterion and
makes it easy to incorporate with the solvent to form an ylide.
Successive nucleophilic attack of the zwitterion on the oxonium
ion of the ylide resulted in the ring-opening of the cyclic ether
Fig. 1 X-Ray structure (ORTEP drawing) of 2b.§
metric center with the two naphthalene rings located on both
sides of the crown ether ring. The two naphthalene rings are
parallel and are almost perpendicular to the crown ether ring
(the dihedral angle of C14–O1–C7–C8 is 72.8Њ).
Photolysis of 1c in both solvents produced a small amount
of 2-nitro-1-naphthol (5c) together with a large amount of
copolymer [eqn. (4)]. The results are summarized in Table 1.
(4)
§ Crystal data. C30H32O6, M = 488.56, monoclinic, a = 20.549(4), b =
7.456(1), c = 16.856(3) Å3, U = 2491.0(7) Å3, T = 293 K, space group
C2/c, Z = 4, µ (Mo-Kα) = 0.090 mmϪ1, 1573 reflections measured, 1106
unique (Rint = 0.0706) which were used in all calculations. The final
wR(F2) was 0.0726 (all data). CCDC reference number 175319. See
http://www.rsc.org/suppdata/p2/b1/b106968n/ for crystallographic files
in .cif or other electronic format.
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J. Chem. Soc., Perkin Trans. 2, 2002, 1029–1032

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Scheme 2
and formation of the 1 : 1 copolymer. The ylide may also be the
reactions were followed by TLC until the disappearance of the
precursor of 2b, 3b and 3bЈ. Compound 2b may be formed by a
mutual nucleophilic substitution of two ylides and 3 should be
the Stevens rearrangement product of the ylide (Scheme 2).
Compounds 4b and 4bЈ must be α-C–H bond insertion prod-
ucts of the singlet carbene to the cyclic ether. On the other
hand, 5b and 5c are certainly the H-abstraction products of the
triplet carbene.
The significantly different reaction behaviour of 1a, 1b and
1c demonstrates the subtle influence of the substituent on the
reaction of the ketocarbenes. Methyl substitution may decrease
the electrophilicity of the zwitterion, and the steric hindrance
may decrease the reactivity of the phenoxide anion in the ylide,
hence the yield of polymers decreases and the competitive ylide
reaction products 2 and 3 become predominant, and the triplet
reaction product 5 appears. The strong electron-withdrawing
nitro group in 1c increases the electrophilicity of its zwitter-
ion and facilitates formation of the ylide with the cyclic ether,
making the formation of the copolymer predominant.
substrate and the crude products were separated by column
chromatography with silica gel and eluted with petroleum
ether–benzene–chloroform (20 : 10 : 1 v/v/v).
2,3:11,12-Bis(2-methyl-1,4-naphthylene)-18-crown-6
(2b).
Colourless needles, mp: 187–188 ЊC. HR-SIMS: 488.2190
(C30H32O4, calc. 488.2193). EIMS: (m/z, %) 488 (Mϩ, 100), 244
(48), 201 (62), 199 (60), 173 (65), 128 (69), 115 (44), 104 (20).
1H NMR (CDCl3) δ: 2.26 (2 × 3H, s), 3.49 (2 × 2H, dd, J = 3.6,
4.0 Hz), 3.73 (2 × 2H, dd, J = 3.6, 4.0 Hz), 3.83 (2 × 2H, dd, J =
4.2, 4.5 Hz), 4.31 (2 × 2H, dd, J = 4.2, 4.4 Hz), 5.88 (2 × 1H, s),
7.28 (2 × 1H, dd, J = 7.2, 8.4 Hz), 7.41 (2 × 1H, dd, J = 7.2,
8.4 Hz), 7.81 (2 × 1H, d, J = 8.8 Hz), 8.09 (2 × 1H, d, J =
8.4 Hz). 13C NMR (CDCl3) δ: 17.17, 68.48, 69.85, 71.07, 72.16,
108.01, 121.79, 122.59, 123.66, 124.71, 125.30, 129.09, 145.37,
149.75. H,H COSY, HMQC and HMBC spectra suggested
the presence of –O–CH2–CH2–O–CH2–CH2–O– moiety. The
NOESY correlation of the methyl protons with the 5-H in the
naphthalene ring suggested that the two naphthalene rings must
stay parallel on each side of the crown ether ring. The signifi-
cant high-field shift of the chemical shift of C-3 (δ 108.1) and
H-3 (δ 5.88) also suggested that this C and H are shielded by
another naphthalene ring.
