Ullmann coupling reaction of 1,3-bistriflate esters of calix[4]arenes: facile syntheses of monoaminocalix[4]arenes and 4,4′:6,6′-diepithiobis(phenoxathiine)

Article abstract of DOI:10.1016/j.tetlet.2007.08.095

Treatment of 1,3-bistriflate esters of thiacalix- (6a) and calix[4]arenes 6b with benzylamine in the presence of CuI and K₃PO₄ results in the displacement of a TfO moiety with a benzylamino group, which provides an easy access to mon

Full text of DOI:10.1016/j.tetlet.2007.08.095

Tetrahedron Letters 48 (2007) 7660–7664
Ullmann coupling reaction of 1,3-bistriflate esters of
calix[4]arenes: facile syntheses of monoaminocalix[4]arenes
and 4,40:6,60-diepithiobis(phenoxathiine)
Shinya Tanaka, Ryuichi Serizawa, Naoya Morohashi and Tetsutaro Hattori*
Department of Environmental Studies, Graduate School of Environmental Studies, Tohoku University,
6-6-11 Aramaki-Aoba, Aoba-ku, Sendai 980-8579, Japan
Received 26 May 2007; revised 20 August 2007; accepted 28 August 2007
Available online 31 August 2007
Abstract—Treatment of 1,3-bistriflate esters of thiacalix- (6a) and calix[4]arenes 6b with benzylamine in the presence of CuI and
K3PO4 results in the displacement of a TfO moiety with a benzylamino group, which provides an easy access to monoaminothia-
calix[4]arene 4a and its methylene-bridged counterpart 4b. On the other hand, the reaction of 6a in the absence of benzylamine leads
to intramolecular dietherification, giving 4,40:6,60-diepithiobis(phenoxathiine) 7a.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Calix[4]arenes are one of the most important molecular
scaffolds in supramolecular chemistry.1 A variety of
sophisticated molecular hosts have been prepared by
introducing substituents into the calixarene skeleton
via the etherification or esterification of the hydroxy
groups and/or the electrophilic substitution on the
aromatic nuclei. However, the replacement of the hydr-
oxy groups with other functions by cleaving the aryl-
oxygen bonds is quite difficult particularly in the case
of calixarenes with a small ring size because of the steric
hindrance arisen from the sterically crowded cyclic
structure, beside the poor nucleofugacity of the hydroxy
group and the resonance-stabilized double-bond charac-
ter of the aryl-oxygen linkage.2 Although the C–O
bond cleavage reactions of aryl triflates or other esters
by using palladium or nickel catalysts, such as the
Suzuki–Miyaura3 and Migita–Kosugi–Stille coupling
reactions,4 are one of the most reliable ways for the dis-
placement of the phenolic hydroxy group, such reac-
tions have been applied in vain to calix[4]arenes,5 with
an exception of the recent report by Georghiou and
co-workers, in which the Sonogashira coupling reaction
of 1,3-bistriflate ester 6b successfully afforded 1,3-di-
alkynylcalix[4]arenes.6 We have been engaged in the
development of novel functions of thiacalixarenes (e.g.,
1a), which have epithio linkages instead of the methyl-
ene bridges in the conventional calixarenes.7 Recently,
we succeeded in the synthesis of tetraaminothia-
calix[4]arene 2 via a chelation-assisted nucleophilic
aromatic substitution (SNAr) reaction of the rtct stereo-
isomer8 of tetra-O-methylsulfinylcalix[4]arene 3 with
lithium benzylamide, followed by the debenzylation of
the resulting tetra(benzylamino)sulfinylcalix[4]arene
and the successive reduction of the sulfinyl functions.9
In the solvent extraction experiment, while thiacalix-
arene 1a extracted a variety of soft to intermediate metal
ions, tetraaminothiacalixarene 2 selectively extracted the
softest metal ions, gold and palladium,10 owing to the
softer nature of the amino nitrogen than the hydroxy
oxygen to bind metal ions. This observation brought
about further interest in the complexation ability of
partially aminated thiacalixarenes toward metal ions.
