Synthesis of 1,2-naphthalenediol diacetates by rhodium(II)-catalyzed reaction of 1,2-diazonaphthoquinones with acetic anhydride

Article abstract of DOI:10.1002/ejoc.201101698

A metal-catalyzed reaction of α-diazocarbonyl compounds with an acid anhydride is reported. In particular, 1,2-naphthalenediol diacetates were synthesized by the reaction of 1,2-diazonaphthoquinones with acetic anhydride catalyzed by Rh₂(OAc)

Full text of DOI:10.1002/ejoc.201101698

SHORT COMMUNICATION
DOI: 10.1002/ejoc.201101698
Synthesis of 1,2-Naphthalenediol Diacetates by Rhodium(II)-Catalyzed
Reaction of 1,2-Diazonaphthoquinones with Acetic Anhydride
Mitsuru Kitamura,*[a] Masato Kisanuki,[a] and Tatsuo Okauchi[a]
Keywords: Diazo compounds / Diazonaphthoquinones / Naphthalenediols / Rhodium / Homogeneous catalysis
A metal-catalyzed reaction of α-diazocarbonyl compounds
with an acid anhydride is reported. In particular, 1,2-naphth-
alenediol diacetates were synthesized by the reaction of 1,2-
diazonaphthoquinones with acetic anhydride catalyzed by
Rh2(OAc)4.
Introduction
Results and Discussion
1,2-Naphthalenediols are attractive candidates for aro-
matic functional materials (or their building blocks), such
as solar cells, metal ligands, and antioxidants, similar to
catechol derivatives.[1,2] However, to date, only a few syn-
thetically useful processes have been reported for the syn-
thesis of 1,2-naphthalenediols.[3]
1,2-Diazonaphthoquinones 1 and 3 were readily pre-
pared regioselectively from the corresponding naphthols in
one step by diazo-transfer by using 2-azido-1,3-dimethyl-
imidazolinium chloride (4, ADMC) (Scheme 2).[7]
Recently, we reported the Pd(OAc)2-catalyzed synthesis
of 1,2-naphthalenediol monoacetates by the reaction of 1,2-
diazonaphthoquinones with acetic acid (Scheme 1).[4] In the
reaction, copper salts (CuI or CuII) and RhII complexes
were ineffective.
Scheme 2. Synthesis of 1,2-diazonaphthoquinones 1 and 3 from
naphthols by the diazo-transfer reaction with ADMC 4.
Initially, the reaction of 2-diazonaphthoquinone 1a with
acetic anhydride was examined under several reaction con-
ditions (Table 1). No product was formed by stirring a solu-
tion of 1a in acetic anhydride at 50 °C for 3 h, while the
reaction mixture became complex at reflux temperature
(Runs 1 and 2). Next, the reaction was examined in the
presence of metal catalysts (Runs 3–14). When Pd(OAc)2 or
Pd(OCOCF3)2 was used as a catalyst, 1a was consumed at
room temperature within 1 h, but no products were iden-
tified (Runs 3 and 4). When using PdCl2, the formation of
diacetate 5a was observed, but the yield was low (5%, Run
5). A Pd0 catalyst such as tris(dibenzylideneacetone)dipalla-
dium(0) [Pd2(dba)3] was not suitable for the formation of
5a, as shown in Run 6. In the series examining the use of
Cu reagents (Runs 7–12), salts with the chloride ion, such as
CuCl and CuCl2, and [Cu(CH3CN)4]BF4 showed a positive
effect for the formation of diacetate 5a, but a significant
improvement of the yield was not observed (Runs 8–10).
When the reaction of 1a was carried out in the presence of
1 mol-% RhII acetate [Rh2(OAc)4], diacetate 5a was ob-
Scheme 1. Pd(OAc)2-catalyzed synthesis of 1,2-naphthalenediol
monoacetate (2a) from 1,2-diazonaphthoquinone (1a).
In the further study of the metal-catalyzed reaction of
1,2-diazonaphthoquinones, we found that 1,2-diazo-
naphthoquinones react with acetic anhydride in the pres-
ence of Rh2(OAc)4 to form 1,2-naphthalenediol diacetates.
To the best of our knowledge, a practical and efficient reac-
tion of α-diazocarbonyl compounds with an acid anhydride
has not been reported.[5,6] In this communication, we de-
scribe the results of an investigation of this process.
