Tetrabutylammonium Iodide Catalyzed Epoxidation of Naphthoquinone Derivatives with tert -Butyl Hydroperoxide as an Oxidant

Article abstract of DOI:10.1055/s-0036-1589035

An efficient and environmentally benign procedure has been developed for the epoxidation of naphthoquinone derivatives by using tetrabutylammonium iodide as a catalyst and tert -butyl hydroperoxide as an oxidant in the presence of silicon dioxide. This protocol, which provides a facile base-free methodology for the synthesis of some new naphthoquinone-based epoxides, features mild reaction conditions, high yields, remarkably short reaction time, and broad substrate scope.

Full text of DOI:10.1055/s-0036-1589035

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–H
paper
A
en
B.-R. Ai et al.
Paper
Synthesis
Tetrabutylammonium Iodide Catalyzed Epoxidation of Naphtho-
quinone Derivatives with tert-Butyl Hydroperoxide as an Oxidant
Bai-Ru Aia,b
Xu-Ling Chena,b
Yu Donga,b
Lei Tang*c
Ji-Yu Wang*a
O
O
TBAI, TBHP
R1
O
R1
R2
SiO2, THF, r.t.
Base-free !
R2
O
O
R
1 = Alkyl, Aryl, Allyl
R2 = Alkyl, H
• 20 examples up to 98% yield
• mild reaction conditions
• short reaction time
a Chengdu Institute of Organic Chemistry, Chinese Academy
of Sciences, Chengdu 610041, P. R. of China
Jiyuwang@cioc.ac.cn
b University of Chinese Academy of Sciences, Beijing
100049, P. R. of China
• broad substrate scope
c Laboratory of Anaestheisa & Critical Care Medicine, Trans-
lational Neuroscience Center, and Department of Anaes-
thesiology, West China Hospital, Sichuan University,
Chengdu 610041, P. R. of China
manstein_1984@sina.com
Received: 19.03.2017
Accepted after revision: 02.05.2017
Published online: 20.06.2017
DOI: 10.1055/s-0036-1589035; Art ID: ss-2017-h0174-op
OH
OH
O
O
O
O
O
O
OH
OH
O
H
O
O
O
O
Abstract An efficient and environmentally benign procedure has been
developed for the epoxidation of naphthoquinone derivatives by using
tetrabutylammonium iodide as a catalyst and tert-butyl hydroperoxide
as an oxidant in the presence of silicon dioxide. This protocol, which
provides a facile base-free methodology for the synthesis of some new
naphthoquinone-based epoxides, features mild reaction conditions,
high yields, remarkably short reaction time, and broad substrate scope
H
OH
O
HO2C
Zeylanone epoxide
2,3-Epoxysesamone
Frenolicin
OH
O
O
OH
O
O
H
3
O
Key words naphthoquinone derivates, expoxidation, tetrabutyl-
ammonium iodide, tert-butyl hydroperoxide, silicon dioxide
O
O
O
Diosquinone
Vitamin K1-epoxide
Figure 1 Some naphthoquinone-based epoxides with biological activi-
ties
Quinones are important frameworks in many natural
products.1 Molecules bearing a quinone framework have
been widely applied in the realm of material sciences, phar-
maceuticals, and biochemistry.1 Furthermore, quinone de-
rivatives are also widely used as oxidizing reagents, ligands,
and synthons in organic synthesis.2 Due to the high impor-
tance of these compounds, there is clearly significant inter-
est in developing new synthetic procedures for functional-
ization of quinones to widen their structural diversity. The
1,4-naphthoquinone-based epoxide fragment is a core
structure in a number of biologically active natural prod-
ucts, such as 2,3-epoxysesamone,3 frenolicin,4 diosqui-
none,5 zeylanone epoxide,6 and naphthoquinone epoxides
of the Vitamin K series (Figure 1).7
Epoxidation of naphthoquinone derivatives are general-
ly achieved under basic conditions by using hypohalites,9
hydrogen peroxide,10 or hydroperoxides11 as oxidants. Rep-
resentative examples included NaOCl/cinchona alkaloid,9a
H2O2/TBA2S2O8/NaOH,10a H2O2/PTC/LiOH,10b TBHP/guani-
dine,11g and TBHP/β-cyclodextrin/Na2CO3.11h However, most
of the existing methods suffer from the requirement for
strong alkaline conditions, low yields, and fairly limited
substrate scope. Therefore, the development of a new, effi-
cient epoxidation method that can be applied to naphtho-
quinone derivatives is highly desirable.
These natural products have already shown antibacteri-
al, antifungal, and antiproliferative activities. Furthermore,
epoxides are valuable building blocks that can be potential
intermediates and precursors for further chemical transfor-
mations.8 Therefore, the construction of 1,4-naphthoqui-
none-based epoxides has become a very important aspect
of functionalization of quinones.
