Synthesis and reactivity of benzylic sulfonium salts: Benzylation of phenol and thiophenol under near-neutral conditions

Article abstract of DOI:10.1016/S0040-4020(01)00137-5

A series of benzyldimethylsulfonium - and related hydrogensulfate salts have been synthesized from the ternary system ArCH₂OH:H₂SO₄: Me₂S or tetrahydrothiophene. The salts are generally stable crystalline solids, but anomalously high reactivity is observed for 9-(anthrylmethyl)dimethylsulfonium hydrogensulfate. Selected sulfonium salts have been used for the O- and S-benzylation of phenol and thiophenol, respectively, in a two phase system under near-neutral conditions. The benzylation of oximes and benzimidazole under basic conditions is also described.

Full text of DOI:10.1016/S0040-4020(01)00137-5

TETRAHEDRON
Pergamon
Tetrahedron 57 (2001) 2871±2884
Synthesis and reactivity of benzylic sulfonium salts: benzylation of
phenol and thiophenol under near-neutral conditions
Julie Forrester,a Ray V. H. Jones,a,p Lee Newtonb and Peter N. Prestonb,p
aSyngenta, Earls Road, Grangemouth, Stirlingshire FK3 8XG, UK
bDepartment of Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK
Received 2 November 2000; revised 11 January 2001; accepted 25 January 2001
AbstractÐA series of benzyldimethylsulfonium - and related hydrogensulfate salts have been synthesized from the ternary system
ArCH2OH:H2SO4: Me2S or tetrahydrothiophene. The salts are generally stable crystalline solids, but anomalously high reactivity is observed
for 9-(anthrylmethyl)dimethylsulfonium hydrogensulfate. Selected sulfonium salts have been used for the O- and S-benzylation of phenol
and thiophenol, respectively, in a two phase system under near-neutral conditions. The benzylation of oximes and benzimidazole under basic
conditions is also described. q 2001 Elsevier Science Ltd. All rights reserved.
_
+
1. Introduction
R3S HSO4 + H2O
ROH + H2SO4 + RSR
The synthesis and reactions of sulfonium salts have been
widely studied. Prominent amongst the uses of such salts are
their conversion into sulfonium ylides for use in the Corey
epoxidation procedure1 and for the alkylation of nucleo-
philes; examples of the latter include reactions with azide
ion,2 carboxylates,3 nucleosides,4 thiophenols,5 amines,6
cyanide,7 amides,8 enolates9,10 and sulfenates.11
in process recycle
_
_
+
R3S HSO4
+
Nuc E+
Nuc-R + RSR + E(HSO4)
Scheme 1.
the ternary system as a method for generating a range of
benzylsulfonium salts and to evaluate the utility of selected
salts for the benzylation of nucleophiles, with particular
regard to developing procedures that would operate under
near-neutral conditions. It may be noted that conventional
group protection, e.g. of phenols and amines, through
benzylation involves the use of benzyl halides and strong
bases14 or of benzyl-2,2,2 trichloroacetimidate under acidic
conditions.15
Investigations on sulfonium salts in our laboratories have
been directed, in part, towards development of the ternary
system CH3OH:conc. H2SO4:Me2S as an inexpensive pro-
cedure for production of trimethylsulfonium hydrogensul-
12
fate (Me3S1HSO2
) thence its use through the sulfonium
4
ylide for epoxidation.13 In addition to environmental bene-
®ts in avoiding the use of toxic alkyl halides, the process has
the advantage that dimethyl sul®de (bp 398C), which
mediates epoxide formation, can be recovered and recycled;
it may be noted that the latter is an inexpensive bulk chemi-
cal that can be manipulated through standard industrial
process technology. The above advantages would also
accrue for alkylation of nucleophiles through sulfonium
hydrogen sulfates (Scheme 1). Many industrial alkylation
reactions involve the use of toxic or volatile alkyl halides or
dialkyl sulfates with occasional use of undesirable bases
such as sodium hydride; a process of the type outlined in
Scheme 1 would circumvent these problems, to an extent.
2. Results and discussion
2.1. Synthesis
A series of benzyldimethylsulfonium hydrogensulfate salts
(1a±j) and related compounds (4a,b; Scheme 3) were
prepared in variable yield (4±85%) from the ternary system
ArCH2OH (1 mol equiv.): 98% H2SO4 (ca. 1 mol equiv.):
Me2S (excess); analogous compounds (2a; Scheme 2,
4c,d) were prepared from related reactions of tetra-
hydrothiophene. These salts (1a±j, 2a, 4c,d) were generally
stable, crystalline solids that were obtained in analytically
pure form; exceptions were 1i and 1j which were character-
ized spectroscopically, but which could not be puri®ed to
analytical standard. The former (1i) was a deliquescent solid
The aims of the present project were to extend the scope of
Keywords: sulfonium salts; benzylation; phenols; thiols.
Corresponding authors.
p
Fax: 101324-494747; e-mail: raymond.jones@syngenta.com;
Fax: 10131-451-3180; e-mail: p.n.preston@hw.ac.uk
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(01)00137-5

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J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
and the latter (1j) slowly decomposed at room temperature
with loss of dimethyl sul®de, in a process that may be driven
by formation of a relatively stable carbocation. Preparation
of the parent salt (1a) was hampered by puri®cation
problems: a slight excess of sulfuric acid (0.3 mol equiv./
mol equiv. of PhCH2OH) was required to drive the reaction
to completion and the salt (1a) could not be puri®ed from
this contaminant. This compound (1a) was more conveni-
ently prepared from sulfuric acid, dimethyl sul®de and ben-
zyl formate.16 The ternary system ArCH2OH:H2SO4:Me2S
was also successfully used in this work for the synthesis of
1- and 2-naphthylmethyl-(1k, l), 9-phenanthrylmethyl-
(1m), 9-anthrylmethyl-(1n), 9-¯uorenyl-(1o) and benzhy-
dryl-(1p) dimethylsulfonium hydrogensulfates.
_
+
_
+
(X)
RCH2
(2)
S
(PhCH2)3S (X)
(3)
X
X
HSO4
BF4
HSO4
R
Ph
Ph
Me
a
b
HSO4
BF4
a
b
c
Scheme 2.
2.2. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate
The anomalous reactivity of this poorly soluble salt (1n)
1
A useful technique for puri®cation of compounds 1k±p was
found to be repeated batch sonication under solvents such as
ethyl acetate in which sulfuric acid and water have higher
solubility than the salts. Compounds 1k±p were character-
ized analytically and spectroscopically, but 9-anthryl-
methylsulfonium hydrogensulfate (1n) was found to be
extraordinarily reactive and was additionally identi®ed
through solid state (CP MAS) 13C NMR spectroscopy; the
mode of reactivity of 1n is discussed in a separate section
below.
was recognized through attempted acquisition of H and
13C NMR spectra in d6-DMSO and d7-DMF solutions. For
example, both 1H NMR spectra contained two sets of peaks,
one set of which could be assigned to the desired salt (1n) by
reference to the solid state (CP MAS) spectrum. Also
present in the solution spectra were resonances arising
from dimethyl sul®de, and evidence for formation of
alkoxysulfonium (6a) and alkoxymethyleneiminium-(6b)
salts, respectively (Scheme 4). Further evidence of the
highly electrophilic character of the salt (1n) was apparent
from solvolysis at ,508C with separately, water, methanol
and ethanol which led to the formation of 6c±e, respec-
tively. N,N-Dimethylformamide was also used as a
(reactive) solvent to mediate the reaction of 1n with
nucleophiles, presumably in part, through the iminium salt
(cf. 6b); reactions with CN2, SCN2, AcO2 and
PhCHvNO2 leading to 6f±i, respectively, exemplify this
type of process. Attempts to use other solvents for
mediation of reactions of 1n with nucleophiles were
unsuccessful. For example, treatment of 1n with ethanol
in dimethylsulfoxide afforded 9-anthraldehyde in a process
akin to the Swern oxidation.18 Solvolysis of the salt (1n) in
acetonitrile and N,N-dimethylformamide followed by
aqueous work up afforded [N-(9-anthrylmethyl)]acetamide
(6j), albeit in poor yield (15%). When the salt (1n) was
heated in a mixture of nitromethane and N,N-dimethyl-
formamide, a complex mixture was obtained which could
not be separated chromatographically. The 1H NMR
spectrum showed very broad peaks in the aliphatic (d
4.0±4.6) and aromatic regions (d 6.3±8.7) and the mass
spectrum showed peaks corresponding to ions
[(anthrylCH2)n1H]1 (nˆ1±3). We suggest that the salt
(1n) oligomerises in this solvent system in a process
having analogy with the formation of poly[benzyl] from
benzyl alcohol in anhydrous hydrogen ¯uoride.19 Finally,
treatment of 1n with phenol in nitromethane under re¯ux
afforded 9-anthraldehyde (46%, cf. reaction with ethanol in
DMSO) and 9-(4-hydroxybenzyl)anthracene (6k) [20%];
the ring (C) alkylation of phenol observed in this process
contrasts with the side-chain (O)-alkylation reactions
described below.
Also prepared in this work were sulfonium salts analogous
to the above hydrogensulfates in which the counterion is
Cl2 (1q), CF3CO2 (1r) and BF4 (1s±u, 2b, 3b, 4e
and 5); with the exception of 5 the above were all
obtained in analytically pure form. A notable feature of
the present work is the isolation of anhydrous bis
sulfonium salts (4); this contrasts with the analogous bis
chloride salt (4f) which is normally used with ca. 2±5%
water content.17
2
2
(1)
[ArSMe2]1(X2)
Ar
X
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
PhCH2
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
HSO4
Cl
o-ClC6H4CH2
m-ClC6H4CH2
2,6-Cl2C6H3CH2
2,6-F2C6H3CH2
o-O2NC6H4CH2
p-O2NC6H4CH2
p-MeOC6H4CH2
p-MeC6H4 CH2
2,6-(MeO)2C6H3CH2
1-naphthylCH2
2-naphthylCH2
9-phenanthrylCH2
9-anthrylCH2
9-¯uorenyl
Benzhydryl
PhCH2
PhCH2
PhCH2
o-ClC6H4CH2
Benzhydryl
The relatively high reactivity of 1n may be contrasted
with that of its structural analogues: for example,
dimethyl(9-phenanthrylmethyl)sulfonium hydrogen sulfate
(1m) is stable for one week at 1008C in d7-DMF and is
unreactive to water and alcohols in the absence of a base.
The unusual behaviour of 1n may have analogy in the
CF3CO2
BF4
BF4
s
t
u
BF4

J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
2873
+
F
F
CH2S(CH2R)2
_
X
X
X
_
2Y
(BF4)
CH2OH
+
S
X
F
F
+
CH2S(CH2R)2
(5)
(4)
X
R
or R
R
Y
a
b
H
F
HSO4
HSO4
HSO4
HSO4
H
H
c
H
F
CH2CH2
CH2CH2
d
BF4
Cl
e
f
F
CH2CH2
CH2CH2
H
Scheme 3.
contrasting electrophilic reactivity of 9-chloromethyl-
anthracene and 9-(anthrylmethyl)trialkylammonium salts
(6l)20 in which nucleophilic attack at the latter
proceeds, initially at least, in cine fashion at the 10-position.
to 6.5 at the end of the reaction. Benzylations were
equally effective with sulfonium tetra¯uoroborates (for
8a,d; .96%) and a tri¯uoroacetate (8d, 96%). Thiophenol
was also rapidly benzylated with salt 1d in the two-
phase system described above to give the thioether (8g)
quantitatively.
2.3. Reactions with O-, S- and N-centred nucleophiles
It is known that certain trialkylsulfonium salts,21 including
polymer-supported species,22 can function as phase transfer
catalysts. With this in mind, optimized conditions for
conversion of phenol into benzyl ethers (8a±f; Scheme 5)
were developed as follows: PhOH (1 mol equiv.)/sulfonium
hydrogensulfate salt (1.05 mol equiv.)/NaHCO3 (2.5 mol
equiv.) in a mixture of toluene and water at 508C. Yields
were generally high (82±96%) with the exception of
formation of 8e (70%), which was accompanied by
p-methoxybenzyl alcohol from hydrolysis of the salt 1h. It
was noted that the pH of the aqueous layer was 7.5
after thorough mixing of the reagents and the value fell
A number of alkylations were also effected under basic
conditions. For example, treatment of either syn or anti-
benzaldoxime with the salt (1b) in the two phase system
PhMe/aq. KOH afforded mixtures of predominantly
O-(,50%) and N-alkylated products (,5%) [(9,10]. The
regiochemistry of this process is similar to the outcome of
base-promoted alkylation of syn-benzaldoxime with benzyl
chloride;23 in contrast, the reaction of anti-benzaldoxime
with benzyl chloride affords exclusively the N-alkylated
product (10).23 It can be assumed that the anti-oxime
isomerises rapidly under the reaction conditions. Alkylation
of cyclohexanone oxime with salts 1b and 1d gave only
products of O-(11a, b), and not N-alkylation, in variable
yield (38, 75%). Finally, benzimidazole was benzylated
under alkaline conditions in the two phase system (1a,
1b!12a, b, respectively) in moderate yield (50, 59%).
The selective exocyclic electrophilic reaction of 2a
contrasts with the reaction of benzimidazole with 1-methyl-
tetrahydrothiophenium hydrogensulfate (2c) which results
in products (12c, d) arising predominantly from endocyclic
ring-opening (cf. reaction of the iodide analogue of 2c with
azide ion24).
n
X
(6)
X
_
(7)
+
a
OS(CD3)2 HSO4
_
+
b
c
d
e
f
OC(D)=N(CD3)2 HSO4
OH
3. Conclusion
OMe
OEt
CN
The inexpensive ternary system ArCH2OH:H2SO4:Me2S
provides a useful procedure for the preparation of a variety
of benzylic sulfonium hydrogensulfates. 9-(Anthrylmethyl)-
dimethylsulfonium hydrogen sulfate (1n) has consider-
ably higher reactivity than analogous benzylic salts
synthesized in this work. Selected benzylic sulfonium
salts have been used for the benzylation of phenol
and thiophenol under near-neutral conditions in pro-
cedures that could be valuable in the chemistry of
protecting groups.
g
h
i
SCN
OCOCH3
ON=CHPh
NHCOCH3
j
k
l
C6H4OH-p
_
+
NR3 Cl
Scheme 4.

