Metal triflate promoted synthesis of naphthalenes

Article abstract of DOI:10.1039/c7ra04960a

A synthetic route to derive the skeleton of naphthalenes starting with isovanillin is described with modest total yields via the key transformation of metal triflate-mediated intramolecular benzannulation of o-formyl or o-benzoyl allylbenzenes in MeNO₂ at rt.

Full text of DOI:10.1039/c7ra04960a

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Metal triflate promoted synthesis of naphthalenes†
*
Chieh-Kai Chan, Heui-Sin Wang, Yu-Lin Tsai and Meng-Yang Chang
Cite this: RSC Adv., 2017, 7, 29321
A synthetic route to derive the skeleton of naphthalenes starting with isovanillin is described with modest
total yields via the key transformation of metal triflate-mediated intramolecular benzannulation of o-
formyl or o-benzoyl allylbenzenes in MeNO2 at rt.
Received 3rd May 2017
Accepted 30th May 2017
DOI: 10.1039/c7ra04960a
rsc.li/rsc-advances
yield than the other scanned catalysts.10b The adopted synthetic
routes are described in Scheme 1. Our aim was to nd an
Introduction
A naphthalene ring system1 is a key core skeleton for bioactive
molecules,2 natural products3 and functionalized materials.4 A
considerable number of attempts have been developed to
determine the synthetic routes of the bicyclic skeleton. Two
major key transformations for the formation of a functionalized
naphthalene skeleton include: (1) acids (or Lewis acids)
promote intramolecular Friedel–Cras type annulations,5 and
(2) bases promote intramolecular anionic annulations.6 Tran-
sition metal (e.g., Cr, Mn, Pd, W, Rh, Co, Ru, Ni, Co, Zn, Ti and
Au) catalyzed benzannulations provide another approach for
preparing the core structure.7 Therefore, a new synthetic route
for diverse naphthalenes via intramolecular annulation of the
readily available starting materials is still a continuing need in
the synthetic eld.
As part of our efforts in the synthetic applications of dialkoxy
o-formyl allylbenzenes 18 and the development of metal triate-
promoted robust and efficient reactions,9 we have now
streamlined the facile synthesis of substituted naphthalenes via
metal triate-mediated intramolecular benzannulation of o-
carbonyl synthon allylbenzenes, such as o-formyl or o-benzoyl
allylbenzenes, in MeNO2 at rt. To the best of our knowledge, few
reports on the metal triate-mediated intramolecular annula-
tion of o-carbonyl synthon allylbenzenes have been docu-
mented.10 In 2011, Kuninobu and Takai described that metal
triates-catalyzed the dehydrative cycloaromatization of o-ben-
zylbenzaldehyde 2 provided tricyclic anthracene in a 97%
yield.10a Among the metal triates-mediated syntheses, In(OTf)3
and Sc(OTf)3 demonstrated excellent transformation. In 2014,
Luo demonstrated that Cu(OTf)2 provided a tetralin skeleton via
the conjugate addition of 20-allylchalcone 3 in a higher (90%)
optimal metal triate as the catalyst for synthesizing naphtha-
lenes 5 via the intramolecular benzannulation of o-formyl
allylbenzene 4 (a hybrid combining the formyl motif of 2 and
the allyl group of 3).
Results and discussion
Initially, six metal triates were chosen as the catalysts for
examining the benzannulation of o-formyl allylbenzene 4a.11,12
In line with two preliminary studies, 10 mol% catalytic amounts
of In(OTf)3, Sc(OTf)3, Cu(OTf)2, Bi(OTf)3, and AgOTf were rst
scanned for the formation of 1,2-dimethoxynaphthalene (5a) in
MeNO2 at rt for 8 h, as shown in Table 1 and entries 1–5.
However, 5a was isolated in a range of poor to moderate yields
(18–72%). When Sn(OTf)2 or Fe(OTf)3 was applied to the reac-
tion conditions, yields were increased to 95% or 88% (entries 6
and 7). Under the same conditions, treatment of 4a with
Ga(OTf)3 provided 5a in a 44% yield along with a 38% yield of 6a
Department of Medicinal and Applied Chemistry, Kaohsiung Medical University
Hospital, Kaohsiung Medical University, Kaohsiung 80708, Taiwan. E-mail:
mychang@kmu.edu.tw
† Electronic supplementary information (ESI) available. CCDC 790259,
923282–923284, 1519809 and 1523594. For ESI and crystallographic data in CIF
or other electronic format see DOI: 10.1039/c7ra04960a
Scheme 1 Metal triflates-catalyzed annulations.
RSC Adv., 2017, 7, 29321–29329 | 29321
This journal is © The Royal Society of Chemistry 2017

View Article Online
RSC Advances
Paper
Table 1 Metal triflates mediated reaction conditionsa
mol%) was involved in the reaction system (entry 16). The
resulting mixture failed to promote dehydrative benzannulation
in the presence of 4a due to the proton scavenger could block in
situ generated TfOH. To examine the stability and reactivity of
Sn(OTf)2 in the presence of water, H2O (10 mg) was added to the
reaction condition and a 90% yield of 5a was generated (entry
17). According to the results, a 10 mol% of Sn(OTf)2/MeNO2/rt
condition would be an optimal combination for yielding 5a.
Aside from the present benzannulation of o-formyl allyl-
benzene 4a, Sn(OTf)2 has also been reported as a catalyst for
Entry Catalyst (mol%) Solvent
Temp (ꢀC) Time (h) 5ab (%)
1
2
3
4
5
6
7
8
Bi(OTf)3 (10)
In(OTf)3 (10)
AgOTf (10)
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
CH2Cl2
Toluene
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
MeNO2
25
25
25
25
25
25
25
25
25
25
25
101
25
25
25
25
25
8
8
8
8
8
8
8
8
8
8
8
8
20
8
8
8
8
72
70
aldol
reactions,13a
Mannish-type
reactions,13b,c
rear-
rangements,13d,e (3 + 2) annulations,13f–h and other routes.13i–k For
branched, linear and cyclic alkyl substituents of o-formyl allyl-
benzenes 4b–d (R ¼ Me, iPr, nBu, and c-C5H9), 5b–d provided
good yields (90%, 91% or 88%) under the above-mentioned
conditions (Scheme 2).
64
Sc(OTf)3 (10)
Cu(OTf)2 (10)
Sn(OTf)2 (10)
Fe(OTf)3 (10)
Ga(OTf)3 (10)
Sn(OTf)2 (5)
Sn(OTf)2 (10)
Sn(OTf)2 (10)
Sn(OTf)2 (10)
Sn(OTf)2 (10)
SnCl2 (10)
40c
18c
95
88
44 (38)d
72
9
On the basis of the results, a plausible reaction mechanism
is shown in Scheme 3. Mechanistically, two general distinctive
activation modes of the o-allylbenzaldehydes can be proposed
for intramolecular dehydrative benzannulations. The rst one
is a purely metallic-based Lewis acid pathway. The sequence
initiates the formation of intermediate A by complexation of
a carbonyl motif of 3a with Sn(OTf)2. The in situ generated tri-
ate anion deprotonates the Ha (blue) of A to give B as the result
of a tandem intramolecular electrophilic annulation. Following
the protonation of B with the TfOH, C is obtained. On the basis
of the triate anion-mediated deprotonation of C (for Hb, pink),
5a is provided via the removal of Sn(OH)OTf and TfOH.
Subsequently, Sn(OTf)2 is regenerated for the next catalytic cycle
by the complexation of Sn(OH)OTf and TfOH. The second
10
11
12
13
14
15
16
17
79
69
42e
83
<5
TfOH (10)
60
Sn(OTf)2 (10)f
Sn(OTf)2 (10)h
—
c,g
90
a
Reactions were run on 4a (0.5 mmol), solvent (5 mL). b Isolated yields.
4a was recovered (entry 5, 26%; entry 6, 54%; entry 14, 85%; entry 16,
c
d
e
80%). 6a (25%) was isolated. Unknown product (35%) was formed.
f
Proton scavenger (2,6-di-tert-butylpyridine, 10 mol%) was added.
g
No reaction. h Water (10 mg) was added.
(entry 8). In addition, 6a was generated via Ga(OTf)3-mediated
by the addition of 4a with MeNO2. With these results in mind,
a series of commercially available lanthanide triates (Ln(OTf)3)
were examined next, including: La(OTf)3, Ce(OTf)3, Pr(OTf)3,
Nd(OTf)3, Sm(OTf)3, Eu(OTf)3, Gd(OTf)3, Tb(OTf)3, Dy(OTf)3,
Ho(OTf)3, Er(OTf)3, Yb(OTf)3 and Tm(OTf)3. However, no isola-
tion of the desired 5a was observed and only 4a was recovered
under Ln(OTf)3-mediated reactions. With the results in hand,
we found that Sn(OTf)2 was among the most reactive and used
catalyst compared to other metal triate derivatives. Along this
line, we planned to take advantage of the intrinsically high
catalytic ability of Sn(OTf)2 to construct the naphthalene
system. Aer decreasing the catalytic amounts (10 / 5 mol%),
a poor yield (72%) was observed (entry 9). Furthermore, we
studied the factors of solvent and temperature. Aer changing
the solvents (from MeNO2 to CH2Cl2 and toluene), different
results were observed (entries 10 and 11). In entry 12, the
complex mixture occurred (35%) when elevating the tempera-
ture (25 / 101).
Scheme 2 Synthesis of 5a–d.
