(Phenyl)[3-(trimethylsilyl)-2-naphthyl]-iodonium triflate as a new precursor of 2,3-didehydronaphthalene

Full text of DOI:10.1021/jo9812476

J . Org. Chem. 1998, 63, 8579-8581
8579
flate, is an excellent precursor of benzyne.6 This benzyne
precursor generates benzyne under very mild conditions
(
P h en yl)[3-(Tr im eth ylsilyl)-2-n a p h th yl]-
iod on iu m Tr ifla te a s a New P r ecu r sor of
,3-Did eh yd r on a p h th a len e
(room temperature and neutral conditions). The gener-
2
ated benzyne can be efficiently trapped with furan to give
1
1
,4-dihydro-1,4-epoxynaphthalene quantitatively (Scheme
).
Tsugio Kitamura,* Norihiko Fukatsu, and
Yuzo Fujiwara
Hypervalent iodine precursors have been also applied
Department of Chemistry and Biochemistry, Graduate
School of Engineering, Kyushu University,
Hakozaki, Fukuoka 812-8581, J apan
7
to the generation of 2,3-didehydronaphthalene (1). The
reaction of a 2-naphthyl aryliodonium-3-carboxylate in
the presence of tetraphenylcyclopentadienone gives the
adduct, 1,2,3,4-tetraphenylanthracene, in 55% yield
Received J une 26, 1998
(Scheme 2).
However, the reaction using the 2-naphthyl aryliodo-
In tr od u ction
nium-3-carboxylate requires temperatures of about 200
°C or higher and the yield of the adduct is not high.
Thus, we examined the preparation and reaction of a
highly efficient hypervalent iodine precursor of 1. In this
paper, we report the hypervalent iodine precursor (phen-
yl)[3-(trimethylsilyl)-2-naphthyl]iodonium triflate (2) as
a new 2,3-didehydronaphthalene precursor.
2
,3-Didehydronaphthalene (1) is a useful intermediate
available for construction of polycyclic aromatic hydro-
carbons. There has been reported the generation of 2,3-
didehydronaphthalene (1) in different reactions involving
several precursors such as 3-amino-2-naphthoic acid,
-amino-1H-naphtho[2,3-d]triazole, and mono- and di-
1
2
1
3
halonaphthalenes. The reported generation of 1 either
involves a lengthy procedure for the precursor synthesis
and/or gives the Diels-Alder adduct in poor yield.
Resu lts a n d Discu ssion
4
The hypervalent iodine precursor (phenyl)[3-(trimeth-
ylsilyl)-2-naphthyl]iodonium triflate (2), was prepared in
two steps from 2,3-dibromonaphthalene (eqs 1 and 2). 2,3-
LeHoullier and Gribble reported a convenient genera-
tion of 1 using 2,3-dibromonaphthalene and phenyl-
lithium (eq 1). This method is practically useful for the
generation of 1 and seems to have wide application to
synthesis of polycyclic aromatic hydrocarbons. However,
a strong base such as phenyllithium is essential for the
generation of 2,3-didehydronaphthalene in this proce-
dure.
Bis(trimethylsilyl)naphthalene was prepared by bis-
(trimethylsilyl)ation of 2,3-dibromonaphthalene with chlo-
rotrimethylsilane and Mg in a procedure similar to that
for preparing 1,2-bis(trimethylsilyl)benzene from 1,2-
dibromobenzene.8 Phenyliodination of 2,3-bis(trimeth-
ylsilyl)naphthalene (3) was conducted with a hypervalent
On the other hand, hypervalent iodine compounds have
been recognized as useful reagents in organic synthesis.5
Recently, we have found that a hypervalent iodine
compound, (phenyl)[o-(trimethylsilyl)phenyl]iodonium tri-
(
1) Wilcox, C. F., J r.; Talwar, S. S. J . Chem. Soc. C 1970, 2162-
iodine reagent system, PhI(OAc)
with PhI(OAc) activated with TfOH gave 2 as stable
crystals.