2874
J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
PhXCH2R
R
X
(8)
OCH2C6H4Cl-o
(9)
O
O
O
O
a
b
c
C6H4Cl-o
Ph
Ph
N
C6H3Cl2-2,6
1-napth
C6H5
yl
d
e
f
_
+
O
C6H4OMe-p
O
O
S
N
C6H4CH2OPh-p
C6H3Cl2-2,6
g
C6H4Cl-o
(10)
Cl
N
N
O
N
R
R
(11)
R
R
(12)
a
H
a
b
Ph
b
Cl
C6H4Cl-o
(CH2)3SMe
Me
c
d
Scheme 5.
4. Experimental
This compound (1a) was also prepared in quantitative yield
by the reaction of 98% sulfuric acid (5.0 g, 50 mmol),
benzyl formate (8.59 g, 55 mmol) and dimethyl sul®de
(20 cm3), by analogy with a literature procedure.16
4.1. General
Solvents used were dried under re¯ux and freshly distilled
under a dry nitrogen atmosphere before use. Drying agents
were: Na±benzophenone {for petroleum ether (bp 60±
808C), diethyl ether, tetrahydrofuran (THF), and toluene};
and P2O5 (for dichloromethane). Infrared (IR) spectra were
recorded on Perkin±Elmer 580 and 1600 instruments and
calibrated against polystyrene. 1H, 13C and 19F NMR spectra
in solution were recorded at 200.13, 50.32 and 376.5 MHz,
unless otherwise stated, respectively, on a Bruker WP 200
4.3. General procedure for benzylic sulfonium salts
(1b±e)
98% Sulfuric acid was added dropwise to a mechanically
stirred solution of the appropriate alcohol in dimethyl sul-
®de over ca. 30 min. at ambient temperature. After stirring
overnight at ambient temperature, a white precipitate was
observed. The dimethyl sul®de and water were removed by
evaporation under reduced pressure and the residue was
treated as outlined below.
1
SY spectrometer; H and 19F Chemical shifts (ppm) are
reported relative to tetramethylsilane and trichloro¯uoro-
methane as references, respectively, and coupling constants
are quoted in Hz. The solid state CPMAS 13C{1H} NMR
spectrum (75.43 MHz) was recorded at the University of
Durham, UK.
4.3.1. 2-Chlorobenzyldimethylsulfonium hydrogensul-
fate (1b). From H2SO4 (7.0 g, 70 mmol), 2-chlorobenzyl
alcohol (10.0 g, 70 mmol) and Me2S (17.6 g, 280 mmol).
The residue was treated with acetone (50 cm3) and the
resultant slurry was ®ltered. The solid was washed with
ice-cold acetone (10 cm3), and then dried under high
vacuum to give 2-chlorobenzyldimethylsulfonium hydro-
gensulfate (1b) as a colorless, crystalline solid (8.8 g,
4.2. Synthesis of sulfonium salts
4.2.1. Benzyldimethylsulfonium hydrogensulfate (1a).
98% Sulfuric acid (6.5 g, 65 mmol) was added dropwise
to a mechanically stirred solution of benzyl alcohol (5.4 g,
50 mmol) in dimethyl sul®de (12.4 g, 0.2 mol) over ca.
30 min and the resultant mixture was stirred at ambient
temperature overnight. The lower layer was separated and
evaporated under reduced pressure to give benzyldimethyl-
sulfonium hydrogensulfate (1a) as a colorless oil; dH
(d6-DMSO), 2.8 (s, 6H, CH3); 4.7 (s, 2H, CH2); 7.5 (s,
5H, Ar±H); dC (d6-DMSO), 24.1 (CH3); 45.9 (CH2);
128.8 (quaternary C) 129.7, 130.0, 131.2; m/z (FAB for
salt AB) 153 (69%, A1), 91 (100, A1±S(CH3)2), 403 (2.4,
44%); mp 143±1448C (EtOH/EtOAc); nmax (KBr)/cm21
,
2940, 1470, 1430, 1290, 1170, 1000; dH (d6-DMSO), 2.9
(s, 6H, CH3); 4.8 (s, 2H, CH2); 7.4±7.7 (m, 4H, Ar±H); dC
(d6-DMSO), 24.4 (CH3); 44.0 (CH2); 128.5, 130.6, 132.2,
134.0 (4£CH); 127.2, 134.5 (2 quaternary C's); m/z
(FAB for salt AB) 187 (35Cl isotope) [100%, A1]), 125
(51, A1±S(CH3)2), 471 (3.5, A2B1 cluster), 756 (0.27,
1
A3B2 cluster); (Found: C, 38.0; H, 4.7%. C9H13ClO4S2
requires: C, 38.0; H, 4.60%).
1
A2B1 cluster), 653 (0.05, A3B21 cluster), 903 (0.05, A4B3
4.3.2. 3-Chlorobenzyldimethylsulfonium hydrogensul-
fate (1c). From H2SO4 (7.0 g, 70 mmol), 3-chlorobenzyl-
alcohol (10.0 g, 70 mmol) and Me2S (17.6 g, 280 mmol).
cluster); (Found: A2B1 403.1093 (FAB). C18H27O4S3
requires: 403.1071).

J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
2875
The residual clear yellow syrup was triturated with diethyl
ether to give a white paste, which was ®ltered on a glass
sinter. The resulting solid was washed with ice-cold ethanol
(5 cm3) and dried under high vacuum to give 3-chloro-
benzyldimethylsulfonium hydrogensulfate (1c) as a white
powder (780 mg, 4%); mp 86±888C (EtOH); nmax (KBr)/
cm21, 3000, 1580, 1480, 1430, 1210, 1050; dH (d6-DMSO),
2.85 (s, 6H, CH3); 4.7 (s, 2H, CH2); 7.45±7.65 (m, 4H, Ar±
H); dC (d6-DMSO), 24.2 (CH3), 45.2 (CH2); 129.9, 130.0,
130.8, 131.6 (4£CH); 131.4, 134.1 (2 quaternary C's); m/z
(FAB for salt AB) 187 (35Cl isotope) [100%, A1]), 125 (27,
A1±S(CH3)2), 471 (2.4), (A2B1 cluster); (Found: C, 37.8;
H, 4.6; S, 22.6%. C9H13ClO4S2 requires: C, 38.0; H, 4.6; S,
22.5%).
dimethyl-(2-nitrobenzyl)sulfonium hydrogensulfate (1f) as
a yellowish white, crystalline solid (5.68 g, 38%); mp 178±
1808C (EtOH/EtOAc); nmax (KBr)/cm21, 3459, 3393, 3019,
2548, 1609, 1577, 1526, 1430, 1339, 1238, 1061, 1009, 848,
710, 577; dH (d6-DMSO), 3.0 (s, 6H, CH3); 5.0 (s, 2H, CH2);
7.7±7.9 (m, 3H, Ar±H); 8.2 (d, Jˆ7.5 Hz, 1H, Ar±H); dC
(d6-DMSO), 25.1 (CH3); 44.8 (CH2); 124.6, 148.7 (2
quaternary C's); 126.4, 131.9, 135.0, 135.2 (4£CH). m/z
(FAB for salt AB) 198 (100% A1), 136 (53, A1±
S(CH3)2), 493 (3.8, A2B1 cluster); (Found: C, 36.5; H,
4.5; N, 4.5%. C9H13NO6S2 requires: C, 36.6; H, 4.4; N,
4.7%).
4.3.6. Dimethyl-(4-nitrobenzyl)sulfonium hydrogensul-
fate (1g). 98% Sulfuric acid (5.0 g, 50 mmol) was added
dropwise to a mechanically stirred solution of 4-nitrobenzyl
alcohol (7.67 g, 50 mmol) in dimethyl sul®de (120 cm3)
over ca. 20 min., at 08C. After stirring overnight at ambient
temperature, yellow oil formed as the lower of two layers.
The upper dimethyl sul®de layer was decanted and the
lower layer was sonicated under ethyl acetate for 6 h before
trituration with acetone. The resulting slurry was ®ltered
and the solid was washed with ice-cold ethyl acetate
(5£10 cm3) and then dried under high vacuum to give
dimethyl-(4-nitrobenzyl)sulfonium hydrogensulfate (1g) as
a colorless crystalline solid (6.10 g, 41%); mp 130.5±
131.58C (EtOH/EtOAc); nmax (KBr)/cm21, 3408, 3003,
2916, 1606, 1522, 1422, 1352, 1223, 1110, 1080, 1048,
1011, 860, 710, 590; dH (d6-DMSO), 2.9 (s, 6H, CH3); 4.9
(s, 2H, CH2); 7.7 (d, Jˆ8.7 Hz, 2H, Ar±H); 8.3 (d,
Jˆ8.7 Hz, 2H, Ar±H); dC (d6-DMSO), 24.2 (CH3); 44.8
(CH2); 124.6, 132.7 (2£CH); 136.6, 148.5 (2 quaternary
C's); m/z (FAB for salt AB) 198 (54%, A1), 136 (29,
A1±S(CH3)2), 31 (100), 493 (1.5, A2B1 cluster); (Found:
C, 36.5; H, 4.5; N, 4.6%. C9H13NO6S2 requires: C, 36.6; H,
4.4; N, 4.7%).
4.3.3. 2,6-Dichlorobenzyldimethylsulfonium hydrogen-
sulfate (1d). From H2SO4 (14.0 g, 140 mmol), 2,6-dichloro-
benzyl alcohol (24.8 g, 140 mmol) and Me2S(35.2 g,
560 mmol). Ethyl acetate (100 cm3) was added to the
residue and the resultant slurry was ®ltered. The solid was
washed with ethyl acetate (50 cm3) and ®nally dried under
high vacuum to give 2,6-dichlorobenzyldimethylsulfonium
hydrogensulfate (1d) as a colorless, crystalline solid (27.5 g,
62%); mp 160±1618C (EtOH/EtOAc); nmax (KBr)/cm21
,
2950, 1580, 1560, 1430, 1290, 1170, 1010; dH
(d6-DMSO), 3.1 (s, 6H, CH3); 4.9 (s, 2H, CH2); 7.5±7.55
(m, 3H, Ar±H); dC (d6-DMSO), 25.8 (CH3); 43.2 (CH2);
126.5, 130.2 (2£CH); 133.4, 136.9 (2 quaternary C's); m/z
(FAB for salt AB) 221 (35Cl isotopes) [(100%, A1)], 159
(32, A1±S(CH3)2), 541 (2.2, A2B1 cluster); (Found: C,
33.9; H, 3.9%. C9H12Cl2O4S2 requires: C, 33.9; H, 3.8%).
4.3.4. 2,6-Di¯uorobenzyldimethylsulfonium hydrogen-
sulfate (1e). From H2SO4 (2.5 g, 25 mol), 2,6-di¯uoro-
benzyl alcohol (4.6 g, 32 mmol) and Me2 S (12.8 g,
200 mmol). Ethanol (10 cm3) was added to the residue
and the resultant slurry was ®ltered. The solid was washed
with ethanol (10 cm3) and ®nally dried under high vacuum
to give 2,6-di¯uorobenzyldimethylsulfonium hydrogen-
sulfate (1e) as a colorless, crystalline solid (2.3 g, 25%);
mp 147±1488C (EtOH); nmax (KBr)/cm21, 2980, 1630,
1590, 1470, 1220, 1030; dH (d6-DMSO), 2.9 (s, 6H, CH3);
4.8 (s, 2H, CH2); 7.25±7.35 (m, 2H, Ar±H); 7.55±7.7
(m, 1H, Ar±H); dC (d6-DMSO), 24.3 (CH3); 34.0 (CH2);
105.1 (t, JC±Fˆ19 Hz, C1); 112.8 (d, JC±Fˆ22 Hz, C3,C5);
4.3.7. 4-Methoxybenzyldimethylsulfonium hydrogensul-
fate (1h). 98% Sulfuric acid (10.0 g, 100 mmol) was added
dropwise to a mechanically stirred solution of 4-methoxy-
benzyl alcohol (13.82 g, 100 mmol) in dimethyl sul®de
(100 cm3) over ca. 20 min. After stirring for 4 h at ambient
temperature, a thick, white paste was observed. The upper
dimethyl sul®de layer was decanted and the paste was
sonicated under ethyl acetate for 6 h before immediate
recrystallization to give 4-methoxybenzyldimethylsul-
fonium hydrogensulfate 1h as a colorless, crystalline solid
(22.5 g, 85%); mp 83±848C (EtOH/EtOAc); nmax (KBr)/
cm21, 3400, 3001, 1610, 1514, 1426, 1253, 1027, 841,
750, 585; dH (d6-DMSO), 2.8 (s, 6H, SMe); 3.75 (s, 3H,
OMe); 4.65 (s, 2H, CH2); 7.0 (d, Jˆ8.7 Hz, 2H, Ar±H);
7.4 (d, Jˆ8.7 Hz, 2H, Ar±H); dC (d6-DMSO), 23.6 (SMe);
44.8 (CH2); 55.7 (OMe); 115.0, 132.7 (2£CH); 120.2, 160.5
(2 quaternary C's); m/z (FAB for salt AB) 167 (5.9%, A1),
121 (100, A1±S(CH3)2).
133.6 (t, JC±Fˆ10 Hz, C4); 161.4 (JC2±F2,
ˆ249 Hz,
C6±F6
JC2±F6, C6±F2ˆ6.5 Hz, C2,C6); dF (C2D6SO), 2111.49 (over-
lapping dd, JHF and JHF,8 Hz); m/z (FAB for salt AB) 189
(100%, A1), 475 (5.7, A2B1 cluster), 762 (0.6, A3B21 clus-
ter); (Found: C, 37.5; H, 4.3; S, 22.2%. C9H12F2O4S2
requires: C, 37.8; H, 4.2; S, 22.4%).
4.3.5. Dimethyl-(2-nitrobenzyl)sulfonium hydrogensul-
fate (1f). 98% Sulfuric acid (5.0 g, 50 mmol) was added
dropwise to a mechanically stirred solution of 2-nitrobenzyl
alcohol (7.67 g, 50 mmol) in dimethyl sul®de (100 cm3)
over ca. 30 min., at 08C. At ®rst, a white solid formed but
after stirring overnight at ambient temperature yellow oil
appeared as the lower of two layers. The dimethyl sul®de
(top) layer was decanted and the lower layer was triturated
under ethyl acetate. The resulting slurry was ®ltered and the
solid product was washed with ice-cold ethyl acetate
(5£10 cm3) and then dried under high vacuum to give
This sulfonium salt was very unstable until it had been
recrystallized, after which it was stable at 48C for a few
weeks.
4.3.8. Dimethyl-(4-methylbenzyl)sulfonium hydrogen-
sulfate (1i). 98% Sulfuric acid (10.0 g, 100 mmol) was
added dropwise to a mechanically stirred solution of