In this regard, we have found that mono- (4a) and 1,3-
diaminothiacalixarenes 5a can be prepared by applying
the SNAr protocol to another stereoisomer (rctt) of
3.11 As for the methylene-bridged counterparts, Biali
and co-workers reported a method for the preparation
of monoaminocalixarene 4b via the oxidation of 1b to
a spirodienone derivative, followed by the imination of
the carbonyl group with hydrazine and the subsequent
rearomatization of the resulting Schiff base with Pd/C.2c
Shinkai and co-workers succeeded in the preparation
Keywords: Ullmann coupling reaction; Aminocalixarenes; Intramole-
cularly-bridged calixarene.
*
Corresponding author. Tel.: +81 22 795 7262; fax: +81 22 795
7293; e-mail: hattori@orgsynth.che.tohoku.ac.jp
0040-4039/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.08.095

S. Tanaka et al. / Tetrahedron Letters 48 (2007) 7660–7664
7661
of 1,3-diaminocalixarene 5b by the reaction of 1,3-
bis(diethylphosphate) ester of 1b with potassium amide
in liquid ammonia using HMPA as a cosolvent.2b How-
ever, these methods require many steps and suffer from
low yields. Therefore, the development of an alternative
method for introducing amino substituents to the lower
rim (narrow rim) is highly desirable. Herein, we wish
to report a novel synthetic route to monoaminothia-
calix[4]arene 4a, as well as its methylene-bridged coun-
terpart 4b, by using an Ullmann-type amination12 of
1,3-bistriflate esters 6 with benzylamine as a key step.
Also reported is an Ullmann-type intramolecular
etherification of 6a, which provides an easy access to
phenoxathiine-type thiacalixarene 7a.
3.0 mol equiv of trifluoroacetic anhydride in the pres-
ence of pyridine in dichloromethane at room tempera-
ture.13 The amination of 6a was first examined by
using 2.4 mol equiv of benzylamine and an excess of
CuI in refluxing toluene, varying a base (Table 1).14
While Hunig’s base, 1,4-diazabicyclo[2.2.2]octane
(DABCO) and imidazole did not afford any products
in meaningful yields under the conditions, K3PO4 gave
monoamine 8a together with bis(phenoxathiine) 7a,
1,2-bistriflate 10a and a certain number of other byprod-
ucts, exhausting substrate 6a (entry 1). One reason for
the complexity of the reaction products is that the Tf
moieties of 6a intra- and intermolecularly migrate under
the basic conditions.15 A carbonate, Cs2CO3, was also
effective, giving 8a in 22% yield (entry 2). Lowering
the reaction temperature to 80 ꢁC caused prolongation
of the reaction time but improved the yield of 8a to
32% at the expense of bis(phenoxathiine) 7a and 1,2-
bistriflate 10a (entry 3). Therefore, the reaction condi-
tions employed in entry 3 were adopted as the standard
thereafter. When the reaction was carried out either in
THF at reflux or in DMF or DMSO at 80 ꢁC, monotri-
flate 9 and reduced product 12 formed predominantly
(entries 4–6). Reducing the amounts of the reagents
somewhat increased the yield of 8a (entry 7). The reac-
tion of methylene-bridged calix[4]arene 6b was some-
what sluggish but gave monoamine 8b in a good yield
(entries 8 and 9). It should be noted that the treatment
of monotriflate 9, 1,2-bistriflate 10a,15 and dimethyl
ether (11) of 1,3-bistriflate 6a with benzylamine under
the standard conditions resulted in no reaction. On the
other hand, bis(phenoxathiine) 7a was obtained as a
main product in 68% yield by the reaction of bistri-
flate 6a conducted at reflux in the absence of benzyl-
amine,16 while the same treatment of 6b did not
improve the yield of bis(xanthene) 7b (3%). Also
attempted were the reactions of 6a with lithium amide,
acetamide, and p-toluenesulfonamide with the intention
of developing an easier access to free amine 4a without
the need of debenzylation (vide infra) but they did not
afford any aminated products under the standard
conditions.