The generation and reaction of 2,3-didehydronaphtha-
lene (1) could be conducted by simply adding Bu NF to
/TfOH.9 Treatment of
2
2
4
167. Zimmerman, H. E.; Bender, C. O. J . Am. Chem. Soc. 1970, 92,
366-4376. Sugihashi, M.; Kawagita, R.; Otsubo, T.; Sakata, Y.;
3
2
Misumi, S. Bull. Chem. Soc. J pn. 1972, 45, 2836-2841. Thummel, R.
P.; Cravey, W. E.; Nutakul, W. J . Org. Chem. 1978, 43, 2473-2477.
(
(
2) Rees, C. W.; Storr, R. C. J . Chem. Soc. C 1963, 765-769.
3) Ward, E. R.; Pearson, B. D. J . Chem. Soc. 1959, 1676-1680.
4
Ward, E. R.; Marriott, J . E. J . Chem. Soc. 1963, 4999-5001. Huisgen,
R.; Zirngibl, L. Chem. Ber. 1958, 91, 1438-1452.
the solution of the precursor 2 in the presence of trapping
reagents (Scheme 3). Treatment of [3-(trimethylsilyl)-
(
4) LeHoullier, C. S.; Gribble, G. W. J . Org. Chem. 1983, 48, 2364-
2
366.
5) For recent reviews and books, see: Koser, G. F. The Chemistry
2
4
-naphthyl]iodonium triflate (2) with Bu NF in the
(
of Functional Groups, Supplement D; Patai, S., Rappoport, Z., Eds.;
J ohn Wiley & Sons: New York, 1983; Chapters 18 and 25. Ochiai, M.
Rev. Heteroatom Chem. 1989, 2, 92-111. Moriarty, R. M.; Vaid, R. K.
Synthesis 1990, 431-447. Varvoglis, A. The Organic Chemistry of
Polycoordinated Iodine; VCH Publishers: New York, 1992. Stang, P.
J . Angew. Chem., Int. Ed. Engl. 1992, 31, 274-285. Stang, P. J . In
Supplement C: The chemistry of triple-bonded functional groups; Patai,
S., Ed.; J ohn Wiley & Sons: Chichester, U.K., 1994, Chapter 20. Koser,
G. F. In Supplement D2: The chemistry of halides, pseudo-halides and
azides; Patai, S., Rappoport, Z., Eds.; J ohn Wiley & Sons: Chichester,
U.K., 1995, Chapter 21. Stang, P. J . In Modern Acetylene Chemistry;
Stang, P. J ., Diederich, F., Eds.; VCH: Weinheim, Germany, 1995;
Chapter 3. Stang, P. J .; Zhdankin, V. V. Chem. Rev. 1996, 96, 1123-
presence of furan (5 equiv) gave 1,4-dihydro-1,4-epoxy-
anthracene (4a ) in 82% yield. Similar reactions of 2 with
Bu NF in the presence of 2-acetylfuran or 2,5-dimethyl-
4
furan (5 equiv) gave the corresponding adducts, 1,4-
dihydro-1,4-epoxyanthracenes (4b,c), respectively, in 89
(6) Kitamura, T.; Yamane, M. J . Chem. Soc., Chem. Commun. 1995,
983-984.
(7) Luis, S. V.; Gavina, F.; Ferrer, P.; Safont, V. S.; Torres, M. C.;
Burguete, M. I. Tetrahedron 1989, 45, 6281-6296.
(8) Bourgeois, P.; Calas, R. J . Organomet. Chem. 1975, 84, 165-
1
178. Varvoglis, A. Hypervalent Iodine in Organic Synthesis; Academic
175.
Press: San Diego, CA, 1997. Kitamura, T.; Fujiwara, Y. Org. Prep.
Proc. Int. 1997, 29, 409-458.
(9) Kitamura, T.; Matsuyuki, J .; Taniguchi, H. Synthesis 1994, 147-
148.
1
0.1021/jo9812476 CCC: $15.00 © 1998 American Chemical Society
Published on Web 10/28/1998

8
580 J . Org. Chem., Vol. 63, No. 23, 1998
Notes
Compared with previous precursors,1
-4,7
the present
Sch em e 1
hypervalent iodine reagent 2 provides the best results,
in addition to the use of mild and neutral conditions.
Exp er im en ta l Section
Gen er a l Meth od s. Melting points are uncorrected. 1NMR
1
3
spectra were obtained at 250 or 300 MHz.