2876
J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
dimethyl sul®de (80 cm3) and 4-methylbenzyl alcohol
(12.22 g, 100 mmol) over ca. 30 min at 08C. The mixture
was stirred at ambient temperature overnight. The upper
dimethylsul®de layer was decanted and the aqueous layer
was sonicated under ethyl acetate (100 cm3) for 6 h and then
diethyl ether (100 cm3) for 4 h. The resulting colorless oil
was triturated at 2208C in the presence of diethyl ether
(50 cm3) and the colorless crystals produced were separated
by cold ®ltration to give dimethyl-(4-methybenzyl)sul-
fonium hydrogensulfate (1i) as a deliquescent, colorless,
crystalline solid; dH (d6-DMSO), 2.3, s, 3H (CH3±C); 2.8,
s, 6H (CH3±S); 4.7, s, 2H (CH2); 7.3 (d, Jˆ8 Hz, 2H, Ar±
H); 7.4 (d, Jˆ8 Hz, 2H, Ar±H); dC (d6-DMSO); 21.3 (CH3±
C); 23.9 (CH3±S) 45.7 (CH2); 130.3, 131.1 (2£CH); 125.7,
139.6 (2 quaternary C's); m/z (FAB for salt AB) 167 (63%,
A1), 105 (100, A1±S(CH3)2), 431 (1.4, A2B1 cluster); (Found:
A2B1 431.1417 (FAB). C20H31O4S3 requires: 431.1385).
4.3.10. Dimethyl-(1-naphthylmethyl)sulfonium hydro-
gensulfate (1k). 98% Sulfuric acid (580 mg, 5.8 mmol)
was added dropwise to a mechanically stirred solution of
1-naphthalenemethanol (913 mg, 5.8 mmol) in dimethyl
sul®de (30 cm3) over ca. 5 min. at ambient temperature.
The mixture was stirred at ambient temperature overnight,
whereupon a thick, brownish sludge formed. The upper
layer of excess dimethyl sul®de was then decanted and
ethyl acetate (20 cm3) was added. The mixture was placed
in a sonic bath for 1 h, after which time the ethyl acetate was
decanted and a fresh portion added. This procedure was
repeated until the product was a ®ne powder. The product
was ®ltered on a glass sinter, dried under vacuum and the
residual solid was recrystallized to give dimethyl-(1-
naphthylmethyl)sulfonium hydrogensulfate (1k) as an off-
white, crystalline solid. (920 mg, 53%); mp 156.5±1588C
(EtOH); nmax (KBr)/cm21, 2984, 2932, 1596, 1512, 1404,
1284, 1171, 1070, 1002, 887, 850, 808, 778, 575; nH
(d6-DMSO), 2.9 (s, 6H, CH3); 5.2 (s, 2H, CH2); 7.5±7.7
(m, 4H, Ar±H); 8.0 (m, 2H, Ar±H); 8.4 (d, Jˆ8 Hz, 1H,
Ar±H); dC (d6-DMSO), 24.6, (CH3); 44.3 (CH2); 124.2,
126.1, 127.1, 129.4, 131.0, 131.2 (7£CH), 125.0, 131.6,
134.0 (3 quaternary C's). m/z (FAB for salt AB), 203
(30%, A1), 141 (100, A1±S(CH3)2), 503 (1.1, A2B1 clus-
Due to the extremely hygroscopic nature of this salt, it was
not possible to obtain a melting point, an accurate yield, or
an analytically pure sample.
4.3.9. 2,6-Dimethoxybenzyldimethylsulfonium hydro-
gensulfate (1j). 2,6-Dimethoxybenzyl alcohol. 2,6-
Dimethoxybenzoic acid (21.5 g, 128 mmol) was added in
portions to a mechanically stirred suspension of lithium
aluminium hydride (21.5 g, 565 mmol) in dry THF
(300 cm3) at 08C. The mixture was allowed to warm to
ambient temperature and then heated under re¯ux for
20 h. Successive dropwise addition of water (20 cm3), 6 M
sodium hydroxide solution (20 cm3) and ®nally water
(65 cm3), all with vigorous stirring precipitated the metals
as their insoluble hydroxides. The mixture was ®ltered and
the resulting solid was washed with THF (2£50 cm3) and
the combined solvents evaporated under reduced pressure.
The crude residue was dissolved in ethyl acetate (100 cm3)
and the solution was washed with water (50 cm3) followed
by saturated brine (50 cm3). This solution was dried
(MgSO4), ®ltered, and the solvent evaporated under reduced
pressure to give 2,6-dimethoxybenzyl alcohol as a colorless,
crystalline solid (15.46 g, 80%); mp 54±568C (lit. 25 55.5±
568C); dH (d6-DMSO), 3.8 (s, 6H, OCH3); 4.35 (t, Jˆ6 Hz,
1H, OH); 4.5 (d, Jˆ6 Hz, 2H, CH2); 6.6 (d, Jˆ8 Hz, 2H,
Ar±H); 7.25 (t, Jˆ8 Hz, 1H, Ar±H); dC (d6-DMSO), 51.9
(CH2); 56.0 (OCH3); 104.3, 117.7 (2£CH); 129.4, 158.8 (2
quaternary C's).
1
ter), 804 (0.08, A3B2 cluster); (Found: C, 52.1; H, 5.3%.
C13H16O4S2 requires: C, 52.0; H, 5.4%).
4.3.11. Dimethyl-(2-naphthylmethyl)sulfonium hydro-
gensulfate (1l). This was prepared as above (for 1k) from
98% sulfuric acid (3.0 g, 30 mmol), 2-naphthalenemethanol
(4.745 g, 30 mmol) and dimethyl sul®de (100 cm3) to give
dimethyl-(2-naphthylmethyl)sulfonium
hydrogensulfate
(1l) as a colorless crystalline solid. (5.2 g, 58%); mp
108.5±1098C (EtOH/EtOAc); nmax (KBr)/cm21, 3019,
1598, 1502, 1420, 1336, 1171, 1052, 1006, 854, 825, 758;
dH (d6-DMSO), 2.85 (s, 6H, CH3); 4.85 (s, 2H, CH2); 7.6 (m,
3H, Ar±H); 8.0 (m, 4H, Ar±H); dC (d6-DMSO), 24.2,
(CH3); 46.3 (CH2); 127.4, 127.7, 127.9, 128.2, 128.5,
129.5, 130.9 (7£CH), 126.3, 133.2, 133.5 (3 quaternary
C's). m/z (FAB for salt AB), 203 (46%, A1), 141 (100,
A1±S(CH3)2), 503 (2.0, A2B1 cluster); (Found: C, 51.8;
H, 5.3%. C13H16O4S2 requires: C, 52.0; H, 5.4%).
4.3.12. Dimethyl-(9-phenanthrylmethyl)sulfonium hydro-
gensulfate (1m). 9-Phenanthrenemethanol. Sodium boro-
hydride (284 mg, 7.5 mmol, 3 equiv.) was suspended in a
solution of 9-phenanthrene carboxaldehyde (516 mg,
2.5 mmol) in dry THF (10 cm3). Isopropanol (5 cm3) was
added and the mixture stirred until reaction was complete
(t.l.c.). After the addition of water (2 cm3) the solvents were
evaporated under reduced pressure. The crude product was
dissolved in chloroform (20 cm3) and the solution was
washed with water (10 cm3) then saturated brine (10 cm3),
and ®nally dried (MgSO4). The mixture was ®ltered and the
®ltrate was evaporated under reduced pressure to give
9-phenanthrenemethanol as a colorless, crystalline solid
(496 mg, 95%); mp 146±148.58C (lit. 26 149±149.58C);
dH (d6-DMSO), 5.0 (d, Jˆ5.4 Hz, 2H, CH2); 5.4 (t,
Jˆ5.4 Hz, 1H, OH); 7.6±7.7 (m, 4H, Ar±H); 7.85 (s, 1H,
H10); 7.95 (m, 1H, Ar±H); 8.1 (m, 1H, Ar±H); 8.75±8.9 (m,
2H, Ar±H); dC (d6-DMSO), 61.9 (CH2); 123.2; 123.7,
124.7, 124.7, 127.0, 127.0, 127.2, 127.3, 128.8 (9£CH)
129.9, 130.3, 130.4, 131.7, 136.5 (5 quaternary C's).
98% Sulfuric acid (3.0 g, 30 mmol) was added dropwise to a
mechanically stirred solution of dimethyl sul®de (12.4 g,
0.2 mol) and 2,6-dimethoxybenzyl alcohol (5.05 g,
30 mmol, prepared as above) over ca. 30 min. The mixture
was stirred at ambient temperature overnight. The lower
layer was separated and evaporated under reduced pressure
to give crude 2,6-dimethoxybenzyldimethylsulfonium
hydrogensulfate (1j) as a white paste (7.5 g, 80% approx.);
dH (d6-DMSO), 2.85 (s, 6H, SCH3); 3.85 (s, 6H, OCH3);
4.55 (s, 2H, CH2); 6.8 (d, Jˆ6.5 Hz, 2H, Ar±H); 7.4 (t,
Jˆ6.5 Hz, 1H, Ar±H); dC (d6-DMSO); 24.8 (CH3); 36.4
(CH2); 56.5 (OCH3); 104.0 (C±CH2); 104.8, 132.4
(2£CH); 159.2 (C±OCH3); m/z (FAB for salt AB) 213
(11% A1), 151 (100, A1±S(CH3)2), 523 (0.45, A2B1 clus-
ter). This compound was found to be extremely unstable and
it proved impossible to obtain an analytically pure sample.