Recently, tetrabutylammonium iodide (TBAI) and tert-
butyl hydroperoxide (TBHP) have attracted great interest in
oxidative C–H functionalization due to their mild, highly ef-
ficient, easily removable, and environmentally friendly
characteristics.12 The combined use of TBAI as the catalyst
and TBHP as the oxidant has been widely used in various
oxidative coupling reactions, such as C–C,13 C–N,14 C–O,15 C–
S,16 and C–P17 bond formation. For example, the TBAI-TBHP
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–H

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B.-R. Ai et al.
Paper
Synthesis
oxidative system has been utilized for the synthesis of ester
compounds from cross-coupling of alkylbenzenes,18
ethers,19 and allylic compounds20 with acyl radical precur-
sors, such as carboxylic acids, aldehydes, alcohols, or tolu-
ene, via C(sp3)–H functionalization.
Table 1 Optimization of Reaction Conditionsa
O
O
Catalyst, Oxidant
O
Additive, Solvent
Meanwhile, the TBAI-TBHP oxidative system could also
be used for the construction of heterocyclic oxazoles,21 or
pyrazoles22 from β-keto esters or 1,3-diones with benzyl-
amines, or sulfonyl hydrazides, respectively. Furthermore,
TBAI-TBHP has been successfully applied to [3+2]-cycload-
dition/oxidative aromatization cascade reactions for the
synthesis of pyrrolo[2,1-a]isoquinolines23 and indoliz-
ino[8,7-b]indoles.24 Considering significant advancement
has been made in this fascinating field, we are especially in-
terested in TBAI-TBHP catalyzed cross-coupling reactions
utilizing naphthoquinone derivatives as the coupling part-
ners. To our surprise, unexpected epoxy products were se-
lectively formed in moderate yields at room temperature.
To our knowledge, no reports have described the epoxida-
tion of olefins by using TBAI-TBHP as an oxidative system.
Herein, we report a novel and efficient epoxidation strategy
of naphthoquinone derivatives by using TBAI as a catalyst
and TBHP as an oxidant.
O
O
2a
1a
Entry Catalyst Oxidant
Additive Solvent
Time (h) Yield (%)b
1
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAB
KI
TBHP
H2O2
DTBP
(NH4)2S2O8
TBHP
TBHP
–
–
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
24
24
24
24
24
24
24
24
24
24
24
68
53
0
2
–
3
–
4
–
0
5c
6d
7
–
54
47
0
–
–
8
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHPh
–
0
9
–
20
0
10
I2
–
11
12
13
14
15
16
17
18
19
20
21
22
–
–
0
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
–
cyclohexane 24
55
58
40
53
73
82
80
68
85
87
83
Initially, we chose 2-methyl-1,4-naphthoquinone (vita-
min K3) as the model substrate to optimize the reaction
conditions (Table 1). The reaction was undertaken in the
presence of TBAI (20 mol%) and TBHP (4.0 equiv, 70% aque-
ous solution) in CH2Cl2 at room temperature.
–
toluene
CH3CN
PhCF3
THF
24
24
24
4
–
–
–
To our delight, the desired epoxide 2a was obtained in
68% yield (Table 1, entry 1). Other oxidants, such as hydro-
gen peroxide (30% H2O2), di-tert-butyl peroxide (DTBP) and
(NH4)2S2O8, were separately examined, but showed either
less efficiency or no reaction (entries 2–4). Decreasing the
amount of TBHP (70% aqueous solution) from 4 to 3 or 2
equiv resulted in a reduced yield of 54% and 47%, respec-
tively (entries 5 and 6). Replacing TBAI with other catalysts
such as TBAB, KI, and I2, did not improve the reaction effi-
ciency (entries 8–10). Moreover, the desired product was
not formed in the absence of either TBAI or TBHP (entries 7
and 11), which indicated that both TBAI and TBHP played
crucial roles in this transformation. Subsequently, various
solvents were evaluated in the reaction (entries 12–16).
THF was found to be the optimal solvent, giving the product
in 73% isolated yield within 4 hours (entry 16). Other sol-
vents, such as CH2Cl2, cyclohexane, toluene, acetonitrile,
and PhCF3 were inferior to THF in terms of both reaction
time and yield. To improve the reaction yield, we investigat-
ed the use of other additives in combination with the TBAI-
TBHP system. Surprisingly, when activated carbon was add-
ed, the reaction completed within a remarkably shorter pe-
riod (15 min) and with an improved product yield (82%, en-
try 17). Several other heterogeneous additives, such as
powdered 4 Å molecular sieves, Al2O3, and SiO2, were exam-
ined (entries 18–20). Among these additives, SiO2 stood out
ACe
THF
0.25
4 Å MSf THF
0.25
0.25
0.25
0.25
0.25
Al2O3
SiO2
THF
THF
THF
THF
g
SiO2
g
SiO2
a Reaction conditions: 1a (0.4 mmol), catalyst (20 mol%), oxidant (4 equiv),
additive (50 mg), solvent (2 mL), r.t., under air.