C NMR spectra
were recorded at 63 or 75 MHz. Elemental analyses were
performed by the Service Center of the Elementary Analysis of
Organic Compounds, Faculty of Science, Kyushu University. 2,3-
Dibromonaphthalene was prepared by the reported proce-
dures.4
Sch em e 2
,11
2
,3-Bis(tr im eth ylsilyl)n a p h th a len e. To a mixture of Mg
(90 mmol), chlorotrimethylsilane (80 mmol), and THF (10 mL)
was added a solution of 2,3-dibromonaphthalene (20 mmol) in
THF (50 mL), and the mixture was heated at 80 °C for 24 h.
After removal of THF in vacuo at room temperature, hexane
was added to the residue and the whole contents were poured
onto ice and water. The precipitates and unreacted Mg were
filtered off, and the product was extracted with hexane. The
hexane extract was washed with water and brine and dried over
anhydrous Na SO . After evaporation of the solvent, the residue
2 4
was separated by a bulb-bulb distillation. After removing
volatile materials at 100 °C (oven temperature)/0.5 mmHg, the
product was collected at 150 °C (0.5 mmHg) to give 2.08 g (38%
1
yield) of 2,3-bis(trimethylsilyl)naphthalene: H NMR (CDCl
3
)
δ 0.44 (s, 18 H), 7.46-7.49 (m, 2 H), 7.77-7.80 (m, 2 H), 8.14 (s,
and 92% yields. Tetraphenylcyclopentadienone is also
a representative trapping agent of arynes.10 Treatment
13
2
3
H); C NMR (CDCl ) δ 2.0, 126.5, 127.7, 132.3, 135.6, 142.0.
Anal. Calcd for C16H24Si : C, 70.51; H, 8.88. Found: C, 70.30;
2
of 2 with Bu
4
NF in the presence of tetraphenylcyclopen-
H, 8.71.
(
P h en yl)[3-(t r im et h ylsilyl)-2-n a p h t h yl]iod on iu m Tr i-
fla te (2). To a suspension of PhI(OAc) (0.5 mmol) in CH Cl
5 mL) was added TfOH (1 mmol) dropwise at 0 °C, and the
mixture was stirred for 30 min at that temperature. 2,3-Bis-
trimethylsilyl)naphthalene (0.5 mmol) was added at 0 °C, and
tadienone (2 equiv) afforded 1,2,3,4-tetraphenylan-
thracene (5) in 90% yield.
The hypervalent iodine precursor 2 has the following
advantages in the generation and reactions of 1. The
trapping reactions of 1 with furan reported previously
were conducted by use of a large excess of furan (about
2
2
2
(
(
the reaction mixture was stirred for 30 min. After evaporation
of the solvent, the residue was crystallized by adding ether. The
crystals were collected, washed with ether, and dried in vacuo
to give 2 (149 mg, 54%): mp 182-184 °C (CH
NMR (CDCl
4
2
7
7 times the molar quantity of furan or as the solvent ).
1
2
Cl
2
-ether); H
The present reaction using 2 does not require a large
excess of furan. The trapping reactions with tetraphe-
nylcyclopentadienone using 2-naphthyl aryliodonium-3-
carboxylate7 and 1-aminonaphtho[2,3-d]triazole2 gave
3
) δ 0.46 (s, 9 H), 7.44-7.93 (m, 9 H), 8.16 (s, 1 H),
13
8
1
.69 (s, 1 H). C NMR (CDCl
27.4, 127.8, 128.2, 129.1, 131.0, 131.3, 132.1, 133.0, 134.3, 138.9,
3
+ DMSO-d
6
) δ -0.2, 114.1, 117.9,
139.6, 140.0. Anal. Calcd for C20
Found: C, 43.32; H, 3.74.
H
20
F
3
IO
3
SSi: C, 43.48; H, 3.65.
1
,2,3,4-tetraphenylanthracene in 55% yield, respectively.
The similar reaction using PhI(OAc)
mmol), CH Cl (10 mL), and 2,3-bis(trimethylsilyl)naphthalene
4.0 mmol) gave 1.03 g (47%) of 2.