J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
2877
98% Sulfuric acid (1.34 g, 13.4 mmol) was added dropwise
to a mechanically stirred solution of 9-phenanthrenemetha-
nol (2.78 13.4 mmol, prepared as above) in dimethyl sul®de
(150 cm3) over ca. 5 min., at ambient temperature. After
1 h, a thick, grey paste formed. The upper dimethyl sul®de
layer was decanted and ethyl acetate (50 cm3) was added.
The mixture was placed in a sonic bath for 1 h, after which
time the ethyl acetate was decanted and a fresh portion
added. This procedure was repeated until the product was
a ®ne powder. The product was ®ltered on a glass sinter and
dried under vacuum to give dimethyl-(9-phenanthryl-
methyl)sulfonium hydrogensulfate (1m) as an off-white
powder which became pale brown after recrystallization
(1.96 g, 42%); mp 177±1798C (H2O/EtOH/EtOAc); nmax
(KBr)/cm21, 3020, 1498, 1431, 1306, 1227, 1170, 1067,
1002, 852, 770, 754, 728; dH (d6-DMSO), 2.95 (s, 6H,
CH3); 5.2 (s, 2H, (CH2); 7.7±7.9 (m, 4H, Ar±H); 8.0±
8.15 (m, 2H, Ar±H); 8.45 (m, 1H, Ar±H); 8.85±9.0 (m,
2H, Ar±H); dC (d6-DMSO), 25.0 (CH3), 45.3 (CH2),
123.5, 124.3, 125.0, 127.9, 127.9, 128.0, 128.8, 129.5,
132.5 (9£CH), 123.7, 129.8, 130.8, 130.9, 131.0 (5 quatern-
ary C's); m/z (FAB for salt AB) 253 (27%, A1), 191 (100,
A1±S(CH3)2) 602 (0.67, A2B1 cluster); (Found: C, 58.4; H,
5.2%. C17H18O4S2 requires: C, 58.3; H, 5.2%).
S(CH3)2), 554 (0.36, A2B1 cluster); (Found: C, 55.15; H,
5.5%; C15H18O4S2 requires: C, 55.2; H, 5.6%).
4.3.16. Benzyldimethylsufonium chloride (1q). Gaseous
hydrogen chloride was bubbled through a mixture of
dimethyl sul®de (29 cm3, 0.4 mol) and diethyl ether
(29 cm3) for ca. 20 min. Benzyl alcohol (4.32 g, 40 mmol)
was added and the solution was stirred overnight. The
solvents were evaporated under reduced pressure and the
residue was partitioned between distilled water and diethyl
ether. The aqueous layer was separated and the water
evaporated under high vacuum to leave benzyldimethyl-
sulfonium chloride (1q) as a colorless oil. (5.65 g, 75%);
dH (d6-DMSO), 2.95 (s, 6H, CH3); 4.9 (s, 2H, CH2); 7.5 (m,
5H, Ar±H); dC (d6-DMSO), 24.1 (CH3); 46.0 (CH2); 128.8
(quaternary C) 129.7, 130.0, 131.1 (3£CH); m/z (FAB for
salt AB) 153 (100%, A1), 91 (85, A1±S(CH3)2), 341 (8.3,
1
A2B1 cluster), 529 (0.16, A3B2 cluster).
4.3.17. Benzyldimethylsulfonium tri¯uoroacetate (1r).
Tri¯uoroacetic acid (22.8 g, 0.2 mol) was added dropwise
to a mechanically stirred solution of benzyl alcohol (10.8 g,
0.1 mol) in dimethyl sul®de (29 cm3, 0.4 mol) over ca.
30 min and the mixture was stirred at ambient temperature
overnight. The solvents were evaporated under reduced
pressure and the residue was partitioned between distilled
water and diethyl ether. The aqueous layer was separated,
the water was evaporated under reduced pressure, and the
residual solid was triturated with diethyl ether. The slurry
was ®ltered and the solid was dried under high vacuum to
give benzyldimethylsulfonium tri¯uoroacetate (1r) as a
colorless, crystalline solid (5.32 g, 20%); mp 64±65.58C
(EtOH/EtOAc); nmax (KBr)/cm21, 3452, 3018, 2930, 1687,
1426, 1203, 1127, 700; dH (d6-DMSO), 2.8 (s, 6H, CH3); 4.7
(s, 2H, CH2); 7.45 (m, 5H, Ar±H); dC (d6-DMSO), 24.1
(CH3); 46.0 (CH2); 128.8 (quaternary C) 129.8, 130.0,
131.1 (3£CH); m/z (FAB for salt AB) 153 (100%, A1), 91
(76, A1±S(CH3)2), 419 (8.3, A2B1 cluster); (Found: C,
49.3; H, 5.0%; C11H13F3O2S requires: C, 49.6; H, 4.9%).
4.3.13. (9-Anthrylmethyl)dimethylsulfonium hydrogen-
sulfate (1n). This was prepared as above for 1m from
H2SO4 (2.0 g, 20 mmol), 9-anthracenemethanol (4.16 g,
20 mmol) and Me2S (150 cm3). Compound (1n) was a
yellowish green powder (6.01 g, 86%); mp 150±150.58C
(dec.); nmax (KBr)/cm21, 3005, 1624, 1436, 1220, 1062,
884, 850, 743, 584; dH (d6-DMSO), 3.0 (s, 6H, CH3); 5.7
(s, 2H, CH2); 7.5±9.0 (m, 9H, Ar±H). dC (CP MAS), 26.9
(CH3), 38.8 (CH2) 116.9, 123.3, 126.0, 130.2; m/z (FAB for
salt AB) 253 (3.1%, A1), 191 (100, A1±S(CH3)2); (Found:
C, 57.7; H, 5.2; S, 18.1%. C17H18O4S2 requires: C, 58.3; H,
5.2; S, 18.3%).
4.3.14. 9-Fluorenyldimethylsulfonium hydrogensulfate
(1o). This was prepared as above for 1m from H2SO4
(2.0 g, 20 mmol), 9-hydroxy¯uorene (3.64 g, 20 mmol)
and Me2S (200 cm3). Compound (1o) was an off-white
The diethyl ether layer described above was evaporated
under reduced pressure to leave benzyl tri¯uoroacetate as
a colorless liquid (10.2 g, 50%); bp 174±1788C/760 Torr
(lit. 27 1758C/760 Torr); nmax (KBr)/cm21, 3550, 3039,
1784, 1500, 1457, 1395, 1347, 1148, 907; dH (d6-DMSO),
5.3 (s, 2H, CH2); 7.35 (m, 5H, Ar±H); dC (d6-DMSO), 69.5
(CH2); 114.5 (q, JC±Fˆ248 Hz, CF3); 128.6, 128.8, 129.2
powder (3.05 g, 45%); mp 148±1508C; nmax (KBr)/cm21
,
2997, 2908, 1412, 1286, 1178, 1069, 1006, 850, 733, 574;
dH (d6-DMSO), 2.65 (s, 6H, CH3); 6.2 (s, 1H, H-9); 7.55.(t,
Jˆ7.5 Hz, 2H, ArH); 7.65 (t, Jˆ7.5 Hz, 2H, Ar±H); 7.9 (d,
Jˆ7.5 Hz, 2H, Ar±H); 8.1 (d, Jˆ7.5 Hz, 2H, Ar±H); dC
(d6-DMSO), 22.0 (CH3); 55.1 (C-9); 121.9, 127.0, 129.1,
131.3 (4£CH); 135.4, 141.8 (2 quaternary C's); m/z (FAB
for salt AB), 227 (241, A1), 165 (100, A1 S(CH3)2) 551
2
(3£CH); 133.2 (quaternary C); 157.4 (q, JCFˆ42 Hz,
CvO);.
1
(1.1, A2B1 cluster), 875 (0.07, A3B2 cluster); (Found:
4.3.18. 1-Benzyltetrahydrothiophenium hydrogensulfate
(2a). 98% Sulfuric acid (10.0 g, 0.1 mol) was added drop-
wise to a mechanically stirred solution of benzyl alcohol
(10.8 g, 0.1 mol) in tetrahydrothiophene (26.4 g, 0.3 mol)
over ca. 20 min at 08C. The resultant mixture was allowed
to warm to ambient temperature and stirred overnight. The
lower dark green aqueous layer was separated and sonicated
under ethyl acetate (100 cm3) for 4 h. The ethyl acetate was
decanted and any residual solvents evaporated under
reduced pressure to give the crude product as an extremely
viscous oil. This oil was cooled to 2188C and crystallization
occurred. The solid was separated and washed with a little
ice-cold ethanol to give pure 1-benzyltetrahydrothio-
551.1436. A2B1 cluster requires: 551.1385).
4.3.15. Benzhydryldimethylsulfonium hydrogensulfate
(1p). This was prepared as above for 1m from H2SO4
(10.0 g, 0.1 mol), benzhydrol (18.42 g, 0.1 mol) and Me2S
(100 cm3). Compound (1p) was a colorless crystalline solid
(22.70 g, 70%); mp 118±1198C; nmax (KBr)/cm21, 2921,
2618, 1315, 1169, 1062, 847, 713, 581; dH (d6-DMSO),
2.8 (s, 6H, CH3); 6.3 (s, 1H, CH±S); 7.4±7.5(m, 6H, Ar±
H); 7.65±7.75 (m, 4H, Ar±H); dC (d6-DMSO), 24.6 (CH3);
63.9 (CH±S); 129.0, 130.2 (CH); 134.2 (quaternary C); m/z
(FAB for salt AB), 229 (3.7%, A1), 167 (100, A1±

