Diastereoselective aerial oxidative cyclization of methylenebisnaphthols catalyzed by N-hydroxyimides in the presence of Fe3+ and Co 2+-Mn2+ catalysts

Article abstract of DOI:10.5560/ZNB.2014-3315

Aerial oxidative cyclization of methylenebisnaphthols to their corresponding spirans has been carried out using catalytic amounts of N-hydroxyimides and FeCl₃·6H₂O or Co(OAc) ₂·4H₂OMn(OAc)₂·4H₂

Full text of DOI:10.5560/ZNB.2014-3315

Diastereoselective Aerial Oxidative Cyclization of Methylenebisnaphthols
Catalyzed by N-Hydroxyimides in the Presence of Fe3+ and Co2+-Mn2+
Catalysts
Ahmad Khorramabadi-zad, Somaye Mohammadi and Mohammad Azadmanesh
Faculty of Chemistry, Bu-Ali Sina University, Hamadan 65174, I. R. Iran
Reprint requests to A. Khorramabadi-zad, E-mail: khoram@gmail.com
Z. Naturforsch. 2014, 69b, 444 – 450 / DOI: 10.5560/ZNB.2014-3315
Received November 22, 2013
Aerial oxidative cyclization of methylenebisnaphthols to their corresponding spirans has been
carried out using catalytic amounts of N-hydroxyimides and FeCl3·6H2O or Co(OAc)2·4H2O-
Mn(OAc)2·4H2O. In this article we focus on the use of FeCl3·6H2O as a highly green and sustainable
catalyst.
Key words: Aerial Oxidative Cyclization, Bisnaphthols, Spirodienones, N-Hydroxyimides
6
Introduction
5
Abel was the first to report the alkaline oxida-
tion of methylenebisnaphthols to spirodienones with
Br2 in 1892 though the product of the unsubstituted
methylenebisnaphthol 1 was proposed to be a perox-
ide [1]. However, on the basis of chemical evidence
its structure was later determined to be the spiro-
dienone 2 [2, 3]. Spirodienone derivatives of substi-
tuted and unsubstituted methylenebisnaphthols have
been thoroughly investigated and yet remain one of
the most interesting members of the spirodienone
family [4 – 18].
As Kasturi has stated in his reports, Abel’s ke-
tone derivatives have two sets of diastereomers 3
and 4, the latter being formed when steric hindrance
is the decisive factor [18]. For example, potassium
hypobromite, persulfate, trichloroisocyanuric acid
(TCCA) [19], chloramine-T and N-chlorosuccinimide
(NCS) give 3 [12], whereas iodine oxyacids, (diace-
toxyiodo)benzene in benzene and aerial oxidation of
methylenebisnaphthols catalyzed by Ph3Bi are spe-
4
3
OH
OH
Br2
1
O
2
Alkaline
O
1'
3'
5'
4'
2
1
O
O
R
3'
3
4
O
O
H
5
D
E
4'
5'
1'
2
D
E
H
B
B
1
A
A
9
R
3
4
The isomers of series 3 show in their 1H NMR spec-
cific for 4. Radical-type oxidants such as hexacyano- tra a doublet near δ = 6.1 ppm (vinylic 3-H0), while
ferrate(III) in benzene and pyridine, 2,4-di-tert-butyl- for isomers of series 4, this hydrogen appears at about
6-phenylphenoxyl and electrochemical oxidation give δ = 5.4 ppm, the up-field shift for the latter being due
mixtures [11 – 13, 19]. In addition, H2O2/MoO3 as an to the shielding effect of the vicinal phenyl ring. There-
oxidizing system and aerial oxidation in the presence fore, the chemical shift of the vinylic proton 30-H is
of TEMPO/FeCl3 are two other green procedures for a good evidence to determine which of the two dia-
the same purpose [20, 21].
stereomers is formed.
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A. Khorramabadi-zad et al. · Oxidative Cyclization of Methylenebisnaphthols
445
Cl
Cl
O
O
O
O
Cl
Cl
HON
NOH
O
NOH
NOH
O
O
O
Tetrachloro-N-hydroxyphthalimide
N-Hydroxyphthalimide
N,N'-Dihydroxyphthaldiimide
(TCNHPI)
(NHPI)
(NDHPI)
O
O
O
HO
NOH
NOH
O
O
N-Hydroxyphthalimide-4-carboxylic acid
N-Hydroxysuccinimide
(NHPI-4-COOH)
(NHSI)
Scheme 1. N-Hydroxyimides and their abbreviations.