Next, Sn(OTf)2 exhibited a low yield (83%) under an elon-
gated reaction time (8 / 20 h), as shown in entry 13. Another
type of tin(II) salt (e.g. SnCl2) was examined. In entry 14, 5a was
isolated in trace amounts only. By the involvement of 10 mol%
TfOH (entry 15), 60% of 5a was generated. The control experi-
ment revealed that the real catalyst was the trace amount of
TfOH resulting from the hydrolysis of the metal triates. In the
other hand, proton scavenger (2,6-di-tert-butylpyridine, 10 Scheme 3 Proposed mechanism.
29322 | RSC Adv., 2017, 7, 29321–29329
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
possibility would involve a Brønsted acid catalysis. By Sn(OTf)2 substituent was unaffected. With the results in hands, 10 mol%
assisted in situ formed TfOH, D is generated.17 Following the of Sn(OTf)2 was applied to the annulation of two substrates 4j
above similar route, 5a is also produced via (i) the triate anion (Ar ¼ 4-MeOC6H4) or 4l (Ar ¼ 3,4-CH2O2C6H3) having two allyl
deprotonates the Ha of D, (ii) protonation of E with the TfOH, arms: one o-allyl group (blue) and one C-allyl group (red). Under
(iii) triate anion-mediated deprotonation of F (for Hb), (iv) the a two-step procedure of Sn(OTf)2-mediated reaction and then O-
removal of water and the regeneration of TfOH. Although metal methylation (K2CO3, MeI), we observed C-allyl isomers 7a or 7b
triate-mediated transformations have been described were produced in only 21% and 15% yields, respectively via
proceeding via proton transfer, we think that the nature of the a one-pot tandem intramolecular dehydrative benzannulation
catalytic species may be still under debate.18 For the overall and Claisen rearrangement (Scheme 6). By increasing the use of
benzannulation procedure, water is the only by-product. Sn(OTf)2 from catalytic amounts (10 mol%) to stoichiometric
Therefore, it is important to use Sn(OTf)2 that are stable and amounts (1.0 equivalent),15 the yields of 7a or 7b were enhanced
show high reactivity even in the presence of water.9a,b,g,10a Metal to 85% and 80% yields, respectively via the two-step route. The
cations (e.g. Bi3+, Al3+ or Sn2+) in water exhibit strong acidic non-catalytic amounts (1.0 equivalent) of Sn(OTf)2 which
properties because of the acidication through coordination of mediated the tandem intramolecular procedure included: (1)
water molecules present in the “inner-sphere” of the cation.19 benzannulation of o-allyl and aroyl groups and (2) double
18d
˜
According to Dunach report, metal triates such as Bi(OTf)3 Claisen rearrangement of the o-allyl group. In particular, the
are generally obtained and used as its hydrate form and there- present double Claisen rearrangement occurred at room
fore presents indubitably a strong induced Brønsted acidity.
temperature. In comparison with the literature reports (150–200
Furthermore, Sn(OTf)2-mediated conversion of o-aroyl allyl- ꢀC),16 a few examples were described.
benzenes 4e–l into arylnaphthalenes 5e–l was examined, as
To change the position of the aryl group on the naphthalene
shown in Scheme 4. The starting materials 4e–l (R ¼ H, allyl; Ar skeleton, eight 4p–v (Ar ¼ Ph, 4-FC6H4, 4-MeC6H4, 4-MeOC6H4,
¼
Ph, 4-FC6H4, 2-MeC6H4, 2-MeOC6H4, 3-MeOC6H4, 4- 4-CF3C6H4, 2-MeOC6H4, 4-PhC6H4) were investigated next. By
MeOC6H4, 3,4-CH2O2C6H3) were prepared by our previous this synthetic protocol, 8a–g were synthesized in 74–81% yields,
reports.8p The substituents of R and Ar on 4e–l did not affect the as shown in Scheme 7. By the removal of the m-oxygenated
yield outcome for the benzannulation procedure and no group, 4w–x having the o-allyl side arms (Y ¼ H, MeO) were then
obvious yield changes were observed for the generation of 5e–l. examined. When benzannulation of 4w–x was treated with
The isolated yields were provided in the range of 88–95%. The Sn(OTf)2, the yields of 9a (61%) and 9b (40%) provide good
structures of 5e and 5f were determined by single-crystal X-ray results (Scheme 8). The structures of 8d, 8g, 9a and 9b were
crystallography.14
determined by single-crystal X-ray crystallography.14 By a one-
As an extension of the benzannulation, the skeleton of pot two-step route (Suzuki–Miyaura coupling and our meth-
aroylbenzene having two allyl arms (ortho and para positions) od),8p a simple naphthalene 10a could be obtained from o-
was studied (Scheme 5). Treatment of 4m–o (R ¼ H, Me; Ar ¼ 4- formyl phenyl boronic acids in a 70% yield via the formation of
MeOC6H4, 3,4-CH2O2C6H3)8p with Sn(OTf)2 provided 5m–o in
95%, 90% and 91% yields, respectively. Notably, the p-allyl
Scheme 6 Synthesis of 7a–b.
Scheme 4 Synthesis of 5e–l.
Scheme 5 Synthesis of 5m–o.
Scheme 7 Synthesis of 8a–g.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29321–29329 | 29323

View Article Online
RSC Advances
Paper
extracted with CH2Cl2 (3 ꢁ 20 mL). The combined organic
layers were washed with brine, dried, ltered and evaporated to
afford crude product. Purication on silica gel (hexanes/EtOAc
¼ 100/1–10/1) afforded 5 and 6a.
1,2-Dimethoxynaphthalene (5a). Yield ¼ 95% (179 mg);
colorless oil; HRMS (ESI, M+ + 1) calcd for C12H13O2 189.0916,
found 189.0919; 1H NMR (400 MHz, CDCl3): d 8.15 (d, J ¼ 8.4 Hz,
1H), 7.80 (d, J ¼ 8.4 Hz, 1H), 7.62 (d, J ¼ 8.8 Hz, 1H), 7.52–7.48
(m, 1H), 7.40–7.36 (m, 1H), 7.31 (d, J ¼ 8.8 Hz, 1H), 4.03 (s, 3H),
4.01 (s, 3H); 13C NMR (100 MHz, CDCl3): d 148.28, 142.84,
129.63, 128.98, 127.61, 126.05, 124.17, 124.01, 121.23, 115.15,
61.06, 56.83.
Scheme 8 Synthesis of 9a–b.
1-(2-Allyl-3,4-dimethoxyphenyl)-2-nitroethanol (6a). For
Ga(OTf)3 promoted reaction, 6a was generated in 38% (101 mg);
colorless solid; mp ¼ 78–80 ꢀC (recrystallized from hexanes and
EtOAc); HRMS (ESI, M+ + 1) calcd for C13H18NO5 268.1185,
found 268.1188; 1H NMR (400 MHz, CDCl3): d 7.24 (d, J ¼ 8.4 Hz,
1H), 6.87 (d, J ¼ 8.4 Hz, 1H), 6.02–5.92 (m, 1H), 5.60 (dd, J ¼ 2.8,
10.0 Hz, 1H), 5.60 (dq, J ¼ 1.6, 10.0 Hz, 1H), 4.93 (dq, J ¼ 1.6,
17.2 Hz, 1H), 4.49 (q, J ¼ 13.2 Hz, 1H), 4.48 (q, J ¼ 13.2 Hz, 1H),
3.87 (s, 3H), 3.80 (s, 3H), 3.53 (t, J ¼ 5.6 Hz, 2H), 2.41 (br s, 1H);
13C NMR (100 MHz, CDCl3): d 152.87, 147.13, 136.98, 130.59,
129.66, 121.95, 115.74, 110.93, 80.88, 67.28, 60.89, 55.66, 29.86.
1-Isopropoxy-2-methoxynaphthalene (5b). Yield ¼ 90% (194
mg); colorless oil; HRMS (ESI, M+ + 1) calcd for C14H17O2
217.1229, found 217.1230; 1H NMR (400 MHz, CDCl3): d 8.19 (d,
J ¼ 8.4 Hz, 1H), 7.78 (d, J ¼ 8.4 Hz, 1H), 7.59 (d, J ¼ 9.2 Hz, 1H),
7.49–7.45 (m, 1H), 7.38–7.34 (m, 1H), 7.30 (d, J ¼ 8.8 Hz, 1H),
4.72–4.65 (m, 1H), 3.98 (s, 3H), 1.40 (d, J ¼ 6.0 Hz, 6H); 13C NMR
(100 MHz, CDCl3): d 148.53, 140.93, 130.40, 129.72, 127.43,
125.67, 123.88, 123.67, 122.17, 115.36, 75.30, 56.84, 22.71 (2x).
1-Butoxy-2-methoxynaphthalene (5c). Yield ¼ 91% (209 mg);
colorless oil; HRMS (ESI, M+ + 1) calcd for C15H19O2 231.1385,
found 231.1388; 1H NMR (400 MHz, CDCl3): d 8.17 (d, J ¼ 8.4 Hz,
1H), 7.79 (d, J ¼ 8.4 Hz, 1H), 7.60 (d, J ¼ 8.8 Hz, 1H), 7.50–7.46
(m, 1H), 7.39–7.35 (m, 1H), 7.30 (d, J ¼ 8.8 Hz, 1H), 4.16 (t, J ¼
6.4 Hz, 2H), 3.99 (s, 3H), 1.94–1.87 (m, 2H), 1.67–1.58 (m, 2H),
1.04 (t, J ¼ 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d 148.36,
142.34, 129.77, 129.45, 127.55, 125.88, 123.98, 123.86, 121.52,
115.53, 73.43, 57.00, 32.50, 19.34, 13.94.