2878
J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
phenium hydrogensulfate (2a) as a very hygroscopic, color-
less, crystalline solid (2.75 g, 10%); mp 76±798C; nmax
(KBr)/cm21, 3389, 2944, 1494, 1456, 1417, 1200, 1072,
1011, 883, 844, 772, 707; dH (d6-DMSO), 2.05±2.3 (m,
4H, CH2±CH2±S); 3.3±3.55 (m, 4H, CH2±CH2±S); 4.55
(s, 2H, PhCH2); 7.45 (m, 3H, Ar±H); 7.55 (m, 2H, Ar±
H); dC (d6-DMSO), 28.6 (CH2±CH2±S); 42.9 (CH2±CH2±
S); 45.2 (benzyl CH2); 129.8, 129.9, 130.9 (3£CH); 130.4
(quaternary C); m/z (FAB for salt AB) 179 (83%, A1), 91
(100, A1±(CH2)4S), 455 (2.9, A2B1 cluster), 731 (0.11,
4.4.3. Benzhydryldimethylsulfonium tetra¯uoroborate
(1u). Colorless, crystalline solid (14.56 g, 92%); mp 155±
1608C dec.; nmax (KBr)/cm21, 3480, 2981, 2905, 1630,
1494, 1455, 1425, 1028, 732, 626; dH (d6-DMSO), 2.8 (s,
6H, CH3); 6.1 (s, 1H, CH±S); 7.5±7.7(m, 10H, Ar±H); dC
(d6-DMSO), 24.8 (CH3); 64.6 (CH±S); 128.9, 128.9, 130.2
(3£CH); 133.9 (quaternary C); m/z (FAB for salt AB), 229
(3.7%, A1), 167 (100, A1±S(CH3)2) 544 (0.36, A2B1
cluster); this compound could not be puri®ed to analytical
standard. (Found: C, 56.0; H, 5.3%; C15H17BF4S requires C,
57.0; H, 5.4%).
1
1
A3B2 cluster), 1005 (0.31, A4B3 cluster); (Found: C,
46.9; H, 6.1%. C11H16O4S2 requires: C, 47.8; H, 5.8%).
4.4.4. 1-Benzyltetrahydrothiophenium tetra¯uoroborate
(2b). Colorless, crystalline solid (11.75 g, 88%); mp 79±
, 3420,
4.3.19. Tribenzylsulfonium hydrogensulfate (3a). 98%
Sulfuric acid (3.0 g, 30 mmol) was added dropwise to a
mechanically stirred mixture of benzyl formate (4.49 g,
33 mmol) in dibenzyl sul®de (6.43 g, 30 mmol) over ca.
5 min, at 08C. The mixture was stirred overnight at ambient
temperature, after which time a white precipitate had
formed. This was separated and washed with ice-cold
diethyl ether (20 cm3), and then recrystallized to give tri-
benzylsulfonium hydrogensulfate (3a) as a colorless, crys-
talline solid (10.2 g, 92%); mp 167±1688C (H2O/EtOH/
EtOAc), (lit. 28 170±1758C); dH (d6-DMSO), 4.9 (s, 6H,
CH2); 7.3 (m, 15H, Ar±H); dC (d6-DMSO), 45.2 (CH2);
129.2 (quaternary C); 129.5, 129.7, 130.8 (3£CH); m/z
(FAB for salt AB) 91 (100%, A1±(PhCH2)2S), 305 (31,
A1), 707 (1.2, A2B1 cluster); (Found: C, 63.0; H, 5.9%.
C21H22O4S requires: C, 62.7; H, 5.5%).
79.58C (H2O/EtOH/EtOAc); nmax (KBr)/cm21
2944, 1458, 1036, 770, 703; dH (d6-DMSO), 2.1±2.3 (m,
4H, CH2±CH2±S); 3.3±3.5 (m, 4H, CH2±CH2±S); 4.5 (s,
2H, PhCH2); 7.45 (m, 3H, Ar±H); 7.55 (m, 2H, Ar±H); dC
(d6-DMSO), 28.6 (CH2±CH2±S); 43.0 (CH2±CH2±S); 45.4
(benzyl CH2); 129.9, 130.0, 130.8 (3£CH); 130.2 (quatern-
ary C); m/z (FAB for salt AB) 179 (100%, A1), 91 (87, A1±
(CH2)4S), 445 (2.3, A2B1 cluster); (Found: C, 49.5; H,
5.6%. C11H15BF4S requires: C, 49.65; H, 5.7%).
4.4.5. Tribenzylsulfonium tetra¯uoroborate (3b). Color-
less, crystalline solid (10.80 g, 55%); mp 170±1718C
(EtOH); nmax (KBr)/cm21, 2991, 1497, 1456, 1423, 1254,
1070, 775, 708; dH (d6-DMSO), 4.8 (s, 6H, CH2); 7.3 (m,
15H, Ar±H); dC (d6-DMSO), 45.4 (CH2); 129.0 (quaternary
C); 129.6, 129.8, 130.8 (3£CH); m/z (FAB for salt AB) 91
(100%, A1±(PhCH2)2S), 305 (52, A1), 697 (1.4, A2B1
cluster); (Found: C, 64.3; H, 5.6%. C21H21BF4S requires:
C, 64.3; H, 5.4%).
4.4. General procedure for the preparation of
tetra¯uoroborate salts (1s±u, 2b, 3b)
The appropriate sul®de (0.1 mol) and the alcohol (50 mmol)
were dissolved in dichloromethane (50 cm3). A 54% w/w
solution of tetra¯uoroboric acid in diethyl ether (7 cm3,
8.1 g, equivalent to 4.4 g of HBF4, 50 mmol) was added
dropwise over ca. 5 min. at 08C. The mixture was stirred
overnight at ambient temperature. The solvents were evapo-
rated under reduced pressure to give a thick, colorless oil,
which was triturated with diethyl ether to crystallise the salt.
The following were prepared:
4.4.6. 1-Methyltetrahydrothiophenium hydrogensulfate
(2c). 98% Sulfuric acid (10.0 g, 0.1 mol) was added drop-
wise to a mechanically stirred mixture of tetrahydrothio-
phene (17.6 g, 0.2 mol) and methanol (4 cm3, 3.2 g,
0.1 mol) over ca. 30 min. The mixture was stirred at ambient
temperature overnight, and the lower layer was separated
and evaporated under reduced pressure to afford 1-methyl-
tetrahydrothiophenium hydrogensulfate (2c) as a colorless
oil; dH (d6-DMSO), 2.0±2.3 (m, 4H, CH2CH2S); 2.8 (s, 3H,
CH3); 3.2±3.5 (m, 4H, CH2CH2 S); dC (d6-DMSO), 25.3
(CH3); 28.1 (CH2CH2S); 44.7 (CH2CH2 S); m/z (FAB for
salt AB) 103 (100%, A1), 303 (2.3, A2B1 cluster); [Found:
A2B1 303.0784; C10 H23O4 S3 requires: 303.0758].
4.4.1. Benzyldimethylsulfonium tetra¯uoroborate (1s).
Colorless, crystalline solid (10.04 g, 84%); mp 103±1048C
(H2O/EtOH/EtOAc); nmax (KBr)/cm21, 3420, 3025, 1470,
1438, 1053, 703; dH (d6-DMSO), 2.8 (s, 6H, CH3); 4.7 (s,
2H, CH2); 7.5 (m, 5H, Ar±H); dC (d6-DMSO), 24.1 (CH3);
46.1 (CH2); 128.6 (quaternary C) 129.8, 130.1, 131.1
(3£CH); m/z (FAB for salt AB) 153 (100%, A1), 91 (74,
A1±S(CH3)2), 393 (8.3, A2B1 cluster); (Found: C, 44.6; H,
5.4%; C9H13BF4S requires: C, 45.0; H, 5.5%).
4.5. Synthesis of bis sulfonium salts
4.5.1. 1,4-Phenylene bis-(methylene) bis-(dimethylsulfo-
nium hydrogensulfate) (4a). 98% Sulfuric acid (4.0 g,
40 mmol) was added dropwise to a mechanically stirred
solution of 1,4-benzenedimethanol (2.76 g, 20 mmol) in
dimethyl sul®de (100 cm3) over ca. 15 min. After stirring
overnight at ambient temperature, the lower aqueous layer
was separated and sonicated under ethyl acetate for 5 h
before trituration with ethanol. The resulting slurry was
®ltered and the solid was dried under high vacuum to give
the title compound (4a) as a colorless, crystalline solid
(4.11 g, 49%); mp 164±1658C (dec.) (EtOH); nmax (KBr)/
cm21, 2982, 2486, 1432, 1290, 1167, 1070, 1006, 851; dH
(d6-DMSO), 2.85 (s, 12H, CH3); 4.75 (s, 4H, CH2); 7.6 (s,
4.4.2. 2-Chlorobenzyldimethylsulfonium tetra¯uoro-
borate (1t). Colorless, crystalline solid (9.35 g, 68%); mp
69±708C (H2O/EtOH/EtOAc); nmax (KBr)/cm21, 3442,
3037, 2935, 1473, 1425, 1053, 762; dH (d6-DMSO), 2.9
(s, 6H, CH3); 4.7 (s, 2H, CH2); 7.45±7.65 (m, 4H, Ar±H);
dC (d6-DMSO), 24.7 (CH3); 44.3 (CH2); 127.0, 134.5 (2
quaternary C's) 128.6, 130.7, 132.2, 133.8 (4£CH); m/z
(FAB for salt AB) 187 (100%, A1), 125 (58, A1±
S(CH3)2), 461 (3.1, A2B1 cluster); (Found: C, 39.3; H,
4.4%; C9H12BClF4S requires: C, 39.4; H, 4.4%).

J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
2879
4H, Ar±H); dC (d6-DMSO), 23.9 (CH3); 45.2 (CH2); 130.2
(quaternary C); 132.0 (CH); m/z (FAB for salt AB2) 165
(100%, A±S(CH3)21), 325 (57, AB1 cluster), 747 (1.3,
A2B3 cluster); (Found: C, 33.9; H, 5.2%. C12H22O8S4
requires: C, 34.1; H, 5.25%).
1190, 1042, 998, 831, 584; dH (d6-DMSO), 2.25 (m, 8H,
CH2±CH2±S); 3.3±3.65 (m, 8H, CH2±CH2±S); 4.8 (s, 4H,
benzyl CH2); dC (100.6 MHz, d6-DMSO), 28.0 (CH2±CH2±
S); 32.6 (benzyl CH2); 44.2 (CH2±CH2±S); 111.2 (t,
1
1
2JCFˆ10 Hz, quaternary C); 145.3 (dt, JCFˆ245 Hz,
2JCFˆ11 Hz, CF); dF (376.5 MHz, d6-DMSO), 2139.3 (s);
m/z (FAB for salt AB2) 264 (3.7%, A±S(CH2)41), 361 (2.4,
AB1±S(CH2)41); (Found: C, 34.7; H, 4.3%. C16H22F4O8S4
requires: C, 35.2; H, 4.1%).
4.5.2. (2,3,5,6-Tetra¯uoro-1,4-phenylene) bis-(methyl-
ene) bis-(dimethyl sulfonium hydrogensulfate) (4b).
98% Sulfuric acid (10.0 g, 100 mmol) was added dropwise
to a mechanically stirred solution of 1,4-(2,3,5,6-tetra¯uoro)-
benzenedimethanol (5.26 g, 50 mmol) in dimethyl sul®de
(100 cm3) over ca. 15 min. After stirring for 4 h at ambient
temperature the lower dark brown aqueous layer was sepa-
rated and sonicated under ethyl acetate for 4 h. The resulting
mixture contained some solid and was left for three days to
crystallise. The solids were separated, triturated with hot
ethanol, then ®ltered, and the residual material was dried
under high vacuum to give the title compound 4b as a
colorless, crystalline solid (10.04 g, 41%); mp 200±2028C
(H2O, EtOH); nmax (KBr)/cm21, 3003, 2475, 1496, 1435,
1299, 1224, 1061, 1017, 875, 843; dH (d6-DMSO), 2.95
(s, 12H, CH3); 4.9 (s, 4H, CH2); dC (100.6 MHz
d6-DMSO), 24.0 (CH3); 33.5 (CH2); 109.9 (C±CH2);
4.5.5. 1,10[(2,3,5,6-Tetra¯uoro-1,4-phenylene) bis-(meth-
ylene)] bis-(tetrahydrothiophenium tetra¯uoroborate)
(4e)
and
1-[2,3,5,6-tetra¯uoro-4-hydroxymethyl)
benzyl]tetrahydrothiophenium tetra¯uoroborate (5). A
54% w/w solution of tetra¯uoroboric acid in diethyl ether
(2.76 cm3, 3.25 g, equivalent to 1.76 g of acid, 20 mmol)
was added to a stirred solution of 1,4-(2,3,5,6-tetra¯uoro)-
benzenedimethanol (2.10 g, 10 mmol) and tetrahydrothio-
phene (3.88 g, 44 mmol) in acetonitrile (20 cm3) at 08C.
The mixture was allowed to warm to 208C and stirred over-
night. The solvents were evaporated under reduced pressure
to give a viscous, yellow oil. Unreacted starting material
(1.5 g) was removed from this oil by repeated sonication
under diethyl ether (6£30 cm3, 1 h). Finally, sonication
under acetone (3£30 cm3) left a greyish powder which
was dried (0.1 Torr, 258C) to give 1,10-[(2,3,5,6-tetra-
¯uoro-1,4-phenylene) bis-(methylene)] bis-(tetrahydrothio-
phenium tetra¯uoroborate) (4e) as an off-white powder
(140 mg, 2.5%) mp 2508C (dec.); nmax (KBr)/cm21, 3424,
2952, 1497, 1305, 1032; dH (d6-DMSO), 2.1±2.5 (m, 8H,
CH2±CH2±S); 3.3±3.6 (m, 8H, CH2±CH2±S); 4.8 (s, 4H,
benzyl CH2); dC (100.6 MHz, d6-DMSO), {1H} 28.1 (CH2±
CH2±S); 32.6 (benzyl CH2); 44.3 (CH2±CH2±S); {19F}
111.0 (quaternary C); 145.3 (CF); dF (376.5 MHz, d6-
DMSO), 2148.80 (BF42); 2139.28 (s, CF); m/z(FAB for
salt AB2) 263 (100%, A±S(CH2)4±ZH1), 439 (86, AB1);
(Found: C, 36.2; H, 3.8%. C16H20B2F12S2 requires: C, 36.5;
H, 3.8%).
1
2
145.3 (dd, JCFˆ250 Hz; JCFˆ11 Hz); dF (C2D6SO),
2138.8 (s); m/z(FAB for salt AB2) 238 (33%, A±
S(CH3)21), 335 (72, AB±S(CH3)21), 397 (6.8, AB1 cluster);
(Found: C, 29.0; H, 3.6%. C12H18F4O8S4 requires: C, 29.15;
H, 3.7%).
4.5.3. 1,10-[1,4-Phenylene bis-(methylene)] bis-(tetra-
hydrothiophenium hydrogensulfate) (4c). 98% Sulfuric
acid (8.0 g, 80 mmol) was added dropwise to a mechani-
cally stirred solution of 1,4-benzenedimethanol (5.53 g,
40 mmol) in tetrahydrothiophene (80 cm3) over ca.
15 min. After stirring overnight at ambient temperature,
the (lower) dark red aqueous layer was separated and soni-
cated under ethyl acetate for 4 h. This mixture was left to
crystallise for two weeks. The resultant solid was slurried
with ethanol and ground in a mortar and pestle. This slurry
was ®ltered and the solid was recrystallized from a mixture
of water, ethanol and acetone and ®nally dried under high
vacuum to give the title compound (4c) as a colorless, crys-
talline solid (13.90 g, 85%); mp 183.5±1858C (H2O/EtOH/
acetone); nmax (KBr)/cm21, 3408, 3998, 2486, 1405, 1187,
1020, 882, 826, 700, 572; dH (d6-DMSO), 2.1±2.3 (m, 8H,
CH2±CH2±S); 3.35±3.5 (m, 8H, CH2±CH2±S); 4.6 (s, 4H,
benzyl CH2); 7.65 (s, 4H, Ar±H); dC (d6-DMSO), 28.2
(CH2±CH2±S); 42.8 (CH2±CH2±S); 44.3 (benzyl CH2);
131.45 (quaternary C); 131.45 (CH); m/z (FAB for salt
AB2) 191 (100%, A±S(CH2)41), 289 (11, AB±S(CH2)41),
377 (31, AB cluster); (Found: C, 40.6; H, 5.5%. C16H26O8S4
requires: C, 40.5; H, 5.5%).
4.6. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n)
The acetone extracts from above were evaporated under
reduced pressure to afford 1-[(2,3,5,6-tetra¯uoro-4-hydro-
xymethyl)benzyl] tetrahydrothiophenium tetra¯uoroborate
(5) as a brown oil (2.9 g, 79%); dH (d6-DMSO), 2.1±2.35
(m, 4H, CH2±CH2±S); 3.3±3.6 (m, 4H, CH2±CH2±S); 4.5
(broad s, 1H, OH); 4.55, 4.75 (s, 4H, 2£benzyl CH2); dC
(100.6 MHz, C2D6SO), {1H} 28.1 (CH2±CH2±S); 36.0
(benzyl CH2±S); 42.3 (CH2±CH2±S); 51.1 (CH2OH);
{19F} 108.7, 121.8 (2 quaternary C's); 144.6, 145.0 (CF);
dF (376.5 MHz, d6-DMSO), 2148.80 (s, BF42); 2146.04
(s); 2144.33 (q, Jˆ11 Hz); 2140.96 (q, Jˆ11 Hz);
2139.28 (s); m/z (FAB for salt AB) 117 (100%); 193
(6.7, A±S(CH2)41), 281 (26, A1), 649 (0.43, A2B1
cluster). This compound could not be obtained analytically
pure.
4.5.4.
1,10-[(2,3,5,6-Tetra¯uoro-1,4-phenylene) bis-
(methylene)] bis-(tetrahydrothiophenium hydrogensul-
fate) (4d). This was prepared as above for 4c from 98%
sulfuric acid (10.0 g, 100 mmol), 1,4-(2,3,5,6-tetra¯uoro)-
benzenedimethanol (5.26 g, 50 mmol) and tetrahydrothio-
phene (30 cm3). After work up, the resulting solid was
triturated with hot ethanol, ®ltered and the solid was dried
under high vacuum to give the title compound (4d) as an off-
white, crystalline solid (6.31 g, 23%); mp 184±184.58C;
nmax (KBr)/cm21, 3396, 2991, 2593, 1498, 1426, 1310,
4.6.1. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with d6-dimethyl sulfoxide. (9-
Anthrylmethyl)dimethylsulfonium hydrogensulfate (1n)
(70 mg, 0.2 mmol) was added to d6-DMSO (0.7 cm3) in an
NMR tube. The proton and carbon-13 spectra showed the