X
S
Y1
Y2
Y3
Y4
1a
1b
2
OH OH OH OH
But
But
CH2 OH OH OH OH
NH2 NH2 NH2 NH2
SO OMe OMe OMe OMe
NH2 OH OH OH
CH2 NH2 OH OH OH
NH2 OH NH2 OH
X
S
3
Y3
Y2
Y4
Y1
4a
4b
5a
S
X
X
S
5b CH2 NH2 OH NH2 OH
6a OTf OH OTf OH
6b CH2 OTf OH OTf OH
X
But
But
S
But
X
O
O
X
But
X
X
But
But
7a X=S
7b X=CH2
Prerequisite 1,3-bistriflate 6a was obtained in 85%
yield by the treatment of thiacalix[4]arene 1a with
Table 1. Amination of 1,3-bistriflates 6
Entry
Substrate
BnNH2 (mol equiv)
CuI (mol equiv)
Base (mol equiv)
Solvent
Temperature [time (h)]
Yielda (%)
8
7
10
1
2
3
6a
6a
6a
6a
6a
6a
6a
6b
6b
2.4
2.4
2.4
2.4
2.4
2.4
1.2
1.2
2.0
6.0
6.0
6.0
6.0
6.0
6.0
2.2
2.2
4.0
K3PO4 (4.0)
Cs2CO3 (4.0)
K3PO4 (4.0)
K3PO4 (4.0)
K3PO4 (4.0)
K3PO4 (4.0)
K3PO4 (2.0)
K3PO4 (2.0)
K3PO4 (4.0)
Toluene
Toluene
Toluene
THF
Reflux (6)
Reflux (6)
80 ꢁC (15)
Reflux (1)
80 ꢁC (1)
80 ꢁC (1)
80 ꢁC (15)
80 ꢁC (36)
80 ꢁC (18)
24
22
32
8
12
8
43
60
73
11
23
3
9
3
6
4
1
—
35
4
6
8
2
4b
5c
6d
7
DMF
DMSO
Toluene
Toluene
Toluene
4
16
—
—
8e
9
a Isolated yield.
b Compounds 9 (24%) and 12 (24%) were also isolated.
c Compounds 9 (14%) and 12 (28%) were also isolated.
d Compounds 9 (21%) and 12 (40%) were also isolated.
e Compound 13 (8%) was also isolated.

7662
S. Tanaka et al. / Tetrahedron Letters 48 (2007) 7660–7664
Y1
Y2
Y3
Y4
exchange with benzylamine to form another metalacycle
17, which is followed by the reductive elimination of the
aminated product from metal center (18). In the pres-
ence of benzylamine, this reaction path is more favor-
able than the cyclization to predominantly afford
amine 8 after aqueous workup. This agrees with the
observation that lowering the reaction temperature
improved the yield of amine 8a at the expense of
bis(phenoxathiine) 7a (vide supra). Therefore, it may
be concluded that the formation of copper complex 14
enables otherwise difficult oxidative addition of the
Ar–OTf bond of calix class compounds. However, it is
apparent that the presence of an adjacent hydroxy group
to the TfO moiety is important but not sufficient to
cleave the Ar–OTf bond, considering the fact that
monotriflate 9, as well as 1,2-bistriflate 10a, underwent
neither the amination nor the intramolecular cyclization
(vide supra). In addition, it should be noted that mono-
amines 8 did not undergo further amination in spite of
possessing of the hydroxy groups adjacent to the TfO
moiety. It is easily conceivable that the two adjacent
hydroxy groups or hydroxy and amino groups of these
compounds will ligate to a copper ion to form a stable
chelated complex. However such a complex will not be
active enough to further the reaction because the metal
center resides too apart from the aryl–OTf bond to
insert into the covalent bond.
X
S
But
But
8a
8b
9
NHBn OH OTf OH
X
CH2 NHBn OH OTf OH
S
S
OTf
OTf
OH OH OH
OTf OH OH
OTf OH OH
OMe OTf OMe
OH OTf OH
Y3
Y2
Y4
Y1
10a
X
X
10b CH2 OTf
11
12
13
S
S
OTf
H
X
But
But
CH2 OTf OTf OTf OH
Based on these observations, a feasible reaction mecha-
nism is depicted in Scheme 1. A phenoxy oxygen of
bistriflate 6 ligates to a copper ion to form copper com-
plex 14, which facilitates the oxidative addition of an
adjacent aryl–OTf bond to the metal center. This coin-
cides with the fact that hydroxy-protected 1,3-bistriflate
11 underwent neither the amination nor the intramole-
cular cyclization (vide supra). Resulting metalacycle 15
may reductively eliminate phenoxathiine or xanthene
16; metalacycle 15a having epithio linkages exhibited a
higher tendency to eliminate cyclic compound 16 than
methylene-bridged analog 15b. Although the reason is
not clear at present, the larger ring size of the thiacalix-
arene macrocycle than that of the conventional calix-
arene may reduce a steric strain caused by the ring
closure.17 Another reaction path of 15 is the ligand
Compounds 8 were debenzylated to give free amines 19
according to our previously reported procedure,9 that is,
the initial bromination of benzylamine 8, followed by
spontaneous dehydrobromination to the corresponding
imine and subsequent acidic hydrolysis (Scheme 2).