Scheme 9 Synthesis of 10a.
o-allylbenzaldehyde 4y (Scheme 9). Although the isolated yield
of 10a was low, it still provided a novel and efficient trans-
formation from o-formyl phenylboronic acid to naphthalene.
Conclusion
In summary, we have successfully presented a synthetic route
for the synthesis of substituted naphthalenes in good yields via
Sn(OTf)2-mediated benzannulation of o-formyl or o-aroyl allyl-
benzenes. The use of various metal triates was investigated for
the one-pot facile approach and efficient transformation.
Further investigations regarding the synthetic application of
metal triates will be conducted and published in due course.
Experimental
General
All reagents and solvents were obtained from commercial
sources and used without further purication. Reactions were
routinely carried out under an atmosphere of dry air with
magnetic stirring. Products in organic solvents were dried with
anhydrous magnesium sulfate before concentration in vacuo.
Melting points were determined with a SMP3 melting appa-
ratus. 1H and 13C NMR spectra were recorded on a Varian
INOVA-400 spectrometer operating at 400 and at 100 MHz,
respectively. Chemical shis (d) are reported in parts per
million (ppm) and the coupling constants (J) are given in Hertz.
High resolution mass spectra (HRMS) were measured with
a mass spectrometer Finnigan/Thermo Quest MAT 95XL. X-ray
crystal structures were obtained with an Enraf-Nonius FR-590
diffractometer (CAD4, Kappa CCD).
1-Cyclopentyloxy-2-methoxynaphthalene (5d). Yield ¼ 88%
(213 mg); colorless oil; HRMS (ESI, M+ + 1) calcd for C16H19O2
243.1385, found 243.1382; 1H NMR (400 MHz, CDCl3): d 8.13 (d,
J ¼ 8.0 Hz, 1H), 7.76 (d, J ¼ 8.0 Hz, 1H), 7.57 (d, J ¼ 8.8 Hz, 1H),
7.47–7.43 (m, 1H), 7.37–7.33 (m, 1H), 7.29 (d, J ¼ 8.8 Hz, 1H),
5.09–5.05 (m, 1H), 3.97 (s, 3H), 2.04–1.92 (m, 4H), 1.80–1.72 (m,
2H), 1.70–1.61 (m, 2H); 13C NMR (100 MHz, CDCl3): d 148.33,
141.15, 130.34, 129.81, 127.48, 125.70, 123.95, 123.55, 121.98,
115.71, 84.79, 57.00, 32.91 (2x), 23.78 (2x).
2-Methoxy-5-phenylnaphthalen-1-ol (5e). Yield ¼ 95% (238
mg); colorless solid; HRMS (ESI, M+ + 1) calcd for C17H15O2
251.1072, found 251.1078; 1H NMR (400 MHz, CDCl3): d 8.22 (d,
J ¼ 8.4 Hz, 1H), 7.56–7.41 (m, 7H), 7.32 (d, J ¼ 6.8 Hz, 1H), 7.19
A representative procedure of skeleton 5 and compound 6a is
as follows
Sn(OTf)2 (42 mg, 0.1 mmol) was added to a solution of 4a–o (1.0 (d, J ¼ 9.2 Hz, 1H), 6.13 (br s, 1H), 3.98 (s, 3H); 13C NMR (100
mmol) in MeNO2 (5 mL) at 25 ꢀC. The reaction mixture was MHz, CDCl3): d 141.02, 139.83, 139.69, 129.98 (2x), 128.90,
ꢀ
stirred for 8 h at 25 C and the solvent was concentrated. The 128.12 (2x), 127.70, 127.11, 125.33, 124.92, 124.34, 120.72,
residue was diluted with water (10 mL) and the mixture was 117.93, 112.93, 57.00. Single-crystal X-ray diagram: crystal of
29324 | RSC Adv., 2017, 7, 29321–29329
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
compound 5e was grown by slow diffusion of EtOAc into
a solution of compound 5e in CH2Cl2 to yield colorless prisms.
The compound crystallizes in the orthorhombic crystal system,
1-Allyloxy-2-methoxy-5-(4-methoxyphenyl)naphthalene (5j).
Yield ¼ 90% (288 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C21H21O3 321.1491, found 321.1493; 1H NMR (400 MHz,
CDCl3): d 8.15 (dt, J ¼ 0.8, 8.4 Hz, 1H), 7.66 (dd, J ¼ 0.8, 9.2 Hz,
1H), 7.48 (dd, J ¼ 7.2, 8.8 Hz, 1H), 7.40 (d, J ¼ 8.8 Hz, 2H), 7.27
(dd, J ¼ 0.8, 7.2 Hz, 1H), 7.21 (d, J ¼ 9.2 Hz, 1H), 7.01 (d, J ¼
8.8 Hz, 2H), 6.27–6.17 (m, 1H), 5.46 (dq, J ¼ 1.6, 17.2 Hz, 1H),
5.27 (dq, J ¼ 1.6, 10.4 Hz, 1H), 4.68 (dt, J ¼ 1.6, 6.0 Hz, 2H), 3.96
(s, 3H), 3.88 (s, 3H); 13C NMR (100 MHz, CDCl3): d 158.90,
148.19, 141.66, 139.76, 134.43, 133.24, 131.03 (2x), 129.93,
128.05, 125.73, 125.18, 122.67, 120.84, 117.49, 114.76, 113.64
(2x), 74.32, 56.79, 55.32.
˚
˚
space group Fdd2, a ¼ 13.3885(3) A, b ¼ 66.3135(18) A, c ¼
5.5816(2) A, V ¼ 4955.6(2) A , Z ¼ 16, dcalcd ¼ 1.342 g cmꢂ3
,
3
˚
˚
F(000) ¼ 2112, 2q range 1.23–26.39ꢀ, R indices (all data) R1 ¼
0.0428, wR2 ¼ 0.1154.
5-(4-Fluorophenyl)-2-methoxynaphthalen-1-ol (5f). Yield ¼
90% (241 mg); colorless solid; HRMS (ESI, M+ + 1) calcd for
C17H14FO2 269.0978, found 269.0983; 1H NMR (400 MHz,
CDCl3): d 8.26 (d, J ¼ 8.4 Hz, 1H), 7.53–7.39 (m, 4H), 7.7.29 (dd, J
¼ 1.2, 6.8 Hz, 1H), 7.22–7.17 (m, 3H), 6.18 (br s, 1H), 3.99 (s, 3H);
13C NMR (100 MHz, CDCl3): d 162.16 (d, J ¼ 244.1 Hz), 141.08,
139.74, 138.71, 136.87 (d, J ¼ 3.0 Hz), 131.46 (d, J ¼ 17.5 Hz, 2x),
127.71, 125.41, 124.87, 124.35, 120.92, 117.65, 115.02 (d, J ¼
21.2 Hz, 2x), 113.01, 56.94. Single-crystal X-ray diagram: crystal
of compound 5f was grown by slow diffusion of EtOAc into
a solution of compound 5f in CH2Cl2 to yield colorless prisms.
The compound crystallizes in the triclinic crystal system, space
1-Allyloxy-5-(4-uorophenyl)-2-methoxynaphthalene
(5k).
Yield ¼ 91% (280 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C20H18FO2 309.1291, found 309.1293; 1H NMR (400 MHz,
CDCl3): d 8.22 (dt, J ¼ 0.8, 8.4 Hz, 1H), 7.60 (dd, J ¼ 0.8, 9.2 Hz,
1H), 7.51 (dd, J ¼ 6.8, 8.4 Hz, 1H), 7.47–7.42 (m, 2H), 7.27 (dd, J
¼ 1.2, 7.2 Hz, 1H), 7.24 (d, J ¼ 9.2 Hz, 1H), 7.21–7.15 (m, 2H),
6.30–6.20 (m, 1H), 5.49 (dq, J ¼ 1.6, 17.2 Hz, 1H), 5.30 (dq, J ¼
1.6, 10.4 Hz, 1H), 4.72 (dt, J ¼ 1.6, 6.0 Hz, 2H), 3.99 (s, 3H); 13
C
˚
˚
˚
ꢀ
group P1, a ¼ 6.7021(11) A, b ¼ 7.9371(12) A, c ¼ 12.170(2) A, V ¼
631.92(18) A , Z ¼ 2, dcalcd ¼ 1.410 g cmꢂ3, F(000) ¼ 280, 2q
3
˚
NMR (100 MHz, CDCl3): d 162.21 (d, J ¼ 244.1 Hz), 148.26,
141.69, 138.97, 136.76 (d, J ¼ 3.0 Hz), 134.36, 131.46 (d, J ¼
7.5 Hz, 2x), 129.90, 127.82, 125.64, 125.25, 122.31, 121.32,
117.52, 115.09 (d, J ¼ 21.2 Hz, 2x), 114.99, 74.31, 56.75.
range 1.70–26.38ꢀ, R indices (all data) R1 ¼ 0.0431, wR2
¼
0.1097.
1-Allyloxy-2-methoxy-5-o-tolylnaphthalene (5g). Yield ¼ 91%
(277 mg); colorless gum; HRMS (ESI, M+ + 1) calcd for C21H21O2
305.1542, found 305.1549; 1H NMR (400 MHz, CDCl3): d 8.19 (dt,
J ¼ 0.4, 8.4 Hz, 1H), 7.51 (dd, J ¼ 6.8, 8.4 Hz, 1H), 7.38–7.16 (m,
7H), 6.30–6.20 (m, 1H), 5.49 (dq, J ¼ 1.6, 17.2 Hz, 1H), 5.30 (dq, J
¼ 1.6, 10.4 Hz, 1H), 4.71 (dt, J ¼ 1.6, 6.0 Hz, 2H), 3.97 (s, 3H),
2.03 (s, 3H); 13C NMR (100 MHz, CDCl3): d 148.20, 141.77,
140.33, 139.58, 136.76, 134.49, 130.30, 129.81, 129.61, 128.23,
127.50, 125.68, 125.48, 124.89, 122.60, 121.00, 117.39, 114.90,
74.33, 56.80, 20.01.