b Isolated yield.
c TBHP (70% aqueous solution; 3 equiv) was used.
d TBHP (70% aqueous solution; 2 equiv) was used.
e Activated Carbon.
f Powdered 4 Å molecular sieves used after drying.
g The amount of SiO2 was decreased to 1 equiv., 24 mg.
h TBHP (5.0–6.0 M in decane) was used.
as the best choice, affording the desired product in good
yields (85%, 15 min, entry 20), whereas others were less ef-
fective (68–82% yield, entries 17–19). Subsequently, de-
creasing the amounts of SiO2 to 1 equiv did not significantly
affect the yield of 2a (87%, entry 21). Then we surveyed the
reactivity of anhydrous TBHP. It was found that the desired
epoxide was isolated in 83% yield without a substantial im-
provement in yield. Notably, the price of anhydrous TBHP is
much higher than that of aqueous TBHP. So we believe that
utilizing 70% aqueous TBHP as oxidant is more practical
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B.-R. Ai et al.
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Synthesis
and efficient for the reaction. Based on these results, the
best yield of 2a was obtained from the reaction of 1a (0.4
mmol), TBAI (20 mol%), 70% aqueous TBHP (4 equiv), and
SiO2 (1 equiv) in THF (2 mL) at room temperature.
ever, when 1 equiv of K2CO3 was added to the reaction mix-
ture, the desired product 2h was isolated in 57% yield. Next,
a variety of arylated naphthoquinones were evaluated. Both
electron-rich (-Me, -OMe, -Ph) and electron-deficient (-F,
-Cl, and -Br) substrates were suitable for this method, af-
fording the corresponding epoxy products in moderate to
excellent yields in short reaction time (2i–t). Based on these
results, we next surveyed other electron-rich and electron-
deficient alkenes in addition to naphthoquinone deriva-
tives, such as styrene, chromone, and N-phenylmaleimide.
Unfortunately, none of the corresponding epoxy products
were obtained under the standard reaction conditions.
To demonstrate the practicability of this protocol, a
gram-scale experiment was conducted using 2-methyl-1,4-
naphthoquinone as the substrate, and the desired epoxide
2a was obtained in 78% yield without significant loss in
yield (Scheme 2).
With the optimized conditions in hand, we next investi-
gated the scope of this reaction. As shown in Scheme 1, al-
kyl-substituted naphthoquinones with functional groups
including methyl, n-propyl, isopropyl, benzyl, and dioxane
groups were epoxidized smoothly to afford the correspond-
ing products in moderate to good yields (54–87%, 2a–e).
Notably, allyl-substituted naphthoquinones also worked
well under this protocol and afforded the desired product
2f in moderate yield (42%). Dimethyl substituted substrate
exhibited relatively low activity under the standard reac-
tion conditions, probably due to the steric hindrance (2g).
Unfortunately, none of the desired product 2h was obtained
when 1,4-naphthoquinone was used as the substrate. How-
O
O
R1
R2
R1
O
TBAI (20 mol%)
TBHP (4 equiv)
R2
SiO2 (1 equiv), THF, r.t., air
O
O
1
2
O
O
O
O
O
O
O
O
O
O
O
O
2a, 15 min, 87%
2b, 2 h, 67%
2c, 1.5 h, 77%
2d, 2 h, 76%
O
O
O
O
O
O
O
O
O
O
O
O
O
O
2f, 4 h, 42%
2h, 24 h, 57%a
2g, 30 h, 32%
2e, 20 min, 54%
O
Ph
O
O
O
O
O
O
O
O
O
O
O
O
2i, 15 min, 87%
2j, 20 min, 86%
2k, 15 min, 97%
2l, 15 min, 92%
F
Br
Cl
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
2m, 15 min, 56%
2n, 15 min, 88%
2o, 35 min, 89%
2p, 15 min, 95%
Cl
Cl
O
O
O
O
O
O
O
O
O
2r, 15 min, 95%
2q, 20 min, 98%
2t, 15 min, 96%
2s, 9 h, 72%
Scheme 1 Synthesis of 2,3-epoxy-1,4-naphthoquinones. Reagents and conditions: 1 (0.3 mmol), TBAI (20 mol%), TBHP (4 equiv, 70% aqueous solu-
tion), SiO2 (1 equiv), THF (1.5 mL), r.t., under air; isolated yields. a K2CO3 (1 equiv).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–H

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B.-R. Ai et al.
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Synthesis
thoquinone generates the enolate anion A, then the eno-
lized species condenses with the iodite generated in situ to
form more stabilized oxygen-iodinated species B. Subse-
quently, intermediate B undergoes intramolecular electron-
ic movement and a nucleophilic substitution to afford the
epoxide 2a, with iodite and tertiary butanol being released.