Alternatively, deprotection of 8a could be achieved by
refluxing the compound with conc. HCl in THF with
somewhat improved yield. Alkaline hydrolysis of the
resulting amino esters 19 gave desired monoamines 4a
and 4b in total yields of 23% and 47%, respectively, star-
ing from commercially available compounds 1. The
yields of the monoamines have greatly improved as
compared with those achieved by the reported
procedures.2c,11
X
O
But
But
But
X
But
6
16
CuI
K3PO4
Cu
TfO
TfO
O
X
Cu O
X
X
X
But
It has been reported that the thermal dediazoniation of a
diazonium salt of monoaminocalix[5]arene afforded a
But
But
14
15
But
But
But
But
BnNH2
X
X
X
X
Cu
BnHN
Cu O
v
BnHN
O
X
X
X
X
X
X
Y
X
X
But
But
But
But
But
But
But
4a: X=S (99%)
4b: X=CH2 (96%)
8a: X=S, Y=NHBn
18
17
i, ii
or iii
19a: X=S, Y=NH2 (i, ii, 50%; iii, 64%)
8b: X=CH2, Y=NHBn
19b: X=CH2, Y=NH2 (69%)
i, iv
Scheme 2. Reagents and conditions: (i) NBS, BPO, benzene, reflux; (ii)
2 M HCl, CHCl3, room temp; (iii) concd HCl, THF, reflux; (iv) 6 M
HCl, CHCl3, reflux; (v) 2 M NaOH, THF–EtOH (1:1), reflux.
8
14−18a, X = S; b, X = CH2
Scheme 1.

S. Tanaka et al. / Tetrahedron Letters 48 (2007) 7660–7664
7663
Royal Society of Chemistry: Cambridge, 1989; (b) Ikeda,
A.; Shinkai, S. Chem. Rev. 1997, 97, 1713; (c) Gutsche, C.
D. Calixarenes Revisited. In Monographs in Supramole-
cular Chemistry; Stoddart, J. F., Ed.; The Royal Society of
Chemistry: Cambridge, 1998; (d) Calixarenes in Action;
Mandolini, L., Ungaro, R., Eds.; Imperial College Press:
London, 2000; (e) Calixarenes 2001; Asfari, Z., Bo¨hmer,
V., Harrowfield, J. M., Vicens, J., Eds.; Kluwer Academic
Publishers: Dordrecht, 2001.
2. For transformation of the hydroxy groups of calixarenes
into other functions, see: (a) Goren, Z.; Biali, S. E. J.
Chem. Soc., Perkin Trans. 1 1990, 1484; (b) Ohseto, F.;
Murakami, H.; Araki, K.; Shinkai, S. Tetrahedron Lett.
1992, 33, 1217; (c) Aleksiuk, O.; Grynszpan, F.; Biali, S. E.
J. Org. Chem. 1993, 58, 1994; (d) Gibbs, C. G.; Sujeeth, P.
K.; Rogers, J. S.; Stanley, G. G.; Krawiec, M.; Watson,
W. H.; Gutsche, C. D. J. Org. Chem. 1995, 60, 8394; (e)
Zieba, R.; Desroches, C.; Chaput, F.; Sigala, C.; Jean-
neau, E.; Parola, S. Tetrahedron Lett. 2007, 48, 5401.
3. Reviews: (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95,
2457; (b) Kotha, S.; Lahiri, K.; Kashinath, D. Tetrahedron
2002, 58, 9633.