1-Allyloxy-2-methoxy-5-(2-methoxyphenyl)naphthalene (5h).
Yield ¼ 88% (282 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C21H21O3 321.1491, found 321.1496; 1H NMR (400 MHz,
CDCl3): d 8.19 (dt, J ¼ 1.2, 8.4 Hz, 1H), 7.52 (dd, J ¼ 7.2, 8.8 Hz,
1H), 7.43 (ddd, J ¼ 1.6, 7.2, 9.2 Hz, 1H), 7.34 (dd, J ¼ 0.8, 9.2 Hz,
1H), 7.30–7.27 (m, 2H), 7.18 (d, J ¼ 9.2 Hz, 1H), 7.09 (dd, J ¼ 0.8,
7.2 Hz, 1H), 7.05 (d, J ¼ 7.2 Hz, 1H), 6.30–6.20 (m, 1H), 5.49 (dq,
J ¼ 1.6, 17.2 Hz, 1H), 5.29 (dq, J ¼ 1.6, 10.4 Hz, 1H), 4.70 (dt, J ¼
1.6, 6.0 Hz, 2H), 3.97 (s, 3H), 3.71 (s, 3H); 13C NMR (100 MHz,
CDCl3): d 157.19, 148.08, 141.68, 136.74, 134.56, 131.91, 129.64,
129.57, 128.92, 128.36, 125.67, 125.60, 122.94, 121.22, 120.50,
117.34, 114.76, 111.01, 74.33, 56.82, 55.59.
5-(5-Allyloxy-6-methoxynaphthalen-1-yl)benzo[1,3]dioxole (5l).
Yield ¼ 88% (294 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C21H19O4 335.1283, found 335.1288; 1H NMR (400 MHz,
CDCl3): d 8.16 (dt, J ¼ 1.2, 8.4 Hz, 1H), 7.68 (dd, J ¼ 1.2, 9.2 Hz,
1H), 7.48 (dd, J ¼ 6.8, 8.4 Hz, 1H), 7.26 (dd, J ¼ 1.2, 7.2 Hz, 1H),
7.23 (d, J ¼ 9.2 Hz, 1H), 6.96 (br s, 1H), 6.93 (br s, 2H), 6.27–6.17
(m, 1H), 6.04 (s, 2H), 5.47 (dq, J ¼ 1.6, 16.8 Hz, 1H), 5.28 (dq, J ¼
1.6, 10.4 Hz, 1H), 4.68 (dt, J ¼ 1.6, 6.0 Hz, 2H), 3.98 (s, 3H); 13
C
NMR (100 MHz, CDCl3): d 148.23, 147.42, 141.66, 139.66, 134.74,
134.41, 129.92, 127.96, 126.01, 125.67, 125.16, 123.35, 122.58,
121.06, 117.52, 114.85, 110.57, 108.17, 101.09, 74.33, 56.81.
2-Allyl-5-(4-methoxyphenyl)naphthalen-1-ol (5m). Yield ¼
95% (276 mg); colorless gum; HRMS (ESI, M+ + 1) calcd for
1
C20H19O2 291.1385, found 291.1386; H NMR (400 MHz, CDCl3):
d 8.20 (dt, J ¼ 1.2, 8.4 Hz, 1H), 7.51 (dd, J ¼ 6.8, 8.4 Hz, 1H), 7.46
(dd, J ¼ 0.8, 8.4 Hz, 1H), 7.42 (d, J ¼ 8.8 Hz, 2H), 7.38 (dd, J ¼ 1.2,
6.8 Hz, 1H), 7.17 (d, J ¼ 8.4 Hz, 1H), 7.03 (d, J ¼ 8.8 Hz, 2H), 6.14–
6.04 (m, 1H), 5.60 (br s, 1H), 5.30–5.23 (m, 2H), 3.90 (s, 3H), 3.58 (dt,
J ¼ 1.6, 6.4 Hz, 2H); 13C NMR (100 MHz, CDCl3): d 158.88, 149.77,
139.59, 136.05, 133.35, 132.19, 131.07 (2x), 128.27, 126.89, 125.24,
124.86, 120.60, 118.65, 117.57, 117.05, 113.63 (2x), 55.33, 35.73.
1-Allyloxy-2-methoxy-5-(3-methoxyphenyl)naphthalene (5i).
Yield ¼ 95% (304 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C21H21O3 321.1491, found 321.1499; 1H NMR (400 MHz,
CDCl3): d 8.18 (d, J ¼ 8.4 Hz, 1H), 7.68 (d, J ¼ 9.2 Hz, 1H), 7.51 (dd,
J ¼ 7.2, 8.4 Hz, 1H), 7.40 (t, J ¼ 8.0 Hz, 1H), 7.31 (dd, J ¼ 0.8,
6.8 Hz, 1H), 7.23 (d, J ¼ 9.2 Hz, 1H), 7.09–7.06 (m, 1H), 7.04 (t, J ¼
2.4 Hz, 1H), 6.98 (ddd, J ¼ 0.8, 2.8, 8.4 Hz, 1H), 6.29–6.19 (m, 1H),
5.48 (dq, J ¼ 1.6, 17.2 Hz, 1H), 5.29 (dq, J ¼ 1.6, 10.0 Hz, 1H), 4.70
(dt, J ¼ 1.6, 6.0 Hz, 2H), 3.98 (s, 3H), 3.86 (s, 3H); 13C NMR (100
MHz, CDCl3): d 159.41, 148.23, 142.27, 141.63, 139.95, 134.41,
129.87, 129.15, 127.76, 125.65, 125.03, 122.65, 122.51, 121.21,
117.52, 115.52, 114.87, 112.86, 74.33, 56.78, 55.28.
2-Allyl-1-methoxy-5-(4-methoxyphenyl)naphthalene
(5n).
Yield ¼ 90% (274 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C21H21O2 305.1542, found 305.1548; 1H NMR (400 MHz,
CDCl3): d 8.16 (dt, J ¼ 1.2, 8.4 Hz, 1H), 7.69 (dd, J ¼ 0.8, 8.4 Hz,
1H), 7.56 (dd, J ¼ 7.2, 8.4 Hz, 1H), 7.43 (d, J ¼ 8.8 Hz, 2H), 7.40
(dd, J ¼ 1.6, 6.8 Hz, 1H), 7.29 (d, J ¼ 8.8 Hz, 1H), 7.05 (d, J ¼
8.8 Hz, 2H), 6.12–6.02 (m, 1H), 5.16–5.11 (m, 2H), 3.99 (s, 3H),
3.91 (s, 3H), 3.64 (dt, J ¼ 1.6, 6.4 Hz, 2H); 13C NMR (100 MHz,
CDCl3): d 158.89, 153.47, 140.10, 137.11, 133.18, 132.25, 131.03
(2x), 128.55, 128.18, 127.76, 126.64, 125.45, 122.25, 121.25,
115.85, 113.64 (2x), 62.14, 55.29, 33.82.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29321–29329 | 29325

View Article Online
RSC Advances
Paper
ꢀ
stirred for 8 h at 25 C and the solvent was concentrated. The
residue was diluted with water (10 mL) and the mixture was
extracted with CH2Cl2 (3 ꢁ 20 mL). The combined organic
layers were washed with brine, dried, ltered and evaporated to
afford crude product. Purication on silica gel (hexanes/EtOAc
¼ 100/1–10/1) afforded 8.
5-(6-Allyl-5-methoxynaphthalen-1-yl)benzo[1,3]dioxole (5o).
Yield ¼ 91% (289 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C21H19O3 319.1334, found 319.1336; 1H NMR (400 MHz,
CDCl3): d 8.13 (dt, J ¼ 1.2, 8.4 Hz, 1H), 7.67 (d, J ¼ 8.8 Hz, 1H),
7.52 (dd, J ¼ 7.2, 8.4 Hz, 1H), 7.37 (dd, J ¼ 1.2, 6.8 Hz, 1H), 7.27
(d, J ¼ 8.8 Hz, 1H), 6.97 (t, J ¼ 1.6 Hz, 1H), 6.93 (br s, 2H), 6.04 (s,
2H), 6.10–6.00 (m, 1H), 5.14–5.08 (m, 2H), 3.96 (s, 3H), 3.61 (dt, J
¼ 1.6, 6.4 Hz, 2H); 13C NMR (100 MHz, CDCl3): d 153.50, 147.44,
146.86, 140.04, 137.10, 134.70, 132.21, 128.56, 128.30, 127.86,
126.64, 125.41, 123.37, 122.16, 121.48, 115.90, 110.58, 108.17,
101.10, 62.18, 33.82.
1,2-Dimethoxy-4-phenylnaphthalene (8a). Yield ¼ 81% (214
mg); colorless gum; HRMS (ESI, M+ + 1) calcd for C18H17O2
265.1229, found 265.1230; 1H NMR (400 MHz, CDCl3): d 8.22 (d,
J ¼ 8.8 Hz, 1H), 7.81 (d, J ¼ 8.8 Hz, 1H), 7.53–7.43 (m, 6H), 7.34–
7.30 (m, 1H), 7.27 (s, 1H), 4.06 (s, 3H), 4.02 (s, 3H); 13C NMR (100
MHz, CDCl3): d 147.55, 142.32, 140.49, 136.89, 130.07 (2x),
129.32, 128.26 (2x), 127.74, 127.28, 126.05 (2x), 124.14, 121.54,
116.40, 61.14, 56.91.