O
O
O
TBAI (20 mol%)
TBHP (4 eqiv)
O
SiO2 (1 equiv), THF
r.t., 15 min
O
2a
1a
2.2 g, 78%
(15 mmol)
Scheme 2 The gram-scale synthesis of 2a
t-BuOH
t-BuOH
[n-Bu4N]+
[IO]–
[n-Bu4N]+ [IO2]–
n-Bu4NI
t-BuOOH
t-BuOOH
Several control experiments were performed to gain in-
sight into the mechanism (Scheme 3). When the free-
radical scavenger 2,2,6,6-tetramethylpiperidine-1-oxyl
(TEMPO) was introduced into the reaction mixture, product
2a was isolated in 82% yield, thus suggesting that a radical
pathway can be excluded in this transformation (Scheme 3,
eq. 1). Furthermore, the reaction did not occur in the pres-
ence of stoichiometric amounts of n-Bu4NOH and iodine (in
situ generation of hypoiodite [n-Bu4N]+[IO]− or iodite
[n-Bu4N]+[IO2]−, Scheme 3, eq. 2). However, when TBHP was
employed in the reaction in combination with a catalytic
amount of n-Bu4NOH/I2, the desired product 2a was isolat-
ed in 56% yield (Scheme 3, eq. 3). These results suggested
that hypoiodite or iodite acted as active species rather than
as an oxygen source in the epoxidation, and it also indicated
that [O] of the epoxide did not come from water (Scheme 3,
eq. 3). Additionally, as shown in Table 1, no desired product
2a was formed in the absence of TBAI or TBHP. We note that
the presence of SiO2 significantly reduced the reaction time
and enhanced the reaction yield; this is a similar result to
that reported by Motokura et al.25 for the TBAI/SiO2 cata-
lyzed synthesis of cyclocarbonate. It can be speculated that,
as reported by Kondo26 and by Mattson et al.,27 the silanol
hydroxy groups (Si-OH) on the surface of silica could form
intermolecular hydrogen bonds with iodide anions and the
hydroperoxo group of TBHP, and the formation of hydrogen
bonds might significantly promote reaction activity
(Scheme 3).
SiO2
[n-Bu4N]+
O–
O
I
O
O
O
O
O
H
H
O
H
O-
H
O
H
H
O
I-
t-Bu
O
H
Ot-Bu
nucleophilic attack
O
O
A
1a
H
O
[n-Bu4N]+
Ot-Bu
I
O–
t-BuOH
O
O
O
O
O
O
[n-Bu4N]+
[IO2]–
B
2a
Scheme 4 Proposed reaction mechanism
In conclusion, we have developed a novel and efficient
TBAI-catalyzed epoxidation of naphthoquinone derivatives
by utilizing TBHP as the oxidant in the presence of silicon
dioxide. Highlights of this protocol include high yields, re-
markably short reaction time, broad substrate scope, and
base-free characteristics. To our knowledge, this protocol
represents the first example of TBAI-TBHP catalyzed epoxi-
dation of olefins. Further studies focused on expanding the
substrate scope of this reaction and elucidating the mecha-
nism are under way in our laboratory.
Standard conditions
(1)
(2)
(3)
1a
1a
1a
2a, 82% yield
TEMPO
I
2 (1 equiv)
n-Bu4NOH (2 equiv, 10% in water)
2a, trace
SiO2, THF, r.t., 12 h
All reactions were carried out under an air atmosphere. All reagents
were obtained from commercial suppliers and used without further
purification, unless otherwise stated. Purification of the products was
carried out by flash column chromatography using 200–300 mesh sil-
ica gel. Thin-layer chromatography (TLC) was performed with HS-
GF254 silica gel coated plates and visualized by exposure to UV light
(254 nm). 1H and 13C NMR spectra were recorded with a Bruker
Avance 300 MHz instrument operating at 300 MHz and 75 MHz in
CDCl3, respectively. Chemical shift values are expressed in δ (ppm)
with the solvent resonance as the internal standard (1H NMR: CHCl3
at 7.26 ppm; 13C NMR: CDCl3 at 77.0 ppm). Data are reported as fol-
lows: chemical shift, multiplicity (s = singlet, br s = broad singlet, d =
doublet, t = triplet, q = quartet, m = multiplet), coupling constants
I2 (20 mol%)
n-Bu4NOH (20 mol%,10% in water)
2a, 56% yield
TBHP (4 equiv), SiO2
THF, r.t., 5 h
Scheme 3 Control experiments
Based on these experimental findings and on previous
reports,28 a possible competitive mechanism is proposed
(Scheme 4). Initially, TBAI is oxidized by TBHP to form an
active iodite species ([n-Bu4N]+[IO2]−). Subsequently, TBHP
nucleophilic attack on the C=C bond of 2-methyl-1,4-naph-
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Synthesis
(Hz) and integration. ESI HRMS spectra were recorded with a Thermo
Scientific LTQ Orbitrap XL. Melting points were measured with a
Büchi Melting Point M-545.