Figure 1. Stereoview of the X-ray structure of bis(phenoxathiine) 7a.
xanthene-type compound, xanthenocalix[5]arene, by an
intramolecular cyclization between the in situ-generated
phenyl cation and an adjacent hydroxy group.18,19 Xan-
thenocalix[6]arene20 and alkoxy group-incorporated
xanthenocalix[5], [6], and [8]arenes21 have also been
prepared from spirodienone derivatives of the corre-
sponding calix[n]arenes. As for the intramolecularly
cyclized phenoxathiine-type thiacalixarene, however,
bis(phenoxathiine) 7a has only been obtained as a
byproduct in the base-catalyzed rearrangement of 1,3-
bistriflate 6a to 1,2-counterpart 10a.15,22 To our plea-
sure, recrystallization of compound 7a from 1,2-dichlo-
roethane–acetonitrile gave single crystals suitable for
X-ray crystallographic analysis (Fig. 1).23 The X-ray
structure shows that the two phenoxathiine moieties
are folded oppositely to each other along their respective
imaginary lines passing through the S and O atoms of
the 1,4-oxathiine rings. The C–S–C and C–O–C bond
angles and the folding angle between the two benzene
planes are 97.51ꢁ, 116.17ꢁ, and 140.83ꢁ for one phenoxa-
thiine moiety and 97.88ꢁ, 115.95ꢁ, and 140.09ꢁ for the
other, which is in reasonable agreement with those
reported for the parent compound (97.7ꢁ, 117.4ꢁ, and
147.8ꢁ, respectively).24 The two S atoms connecting
these phenoxathiine halves have ordinary bond angles
(98.29ꢁ and 100.92ꢁ). Therefore, no strain is found in
the tricyclic structure. On the other hand, the X-ray data
for amine 8a showed that it adopted a cone conforma-
tion but detailed analysis failed because of its severely
disordered structure.
4. Reviews: (a) Stille, J. K. Angew. Chem., Int. Ed. Engl.
1986, 25, 508; (b) Espinet, P.; Echavarren, A. M. Angew.
Chem., Int. Ed. 2004, 43, 4704.
´
5. (a) Gonzalez, J. J.; Nieto, P. M.; Prados, P.; Echavarren,
A. M.; de Mendoza, J. J. Org. Chem. 1995, 60, 7419; (b)
´
´
Csok, Z.; Szalontai, G.; Czira, G.; Kollar, L. Supramol.
Chem. 1998, 10, 69; (c) Chowdhury, S.; Bridson, J. N.;
Georghiou, P. E. J. Org. Chem. 2000, 65, 3299.
6. Al-Saraierh, H.; Miller, D. O.; Georghiou, P. E. J. Org.
Chem. 2005, 70, 8273.
7. Reviews: (a) Iki, N.; Miyano, S. J. Incl. Phenom. 2001, 41,
99; (b) Morohashi, N.; Narumi, F.; Iki, N.; Hattori, T.;
Miyano, S. Chem. Rev. 2006, 106, 5291.
8. For stereoisomers of sulfinylcalix[4]arene, see: Morohashi,
N.; Katagiri, H.; Iki, N.; Yamane, Y.; Kabuto, C.;
Hattori, T.; Miyano, S. J. Org. Chem. 2003, 68, 2324.
9. Katagiri, H.; Iki, N.; Hattori, T.; Kabuto, C.; Miyano, S.
J. Am. Chem. Soc. 2001, 123, 779.
10. Katagiri, H.; Iki, N.; Matsunaga, Y.; Kabuto, C.; Miyano,
S. Chem. Commun. 2002, 2080.
11. Tanaka, S.; Katagiri, H.; Morohashi, N.; Hattori, T.;
Miyano, S. Tetrahedron Lett. 2007, 48, 5293.
12. Review: Ley, S. V.; Thomas, A. W. Angew. Chem., Int. Ed.
2003, 42, 5400.
13. Compound 6a: mp 296–298 ꢁC (decomp.); IR (KBr) 3460,
1
2966, 1427, 1211, 1138, 1065 cmꢀ1; H NMR (400 MHz,
In conclusion, we have shown here a convenient method
for the synthesis of monoaminothiacalix[4]arene 4a and
its methylene-bridged analog 4b via an Ullmann-type
amination. It has also been shown that bis(phenoxathi-
ine) 7a can be readily prepared by an Ullmann-type
etherification of 1,3-bistriflate 6a.