Most of the above mentioned oxidizing reagents have been carried out such as oxygenation of fluo-
used for the oxidation of methylenebisnaphthols are rene by organocatalytic reactions [28], oxidation of
often hazardous or very toxic, expensive or not read- alkanes [29 – 31], oxidation of alcohols with molec-
ily available. Some reagents often need to be freshly ular oxygen in the presence of cobalt cations [32],
prepared or require drastic conditions, long reaction electrocatalytic oxidation of alcohols [33], selective
times and tedious work up [11, 13]. These drawbacks oxidative deprotection of a variety of structurally di-
and the need for greener procedures for the prepara- verse trimethylsilyl and tert-butyldimethylsilyl ethers
tion of spirodienones on the one hand, and the exten- using molecular oxygen [34], epoxidation of alkanes
sive use of N-hydroxyphthalimide (NHPI, Scheme 1) by peracids generated in situ under mild reaction con-
and its analogs in organic synthesis on the other hand, ditions [35, 36], oxyalkylation of alkenes with alkanes
prompted us to conduct oxidative cyclization reactions and molecular oxygen [37], nitration of light alkanes
in the presence of NHPI or its analogs and transition and the alkyl side chain of aromatic compounds with
metal cations such as Fe3+. It is therefore necessary to NO2 [38], oxidation of hydroaromatic compounds and
name a few reactions in which N-hydroxyimides have diarylalkanes under mild conditions affording the cor-
been used as organic catalysts.
responding hydroperoxides with high selectivity [39].
N-Hydroxyphthalimide is a stable crystalline solid, Two reviews published in 2006, the first by Ishi and
the preparation of which dates back to 1880 [22]. It Sakaguchi and the second by Minisci, describe the
is a weak acid (pKa = 7) which forms highly colored aerial oxidation of organic compounds in the presence
salts with metals, ammonia or amines. It is a cheap of N-hydroxyderivatives and metal cations [40, 41].
and non-toxic reagent easily prepared by the reac-
tion of phthalic anhydride and hydroxylamine hy- Results and Discussion
drochloride [23]. It crystallizes in two forms, color-
less and yellow, which are substantially identical in
With the above background and the emergence
all other physical and chemical characteristics [24]. It of sustainability as one of the key words in dis-
has been revealed that the phthalimide N-oxyl (PINO) cussions in nearly all fields of science, and hence,
radical, generated in situ from the NHPI precursor, the need for finding new procedures with the mini-
is an active catalytic species responsible for oxida- mum waste – a key challenge in today’s environment
tion reactions [25 – 27]. Notably, by employing NHPI – we now report the aerial oxidative cyclization of
as a radical initiator, a range of organic syntheses several methylenebisnaphthols (Fig. 1) using catalytic
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446
A. Khorramabadi-zad et al. · Oxidative Cyclization of Methylenebisnaphthols
As shown in Table 1, when Mn2+ and Co2+ are
used separately, we get no satisfactory results (en-
tries 1 and 2). However, when Co2+ and Mn2+ are
1, X = H
1a, X = C6H5
OH
OH
taken simultaneously, the product yield is 76%. Con-
trol tests show that for Fe3+ its concentration is criti-
cal, i. e. higher amounts lead to the cleavage of the cor-
responding bisnaphthol into 2-naphthol and benzalde-
hyde. This is presumably due to the hydrolysis of bis-
naphthols under these reaction conditions (heating and
low pH caused by high concentration of Fe3+). More-
over, when the reaction is run in the absence of NHPI
with a catalytic amount of Fe3+, no detectable product
X
H
1b, X = 2-ClC6H4
1c, X = 4-CH3C6H4
1d, X = 4-ClC6H4
1e, X = 2,4-Cl2C6H3
1f, X = 4-CH3OC6H4
1g, X = 4-FC6H4
Fig. 1. Compounds 1 used in this study.
amounts of organic catalysts (N-hydroxyimides) and is obtained though, in the case of Co2+-Mn2+, spiro-
metallic cations (Fe3+ or Co2+-Mn2+).
dienones are formed in trace amounts.
In a control experiment, the oxidation of the phenyl
The overall results of aerial oxidative reactions in
derivative 1a was run in the presence of NHPI and the presence of Fe3+ and N-hydroxyimides are repre-
appropriate amounts of metal cations (0.5 mol-% of sented in Scheme 2 and Table 3.