A representative procedure of skeleton 7 is as follows
Sn(OTf)2 (420 mg, 1.0 mmol) was added to a solution of 4j or 4l
4-(4-Fluorophenyl)-1,2-dimethoxynaphthalene (8b). Yield ¼
(1.0 mmol) in MeNO2 (5 mL) at 25 ꢀC. The reaction mixture was
74% (209 mg); colorless gum; HRMS (ESI, M+ + 1) calcd for
ꢀ
stirred for 8 h at 25 C and the solvent was concentrated. The
C
18H16FO2 283.1134, found 283.1139; 1H NMR (400 MHz,
residue was diluted with water (10 mL) and the mixture was
extracted with CH2Cl2 (3 ꢁ 20 mL). The combined organic
layers were washed with brine, dried, ltered and evaporated to
afford crude product. Without further purication, K2CO3
(276 mg, 2.0 mmol) was added to a solution of the resulting
CDCl3): d 8.20 (d, J ¼ 8.8 Hz, 1H), 7.74 (d, J ¼ 8.8 Hz, 1H), 7.52–
7.48 (m, 1H), 7.47–7.42 (m, 2H), 7.34–7.30 (m, 1H), 7.21 (s, 1H),
7.20–7.16 (m, 2H), 4.05 (s, 3H), 4.01 (s, 3H); 13C NMR (100 MHz,
CDCl3): d 162.28 (d, J ¼ 244.9 Hz), 147.54, 142.51, 136.39 (d, J ¼
3.1 Hz), 135.75, 131.59 (d, J ¼ 7.6 Hz, 2x), 129.35, 127.83, 126.12,
125.81, 124.31, 121.63, 116.57, 115.21 (d, J ¼ 21.2 Hz, 2x), 61.16,
56.99.
ꢀ
products in acetone (10 mL) at 25 C for 10 min. MeI (426 mg,
3.0 mmol) was added to the reaction mixture. The reaction
ꢀ
mixture was stirred for 8 h at reux, cooled to 25 C and the
1,2-Dimethoxy-4-p-tolylnaphthalene (8c). Yield ¼ 77% (214
solvent was concentrated. The residue was diluted with water
(10 mL) and the mixture was extracted with CH2Cl2 (3 ꢁ 20 mL).
The combined organic layers were washed with brine, dried,
ltered and evaporated to afford crude product. Purication on
silica gel (hexanes/EtOAc ¼ 100/1–10/1) afforded 7.
mg); colorless gum; HRMS (ESI, M+ + 1) calcd for C19H19O2
1
279.1385, found 279.1388; H NMR (400 MHz, CDCl3): d 8.23–
8.20 (m, 1H), 7.85–7.82 (m, 1H), 7.50 (ddd, J ¼ 1.2, 6.8, 8.4 Hz,
1H), 7.40 (d, J ¼ 8.0 Hz, 2H), 7.34–7.29 (m, 3H), 7.25 (s, 1H), 4.06
(s, 3H), 4.02 (s, 3H), 2.48 (s, 3H); 13C NMR (100 MHz, CDCl3):
d 147.57, 142.17, 137.55, 137.01, 136.91, 129.94 (2x), 129.32,
128.98 (2x), 127.83, 126.13, 125.99, 124.05, 121.51, 116.33,
61.13, 56.88, 21.19.
4-Allyl-1,2-dimethoxy-5-(4-methoxyphenyl)naphthalene (7a).
Yield ¼ 85% (284 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
for C22H23O3 335.1647, found 335.1652; 1H NMR (400 MHz,
CDCl3): d 8.21 (dt, J ¼ 1.2, 8.4 Hz, 1H), 7.44 (dd, J ¼ 6.8, 8.4 Hz,
1H), 7.24 (d, J ¼ 8.8 Hz, 2H), 7.17 (dd, J ¼ 1.2, 6.8 Hz, 1H), 7.13
(s, 1H), 6.93 (d, J ¼ 8.8 Hz, 2H), 5.70–5.60 (m, 1H), 4.92 (dq, J ¼
1.6, 10.0 Hz, 1H), 4.73 (dq, J ¼ 1.6, 17.2 Hz, 1H), 4.01 (s, 3H),
3.98 (s, 3H), 3.88 (s, 3H), 3.13 (dt, J ¼ 1.6, 6.4 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d 158.64, 147.29, 141.43, 139.61, 138.20,
137.16, 134.02, 131.03, 130.21 (2x), 128.53, 124.70, 121.42,
117.95, 115.56, 113.64, 113.17 (2x), 61.08, 56.69, 55.28, 39.75.
5-(8-Allyl-5,6-dimethoxynaphthalen-1-yl)benzo[1,3]dioxole (7b).
Yield ¼ 80% (278 mg); colorless gum; HRMS (ESI, M+ + 1) calcd for
1,2-Dimethoxy-4-(4-methoxyphenyl)naphthalene (8d). Yield
¼ 76% (223 mg); colorless solid; mp ¼ 118–120 ꢀC (recrystal-
lized from hexanes and EtOAc); HRMS (ESI, M+ + 1) calcd for
C
19H19O3 295.1334, found 295.1338; 1H NMR (400 MHz, CDCl3):
d 8.20 (d, J ¼ 8.4 Hz, 1H), 7.82 (d, J ¼ 8.4 Hz, 1H), 7.51–7.47 (m,
1H), 7.35 (d, J ¼ 8.4 Hz, 2H), 7.33–7.29 (m, 1H), 7.23 (s, 1H), 7.41
(d, J ¼ 8.8 Hz, 2H), 4.05 (s, 3H), 4.01 (s, 3H), 3.90 (s, 3H); 13C
NMR (100 MHz, CDCl3): d 159.00, 147.57, 142.10, 136.60,
132.85, 131.11 (2x), 129.34, 127.96, 126.12, 125.99, 124.05,
121.52, 116.36, 113.74 (2x), 61.14, 56.90, 55.36. Single-crystal X-
ray diagram: crystal of compound 8d was grown by slow diffu-
sion of EtOAc into a solution of compound 8d in CH2Cl2 to yield
colorless prisms. The compound crystallizes in the monoclinic
1
C22H21O4 349.1440, found 349.1450; H NMR (400 MHz, CDCl3):
d 8.21 (dd, J ¼ 1.2, 8.4 Hz, 1H), 7.43 (dd, J ¼ 7.2, 8.4 Hz, 1H), 7.17
(dd, J ¼ 1.6, 7.2 Hz, 1H), 7.14 (s, 1H), 6.84 (d, J ¼ 8.0 Hz, 1H), 6.81
(d, J ¼ 1.6 Hz, 1H), 6.77 (dd, J ¼ 1.6, 8.0 Hz, 1H), 6.05 (d, J ¼ 1.2 Hz,
1H), 6.01 (d, J ¼ 1.2 Hz, 1H), 5.74–5.64 (m, 1H), 4.96 (dq, J ¼ 1.6,
10.4 Hz, 1H), 4.78 (dq, J ¼ 1.6, 17.2 Hz, 1H), 4.00 (s, 3H), 3.98 (s,
3H), 3.19 (d, J ¼ 6.0 Hz, 2H); 13C NMR (100 MHz, CDCl3): d 147.35,
147.02, 146.57, 141.44, 139.42, 138.54, 138.18, 133.88, 130.75,
128.40, 126.69, 124.66, 122.54, 121.63, 118.03, 115.65, 110.02,
107.77, 101.03, 61.09, 56.69, 39.61.
˚
crystal system, space group P21/c, a ¼ 13.3450(12) A, b ¼
3
˚
˚
˚
15.2538(14) A, c ¼ 7.5723(7) A, V ¼ 1518.9(2) A , Z ¼ 4, dcalcd
¼
1.287 g cmꢂ3, F(000) ¼ 624, 2q range 2.045–26.421ꢀ, R indices
(all data) R1 ¼ 0.1172, wR2 ¼ 0.1285.
1,2-Dimethoxy-4-(4-triuoromethylphenyl)naphthalene (8e).
Yield ¼ 80% (266 mg); colorless gum; HRMS (ESI, M+ + 1) calcd
1
for C19H16F3O2 333.1102, found 333.1108; H NMR (400 MHz,
CDCl3): d 8.26 (d, J ¼ 8.4 Hz, 1H), 7.78 (d, J ¼ 8.0 Hz, 2H), 7.74 (d,
A representative procedure of skeleton 8 is as follows
J ¼ 8.4 Hz, 1H), 7.63 (d, J ¼ 8.0 Hz, 2H), 7.55–7.51 (m, 1H), 7.37–
Sn(OTf)2 (42 mg, 0.1 mmol) was added to a solution of 4p–v (1.0 7.33 (m, 1H), 4.09 (s, 3H), 4.04 (s, 3H), 7.27 (s, 1H); 13C NMR (100
mmol) in MeNO2 (5 mL) at 25 ꢀC. The reaction mixture was MHz, CDCl3): d 147.54, 144.19, 142.97, 135.19, 130.41 (2x),
29326 | RSC Adv., 2017, 7, 29321–29329
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
129.51 (d, J ¼ 31.9 Hz), 129.40, 127.44, 126.26, 125.48, 125.23 (q,
J ¼ 3.8 Hz, 2x), 124.58, 124.28 (d, J ¼ 270.6 Hz), 121.74, 116.60,
61.14, 56.97.