CDCl3) d 0.92 [18H, s, C(CH3)3 · 2], 1.34 [18H, s,
C(CH3)3 · 2], 6.12 (2H, s, OH · 2), 7.16 (4H, s, ArH),
7.74 (4H, s, ArH); 13C NMR (100 MHz, CDCl3) d 30.65,
31.39, 34.30, 34.45, 121.00, 128.81, 133.37, 134.86, 143.82,
147.69, 151.49, 155.41; FAB-MS m/z 984 (M+). Anal.
Calcd for C42H46F6O8S6: C, 51.20; H, 4.71; S, 19.53.
Found: C, 51.01; H, 4.71; S, 19.82.
14. Typical procedure for the amination: To a suspension
of bistriflate 6a (1.00 g, 1.02 mmol), CuI (425 mg,
2.23 mmol), and K3PO4 (433 mg, 2.04 mmol) in toluene
Acknowledgements
(40 mL) was added benzylamine (d = 0.983 g mLꢀ1
;
This study was supported in part by Grants-in-Aid for
Scientific Research (No. 18037004 and No. 19550100)
from the Ministry of Education, Culture, Sports, Sci-
ence and Technology, Japan.
133 lL, 1.22 mmol) and the mixture was stirred at 80 ꢁC
for 15 h. After aqueous work-up, the crude mixture was
recrystallized from dichloromethane–methanol to give
monoamine 8a (308 mg). The mother liquor was concen-
trated and chromatographed twice on silica gel with
hexane–chloroform (1:1) and then hexane–ethyl acetate
(6:1) to give an additional crop of 8a (100 mg) for a total
yield of 408 mg (43%), mp 241–243 ꢁC (decomp.); IR
References and notes
1
(KBr) 3425, 3283, 2963, 1450, 1427, 1207, 1134 cmꢀ1; H
1. Reviews: (a) Gutsche, C. D. Calixarenes. In Monographs
in Supramolecular Chemistry; Stoddart, J. F., Ed.; The
NMR (400 MHz, CDCl3) d 0.71 [9H, s, C(CH3)3], 1.13

7664
S. Tanaka et al. / Tetrahedron Letters 48 (2007) 7660–7664
[9H, s, C(CH3)3], 1.30 [18H, s, C(CH3)3 · 2], 4.42 (2H, s,
chloroform (1:1) as the eluent to give bis(phenoxathiine)
CH2Ph), 6.94 (2H, s, ArH), 7.32–7.47 (5H, m, ArH), 7.52
(2H, s, ArH), 7.66 (4H, s, ArH); 13C NMR (100 MHz,
CDCl3) d 30.42, 30.97, 31.41, 34.14, 34.20, 34.33, 57.52,
121.36, 121.43, 127.52, 128.61, 128.62, 129.41, 130.01,
132.32, 134.70, 134.90, 136.10, 138.05, 143.01, 146.92,
148.47, 149.40, 151.16, 156.32; FAB-MS m/z 941 (M+).
Anal. Calcd for C48H54F3NO5S5: C, 61.18; H, 5.78; N,
1.49; S, 17.01. Found: C, 61.42; H, 5.77; N, 1.48; S, 16.80.
A similar procedure gave compound 8b. See Table 1 for
the reaction conditions and the yield of 8b, mp 120–
122 ꢁC; IR (KBr) 3584, 3526, 3329, 2955, 1462, 1396, 1362,
7a (95.7 mg, 68%), mp 282–284 ꢁC (decomp.); IR (KBr)
2963, 1427, 1265 cmꢀ1 1H NMR (400 MHz, CDCl3) d
;
1.25 [36H, s, C(CH3)3 · 4], 7.11 (4H, d, J = 2.3 Hz, ArH),
7.59 (4H, d, J = 2.3 Hz, ArH), 13C NMR (100 MHz,
CDCl3) d 31.17, 34.44, 122.18, 124.88, 124.89, 132.91,
147.97, 151.72; FAB-MS m/z 684 (M+). Anal. Calcd for
C40H44O2S4: C, 70.13; H, 6.47; S, 18.72. Found: C, 70.11;
H, 6.51; S, 18.80.