HRMS (ESI): m/z [M + H]+ calcd for C17H13O3: 265.0859; found:
265.0857.
1a-(1,4-Dioxan-2-yl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
Epoxidation of Naphthoquinone Derivatives; Typical Procedure
(2e)
Naphthoquinone derivative 1 (0.3 mmol), TBAI (n-Bu4NI, 20 mol%),
SiO2 (0.3 mmol), and THF (1.5 mL) were added to a test tube in air.
TBHP (1.2 mmol, 0.17 mL, 70% aqueous solution) was added dropwise
after the starting materials dissolved. The reaction mixture was
stirred at r.t. for 15 min (or for the time indicated in Scheme 1). Then
the reaction was quenched with saturated Na2SO3 solution and the
mixture was extracted with EtOAc (3 × 10 mL). The combined organic
layers were dried over anhydrous sodium sulfate and the solvent was
removed in vacuo to afford a residue. The residue was purified by col-
umn chromatography on silica gel (petroleum ether/EtOAc) to afford
the desired pure product.
Yield: 42.3 mg (54%); white solid; Rf = 0.65 (PE/EtOAc, 8:1); mp 165–
167 °C.
1H NMR (300 MHz, CDCl3): δ = 7.97–7.92 (m, 2 H), 7.77–7.71 (m, 2 H),
4.62 (dd, J = 9.9 Hz, 2.6 Hz, 1 H), 4.26 (s, 1 H), 4.19 (dd, J = 11.3, 2.5 Hz,
1 H), 3.82–3.80 (m, 2 H), 3.71 (d, J = 11.5 Hz, 1 H), 3.62–3.58 (m, 1 H),
3.47 (dd, J = 11.1, 1.4 Hz, 1 H).
13C NMR (75 MHz, CDCl3): δ = 190.98, 190.51, 134.64, 134.56, 131.93,
131.59, 127.42, 126.86, 68.55, 67.71, 66.95, 66.07, 62.97, 56.73.
HRMS (ESI): m/z [M + H]+ calcd for C14H13O5: 261.0758; found:
261.0759.
1a-Allylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2f)
Yield: 26.9 mg (42%); red oil; Rf = 0.60 (PE/EtOAc, 7:1).
1H NMR (300 MHz, CDCl3): δ = 8.03–8.00 (m, 1 H), 7.97–7.94 (m, 1 H),
7.76–7.73 (m, 2 H), 5.80–5.77 (m, 1 H), 5.27–5.19 (m, 2 H), 3.89 (s,
1 H), 3.04 (dd, J = 15.0, 7.6 Hz, 1 H), 2.78 (dd, J =15.1, 6.5 Hz, 1 H).
1a-Methylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2a)
Yield: 49.1 mg (87%); white solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 96–
97 °C (lit.29a 96–96.5 °C).
1H NMR (300 MHz, CDCl3): δ = 7.88–7.85 (m, 1 H), 7.81–7.79 (m, 1 H),
7.64–7.61 (m, 2 H), 3.77 (s, 1 H), 1.63 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 191.62, 191.36, 134.55, 134.40, 132.21,
13C NMR (75 MHz, CDCl3): δ = 191.61, 191.45, 134.22, 134.03, 131.74,
131.87, 130.26, 127.44, 126.81, 120.23, 63.04, 59.07, 31.88.
131.62, 127.06, 126.43, 61.19, 61.07, 14.38.
HRMS (ESI): m/z [M + H]+ calcd for C13H11O3: 215.0703; found:
HRMS (ESI): m/z [M + H]+ calcd for C11H9O3: 189.0546; found:
215.0703.
189.0545.
1a,7a-Dimethylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2g)
1a-Propylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2b)
Yield: 43.5 mg (67%); pale-yellow oil; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (300 MHz, CDCl3): δ = 8.02–7.99 (m, 1 H), 7.95–7.92 (m, 1 H),
7.75–7.72 (m, 2 H), 3.86 (s, 1 H), 2.28–2.21 (m, 1 H), 1.88–1.80 (m,
1 H), 1.56–1.48 (m, 2 H), 1.00 (t, J = 7.3 Hz, 3 H).
Yield: 19.2 mg (32%); white solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 104–
106 °C (lit.29b104–104.5 °C).
1H NMR (300 MHz, CDCI3): δ = 7.98–7.95 (m, 2 H), 7.73–7.70 (m, 2 H),
1.73 (s, 6 H).