2,6-Dimethoxy-1-(4-methoxyphenyl)naphthalene (9b). Yield
ꢀ
¼ 40% (118 mg); colorless solid; mp ¼ 65–67 C (recrystallized
from hexanes and EtOAc); HRMS (ESI, M+ + 1) calcd for
1,2-Dimethoxy-4-(2-methoxyphenyl)naphthalene (8f). Yield
¼ 80% (235 mg); colorless gum; HRMS (ESI, M+ + 1) calcd for
C
19H19O3 295.1334, found 295.1335; 1H NMR (400 MHz, CDCl3):
d 7.82 (d, J ¼ 8.8 Hz, 1H), 7.76 (d, J ¼ 8.8 Hz, 1H), 7.51–7.41 (m,
2H), 7.27 (dd, J ¼ 1.2, 6.8 Hz, 1H), 7.21 (d, J ¼ 2.4 Hz, 1H), 7.11
(dd, J ¼ 2.8, 9.2 Hz, 1H), 7.02–6.96 (m, 2H), 3.98 (s, 3H), 3.97 (s,
3H), 3.90 (s, 3H). Single-crystal X-ray diagram: crystal of
compound 9b was grown by slow diffusion of EtOAc into
a solution of compound 9b in CH2Cl2 to yield colorless prisms.
The compound crystallizes in the monoclinic crystal system,
C
19H19O3 295.1334, found 295.1336; 1H NMR (400 MHz, CDCl3):
d 8.20–8.17 (m, 1H), 7.51–7.46 (m, 2H), 7.44 (dd, J ¼ 1.6, 8.0 Hz,
1H), 7.31–7.264 (m, 2H), 7.24 (s, 1H), 7.10 (dd, J ¼ 1.2, 7.6 Hz,
1H), 7.07 (d, J ¼ 8.0 Hz, 1H), 4.06 (s, 3H), 4.00 (s, 3H), 3.73 (s,
3H); 13C NMR (100 MHz, CDCl3): d 157.22, 147.56, 142.21,
133.41, 132.04, 129.18, 129.06, 129.02, 128.23, 126.42, 125.80,
123.76, 121.38, 120.53, 116.74, 111.03, 61.11, 56.81, 55.56.
4-Biphenyl-4-yl-1,2-dimethoxynaphthalene (8g). Yield ¼ 75%
(255 mg); colorless solid; mp ¼ 118–120 ꢀC (recrystallized from
hexanes and EtOAc); HRMS (ESI, M+ + 1) calcd for C24H21O2
˚
˚
space group C1c1, a ¼ 8.6905(3) A, b ¼ 21.9250(7) A, c ¼
8.2652(3) A, V ¼ 1494.97(9) A , Z ¼ 4, dcalcd ¼ 1.308 g cmꢂ3
,
3
˚
˚
F(000) ¼ 624, 2q range 1.86–26.52ꢀ, R indices (all data) R1
0.0291, wR2 ¼ 0.0743.
¼
1
341.1542, found 341.1548; H NMR (400 MHz, CDCl3): d 8.24–
Naphthalene (10a). Na2CO3 (106 mg, 1.0 mmol) was added to
a solution of allyl bromide (240 mg, 2.0 mmol) in dimethoxy-
ethane (DME, 5 mL) at 25 ꢀC. The reaction mixture was stirred at
25 ꢀC for 5 min. Then, o-formylphenylboronic acid (150 mg, 1.0
mmol) was added to the reꢀaction mixture at 25 ꢀC. The reaction
mixture was stirred at 25 C for 5 min. Pd(OAc)2 (11 mg, 0.05
mmol) was added to the reaction mixture at 25 ꢀC. The reaction
mixture was stirred at 80 ꢀC for 5 h. The reaction mixture (in situ
formed 4y) was cooled to 25 ꢀC and Sn(OTf)2 (42 mg, 0.1 mmol)
was added to the reaction mixture. The reaction mixture was
8.21 (m, 1H), 7.90–7.88 (m, 1H), 7.74 (d, J ¼ 8.4 Hz, 2H), 7.71–
7.69 (m, 2H), 7.58 (d, J ¼ 8.4 Hz, 2H), 7.54–7.48 (m, 3H), 7.42–
7.38 (m, 1H), 7.36–7.32 (m, 1H), 7.30 (s, 1H), 4.07 (s, 3H), 4.03 (s,
3H); 13C NMR (100 MHz, CDCl3): d 147.62, 142.42, 140.77,
140.21, 139.48, 136.47, 130.51 (2x), 129.39, 128.85 (2x), 127.76,
127.40, 127.12 (2x), 127.02 (2x), 126.11, 126.06, 124.23, 121.60,
116.42, 61.18, 56.95. Single-crystal X-ray diagram: crystal of
compound 8g was grown by slow diffusion of EtOAc into
a solution of compound 8g in CH2Cl2 to yield colorless prisms.
The compound crystallizes in the triclinic crystal system, space
ꢀ
stirred for 8 h at 25 C and the solvent was concentrated. The
˚
˚
˚
ꢀ
group P1, a ¼ 6.6111(3) A, b ¼ 9.8830(5) A, c ¼ 14.4700(8) A, V ¼
residue was diluted with water (10 mL) and the mixture was
extracted with CH2Cl2 (3 ꢁ 20 mL). The combined organic
layers were washed with brine, dried, ltered and evaporated to
afford crude product. Purication on silica gel (hexanes/EtOAc
¼ 100/1–10/1) afforded 10a (51%, 65 mg).
867.14(8) A , Z ¼ 2, dcalcd ¼ 1.304 g cmꢂ3, F(000) ¼ 360, 2q range
3
˚
1.488–26.356ꢀ, R indices (all data) R1 ¼ 0.0460, wR2 ¼ 0.1231.
A representative procedure of skeleton 9 is as follows
Sn(OTf)2 (42 mg, 0.1 mmol) was added to a solution of 4w–x (1.0
mmol) in MeNO2 (5ꢀmL) at 25 ꢀC. The reaction mixture was
stirred for 8 h at 25 C and the solvent was concentrated. The
residue was diluted with water (10 mL) and the mixture was
extracted with CH2Cl2 (3 ꢁ 20 mL). The combined organic
layers were washed with brine, dried, ltered and evaporated to
afford crude product. Purication on silica gel (hexanes/EtOAc
¼ 100/1–10/1) afforded 9.
Acknowledgements
The authors would like to thank the Ministry of Science and
Technology of the Republic of China for its nancial support
(MOST 105-2113-M-037-001).
Notes and references
6-Methoxy-1-(4-methoxyphenyl)naphthalene (9a). Yield ¼
61% (161 mg); colorless solid; mp ¼ 83–85 ꢀC (recrystallized
from hexanes and EtOAc); HRMS (ESI, M+ + 1) calcd for
1 For reviews on the synthesis of naphthalenes, see: (a) C. B. de
Koning, A. L. Rousseau and W. A. L. van Otterlo, Tetrahedron,
2003, 59, 7–36. For reviews on the benzannulation of
naphthalenes, see: (b) S. Kotha and S. M. Somnath-Halder,
Tetrahedron, 2008, 64, 10775–10790.
2 Bioactive molecules with the core naphthalene skeleton, see:
(a) T. Ukita, Y. Nakamura, A. Kubo, Y. Yamomoto,
M. Takahashi, J. Kotera and T. Ikeo, J. Med. Chem., 1999,
42, 1293–1305; (b) H. Yeo, Y. Li, L. Fu, J.-L. Zhu,
E. A. Gullen, G. E. Dutschman, Y. Lee, R. Chung,
E.-S. Huang, D. J. Austin and Y.-C. Cheng, J. Med. Chem.,
2005, 48, 534–546; (c) W. Shen, X. Zou, M. Chen, P. Liu,
Y. Shen, S. Huang, H. Guo and L. Zhang, Eur. J.
Pharmacol., 2011, 667, 330–338; (d) J. Aszno, K. Chiba,
M. Tada and T. Yoshii, Phytochemistry, 1996, 42, 713–717.
3 Natural products with the core naphthalene skeleton, see: (a)
R. S. Ward, Nat. Prod. Rep., 1999, 16, 75–96; (b) S. Apers,
C
18H17O2 265.1229, found 265.1229; 1H NMR (400 MHz): d 7.84
(d, J ¼ 9.2 Hz, 1H), 7.74 (d, J ¼ 8.4 Hz, 1H), 7.50–7.40 (m, 3H),
7.27 (dd, J ¼ 1.2, 6.8 Hz, 1H), 7.20 (d, J ¼ 2.8 Hz, 1H), 7.10 (dd, J
¼ 2.8, 9.2 Hz, 1H), 7.05–7.01 (m, 2H), 3.95 (s, 3H), 3.90 (s, 3H);
13C NMR (100 MHz): d 158.89, 157.39, 139.89, 135.10, 133.23,
131.02 (2x), 127.70, 127.23, 126.16, 126.03, 124.75, 118.52,
114.14, 113.67 (2x), 55.34, 55.30. Single-crystal X-ray diagram:
crystal of compound 9a was grown by slow diffusion of EtOAc
into a solution of compound 9a in CH2Cl2 to yield colorless
prisms. The compound crystallizes in the monoclinic crystal
˚
˚
system, space group P121/c1, a ¼ 7.654(4) A, b ¼ 13.820(8) A, c ¼
13.657(8) A, V ¼ 1429.0(14) A , Z ¼ 4, dcalcd ¼ 1.229 g cmꢂ3
,
3
˚
˚
F(000) ¼ 560, 2q range 2.11–26.46ꢀ, R indices (all data) R1
0.0711, wR2 ¼ 0.1581.