17. Iki, N.; Kabuto, C.; Fukushima, T.; Kumagai, H.;
Takeya, H.; Miyanari, S.; Miyashi, T.; Miyano, S.
Tetrahedron 2000, 56, 1437.
18. Van Gelder, J. M.; Aleksiuk, O.; Biali, S. E. J. Org. Chem.
1996, 61, 8419.
19. See also: (a) Kogan, K.; Biali, S. E. Org. Lett. 2007, 9,
2393; (b) Al-Saraierh, H.; Miller, D. O.; Georghiou, P. E.
J. Org. Chem. 2007, 72, 4532.
20. Agbaria, K.; Biali, S. E. J. Org. Chem. 2001, 66, 5482.
21. (a) Aleksiuk, O.; Cohen, S.; Biali, S. E. J. Am. Chem. Soc.
1995, 117, 9645; (b) Consoli, G. M. L.; Geraci, C.;
Cunsolo, F.; Neri, P. Tetrahedron Lett. 2003, 44, 53.
22. See also Ref. 2e.
1207, 1138, 1072 cmꢀ1
;
1H NMR (400 MHz, CDCl3) d
0.89 [9H, s, C(CH3)3], 1.06 [9H, s, C(CH3)3], 1.27 [18H, s,
C(CH3)3 · 2], 3.45 (2H, d, J = 13.9 Hz, ArCH2Ar), 3.48
(2H, d, J = 13.9 Hz, ArCH2Ar), 3.94 (2H, d, J = 13.9 Hz,
ArCH2Ar), 4.13 (2H, s, CH2Ph), 4.24 (2H, d, J = 13.9 Hz,
ArCH2Ar), 6.81 (2H, s, ArH), 6.93 (2H, s, ArH), 7.05 (2H,
d, J = 2.4 Hz, ArH), 7.14 (2H, d, J = 2.4 Hz, ArH), 7.29–
7.38 (5H, m, ArH); 13C NMR (100 MHz; CDCl3) d 30.71,
31.04, 31.58, 32.75, 33.88, 34.00, 34.04, 34.78, 56.30,
125.29, 125.66, 125.74, 127.28, 127.33, 127.56, 127.68,
127.83, 128.68, 133.09, 134.60, 138.40, 138.89, 141.47,
142.52, 147.74, 150.21, 150.78; FAB-MS m/z 869(M+).
Anal. Calcd for C52H62F3NO5S: C, 71.78; H, 7.18; N,
1.61. Found: C, 71.68; H, 7.15; N, 1.48.
23. Crystallographic data for 7a: C40H44O2S4, M = 684.99,
˚
˚
monoclinic, a = 11.4917(12) A, b = 10.6563(9) A, c =
3
˚
˚
14.7500(14) A, b = 92.153(3)ꢁ, V = 1805.0(3) A , T =
100(2) K, space group P21, Z = 2, Dcalc = 1.260 g/cm3,
l(Mo-Ka) = 0.297 mmꢀ1, 13,402 reflections measured,
8105 independent reflection (Rint = 0.0233), 6772 reflec-
tions were observed (I > 2r(I)), R1 = 0.0384, wR2 = 0.0739
(observed), R1 = 0.0464, wR2 = 0.0754 (all data),
GOF = 0.922. The details of the crystal data have been
deposited with Cambridge Crystallographic Data Centre
as supplementary publication No. CCDC 648696.
24. Fitzgerald, L. J.; Gallucci, J. C.; Gerkin, R. E. Acta Cryst.
1991, C47, 381.
15. Serizawa, R.; Tanaka, S.; Morohashi, N.; Narumi, F.;
Hattori, T. Tetrahedron Lett. 2007, 48, 6281.
16. Synthesis of bis(phenoxathiine) 7a: To a suspension of CuI
(234 mg, 1.23 mmol) and K3PO4 (181 mg, 0.853 mmol) in
toluene (25 mL) was added dropwise a solution of
bistriflate 6a (203 mg, 0.206 mmol) in toluene (15 mL)
over 30 min at room temperature and the mixture was
heated at reflux for 1 h. After aqueous work-up, the crude
product was chromatographed on silica gel with hexane–