Experimental
General
NMR spectra were recorded on a BRUKER AM-400 NMR
spectrometer in CDCl3 with TMS as an internal standard. HR-
SIMS and EIMS spectra were obtained with a Bruker APEXII
FT-MS and a HP 5988A mass spectrometer, respectively. The
X-ray diffraction data were collected on an ENRAF-NOINUS
CAD diffractometer with Mo-Kα radiation. Melting points
were uncorrected.
1,4-Dioxa-3Ј-methyl-4Ј-oxo-1Ј,4Ј-dihydronaphthalene-1Ј-
spiro-5-cycloheptane (3b). Colourless needles, mp: 111–112 ЊC.
HR-SIMS: 245.1171 (C15H16O3 ϩ H, calc. 245.1172). EIMS
(m/z, %): 244 (Mϩ, 16), 201 (100), 174 (23), 160 (31), 141 (36),
1
128 (43), 115 (48), 104 (20). H NMR (CDCl3) δ: 2.01 (3H, s),
2.07 (1H, ddd, J = 1.2, 7.3, 13.2 Hz) 2.36 (1H, ddd, J = 1.8, 8.7,
13.2 Hz), 3.80 (1H, ddd, J = 1.6, 5.4, 13.2 Hz), 3.94–4.03 (4H,
m), 4.02 (1H, ddd, J = 3.2, 7.6, 14.4 Hz), 7.09 (1H, s), 7.42 (1H,
dd, J = 7.6, 8.0 Hz), 7.58 (1H, dd, J = 7.6, 7.4 Hz), 7.85 (1H, d,
J = 7.4 Hz), 8.09 (1H, d, J = 8.0 Hz). 13C NMR (CDCl3)
δ: 16.03, 45.97, 65.97, 67.55, 72.71, 74.37, 125.61, 127.09,
127.79, 129.35, 132.33, 133.36, 144.61, 147.77, 184.91.
4-Diazonaphthalen-1(4H )-one
(1a),
2-methyl-4-diazo-
naphthalen-1(4H )-one (1b) and 2-nitro-4-diazonaphthalen-
1(4H )-one (1c) were prepared according to the available
procedures.17–19 THF and 1,4-dioxane were dried with sodium
sulfate and distilled over sodium benzophenone ketyl under
nitrogen.
Photolysis was carried out in a Pyrex bottle. A dilute solution
of 1a, 1b or 1c (5 mmol) in 100 ml of dry THF or dioxane was
purged with argon for 20 min and irradiated with a 250 W
high pressure Hg lamp for 12–18 h at 0 ЊC under stirring. The
2-Methyl-4-(1,4-dioxan-2-yl)naphthol
(4b).
Colourless
needles, mp: 147–148 ЊC. HR-SIMS: 245.1176 (C15H16O3 ϩ H,
calc. 245.1172). EIMS (m/z, %): 244 (Mϩ, 58), 186 (100), 185
J. Chem. Soc., Perkin Trans. 2, 2002, 1029–1032
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1
(55), 158 (24), 141 (36), 128 (29), 115 (15). H NMR (CDCl3)
Acknowledgements
δ: 2.42 (3H, s), 3.59 (1H, dd, J = 10.1, 11.4 Hz), 3.81–3.90 (2H,
m), 4.04–4.08 (2H, m), 5.25 (1H, br), 5.32 (1H, dd, J = 2.4, 10.0
Hz), 7.44 (1H, s), 7.49 (2H, d, J = 9.6 Hz), 8.02 (1H, d, J = 9.6
Hz), 8.20 (1H, d, J = 9.6 Hz). 13C NMR (CDCl3) δ: 15.64, 66.61,
67.60, 72.34, 74.67, 115.71, 121.82, 122.60, 124.38, 125.03,
125.78, 127.19, 130.96, 131.58, 148.62.
We thank the National Natural Science Foundation of China
(Grant No. 29972018) for financial support.
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7.6 Hz), 7.79 (1H, d, J = 7.6 Hz), 8.08 (1H, d, J = 7.0 Hz).
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calc. 229.1223). EIMS (m/z, %): 228 (Mϩ, 100), 213 (48), 185
1
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J. Chem. Soc., Perkin Trans. 2, 2002, 1029–1032