2880
J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
presence of 1n, 6a and dimethyl sul®de. dH (d6-DMSO), 2.0
[s, (CH3)2S]; 2.95 [s, (CH3)2S1]; 5.75 [s, CH2±O); 5.8 (s,
CH2±S1); 7.5±8.9 (two sets of overlapping aromatic
protons corresponding to the correct integral for the two
salts 1n and 6a). dC (d6-DMSO), 17.7 [(CH3)2S]; 24.8
[(CH3)2S1]; 39.9 (CH2±S1); 60.7 (CH2±O); 124.5, 124.8,
125.6, 126.0, 126.7,128.0, 128.5, 129.2, 129.9, 130.9
(10£CH, 5 for each of 1n and 6a); 119.9, 128.1, 131.3, (2
unresolved peaks), 131.4, 131.5 (6 quaternary C's, 3 for
each of 1n and 6a).
rated brine. The extract was dried (MgSO4), ®ltered and
evaporated under reduced pressure to give 9-anthraldehyde
as a crystalline, yellow solid (354 mg, 86%) mp 102±1038C
(THF/hexane) (lit. 32 103±1048C).
4.7. Reaction of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with nucleophiles in DMF: general
procedure
(9-Anthrylmethyl)dimethylsulfonium hydrogensulfate (1n)
(700 mg, 2 mmol) was added to DMF (20 cm3) and the
mixture was warmed until dissolution of the salt was
complete. The nucleophile (6 mmol, 3 mol equiv.) was
added and the mixture was placed in a sonic bath overnight
at 308C. The DMF was evaporated under reduced pressure
and the residue partitioned between water (100 cm3) and
dichloromethane (50 cm3). After ®ltration through celite,
the organic layer was separated, washed with 2 M aqueous
sodium hydroxide, then water and ®nally saturated brine
before being separated, dried (MgSO4) and ®ltered. The
solvents were evaporated under reduced pressure to give
the crude products, which were puri®ed as detailed below.
4.6.2. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with d7-N,N-dimethylformamide.
(9-Anthrylmethyl)dimethylsulfonium hydrogensulfate (1n)
(70 mg, 0.2 mmol) was added to d7-DMF (0.7 cm3) in an
NMR tube. The proton and carbon-13 spectra showed that
the presence of 1n, 6b and dimethyl sul®de. dH (400 MHz,
d7-DMF), 2.1 [s, (CH3)2S]; 3.25 [s, (CH3)2S1]; 5.95 (s, CH2±
O); 6.05 (s, CH2±S1); 7.5±8.9 (two sets of overlapping
aromatic H's corresponding to the correct integral for the
two salts 1n and 6b combined). dC (100.6 MHz, d7-DMF),
16.6 [(CH3)2S]; 24.0 [(CH3)2S1]; 39.3 (CH2±S1); 60.1
(CH2±O); 123.8, 124.3, 124.6, 125.2, 125.8,127.3, 127.7,
128.4, 129.1, 130.3 (10£CH, 5 for each of 1n and 6b);
119.1, 128.1, 130.6, (2 unresolved peaks), 131.0, 131.2 (6
quaternary C's, 3 for each of 1n and 6b).
4.7.1. Ethanol. The crude product was a yellow powder
which was recrystallized to give pure 9-ethoxymethyl
anthracene (6e) as a yellow, crystalline solid (330 mg,
1
4.6.3. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with water. (9-Anthrylmethyl)di-
methylsulfonium hydrogensulfate (1n) (35 mg, 0.1 mmol)
was warmed (,408C) with water (2 cm3) for 5 min. The
product was extracted with dichloromethane (2 cm3) and
the extract was evaporated under reduced pressure to give
9-anthracenemethanol (6c) as a yellow, crystalline solid
(20 mg, 96%) mp 160±1638C (lit. 29 162±1648C) which
was identical (ir, NMR) to an authentic sample.
70%); This compound was identical (mp, H NMR) to
that described above.
4.7.2. Potassium cyanide. The crude product was a yellow
powder which was recrystallized to give pure (9-anthryl)-
acetonitrile (6f) as a crystalline, yellow solid (330 mg, 76%)
mp 161.5±1638C (Et2O/hexane) (lit. 33 161±1638C); nmax
(KBr)/cm21, 3052, 2241, 1622, 1403, 1345, 1155, 900, 885,
789, 735; dH (200 MHz, CDCl3), 4.5 (s, 2H, CH2); 7.4±7.7
(m, 4H, Ar±H); 8.0 (d, Jˆ8 Hz, 2H, Ar±H); 8.1 (d, Jˆ8 Hz,
2H, Ar±H); 8.45 (s, 1H, Ar±H); dC (CDCl3), 16.1 (CH2);
122.8, 125.2, 127.2, 128.8, 129.4 (5£CH); 117.7, 120.6,
129.6, 131.3 (4 quaternary C's); m/z (FAB), 217 (100%,
M1) 191 (39, M12CN).
4.6.4. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with alcohols. (9-Anthrylmethyl)di-
methylsulfonium hydrogensulfate (1n) (350 mg, 1 mmol)
was added to the appropriate alcohol (25 cm3) and the
mixture was stirred at 508C until dissolution occurred. The
product was partitioned between chloroform (20 cm3) and
water (40 cm3), the organic layer was separated and the
aqueous layer extracted with chloroform (2£10 cm3). The
combined organic layer was washed with saturated brine,
dried (MgSO4) and then evaporated under reduced pressure
to give, separately: 9-methoxymethyl anthracene (6d)
(206 mg, 93%); mp 89±90.58C (lit. 30 90±918C); and 9-
ethoxymethyl anthracene (6e) (230 mg, 97%); mp 74±
75.58C (lit. 31 74±758C) as yellow crystalline solids.
4.7.3. Potassium thiocyanate. The crude product was a
yellow powder which was recrystallized to give pure
9-(thiocyanatomethyl)anthracene (6g) as a crystalline,
yellow solid (400 mg, 80%) mp 143.5±1448C (THF/
Et2O); nmax (KBr)/cm21, 3050, 2145, 1446, 1217, 896,
851, 794, 732; dH (CDCl3), 5.3 (s, 2H, CH2); 7.45±7.7
(m, 4H, Ar±H); 8.0 (d, Jˆ8.5 Hz, 2H, Ar±H); 8.2 (d,
Jˆ8.5 Hz, 2H, Ar±H); 8.5 (s, 1H, Ar±H); dC (CDCl3),
31.7 (CH2); 112.2 (SCN); 122.8, 125.4, 127.4, 129.5,
129.8 (5£CH); 123.3, 130.1, 131.2 (3 aromatic quaternary
C's); m/z (FAB), 249 (13%, M1) 191 (100, M12SCN),;
(Found: C, 76.9; H, 4.3; N, 5.45%. C16H11NS requires: C,
77.1; H, 4.45; N, 5.6%).
4.6.5. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with ethanol in DMSO. (9-Anthryl-
methyl)dimethylsulfonium hydrogensulfate (1n) (700 mg,
2 mmol) was added to DMSO (20 cm3) and the mixture
was warmed until dissolution of the salt was complete. Eth-
anol (460 mg, 10 mmol) was added and the mixture was
placed in a sonic bath overnight at 308C. The DMSO was
evaporated under reduced pressure and the residue was
partitioned between water (30 cm3) and dichloromethane
(30 cm3). The organic layer was separated, washed with
2 M aqueous sodium hydroxide then water and ®nally satu-
4.7.4. Sodium acetate. The crude product was a yellow
powder which was recrystallized to give pure (9-anthryl)-
methyl acetate (6h) as a crystalline, yellow solid (254 mg,
78%) mp 110±1118C (THF/hexane) (lit. 34 111±1128C); dH
(CDCl3), 2.1 (s, 3H, CH3); 6.15 (s, 2H, CH2); 7.5±7.65 (m,
4H, Ar±H); 8.0 (d, Jˆ8 Hz, 2H, Ar±H); 8.3 (d, Jˆ8 Hz, 2H,
Ar±H); 8.5 (s, 1H, Ar±H).