13C NMR (75 MHz, CDCl3): δ = 193.01, 134.18, 132.03, 126.99, 65.04,
13C NMR (75 MHz, CDCl3): δ = 191.95, 191.66, 134.47, 134.24, 132.38,
11.67.
131.75, 127.39, 126.65, 63.82, 60.05, 30.11, 17.86, 14.09.
HRMS (ESI): m/z [M + H]+ calcd for C12H11O3: 203.0703; found:
HRMS (ESI): m/z [M + H]+ calcd for C13H13O3: 217.0859; found:
203.0700.
217.0856.
Naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2h)
1a-Isopropylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2c)
Yield: 50.2 mg (77%); pale-yellow oil; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (300 MHz, CDCl3): δ = 8.01–7.98 (m, 1 H), 7.93–7.90 (m, 1 H),
7.73–7.70 (m, 2 H), 3.85 (s, 1 H), 2.81–2.71 (m, 1 H), 1.11 (d, J = 6.8 Hz,
3 H), 1.00 (d, J = 7.0 Hz, 3 H).
Yield: 29.9 mg (57%); white solid; Rf = 0.30 (PE/EtOAc, 7:1); mp 132–
133 °C (lit.29b 133–134 °C).
1H NMR (300 MHz, CDCl3): δ = 7.97–7.92 (m, 2 H), 7.77–7.71 (m, 2 H),
4.00 (s, 2 H).
13C NMR (75 MHz, CDCl3): δ = 190.65, 134.61, 131.62, 127.08, 55.19.
13C NMR (75 MHz, CDCl3): δ = 192.21, 191.47, 134.51, 134.22, 132.94,
HRMS (ESI): m/z [M + H]+ calcd for C10H7O3: 175.0390; found:
175.0391.
131.69, 127.50, 126.63, 67.02, 57.93, 25.63, 18.75, 16.22.
HRMS (ESI): m/z [M + H]+ calcd for C13H13O3: 217.0859; found:
217.0859.
1a-Phenylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2i)
1a-Benzylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2d)
Yield: 65.4 mg (87%); pale-yellow solid; Rf = 0.60 (PE/EtOAc, 7:1); mp
62–63 °C (lit.29c 61–62 °C).
Yield: 60.4 mg (76%); pale-yellow solid; Rf = 0.60 (PE/EtOAc, 7:1); mp
1H NMR (300 MHz, CDCI3): δ = 8.11–8.09 (m, 1 H), 8.03–8.01 (m, 1 H),
106–108 °C.
1H NMR (300 MHz, CDCl3): δ = 8.04–8.01 (m, 1 H), 7.94–7.91 (m, 1 H),
7.74–7.71 (m, 2 H), 7.31–7.26 (m, 5 H), 3.67 (t, J = 7.8 Hz, 2 H), 3.31 (d,
J =14.9 Hz, 1 H).
7.81–7.78 (m, 2 H), 7.50–7.44 (m, 5 H), 3.97 (s, 1 H).
13C NMR (75 MHz, CDCl3): δ = 190.92, 190.22, 134.68, 134.54, 132.48,
131.81, 130.78, 129.33, 128.48, 127.87, 127.58, 126.88, 64.51, 62.96.
13C NMR (75 MHz, CDCl3): δ = 191.55, 191.47, 134.57, 134.43, 133.84,
132.22, 131.85, 130.16, 128.58, 127.51, 127.26, 126.80, 63.59, 58.93,
33.55.
HRMS (ESI): m/z [M + H]+ calcd for C16H11O3: 251.0703; found:
251.0703.
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1a-p-Tolylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2j)
13C NMR (75 MHz, CDCl3): δ = 190.51, 189.89, 134.77, 134.68, 132.28,
132.10, 131.74, 129.29, 128.98, 128.77, 127.89, 126.95, 63.93, 63.00.
HRMS (ESI): m/z [M + H]+ calcd for C16H10ClO3: 285.0313; found:
Yield: 68.3 mg (86%); white solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 147–
148 °C (lit.29d 146–148 °C).
1H NMR (300 MHz, CDCl3): δ = 8.08–8.05 (m, 1 H), 8.00–7.97 (m, 1 H),
7.77–7.75 (m, 2 H), 7.38 (d, J = 8.0 Hz, 2 H), 7.25 (d, J = 8.0 Hz, 2 H),
3.95 (s, 1 H), 2.40 (s, 3 H).
285.0313.
1a-(4-Bromophenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
(2o)
13C NMR (75 MHz, CDCl3): δ = 190.93, 190.24, 139.12, 134.45, 134.29,
132.30, 131.62, 128.89, 128.72, 127.63, 127.45, 126.65, 64.43, 62.80,
21.20.
Yield: 87.9 mg (89%); white solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 122–
124 °C.
