synthesize diaryliodanes in an exclusively regioselective
manner under mild conditions.7 Double ligand exchange on
iodine(III) of inorganic λ3-iodanes such as (OI)2SO4, OIOTf,
(RCO2)3I, and (NC)2IOTf with arylsilanes and stannanes
directly affords diaryliodanes.8 â-Chlorovinyl- and â-(tri-
flyloxy)vinyl-λ3-iodanes also undergo ligand exchange on
iodine(III) by the reaction with aryllithiums, yielding di-
aryliodanes.9 We report herein a direct synthesis of 6-chro-
manyl(phenyl)-λ3-iodanes from 3-phenylpropanols by the
reaction with aryl-λ3-iodanes, which involves the oxidative
intramolecular cyclization yielding chromans, followed by
their regioselective phenyl-λ3-iodanation. Interestingly, an
intermediate spirocyclohexadiene 5 favors the 1,2-shift of a
carbon-carbon bond over that of a carbon-oxygen bond.
Scheme 1
this reaction, formation of 3-phenylpropanal was found to
be a minor process with less than 2% yield.
Use of 3 equiv of λ3-iodane complex 1 in refluxing
dichloromethane afforded the 2:1 complex 32-18C6 in 37%
yield (Table 1, entry 2). A good yield of the product was
Recently, we reported a synthesis of a protonated iodo-
sylbenzene monomer-18-crown-6 complex 1 as crystals, in
which intermolecular hypervalent I(III)‚‚‚O interactions play
an essential role in the complexation10 and dramatically
increase the stability of the highly labile hydroxy(phenyl)-
λ3-iodane PhI(OH)BF4.11 The complex 1 serves as an
efficient oxidant for a broad range of functional groups such
as olefins, alkynes, enones, silyl enol ethers, sulfides, and
phenols under mild conditions, especially in water as a
solvent. Very interestingly, exposure of 3-phenyl-1-propanol
(2) to the hydroxy-λ3-iodane complex 1 (1.2 equiv) in
dichloromethane at room temperature resulted in the oxida-
tive intramolecular cyclization yielding chroman, followed
by the phenyl-λ3-iodanation of the aromatic ring, with
formation of 6-[phenyl(tetrafluoroborato)-λ3-iodanyl]chroman
(3) as a 2:1 complex with 18-crown-6 (18C6) albeit in a
low yield (13%) (Scheme 1).12,13 Aryl-λ3-iodanes undergo
oxidation of alcohols to carbonyl compounds;1 however, in
Table 1. Direct Synthesis of 6-Chromanyl(phenyl)-λ3-iodane 3
from Alcohol 2a
additive
(equiv)
temp
(°C)
time
(h)
yield
(%)b
entry
iodane
1
2
3
4
5
6
7
1
1
1
1
25
40
81
40
40
25
40
24
23
5
7
7
23c
37c
41c
51 (63)c,e
38
(41)
61
BF3-Et2O (3)
Tf2NH (3)
HBF4-Me2O (3)
BF3-Et2O (3)
PhIO
PhIO
PhIO
5
3
a
Unless otherwise noted, reactions were carried out using 3-3.1 equiv
of λ3-iodanes in dichloromethane under Ar. Isolated yields. Parentheses
are H NMR yields. Yields of the 2:1 complex 32-18C6. In MeCN.
Diaryl-λ3-iodane 4 (20%) was obtained.
b
1
c
d
e
(7) (a) Koser, G. F.; Wettach, R. H.; Smith, C. S. J. Org. Chem. 1980,
45, 1544. (b) Ochiai, M.; Toyonari, M.; Nagaoka, T.; Chen, D.-W.; Kida,
M. Tetrahedron Lett. 1997, 38, 6709. (c) Pike, V. W.; Butt, F.; Shah, A.;
Widdowson, D. A. J. Chem. Soc., Perkin Trans. 1 1999, 245.
(8) (a) Beringer, F. M.; Falk, R. A.; Karniol, M.; Lillien, I.; Masullo,
G.; Mausner, M.; Sommer, E. J. Am. Chem. Soc. 1959, 81, 342. (b) Stang,
P. J.; Zhdankin, V. V.; Tykwinski, R. Tetrahedron Lett. 1991, 32, 7497.
(c) Tyrra, W.; Butler, H.; Naumann, D. J. Fluorine Chem. 1993, 60, 79.