Fe3+ or up to 5 mol-% of either Co2+ or Mn2+) as
As indicated in Table 3, we have found that aerial
co-catalysts (Table 1). Through another control test oxidation of methylenebisnaphthols in the presence of
the optimized amount of organic catalysts was deter- Fe3+ and N-hydroxyimides gives a mixture of two
1
mined to be 10 mol-% (5 mol-% for NDHPI, which has sets of diastereomers (integration of H NMR signals
two N-OH groups). And finally, the catalytic amount shows the predominance of diasteromer 4). An excep-
of Co2+-Mn2+ co-catalyst was optimized in the ox- tion is 1a, the oxidation product of which is mainly 4a.
idative cyclization of 1a in the presence of NHPI In the case of methylenebisnaphthol 2, trace amounts
(Table 2).
of the oxidation product are obtained with the reaction
Table 1. Reaction time and yield of oxidation of 1a in the presence of NHPI.
Entry
Metal cation salts
Time (min)
Yield (%)
1
2
3
4
6
Mn(OAc)2·4H2O (5 mol-%)
Co(OAc)2·4H2O (5 mol-%)
Co(OAc)2·4H2O-FeCl3·6H2O
Co(OAc)2·4H2O-Mn(OAc)2·4H2O
FeCl3·6H2O (0.5 mol-%)
no reaction
90
90
70
90
18
20
76
45
Table 2. Yields of the NHPI-catalyzed oxidative cyclization of 1a in the presence
of various amounts of Co2+-Mn2+ co-catalyst.
Co(OAc)2·4H2O-Mn(OAc)2·4H2O
0.01 mmol 0.03 mmol 0.05 mmol 0.07 mmol
33% 72% 76% 76%
Table 3. Reaction times and product yields for the synthesis of 3 and 4.
Catalyst
2
4a
3b and 4b
3c and 4c
3d and 4d
3e and 4e
3f and 4f
3g and 4g
Time Yield Time Yield Time Yield Time Yield Time Yield Time Yield Time Yield
(min) (%) (min) (%) (min) (%) (min) (%) (min) (%) (min) (%) (min) (%)
NDHPI
TCNHPI
NHSI
trace
trace
trace
trace
70
70
90
90
40
47
47
48
45
23
80
80
85
80
100
17
28
51
40
54
100
100
100
120
90
36
29
27
56
35
60
60
90
80
110
16
16
27
42
48
70
70
100
120
120
18
10
40
57
54
120
120
110
120
140
24
30
38
37
53
60
60
80
90
40
19
20
27
36
29
NHPI
NHPI-4-COOH trace
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A. Khorramabadi-zad et al. · Oxidative Cyclization of Methylenebisnaphthols
447
O
O
O
O
org. catalyst, Fe3+, air
ethanol, reflux
X
H
OH
OH
+
X
H
H
X
3
4
1, X = H
2, X = H
3a, 4a, X = C6H5
1a, X = C6H5
1b, X = 2-ClC6H4
3b, 4b, X = 2-ClC6H4
1c, X = 4-CH3C6H4
1d, X = 4-ClC6H4
3c, 4c, X = 4-CH3C6H4
3d, 4d, X = 4-ClC6H4
1e
3e 4e
, , X = 2,4-Cl2C6H3
, X = 2,4-Cl2C6H3
, X = 4-CH3OC6H4
1f
3f 4f
,
, X = 4-CH3OC6H4
1g, X = 4-FC6H4
3g, 4g, X = 4-FC6H4
Scheme 2. Synthesis of compounds 3 and 4.
Table 4. Reaction times and yields of oxidation with NHPI Table 5. Oxidation of 1d in the presence of several NHPI and
and Co2+-Mn2+
.
Fe3+ and organic catalysts.
Entry
Product
Timea
Total yield (%) Ratio of 3 to 4
Catalyst
Ratio of 3d to 4d
1
2
3
4
5
6
7
8
2
4a
0 – 7 h
70
60
45
40
40
45
40
trace
76
64
85
68
84
57
98
–
NDHPI
TCNHPI
NHSI
NHPI
NHPI-4-COOH
6 : 94
11 : 89
15 : 85
19 : 81
36 : 64
b
3b, 4b
3c, 4c
3d, 4d
3e, 4e
3f, 4f
3g, 4g
44 : 56
38 : 62
23 : 77
29 : 71
9 : 91
14 : 86
As was mentioned earlier, the distinctive feature of
a
b
Times are in minutes unless stated otherwise; the sole product the two diastereomers, 3 and 4, is the chemical shift
of their corresponding proton 30-H. Therefore, the ra-
tio of these two diastereomers may be obtained from
is 4.
the integral of 30-H signals. As reported in the litera-
time having no significant effect on the product yield. ture, the color of 3 is bright yellow while that of 4 is
An important point deduced from Table 3 is that NHPI very faintly yellow or cream [11]. The other important
is nearly the best organic catalyst. A similar trend is point is that diastereomer 4 has a lower solubility in
also seen when reactions are run in the presence of ethanol as compared to 3, allowing its separation by
NHPI and Co2+-Mn2+ (Table 4).
precipitation from the reaction mixture.