¼
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29321–29329 | 29327

View Article Online
RSC Advances
Paper
A. Vlietinck and L. Pieters, Phytochem. Rev., 2003, 2, 201–217;
(c) N. Abdissa, F. Pan, A. Gruhonjic, J. Grafenstein,
P. A. Fitzpatrick, G. Landberg, K. Rissanen, A. Yenesew and
M. Erdelyi, J. Nat. Prod., 2016, 79, 2181–2187; (d) L. Ding,
S. Fotso, F. Li, S. Qin and H. Laatsch, J. Nat. Prod., 2008,
71, 1068–1069.
4 Functionalized materials with the core naphthalene
skeleton, see: (a) K.-T. Lin, H.-M. Kuo, H.-S. Sheu and
C.-K. Lai, Tetrahedron, 2013, 69, 9045–9055; (b) M. Tanaka,
B. Elias and J. K. Barton, J. Org. Chem., 2010, 75, 2423–
7 Transition metals promoted the synthesis of naphthalene
skeleton, for chromium, see: (a) C. A. Merlic, C. C. Aldrich,
J. Albaneze-Walker and A. Saghatelian, J. Am. Chem. Soc.,
2000, 122, 3224–3225; (b) C. A. Merlic, C. C. Aldrich,
J. Albaneze-Walker, A. Saghatelian and J. Mammen, J. Org.
Chem., 2001, 66, 1297–1309; (c) M. W. Davies,
C. N. Johnson and J. P. A. Harrity, J. Org. Chem., 2001, 66,
3525–3532; (d) W. H. Moser, L. Sun and J. C. Huffman,
Org. Lett., 2001, 3, 3389–3391. For manganese, see: (e)
B. B. Snider and Q. Zhang, J. Org. Chem., 1993, 58, 3185–
3187; (f) J. F. Jamie and R. W. Rickards, J. Chem. Soc.,
Perkin Trans. 1, 1996, 2603–2613; (g) A.-I. Tsai, Y.-L. Wu
and C.-P. Chuang, Tetrahedron, 2001, 57, 7829–7837. For
palladium, see: (h) E. Yoshikawa, K. V. Radhakrishnan and
Y. Yamamoto, J. Am. Chem. Soc., 2000, 122, 7280–7286; (i)
D. Pena, D. Perez, E. Guitian and L. Castedo, J. Org. Chem.,
2000, 65, 6944–6950; (j) R. C. Larock, M. J. Doty, Q. Tian
and J. M. Zenner, J. Org. Chem., 1997, 62, 7536–7537; (k)
R. C. Larock and Q. Tian, J. Org. Chem., 1998, 63, 2002–
2009; (l) H. Mizufune, M. Nakamura and H. Mitsudera,
Tetrahedron Lett., 2001, 42, 437–439. For tungsten, see: (m)
N. Iwasawa, M. Shido, K. Maeyama and H. Kusama, J. Am.
Chem. Soc., 2000, 122, 10226–10227; (n) K. Maeyama and
N. Iwasawa, J. Org. Chem., 1999, 64, 1344–1346. For
rhodium, see: (o) J. W. Dankwardt, Tetrahedron Lett., 2001,
42, 5809–5812. For cobalt, see: (p) Y. Kita, K. Iio,
K. i. Kawaguchi, N. Fukuda, Y. Takeda, H. Ueno,
R. Okunaka, K. Higuchi, T. Tsujino, H. Fujioka and S. Akai,
Chem.–Eur. J., 2000, 6, 3897–3905. For ruthenium, see: (q)
P. Evans, R. Grigg, M. I. Ramzan, V. Sridharan and
M. York, Tetrahedron Lett., 1999, 40, 3021–3024. For nickel,
see: (r) M. A. Bennett, C. J. Cobley, E. Wenger and
A. C. Willis, Chem. Commun., 1998, 1307–1308. For copper,
see: (s) J. W. Lim, K. H. Kim, S. H. Kim and J. N. Kim,
Tetrahedron Lett., 2012, 53, 5449–5454. For zinc, see: (t)
S. Sakthivel and K. Srinivasan, J. Org. Chem., 2014, 79,
3244–3248. For titanium, see: (u) G. W. Kabalka, Y. Ju and
Z. Wu, J. Org. Chem., 2003, 68, 7915–7917. For gold, see: (v)
A. R. Jagdale, J. H. Park and S. W. Youn, J. Org. Chem.,
2011, 76, 7204–7215.
8 Synthetic applications of o-formyl and o-aroyl allylbenzenes
by the authors, see: (a) M.-Y. Chang and N.-C. Lee, Synlett,
2012, 23, 867–872; (b) M.-Y. Chang, M.-H. Wu, N.-C. Lee
and M.-F. Lee, Tetrahedron Lett., 2012, 53, 2125–2128; (c)
M.-Y. Chang and M.-H. Wu, Tetrahedron Lett., 2012, 53,
3173–3177; (d) M.-Y. Chang, M.-H. Wu and T.-W. Lee,
Tetrahedron, 2012, 68, 6224–6230; (e) M.-Y. Chang,
M.-H. Wu and Y.-L. Chen, Tetrahedron Lett., 2012, 53,
4156–4160; (f) M.-Y. Chang, H.-Y. Tai, Y.-L. Chen and
R.-T. Hsu, Tetrahedron, 2012, 68, 7941–7948; (g)
M.-Y. Chang, M.-H. Wu and H.-Y. Tai, Org. Lett., 2012, 14,
3936–3939; (h) M.-Y. Chang, C.-K. Chan, S.-Y. Lin and
R.-T. Hsu, Tetrahedron, 2012, 68, 10272–10279; (i)
M.-Y. Chang and M.-H. Wu, Tetrahedron, 2013, 69, 129–
136; (j) M.-Y. Chang, C.-K. Chan and S.-Y. Lin, Tetrahedron,
2013, 69, 1532–1538; (k) M.-Y. Chang, M.-H. Wu and
Y.-L. Chen, Org. Lett., 2013, 15, 2822–2825; (l) C.-K. Chan,
¨
¨
2428; (c) C. Thalacker, C. Roger and F. Wurthner, J. Org.
Chem., 2006, 71, 8098–8105; (d) J. G. Rodriguez and
J. L. Tejedor, J. Org. Chem., 2002, 67, 7631–7640; (e)
S. Chowdhury and P. E. Georghiou, J. Org. Chem., 2002, 67,
¨
¨
6808–6811; (f) C. Roger and F. Wurthner, J. Org. Chem.,
2007, 72, 8070–8075.
5 Acids or Lewis acids mediated synthesis of naphthalene
skeleton via intramolecular Friedel–Cras annulation, see:
(a) J. Wennerburg, C. Olofsson and T. Frejd, J. Org. Chem.,
1998, 63, 3595–3598; (b) A. I. Meyers and J. J. Willemsen,
Tetrahedron, 1998, 54, 10493–10511; (c) E. A. Couladouros
and A. T. Strongilos, Tetrahedron Lett., 2000, 41, 535–538;
¨
(d) G. Bringmann, M. Ochse and R. Gotz, J. Org. Chem.,
2000, 65, 2069–2077; (e) D. L. Boger and P. Turnbull, J. Org.
Chem., 1998, 63, 8004–8011; (f) A. V. Kelin and
Y. Y. Kozyrkov, Synthesis, 1998, 729–734; (g) A. H. Schmidt,
G. Kircher and E. Brau, J. Org. Chem., 1998, 63, 1954–1960;
(h) T. R. Hoye and L. Mi, J. Org. Chem., 1997, 62, 8586–
8588; (i) A. R. Katritzky, G. Zhang and L. Xie, J. Org. Chem.,
1997, 62, 721–725; (j) M. A. Ciufolini and T. J. Weiss,
Tetrahedron Lett., 1994, 35, 1127–1130; (k) I. Hanna,
V. Michaut and L. Ricard, Tetrahedron Lett., 2001, 42, 231–
234; (l) S. Kajikawa, H. Nishino and K. Kurosawa,
Tetrahedron Lett., 2001, 42, 3351–3354; (m) M.-Y. Chang,
Y.-H. Huang and H.-S. Wang, Tetrahedron, 2016, 72, 1888–
1895; (n) S. Ponra, M. R. Vitale, V. Michelet and
V. Ratovelomanana-Vidal, J. Org. Chem., 2015, 80, 3250–3257.
6 Bases promoted synthesis of naphthalene skeleton via
intramolecular anionic annulation, for 2-allylbenzamides/
MeLi, see: (a) M. P. Sibi, J. W. Dankwardt and V. Snieckus,
J. Org. Chem., 1986, 51, 271–273; (b) J.-m. Fu and
V. Snieckus, Can. J. Chem., 2000, 78, 905–919; (c) X. Wang
and V. Snieckus, Tetrahedron Lett., 1991, 32, 4879–4882.
For 2-allylbenzoates/MeONa, see: (d) T. Hattori, A. Takeda,
K. Suzuki, N. Koike, E. Koshiishi and S. Miyano, J. Chem.
Soc., Perkin Trans. 1, 1998, 3661–3672. For 2-
allylbenzoketones/t-BuOK, see: (e) C. B. de Koning,
J. P. Michael and A. L. Rousseau, J. Chem. Soc., Perkin
Trans. 1, 2000, 787–790; (f) C. B. de Koning, J. P. Michael
and A. L. Rousseau, Tetrahedron Lett., 1997, 38, 893–896;
(g) C. B. de Koning, S. S. Manzini, J. P. Michael,
E. M. Mmutlane, T. R. Tshabidi and W. A. L. van Otterlo,
Tetrahedron, 2005, 61, 555–564. For 2-allylbenzoketones/
DBU, see: (h) M.-Y. Chang and M.-H. Wu, Tetrahedron,
2013, 69, 129–136; For 2-alkynylbenzoketones/KHMDS, see:
(i) F. Makra, J. C. Rohloff, A. V. Muehldorf and J. O. Link,
Tetrahedron Lett., 1995, 36, 6815–6818.