[a] Department of Applied Chemistry, Kyushu Institute of
Technology
1-1 Sensuicho, Tobata, Kitakyushu, 804-8550 Japan
Fax: +81-93-884-3304
E-mail: kita@che.kyutech.ac.jp
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101698.
Eur. J. Org. Chem. 2012, 905–907
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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M. Kitamura, M. Kisanuki, T. Okauchi
SHORT COMMUNICATION
tained in 65% yield (Run 13). In this reaction, the forma- dride, as described above. 2-Diazonaphthoquinones 1b and
tion of a minor amount of 1,2-naphthalenediol monoacet- 1c having an electron-donating or electron-withdrawing
ate (2a) was sometimes observed in the crude reaction mix- group at the C-4 position gave naphthalenediol diacetates
ture (Ͻ 5%).[8] Consequently, pyridine was added to the re- 5b and 5c, respectively in moderate yields (Runs 1 and 2).
action mixture following the reaction with catalytic 3-Ethoxycarbonyl-5,8-dimethoxy-2-diazonaphthoquinone
Rh2(OAc)4 in acetic anhydride to give diacetate 5a in 71% (1d) was transformed to diacetate 5d in 88% yield (Run 3).
yield (Run 14).
The reactions of 1-diazonaphthoquinones proceeded
smoothly to give the corresponding 1,2-naphthalenediol di-
acetates in good to high yields (Runs 4–7). Simple 1-diazo-
naphthoquinone (3a) gave 1,2-diacetoxynaphthalene (5a) in
66% yield (Run 4). 6-Bromo-1-diazonaphthoquinone (3b)
was converted to diacetate 5e in 76% yield (Run 5). 3-Meth-
oxycarbonyl-1-diazonaphthoquinone (3c) gave diacetate 5f
in 81% yield (Run 6). In the reaction of 3-carbamoyl-1-
diazonaphthoquinone (3d), diacetate 5g and imidoyl acetate
6 were formed in 13% and 78% yields, respectively (Run 7).
We also examined the Rh-catalyzed reaction of a bis-
Table 1. Synthesis of 1,2-naphthalenediol diacetate 5a from diazo-
naphthoquinone 1a.[a]
Run
Additive (mol-%)
Conditions
Yield [%]
[b]
1
2
none
none
50 °C, 3 h
reflux, 2 h
room temp., 1 h
room temp., 1 h
50 °C, 3 h
50 °C, 3 h
50 °C, 3 h
50 °C, 3 h
50 °C, 3 h
–
c. m.[c]
c. m.[c]
c. m.[c]
5[d]
(diazo)
compound,
2,4-bis(diazo)-1,2,3,4-tetrahydro-
3
4
5
6
Pd(OAc)2 (10)
Pd(OCOCF3)2 (10)
PdCl2 (10)
Pd2(dba)3 (5)
CuI (10)
naphthalene-1,3-dione (7) [Equation (1)]. In this reaction,
1,2,3,4-tetra(acetoxy)naphthalene (8) was obtained in 41%
yield.
c. m.[c]
[b]
7
–
8
9
CuCl (10)
CuCl2 (10)
4[d]
6[d]
7[d]
10
11
12
13
14
[Cu(CH3CN)4]BF4 (10) 50 °C, 3 h
[b]
Cu(acac)2 (10)
Cu(OAc)2 (10)
Rh2(OAc)4 (1)
Rh2(OAc)4 (1)
50 °C, 3 h
50 °C, 3 h
50 °C, 3 h
50 °C, 3 h
–
–
[b]
65[e]
71[e,f]
Subsequently, we examined the RhII-catalyzed reaction
of typical 2-diazo-1,3-dicarbonyl compounds in Ac2O
[Equation (2)]. 2-Diazo-1,3-diketone 9a reacted at room
[a] Reaction conditions: 1a (0.3 mmol), additive, in Ac2O (0.5 mL).
[b] 1a was recovered. [c] Complex mixture. [d] 1H NMR yield
(1,1,2,2-tetrachloroethane was used as an internal standard). [e]
Isolated yield. [f] After the Rh-catalyzed reaction, pyridine
(0.5 mL) was added, and the reaction mixture was stirred for 1 h temperature to give acetoxylated compound 10a in 66%
at 50 °C.