Generally, oxidation in the presence of N-
The final point to be noted is that the diastereoselec-
hydroxyimide and Fe3+ or Co2+-Mn2+ has several ad- tivity also depends on the N-hydroxyimide used; ex-
vantages such as using oxygen as oxidant, the catalytic periments on 1d as starting material have shown the
amount of N-hydroxyimide, the green reaction solvent following trend (Table 5): NDHPI > TCNHPI > NHSI
ethanol, fairly short reaction times and easy product > NHPI > NHPI-4-COOH.
work-up. Using Fe3+ as co-catalyst has, however, sev-
Suggested mechanisms for the reaction catalyzed by
eral other advantages; it is a highly green, sustainable Fe3+ or Co2+-Mn2+ are shown in Schemes 3 and 4,
and environment-friendly catalyst, its catalytic amount respectively.
is as low as 0.5 mol-% (versus 5 mol-% for Co2+
-
As was said earlier, no detectable product was
Mn2+), and its work-up is very easy with no need for formed with Fe3+ in the absence of NHPI. Therefore,
organic solvents. Though for the Co2+-Mn2+ system it is reasonable to propose that there might be some
higher yields are obtained at short reaction times, final kind of cooperation between Fe3+ and NHPI for the
work-up needs an organic solvent (chloroform). Based reaction to proceed.
on this line of reasoning, therefore, our preferred green
As it is seen in the proposed mechanisms, a diradi-
cal is formed in the final step of hydrogen abstraction.
catalytic system will be N-hydroxyimide/Fe3+
.
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448
A. Khorramabadi-zad et al. · Oxidative Cyclization of Methylenebisnaphthols
O
O2
NOH
FeIII OO
substiuted
Fe(II)
bisnaphthol
spirodienone
bisnaphthol
NHPI
PINO
O
O
FeIII OOH
Fe(III)
NO
O
O
X
OOH
O
spirodienone
Scheme 3. Mechanism for the reaction catalyzed by Fe3+
.
O
O2
NOH
substituted bisnaphthol
CoIII
CoIII
OO
Co(II)
NHPI
PINO
Mn(III)
Mn(II)
NHPI
PINO
O
O
O
OOH
Co(III)
NO
X
O
OOH
O
spirodienone
Scheme 4. Mechanism for the reaction catalyzed by Co2+-Mn2+
.
It is suggested that the key point for the preferable for- fect of these N-hydroxyphthalimides on the diastereo-
mation of diastereomer 4 is its lower-energy transition selectivity of the reactions.
state with respect to that of diastereomer 3.
Experimental Section
Conclusions
All solvents were used as obtained from Merck. All aryl-
bisnaphthols [11, 42, 43], methylenebisnaphthol [44] and
In this study, we have succeeded in running dia-
several NHPIs [45 – 47] were prepared according to known
methods. 1H NMR spectra were recorded on a Jeol 90 MHz
instrument. The progress of all reactions was monitored
by TLC with appropriate mobile phases (acetone-n-hexane
stereoselective aerial oxidative cyclizations of sev-
eral bisnaphthols using catalytic amounts of several
N-hydroxyimides and Fe3+ or Co2+-Mn2+ salts in
a green solvent (ethanol). We have also shown the ef- 2 : 15).
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A. Khorramabadi-zad et al. · Oxidative Cyclization of Methylenebisnaphthols
449
General procedure
10-(4-Methylphenyl)-spiro{naphthalene-1(2H),20(10H)-
naphtho[2,1-b]furan}-2-one (3c and 4c) [19]
(A): Oxidative reaction in the presence of NHPI and Fe3+
salt
1H NMR (CDCl3, TMS): δ = 2.13 and 2.3 (s, 3H), 5.38
and 5.19 (s, 1H, 1-H), 6.27 and 5.56 (d, J = 9.6 Hz and
J = 9.8 Hz, H, 30-H), 6.67 – 7.93 and 6.67 – 7.93 (m,15H, aryl
and 40-H), respectively, for 3c and 4c.