1H NMR (300 MHz, CDCl3): δ = 8.11–8.08 (m, 1 H), 8.03–8.01 (m, 1 H),
7.82–7.79 (m, 2 H), 7.59 (dd, J = 6.7, 1.9 Hz, 2 H), 7.37 (dd, J = 6.7,
1.9 Hz, 2 H), 3.93 (s, 1 H).
HRMS (ESI): m/z [M + H]+ calcd for C17H13O3: 265.0859; found:
265.0859.
1a-(4-Biphenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2k)
13C NMR (75 MHz, CDCl3): δ = 190.49, 189.83, 134.79, 134.71, 132.26,
131.72, 131.27, 131.03, 129.80, 129.23, 127.90, 126.97, 123.69, 63.98,
62.95.
HRMS (ESI): m/z [M + H]+ calcd for C16H10BrO3: 328.9808; found:
328.9811.
Yield: 95.4 mg (97%); yellow solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 119–
121 °C.
1H NMR (300 MHz, CDCl3): δ = 8.14–8.11 (m, 1 H), 8.06–8.03 (m, 1 H),
7.82–7.79 (m, 2 H), 7.69–7.66 (m, 2 H), 7.64–7.61 (m, 2 H), 7.58–7.55
(m, 2 H), 7.49–7.44 (m, 2 H), 7.41–7.38 (m, 1 H), 4.02 (s, 1 H).
1a-m-Tolylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2p)
Yield: 75.6 mg (95%); yellow oil; Rf = 0.60 (PE/EtOAc, 7:1).
1H NMR (300 MHz, CDCl3): δ = 8.11–8.08 (m, 1 H), 8.03–8.00 (m, 1 H),
13CNMR (75 MHz, CDCl3): δ = 190.89, 190.29, 142.30, 140.37, 134.71,
134.59, 132.44, 131.82, 129.65, 128.84, 128.02, 127.90, 127.67,
127.26, 127.20, 126.91, 64.42, 63.05.
HRMS (ESI): m/z [M + H]+ calcd for C22H15O3: 327.1016; found:
7.80–7.77 (m, 2 H), 7.37–7.24 (m, 4 H), 3.96 (s, 1 H), 2.40 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 191.00, 190.31, 138.23, 134.63, 134.48,
132.42, 131.75, 130.63, 130.11, 128.36, 128.14, 127.81, 126.83,
124.66, 64.58, 62.81, 21.40.
327.1018.
1a-(4-Methoxyphenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
(2l)
HRMS (ESI): m/z [M + H]+ calcd for C17H13O3: 265.0859; found:
Yield: 77.3 mg (92%); yellow solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 125–
265.0860.
127 °C (lit.29d 126–128 °C).
1H NMR (300 MHz, CDCl3): δ = 8.08–8.05 (m, 1 H), 8.02–7.96 (m, 1 H),
7.80–7.75 (m, 2 H), 7.41 (d, J = 8.8 Hz, 2 H), 6.96 (d, J = 8.8 Hz, 2 H),
3.96 (s, 1 H), 3.84 (s, 3 H).
1a-(3-Chlorophenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
(2q)
Yield: 83.4 mg (98%); pale-yellow oil; Rf = 0.60 (PE/EtOAc, 7:1).
13C NMR (75 MHz, CDCl3): δ = 191.10, 190.50, 160.21, 134.54, 134.37,
132.37, 131.70, 129.01, 127.73, 126.72, 122.56, 113.86, 64.36, 62.93,
55.24.
HRMS (ESI): m/z [M + H]+ calcd for C17H13O4: 281.0808; found:
281.0808.
1H NMR (300 MHz, CDCl3): δ = 8.12–8.09 (m, 1 H), 8.05–8.02 (m, 1 H),
7.82–7.79 (m, 2 H), 7.48 (s, 1 H), 7.41–7.37 (m, 3 H), 3.95 (s, 1 H).
13C NMR (75 MHz, CDCl3): δ = 190.33, 189.63, 134.76, 134.70, 134.51,
132.74, 132.19, 131.66, 129.76, 129.52, 127.86, 127.63, 126.94,
125.83, 63.73, 62.86.
HRMS (ESI): m/z [M + H]+ calcd for C16H10ClO3: 285.0313; found:
285.0313.
1a-(4-Fluorophenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
(2m)
Yield: 45.0 mg (56%); white solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 143–
1a-o-Tolylnaphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione (2r)
Yield: 75.2 mg (95%); yellow oil; Rf = 0.60 (PE/EtOAc, 7:1).
1H NMR (300 MHz, CDCl3): δ = 8.10–8.03 (m, 2 H), 7.81–7.78 (m, 2 H),
7.38–7.35 (m, 2 H), 7.30–7.26 (m, 2 H), 4.01 (s, 1 H), 2.28 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 191.35, 190.14, 134.69, 134.56, 132.26,
131.89, 130.18, 129.54, 128.55, 127.85, 126.91, 125.97, 61.79, 19.36.