J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
2881
4.7.5. Potassium benzaldoximate (prepared as below).
4.8. Oligomerization in nitromethane
The crude product was a yellow oil which was puri®ed
by ¯ash column chromatography on silica gel, [petroleum
ether (bp 60±808C)/ethyl acetate, 10:1 eluant] to give a
yellow powder. This was recrystallized to give pure
benzaldehyde oxime O-(9-anthryl)methyl ether (6i) as a
crystalline, yellow solid (150 mg, 24%) mp 134±1358C
[petroleum ether (bp 60±808C)]; nmax (KBr)/cm21, 3060,
2942, 1444, 1329, 1206, 1162, 1053, 1015, 940, 883, 858,
756, 725; dH (CDCl3), 6.2 (s, 2H, CH2); 7.3±7.6 (m, 9H,
Ar±H); 8.0 (d, Jˆ8 Hz, 2H, Ar±H); 8.1 (s, 1H, CHvN);
8.45 (s, 1H, Ar±H); 8.48 (d, Jˆ8 Hz, 2H, Ar±H); dC
(CDCl3), 68.6 (CH2); 124.4, 125.0, 126.3, 127.0, 128.6,
128.8, 128.9, 129.8 (8£CH); 127.3, 131.2, 131.4, 132.1
(4 aromatic quaternary C's); 149.0 (CHvN); m/z (FAB),
311 (13%, M1); 191 (100, M12SCN), (Found: C, 84.8;
H, 5.4; N, 4.5%. C22H17NO requires: C, 84.9; H, 5.5; N,
4.5%).
(9-Anthrylmethyl)dimethylsulfonium hydrogensulfate (1n)
(3.50 g, 10 mmol) was suspended in dry nitromethane
(20 cm3). DMF (8 cm3, 10 mmol) was added and the
mixture was heated under re¯ux overnight. The solvents
were evaporated under reduced pressure and the residue
was partitioned between water (20 cm3) and chloroform
(20 cm3). The organic layer was separated and washed
consecutively with water, saturated sodium bicarbonate
solution, water, and ®nally saturated brine. The solution
was dried (MgSO4), ®ltered, and the solvents were evapo-
rated under reduced pressure. The residue was puri®ed by
¯ash column chromatography on silica gel [petroleum ether
(bp 60±808C)/ethyl acetate, 1:1 eluant] to give a dark red
powder believed to be poly-[9(10)-anthrylenemethylene]
(7) (1.50 g, 79%); nmax (KBr)/cm21,; dH (CDCl3), 4.0±4.6
(broad s, CH2); 6.3±8.7 (broad m, Ar±H); dC (CDCl3), 49
(broadened peak, CH2); 124±140 (many aromatic peaks);
m/z (FAB), 571 [4.3, (anthryl-CH2)31H1]; 381 [25,
(anthryl-CH2)21H1]; 191 [100, (anthryl-CH2)1H1],;
(Found: C, 91.6; H, 5.40%. (C15H10)n requires C, 94.7; H,
5.3%).
4.7.6. Potassium syn-benzaldoximate. Potassium hydroxide
(2.78 g, 49.5 mmol) was added in portions to a stirred solu-
tion of syn-benzaldoxime (6.05 g, 0.05 mol) in water
(25 cm3) and ethanol (25 cm3). After stirring overnight at
ambient temperature the solvents were removed by evapora-
tion under reduced pressure and the crude product was
partitioned between water (20 cm3) and diethyl ether
(10 cm3). The aqueous layer was separated and evaporated
to dryness under reduced pressure to give potassium syn-
benzaldoximate as an off-white powder (7.0 g, 90%) mp
245±2508C (dec.); dC (C2D6SO), 123.6, 124.5, 128.4
(3£CH); 139.7 (quaternary C); 142.3 (CHvN). m/z (FAB
4.9. Reactions of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with phenol in nitromethane
(9-Anthrylmethyl)dimethylsulfonium hydrogensulfate (1n)
(1.75 g, 5 mmol) and phenol (471 mg, 5 mmol) were heated
under re¯ux in nitromethane (20 cm3) for three days. The
solvents were evaporated under reduced pressure and the
residue was partitioned between water (20 cm3) and chloro-
form (20 cm3). The organic layer was separated and washed
consecutively with water, 6 M aqueous sodium hydroxide,
saturated aqueous ammonium chloride, water and saturated
brine. The solution was dried (MgSO4) and ®ltered, and
the solvent was evaporated under reduced pressure. The
residual yellow oil was puri®ed by ¯ash column chromato-
graphy on silica gel [petroleum ether (bp 60±808C)/ethyl
acetate, 5:1 eluant] to give 9-anthraldehyde as a crystalline,
1
for salt KB), 357 (0.57%, K3B2 cluster) 198(12, K2B1
cluster), 39 (100, K1).
4.7.7. Reaction of (9-anthrylmethyl)dimethylsulfonium
hydrogensulfate (1n) with acetonitrile. (9-Anthryl-
methyl)dimethylsulfonium hydrogensulfate (1n) (3.50 g,
10 mmol) was suspended in dry acetonitrile (20 cm3).
DMF (0.8 cm3, 10 mmol) was added and the mixture was
heated under re¯ux overnight. The solvents were evaporated
under reduced pressure and the residue was partitioned
between water (20 cm3) and chloroform (20 cm3). The
organic layer was separated and washed consecutively
with water, saturated sodium bicarbonate solution, water
and ®nally saturated brine. The solution was dried
(MgSO4), ®ltered, and the solvents were by evaporated
under reduced pressure. The residue was puri®ed by ¯ash
column chromatography on silica gel, [2% methanol in
dichloromethane, eluant] to give a brown powder. This
product was recrystallized to give [N-(9-anthrylmethyl)]-
acetamide (6j) as a crystalline, orange solid (370 mg,
1
yellow solid (470 mg, 46%); This was identical (mp, H
NMR) to the compound prepared previously (see aboveÐ
`reaction with EtOH in DMSO'). Further elution gave 9-(4-
hydroxybenzyl)anthracene (6k) as a crystalline, yellow
solid (280 mg, 20%); mp 185±1878C (toluene/hexane) (lit.
35 187±1888C); dH (CDCl3), 4.9 (s, 2H, CH2); 6.15 (s, 1H,
OH, lost on deuteration); 6.7 (d, Jˆ8.5 Hz, 2H, Ar±H); 7.0
(d, Jˆ8.5 Hz, 2H, Ar±H); 7.45 (m, 4H, Ar±H); 8.0±8.1 (m,
2H, Ar±H); 8.2±8.3 (m, 2H, Ar±H); 8.45 (s, 1H, Ar±H); dC
(CDCl3), 67.7 (CH2); 106.2, 115.4, 124.8, 124.9, 125.8,
126.4, 129.1 (7£CH); 130.4, 131.6, 132.4, 132.6, 154.1 (5
quaternary C's); m/z (FAB), 284 (3.2%, M1); 71 (100).
15%) mp 253±256.58C (THF/hexane); nmax (KBr)/cm21
,
3232, 3056, 1629, 1548, 1373, 1286, 886, 729; dH
(d6-DMSO), 1.8 (s, 3H, CH3); 5.25 (d, Jˆ5 Hz, 2H, CH2);
7.5±7.65 (m, 4H, Ar±H); 8.1 (d, Jˆ8.5 Hz, 2H, Ar±H);
8.35 (t, Jˆ5 Hz, 1H, NH); 8.4 (d, Jˆ8.5 Hz, 2H, Ar±H);
8.6 (s, 1H, Ar±H); dC (d6-DMSO), 22.8 (CH3); 35.3 (CH2);
125.0, 125.7, 126.7, 127.7, 129.3 (5£CH); 130.4, 130.5,
131.5 (3 aromatic quaternary C's); 169.3 (CvO); m/z
(FAB), 249 (70%, M1); 43 (100, CONH1), [Found (EI,
15 eV) 249.11489, C17H15NO requires: 249.11537];
(Found: C, 81.7; H, 5.9; N, 5.1%. C17H15NO requires: C,
81.9; H, 6.1; N, 5.6%).
4.10. General procedure for benzylation of phenol and
thiophenol with sulfonium salts
A mixture of the appropriate sulfonium salt (see Discussion)
(10.5 mmol), phenol or thiophenol (10 mmol) and sodium
carbonate (25 mmol) in water (25 cm3) and toluene (25 cm3)
was heated to 608C until all the phenol or thiophenol was
consumed (gc analysis). The toluene layer was separated
and the aqueous phase was extracted with toluene
(2£10 cm3). The combined toluene phase was dried

2882
J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
(MgSO4), ®ltered, and evaporated under reduced pressure to
afford the crude products, which were puri®ed as shown
below.
M12OC6H5), (Found: C, 78.5; H, 6.6%. C14H14O2 requires
C, 78.5; H, 6.6%); after further elution, 4-methoxybenzyl
alcohol was obtained as a colorless, crystalline solid (0.39 g,
28%) mp 22±258C (lit. 40 23±258C).
4.10.1. 2-Chlorobenzyl phenyl ether (8a). Puri®ed by
distillation to afford a colorless liquid (96%), bp 118±
1228C/0.1 Torr (lit. 36 140±1458C/2.5 Torr); nmax (KBr)/
cm21, 3063, 2921, 1598, 1495, 1445, 1380, 1304, 1241,
1172, 1036, 881, 752, 691; dH (CDCl3), 5.2 (s, 2H, CH2);
6.95±7.05 (m, 3H, Ar±H); 7.15±7.4 (m, 5H, Ar±H);
7.5±7.6 (m, 1H, Ar±H); dC (CDCl3), 67.0 (CH2);
114.8, 121.1, 126.9, 128.7, 128.9, 129.3, 129.5, (7£CH);
132.5, 134.7, 158.4 (3 quaternary C's); m/z (FAB), 218,
220 (21%, 8.2% M1); 125, 127 (100, 49, M1 2 OC6H5)
(Found (EI), 218.04705, C13H1135ClO requires:
218.04984).
4.10.6. 1,4-Bis(phenoxymethyl)benzene (8f). Puri®ed by
recrystallization to give a colorless, crystalline solid
(1.19 g, 82%), mp 141±1428C (THF/hexane), (lit. 41
140±141.58C); nmax (KBr)/cm21, 2912, 1599, 1496, 1247,
1171, 1010, 873, 803, 747, 689; dH (CDCl3), 5.05 (s, 4H,
CH2); 6.9±7.0 (m, 6H, Ar±H); 7.25±7.35 (m, 4H, Ar±H);
7.45 (s, 4H, Ar±H, central ring); dC (CDCl3), 69.5 (CH2);
114.8, 120.9, 127.6, 129.4, (4£CH); 136.8 (C±CH2); 158.7
(C±O); m/z (FAB), 290 (9.9%, M1), 197 (100, M1
2
OC6H5).
4.10.7. 2,6-Dichlorobenzyl phenyl sul®de (8g). Colorless,
crystalline solid (99%), mp 39±408C (lit. 42 39±408C); dH
(CDCl3), 4.4 (s, 2H, CH2); 7.05±7.3 (m, 6H, Ar±H); 7.35±
7.45 (m, 2H, Ar±H); dC (CDCl3), 30.9 (CH2); 122.6, 123.6,
124.0, 124.1, 127.4, (5£CH); 129.2, 130.6, 131.1 (3
quaternary C's); m/z (FAB), 268, 270, 272 (47, 36, 7.7%,
M1), 159, 161, 163 (100, 61, 12, M2OC6H5).
This compound (8a) was also formed (97%) from phenol
and 2-chlorobenzyldimethylsulfonium tetra¯uoroborate (1t)
using the method described above.
4.10.2. 2,6-Dichlorobenzyl phenyl ether (8b). Puri®ed by
recrystallization to afford a colorless crystalline solid (95%),
mp 49±508C (hexane); nmax (KBr)/cm21, 3073, 2955, 1583,
1493, 1437, 1381, 1291, 1233, 1086, 1011, 866, 756, 690;
dH (CDCl3), 5.25 (s, 2H, CH2); 6.95±7.05 (m, 3H, Ar±H);
7.15±7.4 (m, 5H, Ar±H); dC (CDCl3), 65.1 (CH2); 114.9,
121.3, 128.4, 129.5, 130.4, (5£CH); 132.1, 137.0, 158.8 (3
quaternary C's); m/z (FAB), 252, 254, 256 (27%, 20%,
3.6%, M1); 159, 161, 163 (100, 61, 11, M1 2 OC6H5),
(Found: C, 61.7; H, 3.9%. C13H10Cl2O requires: C, 61.7;
H, 4.0%).
4.11. Reaction of syn-benzaldoxime with 2-chlorobenzyl-
sulfonium hydrogen sulfate (1b)
2-Chlorobenzyldimethylsulfonium hydrogensulfate (1b)
(2.99 g, 10.5 mmol) was added to a solution of syn-benzal-
doxime (1.21 g, 10 mmol) in a mixture of toluene (20 cm3)
and water (20 cm3). After the solution was heated to 808C, a
solution of potassium hydroxide (1.18 g, 21 mmol) in water
(5 cm3) was added dropwise. The mixture was stirred at
808C for 3 days. The toluene layer was separated, and the
aqueous layer extracted with toluene (2£20 cm3). The
organic layers were combined and evaporated under
reduced pressure. The crude product was dissolved in
chloroform (20 cm3) and this solution was washed with
water (10 cm3), then saturated brine (10 cm3) and then
dried (MgSO4). The mixture was ®ltered and the solvent
evaporated under reduced pressure to leave an oil that was
puri®ed chromatographically (silica gel, [petroleum ether
(bp 60±808C)/ethyl acetate, 10:1 eluant]) to give syn-
benzaldoxime O-2-chlorobenzyl ether (9) as a colorless oil
(after distillation), (1.40 g, 57%), bp 2188C/40 Torr; nmax
(KBr)/cm21, 3062, 2953, 1574, 1473, 1446, 1361, 1121,
1071, 1036, 1017, 947, 906, 754; dH (d6-DMSO), 5.2 (s,
2H, CH2); 7.3±7.7 (m, 9H, Ar±H); 8.4 (s, 1H, CH); dC
(d6-DMSO), 73.1 (CH2); 127.4, 127.7, 129.2, 129.7,
130.1, 130.5, 131.0, (7£CH); 132.1, 133.1, 135.5 (3
quaternary C's); 150.1 (CH); m/z (EI), 245, 247 (11%,
3.7%, M1); 125, 127 (100, 31, M1 2 C7H6NO). (Found:
245.06111. C14H1235ClNO requires: 245.06074). After
further elution, N-benzylidene-(2-chlorobenzyl)amine
N-oxide (10) was obtained as a white powder (130 mg,
5%), mp 76±778C (lit. 43 75±778C); dH (CDCl3), 5.2
(s, 2H, CH2); 7.2±7.6 (m, 8H, Ar±H); 8.2 (m, 2H,
CHvN1Ar±H); dC (CDCl3), 68.0 (CH2), 127.3,
128.4, 128.7, 129.7, 130.3, 130.5, 131.8 (7£CH), 130.25,
130.9, 134.3 (3 quaternary Cs), 135.1 (CHvN). m/z (FAB),
246, 248 (83%, 25%, M1H1) 125, 127 (100, 32,
M12C7H6NO).
4.10.3. 1-Naphthylmethyl phenyl ether (8c). Puri®ed by
recrystallization to give an off-white, crystalline solid
(93%), mp 73±758C (hexane) (lit. 37 76±778C); nmax
(KBr)/cm21, 3046, 2919, 1596, 1486, 1468, 1387, 1293,
1229, 1173, 1005, 887, 792, 757, 696; dH (CDCl3), 5.55
(s, 2H, CH2); 7.1±7.7 (m, 9H, Ar±H); 7.9±8.0 (m, 2H,
Ar±H); 8.1±8.2 (m, 1H, Ar±H); dC (CDCl3), 68.6 (CH2);
114.9, 121.1, 123.7, 125.4, 125.9, 126.5, 126.6, 128.7,
129.0, 129.5, (10£CH); 131.6, 132.4, 133.8, 158.9 (4
quaternary C's); m/z (FAB), 234, (4.8%, M1); 141 (100,
M1 2 OC6H5), (Found: C, 87.1; H, 6.0%. C17H14O requires:
C, 87.15; H, 6.4%).
4.10.4. Benzyl phenyl ether (8d). Colorless crystalline
solid [(3.61 g, 98% from 1s; 96% from 1r), mp 39±408C
(lit. 38 39±39.58C); dH (CDCl3), 5.2 (s, 2H, CH2); 7.05±
7.15 (m, 3H, Ar±H); 7.4±7.6 (m, 7H, Ar±H); dC (CDCl3),
69.9 (CH2); 114.9, 121.0, 127.6, 128.0, 128.7, 129.6,
(6£CH); 137.2 (C-CH2), 158.9 (C±O).
4.10.5. 4-Methoxybenzyl phenyl ether (8e). Puri®ed chro-
matographically [silica gel, petroleum ether (bp 60±808C),
ethyl acetate (15:1) eluant] to afford a colorless, crystalline
solid (70%), mp 93±93.58C (lit. 39 92±92.58C); nmax (KBr)/
cm21, 2933, 1585, 1513, 1385, 1234, 1170, 1031, 869, 808,
752, 692; dH (CDCl3), 3.8 (s, 3H, OMe); 4.95 (s, 2H, CH2);
6.85±7.0 (m, 5H, Ar±H); 7.2±7.4 (m, 4H, Ar±H); dC
(CDCl3), 55.2 (CH3); 69.6 (CH2); 113.9, 114.8, 120.8,
129.2, 129.4, (5£CH); 129.0, 158.8, 159.4 (3 quaternary
C's); m/z (FAB), 214 (2.1%, M1); 121 (100,