(d) Hossain, M. D.; Ikegami, Y.; Kitamura, T. J. Org. Chem. 2006, 71,
9903.
(9) (a) Beringer, F. M.; Nathan, R. A. J. Org. Chem. 1969, 34, 685. (b)
Stang, P. J.; Chen, K. J. Am. Chem. Soc. 1995, 117, 1667. (c) Aggarwal,
V. K.; Olofsson, B. Angew. Chem., Int. Ed. 2005, 44, 5516. (d) Kitamura,
T.; Kotani, M.; Fujiwara, Y. Tetrahedron Lett. 1996, 37, 3721.
(10) (a) Ochiai, M.; Suefuji, T.; Miyamoto, K.; Tada, N.; Goto, S.; Shiro,
M.; Sakamoto, S.; Yamaguchi, K. J. Am. Chem. Soc. 2003, 125, 769. (b)
Ochiai, M.; Miyamoto, K.; Suefuji, T.; Sakamoto, S.; Yamaguchi, K.; Shiro,
M. Angew. Chem., Int. Ed. 2003, 42, 2191. (c) Ochiai, M.; Miyamoto, K.;
Suefuji, T.; Shiro, M.; Sakamoto, S.; Yamaguchi, K. Tetrahedron 2003,
59, 10153.
(11) (a) Ochiai, M.; Miyamoto, K.; Shiro, M.; Ozawa, T.; Yamaguchi,
K. J. Am. Chem. Soc. 2003, 125, 13006. (b) Ochiai, M.; Miyamoto, K.;
Yokota, Y.; Suefuji, T.; Shiro, M. Angew. Chem., Int. Ed. 2005, 44, 75. (c)
Ochiai, M. Coord. Chem. ReV. 2006, 250, 2771.
(12) For radical cyclizations of 3-phenylpropanols to 6-iodochromans
by the reaction with (diacetoxyiodo)benzene and molecular iodine under
irradiation with a tungsten lamp, see: (a) Muraki, T.; Togo, H.; Yokoyama,
M. Tetrahedron Lett. 1996, 37, 2441. (b) Togo, H.; Muraki, T.; Hoshina,
Y.; Yamaguchi, K.; Yokoyama, M. J. Chem. Soc., Perkin Trans. 1 1997,
787.
obtained by using a Lewis acid additive, BF3-Et2O, which
probably increases the reactivity of λ3-iodane complex 1 via
the coordination to the oxygen atom of the hydroxy group
(entry 4). In this reaction, simple λ3-iodanation of the
aromatic ring in 2 competes with the oxidative cyclization
and afforded the byproduct diaryl-λ3-iodane 4 in 20% yield.
Instead of the crown ether complex 1, use of iodosylbenzene
in the presence of BF3-Et2O (3 equiv) increased the yield
of 3 to 61% (entry 7).
Figure 1 illustrates solid-state structures of the 2:1 complex
32-18C6, in which two independent molecular complexes
A and B exist.14 In each complex A or B, chromanyl(phenyl)-
λ3-iodanyl groups protrude face of the 18C6, providing a
perching type of host-guest relationship. The 2:1 complex
A adopts a distorted trigonal bipyramidal geometry about
the iodines with a phenyl group and an oxygen O5 occupying
apical positions and with a chromanyl group and two oxygens
(14) Crystallographic data for the 2:1 complex 32-18C6: C42H52B2F8I2O8,
M ) 1112.28, T ) 123 K, orthorhombic, space group Fdd2 (No. 43), a )
18.7743(3) Å, b ) 29.9639(6) Å, c ) 31.9847(8) Å, V ) 17993.0(6) Å3,
Z ) 16, Dc ) 1.642 g cm-3, µ(Mo KR) ) 14.819 cm-1. 10 291 reflections
were collected; 10 291 were unique. R1 ) 0.0270 [I > 2σ(I)], wR2 ) 0.0580
[I > 3σ(I)]. Crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication number CCDC-
data_request/cif.
(13) For cyclizations of 3-(alkoxyphenyl)propanols to chromans by the
reaction with [bis(trifluoroacetoxy)iodo]benzene and montmorillonite K10,
which involve the intermediacy of aromatic cation radicals via single-
electron transfer, see: Hamamoto, H.; Hata, K.; Nambu, H.; Shiozaki, Y.;
Tohma, H.; Kita, Y. Tetrahedron Lett. 2004, 45, 2293.
1996
Org. Lett., Vol. 9, No. 10, 2007