HRMS (ESI): m/z [M + H]+ calcd for C17H13O3: 265.0859; found:
265.0859.
144 °C (lit.29d 143–145 °C).
1H NMR (300 MHz, CDCl3): δ = 8.10–8.07 (m, 1 H), 8.03–8.00 (m, 1 H),
7.81–7.78 (m, 2 H), 7.50–7.45 (m, 2 H), 7.14 (t, J = 8.7 Hz, 2 H), 3.95 (s,
1 H).
13C NMR (75 MHz, CDCl3): δ = 190.71, 190.14, 134.75, 134.65, 132.30,
131.74, 129.63, 129.52, 127.87, 126.92, 126.59, 126.55, 115.77,
115.48, 64.01, 62.98.
HRMS (ESI): m/z [M + H]+ calcd for C16H10FO3: 269.0609; found:
269.0603.
1a-(2-Chlorophenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
(2s)
1a-(4-Chlorophenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-dione
Yield: 61.7 mg (72%); pale-yellow oil; Rf = 0.60 (PE/EtOAc, 7:1).
(2n)
1H NMR (300 MHz, CDCl3): δ = 8.13–8.10 (m, 1 H), 8.07–8.05 (m, 1 H),
7.82–7.79 (m, 2 H), 7.50–7.49 (m, 1 H), 7.45–7.39 (m, 3 H), 3.98 (s,
1 H).
Yield: 75.3 mg (88%); yellow solid; Rf = 0.60 (PE/EtOAc, 7:1); mp 102–
104 °C.
1H NMR (300 MHz, CDCl3): δ = 8.10–8.07 (m, 1 H), 8.04–8.01 (m, 1 H),
7.83–7.77 (m, 2 H), 7.43 (s, 4 H), 3.93 (s, 1 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–H

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Synthesis
13C NMR (75 MHz, CDCl3): δ = 190.37, 188.63, 134.71, 134.68, 133.80,
131.89, 131.83, 130.80, 130.59, 129.19, 129.02, 127.93, 127.09,
127.03, 64.13, 61.77.
HRMS (ESI): m/z [M + H]+ calcd for C16H10ClO3: 285.0313; found:
285.0313.
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dron 2007, 63, 5184. (b) Arai, S.; Tsuge, H.; Oku, M.; Miura, M.;
Shioiri, T. Tetrahedron 2002, 58, 1623. (c) Snatzke, G.; Wynberg,
H.; Feringa, B.; Marsman, B. G.; Greydanus, B.; Pluim, H. J. Org.
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1a-(2,4-Dimethylphenyl)naphtho[2,3-b]oxirene-2,7(1aH,7aH)-di-
one (2t)
Yield: 80.4 mg (96%); pale-yellow oil; Rf = 0.60 (PE/EtOAc, 7:1).
1H NMR (300 MHz, CDCl3): δ = 8.09–8.06 (m, 1 H), 8.04–8.01 (m, 1 H),
7.80–7.77 (m, 2 H), 7.28–7.27 (m, 1 H), 7.10–7.07 (m, 2 H), 4.00 (s,
1 H), 2.34 (s, 3 H), 2.25 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 191.44, 190.29, 139.43, 134.58, 134.43,
132.21, 131.82, 130.99, 127.76, 127.19, 126.79, 126.59, 61.79, 21.18,
19.21.
HRMS (ESI): m/z [M + H]+ calcd for C18H15O3: 279.1016; found:
279.1019.
Funding Information
This work is supported by Science and Technology Department of Si-
(11) (a) Bundu, A.; Berry, N. G.; Gill, C. D.; Dwyer, C. L.; Stachulski, A.
V.; Taylor, R. J.; Whittall, J. Tetrahedron: Asymmetry 2005, 16,
283. (b) Bunge, A.; Hamann, H.-J.; McCalmont, E.; Liebscher, J.
Tetrahedron Lett. 2009, 50, 4629. (c) Lattanzi, A.; Cocilova, M.;
Iannece, P.; Scettri, A. Tetrahedron: Asymmetry 2004, 15, 3751.
(d) Kośnik, W.; Bocian, W.; Kozerski, L.; Tvaroška, I.;
Chmielewski, M. Chem. Eur. J. 2008, 14, 6087. (e) Dwyer, C. L.;
Gill, C. D.; Ichihara, O.; Taylor, R. J. K. Synlett 2000, 704.
(f) Kośnik, W.; Stachulski, A. V.; Chmielewski, M. Tetrahedron:
Asymmetry 2005, 16, 1975. (g) Genski, T.; Macdonald, G.; Wei,
X.; Lewis, N.; Taylor, R. J. K. Synlett 1999, 795. (h) Colonna, S.;
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5862. (i) Valderrama, J. A.; Gonzalez, M. F.; Torres, C. Hetero-
cycles 2003, 60, 2343.
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