J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
2883
4.12. Preparation and benzylation of anti-benzaldoxime
4.13.3. Procedure for the reaction of benzimidazole with
sulfonium salts (1a, b). A solution of potassium hydroxide
(1.18 g, 21 mmol) in water (10 ml) was added to a solution
of benzimidazole (1.18 g, 10 mmol) and either 1a or 1b
(10.5 mmol) in water (20 cm3), ethanol (5 cm3) and toluene
(30 cm3). The mixture was stirred at 708C overnight and the
solvents were then evaporated under reduced pressure and
the residue partitioned between dichloromethane (30 cm3).
and distilled water (30 cm3). The aqueous layer was
extracted with dichloromethane (2£20 cm3) and the
combined organic layer was washed with saturated brine,
dried over (MgSO4), ®ltered, and the solvent evaporated
under reduced pressure to give the crude products as
brown oils. The mixtures were puri®ed chromatographically
(silica gel [2% methanol in DCM, eluant]), to give the
following.
Dry hydrogen chloride gas was bubbled through a solution
of syn-benzaldoxime (5.0 g, 43 mmol) in anhydrous diethyl
ether (150 cm3) via a wide delivery tube. The colorless
crystals of anti-benzaldoxime hydrochloride which pre-
cipitated from the solution were ®ltered and washed with
anhydrous diethyl ether (2£50 cm3). This solid was added,
in portions, to a vigorously stirred, large excess of a
mixture of saturated aqueous sodium bicarbonate solution
and dichloromethane stirring rapidly together in a beaker.
When effervescence had ceased, the dichloromethane layer
was separated and the aqueous layer was extracted with
dichloromethane (2£50 cm3). The combined organic layer
was washed with saturated brine and then dried (MgSO4).
The mixture was ®ltered and the solvents were evaporated
under reduced pressure to give the crude product which
was recrystallized twice to give anti-benzaldoxime
(3.55 g, 71%); mp 131±131.58C (H2O/EtOH) (lit. 44
1328C); dH (C2D6SO), 7.4 (m, 4H, Ar±H); 7.9±8.0 (m,
2H, Ar±H); 11.6 (s, 1H, OH). This compound was allowed
to react with the sulfonium salt (1b) in the manner
described above to afford a mixture of 9 (50%) and 10
(7%).
4.13.4. 1-benzylbenzimidazole (12a). As a colorless crys-
talline solid (8.66 g, 59%) mp 113±1158C [THF/petroleum
ether (60/80)] (lit. 45 115±115.58C).
4.13.5. 1-(2-chlorobenzyl)benzimidazole (12b). As a
colorless crystalline solid (1.20 g, 50%) mp 93±93.58C
[THF/petroleum ether (60/80)]; nmax (KBr)/cm21, 3082,
1614, 1493, 1427, 1351, 1264, 1204, 1179, 1038, 967,
885, 750; dH (CDCl3), 5.4 (s, 2H, CH2); 6.8 (d, Jˆ7.5 Hz,
1H, Ar±H); 7.0±7.4 (m, 6H, Ar±H); 7.8 (m, 1H, Ar±H); 7.9
(s, 1H, CHvN); dC (CDCl3), 46.2 (CH2); 109.9, 120.4,
122.3, 123.1, 127.3, 128.5, 129.5, 129.8 (8£CH); 132.9,
133.0, 133.7, 143.7 (4 quaternary C's); 143.4 (CHvN);
m/z (FAB), 243, 245 (84%, 28%, M1H1); 125, 127 (100,
29, M12benzimidazolyl); (Found: C, 69.2; H, 4.5%.
C14H11N2Cl requires: C, 69.3; H, 4.6%).
4.13. Procedure for the reaction of cyclohexanone oxime
with sulfonium salts (1b, 1d)
A solution of potassium hydroxide (1.18 g, 21 mmol) in
water (10 cm23) was added to a solution of cyclohexanone
oxime (1.13 g, 10 mmol) and either 1b or 1d (10.5 mmol) in
water (20 cm3) over ca. 15 min. The mixture was stirred at
708C for two days. Dichloromethane (30 cm3) was added,
the layers separated, and the aqueous layer was extracted
with dichloromethane (2£20 cm3). The combined organic
layer was washed with saturated brine, then dried
(MgSO4), and ®ltered. The solvent was evaporated under
reduced pressure to give the crude products as yellow oils
that were puri®ed chromatographically (silica gel [petro-
leum ether (bp 60±808C)/ethyl acetate 10:1 eluant]). The
following were isolated.
4.14. Reaction of benzimidazole with 1-methyltetra-
hydrothiophenium hydrogen sulfate (2c)
A
stirred mixture of potassium hydroxide (1.18 g,
21 mmol), benzimidazole (2.03 g, 17.1 mmol), 1-methyl-
tetrahydrothiophenium hydrogensulfate (2c) [3.43 g,
17.1 mmol)], water (25 cm3), ethanol (5 cm3) and toluene
(25 cm3) was heated under re¯ux overnight. The solvents
were evaporated under reduced pressure and the residue was
partitioned between dichloromethane (30 cm3) and distilled
water (30 cm3). The aqueous layer was separated and
extracted with dichloromethane (2£20 cm3). The combined
organic layer was washed with saturated brine, dried
(MgSO4) and ®ltered. The solvents were evaporated under
reduced pressure to give a yellow oil which was puri®ed by
¯ash column chromatography on silica gel [petroleum ether
(bp 60±808C)/ethyl acetate 10:1, eluant], to give 1-[(4-
methylthio)butyl]benzimidazole (12c) as a yellow oil
(1.92 g, 51%) which charred upon attempted distillation;
nmax (KBr)/cm21, 3393, 3086, 2916, 1614, 1495, 1459,
1366, 1286, 1201, 1155, 1007, 893, 746; dH (CDCl3), 1.6
(m, 2H, CH2); 1.95 (m, 2H, CH2); 2.0, (s, 3H, CH3); 2.45 (t,
Jˆ7 Hz, 2H, CH2S); 4.2 (t, Jˆ7 Hz, 2H, CH2N); 7.2±7.4
(m, 3H, Ar±H); 7.8 (m, 1H, Ar±H); 7.85 (s, 1H, CHvN);
dC (CDCl3), 15.3 (CH3); 25.9, 28.6, 33.4, 44.5 (4£CH2);
109.6, 120.2, 121.9, 122.7 (4£CH); 133.6, 143.7 (2 quatern-
ary C's); 142.8 (CHˆN); m/z (FAB), 221 (96%, M1H1);
103 (100, M12benzimidazolyl); 221 (96%, M1H1);
[Found (EI): 220.10250, C12H16N2S requires: 220.10342];
4.13.1. Cyclohexanone oxime O-2-chlorobenzyl ether
(11a). As a pale yellow oil (0.90 g, 38%); dH (CDCl3), 1.5
(m, 6H, CH2); 2.2 (t, 2H, Jˆ6 Hz, CH2); 2.55 (t, 2H,
Jˆ6 Hz, CH2); 5.15 (s, 2H, CH2O); 7.1±7.4 (m, 4H, Ar±
H); dC (CDCl3), 25.4, 25.8, 25.8, 27.0, 32.1 (ring CH2); 72.1
(CH2); 126.5, 128.4, 128.9, 129.1 (4£CH); 132.8,136.1 (2
quaternary C's); 161.2 (CvN); m/z (FAB), 238, 240 (100%,
28%, M1H1);202 (19, M12Cl). (Found (EI): 237.0916,
C13H1635ClNO requires: 237.0920).
4.13.2. Cyclohexanone oxime O-2,6-dichlorobenzyl ether
(11b). As a colorless, crystalline solid (2.04 g, 75%); nmax
(KBr)/cm21, 3254, 2932, 1564, 1436, 1195, 1092, 1037,
992, 933, 890, 780; d1H (CDCl3), 1.5±1.6 (m, 6H, CH2);
2.2 (t, Jˆ6 Hz, 2H, CH2); 2.4 (t, Jˆ6.5 Hz, 2H, CH2); 5.3 (s,
2H, CH2O); 7.2 (m, 3H, Ar±H); d13C (CDCl3), 25.1, 25.7,
25.7, 26.9, 32.1 (ring CH2); 69.4 (CH2); 128.1, 129.7
(2£CH); 132.9, 137.0 (2 quaternary C's); 161.2 (CvN);
m/z (FAB), 272, 274, 276 (100, 66 11%, M1H1 236, 238
(25, 9.9, M12Cl); (Found (EI): 271.0547, C13H1535Cl2NO
requires: 271.0531).

2884
J. Forrester et al. / Tetrahedron 57 (2001) 2871±2884
18. Omura, K.; Swern, D. Tetrahedron 1978, 34, 1651.
19. Banks, R. E.; Francois, P.-Y.; Preston, P. N. Polymer 1992, 33,
3974.
after further elution, 1-methylbenzimidazole (12d) was
obtained as a white powder (700 mg, 31%), mp 60±
62.58C (lit. 46 59±628C).
20. Jaeger, C. W.; Kornblum, N. J. Am. Chem. Soc. 1972, 94,
2545.
Acknowledgements
21. Kondo, S.; Takeda, Y.; Tsuda, K. Synthesis 1988, 403.
22. Kondo, S.; Murayama, T.; Tsuda, K. Makromol. Chem. Rapid
Commun. 1988, 9, 625.
We thank Dr M. F. C. Standen for helpful discussions and
Dr D. C. Apperley for provision of the CP MAS NMR
spectrum acquired through the EPSRC solid state NMR
service at the University of Durham, UK.
23. Buehler, E. J. Org. Chem. 1967, 32, 261.
24. Eliel, E. L.; Hutchins, R. O.; Mebane, R.; Willer, R. L. J. Org.
Chem. 1976, 41, 1052.
25. Bory, S.; Fetizon, M.; Laszlo, P.; Williams, D. H. Bull. Soc.
Chim. Fr. 1965, 254.
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