In a round bottomed flask (50 mL), bisnaphthol (1 mmol),
N-hydroxyimide (0.1 mmol) and FeCl3·6H2O (0.005 mmol)
were dissolved in 15 – 20 mL ethanol. The solution was re-
fluxed for the appropriate time, with the simultaneous bub-
bling of air into it. The progress of the reaction was followed
by TLC. After the completion of the reaction, an aqueous 2 N
solution of NaOH (3 – 5 mL) was added to the flask with stir-
ring. Distilled water (25 mL) was then added to the reaction
mixture in order to precipitate the product. The precipitate
was filtered, washed several times with distilled water and
dried in air.
10-(4-Chlorophenyl)-spiro{naphthalene-1(2H),20(10H)-
naphtho[2,1-b]furan}-2-one (3d and 4d) [19]
1H NMR (CDCl3, TMS): δ = 5.37 and 5.18 (s, 1H, 1-H),
6.27 and 5.58 (d, J = 10.2 Hz and J = 10.1 Hz, 1H, 30-H),
6.86 – 7.94 and 6.86 – 7.94 (m, 15H, aryl and 40-H), respec-
tively, for 3d and 4d.
10-(2,4-Dichlorophenyl)-spiro{naphthalene-1(2H),20(10H)-
naphtho[2,1-b]furan}-2-one (3e and 4e) [12, 20]
(B): Oxidative reaction in the presence of NHPI and
Co2+-Mn2+ salts
1H NMR (CDCl3, TMS): δ = 5.94 and 5.79 (s, 1H, 1-
H), 6.24 and 5.59 (d, 1H, J = 10.1 Hz and J = 9.9 Hz, 30-H),
6.80 – 8.00 and 6.80 – 8.00 (m, 14H, aryl and 40-H), respec-
tively, for 3e and 4e.
The amounts of starting materials were the same
as the above, except for the amount of
a mixture
of Co(OAc)2·4H2O (0.05 mmol) and Mn(OAc)2·4H2O
(0.05 mmol). After completion of the reaction the organic
compounds were extracted with chloroform to remove the in-
organic co-catalysts. After evaporation of the solvent, ethanol
was added to the dried material. The same procedure as de-
scribed for FeCl3 was followed to obtain the product.
10-(4-Methoxyphenyl)-spiro{naphthalene-1(2H),20(10H)-
naphtho[2,1-b]furan}-2-one (3f and 4f) [19]
1H NMR (CDCl3, TMS): δ = 3.63 and 3.74 (3H, s), 5.36
and 5.18 (s, 1H, 1-H), 6.26 and 5.56 (d, 1H, J = 9 Hz and
J = 10.3 Hz, 3-H0), 6.41 – 7.93 and 6.41 – 7.93 (m, 15H, aryl
and 40-H), respectively, for 3f and 4f.
1H NMR spectral data
10-(4-Fluorophenyl)-spiro{naphthalene-1(2H),20 (10H)-
naphtho[2,1-b]furan}-2-one (3g and 4g) [12, 20]
10-Phenyl-spiro{naphthalene-1(2H),20(10H)-
naphtho[2,1-b]furan}-2-one (4a) [19]
1H NMR (CDCl3, TMS): δ = 5.37 and 5.20 (s, 1H, 1-
H), 6.27 and 5.56 (d, 1H, both J = 10 Hz, due to 30-H),
6.54 – 7.96 and 6.54 – 7.96 (m, 15H, aryl and 40-H), respec-
tively, for 3g and 4g.
1H NMR (CDCl3, TMS): δ = 5.21 (s, 1H, 1-H), 5.53 (d,
J = 10 Hz, 1H, 30-H), 6.93 – 7.94 (m, 16H, aryl and 40-H).
10-(2-Chlorophenyl)-spiro{naphthalene-1(2H),20(10H)-
naphtho[2,1-b]furan}-2-one (3b and 4b) [19]
Acknowledgement
1H NMR (CDCl3, TMS): δ = 6.01 and 5.88 (s, 1H, 1-H),
The authors gratefully acknowledge the financial support
6.25 and 5.54 (d, 1H, both J = 9.9 Hz 30-H), 6.52 – 7.84 and for this work from the Bu-Ali Sina University, Hamadan,
6.52 – 7.84 (15H, aryl and 40-H), respectively, for 3b and 4b. Iran.
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