Reaction of [3-(Tr im eth ylsilyl)-2-n aph th yl]iodon iu m Tr i-
fla te 2 w ith Bu NF in th e P r esen ce of F u r a n s. To a solution
2
(4.0 mmol), TfOH (8.0
The present reaction gives a higher yield than the
previously reported ones.
The above experiments illustrate that 1 is generated
efficiently from 2 under very mild conditions and can be
trapped with cyclic dienes to give the corresponding
adducts. Since the yields of the adducts are always high,
2
2
(
4
of 2 (0.2 mmol) and a furan (1.0 mmol) in CH
added a THF solution of Bu NF (1 M, 0.25 mL) at 0 °C, and the
mixture was stirred for 30 min. Water was added to the
mixture, and the product was extracted with CH Cl After
evaporation of the solvent, the product was purified by column
chromatography on silica gel (hexane/CH Cl ) to yield crystals
2 2
Cl (2 mL) was
4
2
1
can be used synthetically as an excellent precursor of
2
2
.
.
Furthermore, we examined the 1,3-dipolar cycloaddi-
2
2
tion of 1 from 2 (Scheme 3). A similar treatment of 2
with Bu NF in the presence of p-tolyl azide or p-
methoxyphenyl azide (5 equiv) gave the corresponding
-arylnaphtho[2,3-e]triazoles (6a ,b) in 62 and 72% yields,
respectively. This result indicates that 2 is also suitable
for the 1,3-dipolar cycloaddition using 1.
of the adduct, 1,4-dihydro-1,4-epoxyanthracenes (4).
1,4-Dih yd r o-1,4-ep oxya n th r a cen e (4a ): 31.9 mg (82%); mp
4
2
1
1
5
7
1
3
63-164 °C (hexane) (lit. mp 164-165 °C); H NMR (CDCl ) δ
.80 (s, 2 H), 6.96 (s, 2 H), 7.41-7.44 (m, 2 H), 7.58 (s, 2 H),
.69-7.72 (m, 2 H); C NMR (CDCl ) δ 81.8, 118.6, 126.1, 128.1,
3
1
1
3
31.9, 141.7, 144.1.
1
-Acetyl-1,4-d ih yd r o-1,4-ep oxya n th r a cen e (4b): 42.1 mg
1
In summary, we have demonstrated that (phenyl)[3-
(89%); mp 140-143 °C (hexane); H NMR (CDCl ) δ 2.44 (s, 3
3
13
(
trimethylsilyl)-2-naphthyl]iodonium triflate (2) is readily
prepared by the reaction of 2,3-bis(trimethylsilyl)naph-
thalene with a PhI(OAc) /TfOH reagent system and acts
as a highly efficient 2,3-didehydronaphthalene precursor.
H), 5.88 (s, 1 H), 6.96-7.02 (m, 2 H), 7.43-7.70 (m, 6 H);
NMR (CDCl ) δ 26.9, 81.8, 95.1, 118.2, 119.1, 126.47, 126.55,
28.0, 128.4, 131.6, 131.7, 141.0, 142.0, 142.5, 143.0, 205.0.
C
3
1
2
Anal. Calcd for C16
H, 5.24.
12 2
H O : C, 81.31; H, 5.12. Found: C, 81.13;
1
,4-Dim eth yl-1,4-d ih yd r o-1,4-ep oxya n th r a cen e (4c): 40.9
1
(10) Hart, H. In Supplement C2: The Chemistry of Triple-Bonded
mg (92%); mp 104-106 °C (hexane); H NMR (CDCl
3
) δ 1.97 (s,
Functional Groups; Patai, S., Ed.; Wiley: Chichester, U.K., 1994;
Chapter 18, pp 1017-1134. Gilchrist, T. L. In The Chemistry of
Functional Groups, Supplement C; Patai, S.; Rappoport, Z., Eds.;
Wiley: Chichester, U.K., 1983; Chapter 11, pp 383-419. Hoffmann,
R. W. Dehydrobenzene and Cycloalkynes; Academic Press: New York,
6
H), 6.72 (s, 2 H), 7.40-7.44 (m, 4 H), 7.70-7.73 (m, 2 H);
13
C
3
NMR (CDCl ) δ 15.3, 88.0, 116.7, 126.0, 128.0, 131.7, 145.4,
(11) Danish, A. A.; Silverman, M.; Tajima, Y. A. J . Am. Chem. Soc.