29328 | RSC Adv., 2017, 7, 29321–29329
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
Y.-L. Chan and M.-Y. Chang, Tetrahedron, 2016, 72, 547–554;
RSC Advances
52, 1549–1552. For rearrangements, see: (d) G.-C. Xu,
M. Ma, L.-P. Liu and M. Shi, Synlett, 2005, 1869–1872; (e)
T. H. Lambert and D. W. C. MacMillan, J. Am. Chem. Soc.,
2002, 124, 13646–13647. For (3 + 2) annulations, see: (f)
A. G. Smith, M. C. Slade and J. S. Johnson, Org. Lett., 2011,
13, 1996–1999; (g) D. P. Kranz, G. A. Meierzu, S. El Sheikh,
J. M. Neudr and H. G. Schmalz, Eur. J. Org. Chem., 2011,
15, 2860–2866; (h) A. F. G. Goldberg, N. R. O'Connor,
R. A. Craig II and B. M. Stoltz, Org. Lett., 2012, 14, 5314–
5317. For other routes, see: (i) D. Ferraris, W. J. Drury III,
C. Cox and T. Lectka, J. Org. Chem., 1998, 63, 4568–4569; (j)
(m) C.-K. Chan, Y.-L. Tsai, Y.-L. Chan and M.-Y. Chang, J. Org.
Chem., 2016, 81, 9836–9847; (n) C.-K. Chan, Y.-H. Chen,
Y.-L. Tsai and M.-Y. Chang, J. Org. Chem., 2017, 82, 3317–
3326; (o) C.-K. Chan, Y.-L. Tsai and M.-Y. Chang, Org. Lett.,
2017, 19, 1358–1361; (p) C.-K. Chan, Y.-L. Tsai and
M.-Y. Chang, Org. Lett., 2017, 19, 1870–1873.
9 Metal Triates mediated synthetic applications by the
authors, for Bi(OTf)3, see: (a) M.-Y. Chang, Y.-C. Cheng and
Y.-J. Lu, Org. Lett., 2015, 17, 3142–3145; (b) M.-Y. Chang,
Y.-C. Cheng and Y.-J. Lu, Org. Lett., 2015, 17, 1264–1267; (c)
C.-K. Chan, Y.-C. Chen, Y.-L. Chen and M.-Y. Chang,
Tetrahedron, 2015, 71, 9187–9195. For In(OTf)3, see: (d)
M.-Y. Chang, Y.-J. Lu and Y.-C. Cheng, Tetrahedron, 2015,
71, 6840–6845. For Sc(OTf)3, see: (e) M.-Y. Chang,
´
´
´
G. Mancilla, M. Femenıa-Rios, A. J. Macıas-Sanchez and
I. G. Collado, Tetrahedron, 2008, 64, 11732–11737; (k)
B. N. Kakde, N. Kumar, P. K. Mondal and A. Bisai, Org.
Lett., 2016, 18, 1752–1755.
Y.-C. Chen, C.-K. Chan and G. G. Huang, Tetrahedron, 14 CCDC 923283 (5e), 923284 (5f), 1519809 (8d), 1523594 (8g),
2015, 71, 2095–2104. For Fe(OTf)3, see: (f) M.-Y. Chang,
Y.-H. Chen and Y.-C. Cheng, Tetrahedron, 2016, 72, 518–
790259 (9a) and 923282 (9b) contain the supplementary
crystallographic data for this paper.†
524. For Sn(OTf)2, see: (g) C.-K. Chan, Y.-H. Chen and 15 Selected examples on the metal triates mediated Claisen
M.-Y. Chang, Tetrahedron, 2016, 72, 5121–5131. For
Ga(OTf)3, see: (h) H.-S. Wang, C.-K. Chan and M.-Y. Chang,
Tetrahedron, 2016, 72, 5132–5141. For Tm(OTf)3, see: (i)
M.-Y. Chang and Y.-C. Cheng, Synlett, 2016, 27, 1931–1935.
10 Metal triates promoted intramolecular annulation, for o-
benzylbenzaldehydes/In(OTf)3, see: (a) Y. Kuninobu,
rearrangement, for Zn(OTf)2, see: (a) M. C. Pirrung and
J. N. Nalbandian, Tetrahedron Lett., 2013, 54, 3752–3754.
For Cu(OTf)2 and Yb(OTf)3, see: (b) M. Hiersemann and
L. Abraham, Org. Lett., 2001, 3, 49–52. For Bi(OTf)3, see: (c)
B. Sreedar, V. Swapna and C. Sridhar, Synth. Commun.,
2004, 34, 1433–1440.
T. Tatsuzaki, T. Matsuki and K. Takai, J. Org. Chem., 2011, 16 For reviews on the Claisen rearrangement, see: (a)
76, 7005–7009. For 20-allylchalcones/Cu(OTf)2, see: (b)
Y. Qin, S. Luo and J.-P. Cheng, Org. Lett., 2014, 16, 5032–
5035.
A. M. Castro, Chem. Rev., 2004, 104, 2939–3002; (b)
U. Nubbemeyer, Synthesis, 2003, 961–1008; (c)
M. Hiersemann and L. Abraham, Eur. J. Org. Chem., 2002,
1461–1471; (d) Y. Chai, S. Hong, H. A. Lindsay,
C. MaFarland and M. C. McIntosh, Tetrahedron, 2002, 58,
2905–2928.
11 For reviews on metal triates-mediated reactions, see: (a)
U. Landziata, ARKIVOC, 2014, i, 307–336; (b) S. Luo,
Z. Lizhi, A. Talukdar, G. Zhang, M. Xueling, J.-P. Cheng
and P. G. Wang, Mini-Rev. Org. Chem., 2005, 2, 177–202; (c) 17 Selected examples on the concept of a Lewis acid assisted
S. Kobayashi, M. Sugimura, H. Kitagawa, L. Hidetoshi and
W. W.-L. Lam, Chem. Rev., 2002, 102, 2227–2302.
12 Selected examples on the metal triates mediated
benzannulation, for In(OTf)3, see: (a) R. Yanada,
K. Hashimoto, R. Tokizane, Y. Miwa, H. Minami,
K. Yanada, M. Ishikura and Y. Takemoto, J. Org. Chem.,
Brønsted acid (LBA), see: (a) H. Yamamoto and
K. Futatsugi, Angew. Chem., Int. Ed., 2005, 44, 1924–1942;
(b) C. H. Cheon, O. Kanno and F. D. Toste, J. Am. Chem.
Soc., 2011, 133, 13248–13251; (c) O. Kanno, W. Kuriyama,
Z. J. Wang and F. D. Toste, Angew. Chem., Int. Ed., 2011,
50, 9919–9922.
2008, 73, 5135–5138. For Yb(OTf)3, see: (b) X.-S. Wang, 18 (a) S. Kobayashi, S. Nagayama and T. Busujima, J. Am. Chem.
J. Zhou, K. Yang and C.-S. Yao, Tetrahedron Lett., 2010, 51,
5721–5723. For Sc(OTf)3, see: (c) Y. Nishina, T. Kida and
T. Ureshino, Org. Lett., 2011, 13, 3960–3963. For Nd(OTf)3,
see: (d) C. Sabot, E. Queis, X. Brune and P.-Y. Renard,
Chem. Commun., 2012, 48, 768–770. For Cu(OTf)2, see:
H. Arslan, F. J. Uribe-Romo, B. J. Smith and W. R. Ditchtel,
Chem. Sci., 2013, 4, 3973–3978. For Fe(OTf)3, see: (e)
Soc., 1998, 120, 8287–8288; (b) T. C. Wabnitz, J.-Q. Yu and
J. B. Spencer, Chem.–Eur. J., 2004, 10, 484–493; (c)
D. C. Rosenfeld, S. Shekhar, A. Takemiya, M. Utsunomiya
and J. F. Hartwig, Org. Lett., 2006, 8, 4179–4182; (d)
B. Cacciuttolo, S. Poulain-Martni, F. Fontaine-Vive,
˜
M. A. H. Abdo, H. El-Kashef and E. Dunach, Eur. J. Org.
Chem., 2014, 7458–7468.
K. Bera, S. Sarkar and U. Jana, Tetrahedron Lett., 2015, 56, 19 (a) C. F. Baes Jr and R. E. Mesmer, The Hydrolysis of Cations,
`
Wiley-Interscience, 1976; (b) G. Lemiere, B. Cacciuttolo,
312–315.
˜
13 Sn(OTf)2-mediated reactions, for aldol reactions, see: (a)
S. Kobayashi and I. Hachiya, J. Org. Chem., 1992, 57, 1324–
1326. For Mannish-type reactions, see: (b) N. A. Kulkarni
and K. Chen, Tetrahedron Lett., 2006, 47, 611–613; (c)
Y. Yang, D. P. Phillips and S. Pan, Tetrahedron Lett., 2011,
E. Belhassen and E. Dunach, Org. Lett., 2012, 14, 2750–
2753; (c) T. Ollevier and E. Nadeau, Org. Biomol. Chem.,
2007, 5, 3126–3134; (d) S. Repichet, A. Zwick, L. Vendier,
C. Le Roux and J. Dubac, Tetrahedron Lett., 2002, 43, 993–
´
995.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29321–29329 | 29329