Next, we examined the scope and limitations of the
Rh2(OAc)4-catalyzed formation of 1,2-naphthalenediol di-
acetates from 1,2-diazonaphthoquinones (Table 2). In all
experiments, pyridine was added to the reaction mixture af-
ter the reaction with catalytic Rh2(OAc)4 in acetic anhy-
Table 2. Synthesis of various naphthalenediol diacetates 5 from 1,2-diazonaphthoquinones.[a]
Run
DNQ[b]
R1
R2
R3
R4
R5
t
Yield [%]
1
2
3
4
5
6
7
1b
1c
1d
3a
3b
3c
3d
H
H
CO2Et
H
H
CO2Me
CONHPh
OMe
Cl
H
H
H
H
H
H
H
OMe
H
H
H
H
H
H
H
H
Br
H
H
H
H
OMe
H
H
H
H
3 h
5b 44
4 h
5c 45
11 h[c]
6 h
5d 88
5a 66
9 h
5e 76
2 h
5f 81
8 h[c]
5g 13 6 78
[a] Reaction conditions. 1) DNQ (0.3 mmol), 1 mol-% Rh2(OAc)4 in Ac2O (1 mL); 2) pyridine (0.5 mL), 50 °C, 1–3 h. [b] Diazonaphtho-
quinone. [c] The Rh-catalyzed reaction was carried out at 70 °C.
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Rhodium(II)-Catalyzed Synthesis of 1,2-Naphthalenediol Diacetates
NaHCO3 at 0 °C, and the mixture was extracted three times with
dichloromethane. The organic extracts were washed with brine and
dried with anhydrous sodium sulfate. The dichloromethane was re-
moved in vacuo, and the crude materials were purified by flash
column chromatography (SiO2: hexane/ethyl acetate = 4:1) to give
1,2-naphthalenediol diacetate 5a (51.1 mg) in 71% yield.
yield. The reaction of 2-diazo-1,3-diketo ester 9b proceeded
at 50 °C, but the yield of acetoxylated compound 10b was
low (14% yield).
In Scheme 3, possible reaction mechanisms are depicted
for the Rh2(OAc)4-catalyzed formation of naphthalenediol
diacetate 5a from 2-diazonaphthoquinone 1a by reaction
with acetic anhydride. First, Rh2(OAc)4 reacts with diazo-
naphthoquinone 1a to form RhII carbene complex I. Nu-
cleophilic attack of Ac2O on carbene complex I proceeds to
form oxonium ylide II,[9] then an Ac group migration
occurs to form 5a by releasing Rh2(OAc)4.
Supporting Information (see footnote on the first page of this arti-
cle): General methods and physical data for 5, 6, 8, and 10.
Acknowledgments
This work was partially supported by the Nagase Science Technol-
ogy Foundation and the JGC-Saneyoshi Scholarship Foundation.
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Scheme 3. Possible reaction mechanism.
Conclusions
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We developed the Rh2(OAc)4-catalyzed synthesis of 1,2-
naphthalenediol diacetates by the reaction of 1,2-diazo-
naphthoquinones with acetic anhydride. Although the reac-
tion of α-diazocarbonyl compounds with acid anhydride
has not been thoroughly examined, our method demon-
strates the first efficient practical reaction. While 1,2-
naphthalenediols are easily oxidized in general,[1] protected
1,2-naphthalenediol derivatives could be readily synthesized
and isolated efficiently by our method.
[6] J. Fetter, K. Lempert, M. Kajtár-Paredy, J. Tamás, J. Chem.
Soc. Perkin Trans. 1 1989, 2251–2257.
Experimental Section
Typical procedure of Rh(OAc)2-catalyzed synthesis of naphthalene-
diols from 1,2-diazonaphthoquinone. (Table 1, run 14).
[7] M. Kitamura, N. Tashiro, R. Sakata, T. Okauchi, Synlett 2010,
2503–2505.
[8] When freshly distilled Ac2O was used in this reaction, the for-
mation of monoacetate 2a was not significant, but the use of
stored Ac2O led to the formation of a greater amount of 2a.
[9] A. Padwa, S. F. Hornbuckle, Chem. Rev. 1991, 91, 263–309.
Received: November 28, 2011
To a solution of 2-diazonaphthoquinone 1a (50.0 mg, 0.294 mmol)
in acetic anhydride (1.0 mL) was added Rh2(OAc)4 (1.3 mg,
0.0028 mmol). After the mixture was stirred for 3 h at 50 °C, pyr-
idine (0.5 mL) was added to the reaction mixture, and the mixture
was stirred for 1 h at 50 °C. The reaction was quenched with
Published Online: January 9, 2012
Eur. J. Org. Chem. 2012, 905–907
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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