1954, 76, 6144-6150.
1
967.

Notes
J . Org. Chem., Vol. 63, No. 23, 1998 8581
Sch em e 3
1
8
48.6. Anal. Calcd for C16
6.34; H, 6.53.
The similar trapping reaction with 2,5-dimethylfuran on a
H
14O: C, 86.45; H, 6.35. Found: C,
1-(4-Meth ylph en yl)n aph th o[2,3-d][1,2,3]tr iazole (6a): 32.2
1
mg (62%); mp 155-157 °C (hexane); H NMR (CDCl
3
) δ 2.51 (s,
1
3
3 H), 7.44-8.11 (m, 8 H), 8.18 (s, 1 H), 8.70 (s, 1 H); C NMR
larger scale (0.5 mmol of 2) gave 4c in 93% yield (103 mg).
(CDCl ) δ 21.2, 106.2, 118.3, 122.6, 124.9, 126.8, 128.1, 129.4,
3
Reaction of [3-(Tr im eth ylsilyl)-2-n aph th yl]iodon iu m Tr i-
1
30.4, 130.7, 130.9, 133.4, 134.9, 138.4, 145.7. Anal. Calcd for
: C, 78.74; H, 5.05; N, 16.20. Found: C, 78.54; H, 5.08;
N, 16.12.
-(4-Meth oxyp h en yl)n a p h th o[2,3-d ][1,2,3]tr ia zole (6b):
fla te (2) w ith Bu
clop en ta d ien on e. To a solution of 2 (0.2 mmol) and an aryl
azide (0.4 mmol) in CH Cl (3 mL) was added a THF solution of
Bu NF (1 M, 0.25 mL) at 0 °C. After the mixture was stirred
for 30 min at 0 °C, water was added and the product was
extracted with CH Cl After evaporation of the solvent, the
product was separated by column chromatography on silica gel
hexane/CH Cl ) to give 1,2,3,4-tetraphenylanthracene (5) in 90%
4
NF in th e P r esen ce of Tetr a p h en ylcy-
17 13 3
C H N
2
2
1
4
1
3
3
(
9.6 mg (72%); mp 173-175 °C (hexane); H NMR (CDCl
.83 (s, 3 H), 7.07 (d, J ) 9 Hz, 2 H), 7.35-7.43 (m, 2 H), 7.68
3
) δ
2
2
.
1
3
d, J ) 9 Hz, 2 H), 7.84-8.03 (m, 3 H), 8.60 (s, 1 H); C NMR
(CDCl ) δ 55.7, 106.0, 115.0, 118.2, 124.4, 124.9, 126.8, 128.0,
129.4, 130.4, 130.7, 131.2, 133.3, 145.5, 159.6. Anal. Calcd for
O: C, 74.17; H, 4.76; N, 15.26. Found: C, 74.07; H,
(
2
2
3
2
,7
yield (86.9 mg): mp 290-293 °C (EtOH-toluene) (lit. mp 293-
1
2
7
94 °C); H NMR (CDCl
.80-7.83 (m, 2 H), 8.19 (s, 2 H).
R ea ct ion of 2 w it h Bu NF in t h e P r esen ce of Ar yl
Azid es. To a solution of 2 (0.2 mmol) and an aryl azide (1.0
mmol) in CH Cl (2 mL) was added a THF solution of Bu NF (1
3
) δ 6.8 (s, 10 H), 7.30-7.39 (m, 12 H),
17 13 3
C H N
4.83; N, 15.21.
4
Ack n ow led gm en t. This work was partly supported
by a Grant-in-Aid for Scientific Research from the
Ministry of Education, Science, Sports, and Culture of
J apan.
2
2
4
M, 0.25 mL) at 0 °C. After the mixture was stirred for 30 min
at 0 °C, water was added and the product was extracted with
CH
separated by column chromatography on silica gel (hexane/
CH Cl ) to give crystals of the adduct, naphthotriazole 6.
2 2
Cl . After evaporation of the solvent, the product was
2
2
J O9812476