Preparation of 4-substitute benzyl sulfoxylates and related chemistry

Article abstract of DOI:10.1021/jo991360b

Preparation of dibenzyl sulfoxylate 7a and 4-substituted benzyl sulfoxylates (7b, 4-NO₂; 7c, 4-Cl; 7d, 4-CH₃O, 7e: 4-CH₃) are reported. The unexpected stability of 7b has permitted the first X-ray determination at room tem

Full text of DOI:10.1021/jo991360b

J . Org. Chem. 2000, 65, 4791-4795
4791
P r ep a r a tion of 4-Su bstitu ted Ben zyl Su lfoxyla tes a n d Rela ted
Ch em istr y
Sylvie L. Tardif and David N. Harpp*
Department of Chemistry, McGill University, Montre´al, Que´bec, Canada H3A 2K6
harpp@chemistry.mcgill.ca
Received August 25, 1999 (Revised Manuscript Received May 26, 2000)
Preparation of dibenzyl sulfoxylate 7a and 4-substituted benzyl sulfoxylates (7b, 4-NO2; 7c, 4-Cl;
7d , 4-CH3O, 7e: 4-CH3) are reported. The unexpected stability of 7b has permitted the first X-ray
determination at room temperature of a sulfoxylate. The thermal isomerization of sulfoxylates 7b-c
to sulfinates 8b-c was studied in different solvents (toluene-d8, CDCl3, and CD3CN) and interpreted
as a concerted unimolecular process following first-order kinetics.
In tr od u ction
The chemistry related to the rearrangement of alkyl,
aryl, and allyl sulfenates 1 to their corresponding sul-
foxides 2 has been reviewed by Braverman (eq 1).1a The
thermal sulfenate-sulfoxide interconversion for benzyl
arylsulfenates, Ar-CH2-O-S-Ar, to their sulfoxides,
Ar-CH2-S(dO)Ar, is believed to occur via a concerted
intramolecular mechanism (Scheme 1).1b
Analogously, Thompson noted that dibenzyl sulfoxyl-
ate, (PhCH2O)2S, rearranges to the benzyl R-toluene-
sulfinate, PhCH2S(dO)OCH2Ph, during preparation.2
Several linear sulfoxylates were prepared by Thompson
in good yield (R ) R′ ) n-Pr, 62%; i-Pr, 67%; n-Bu, 70%;
n-C5H11, 56%; cholesteryl, 16%).2 In that same paper,
some cyclic sulfoxylates were also reported with their
yields (3a , 20%; 3b, 8%; 4, 58%). Sulfoxylates 53a and 63b,c
F igu r e 1. ORTEP drawing of bis(4-nitrobenzyl) sulfoxylate
7b.
were claimed but no yields were reported.
Sch em e 1
the nature of the para substituent on the benzene ring
is important in relation of the stability of sulfoxylates
7a -e. The above proposal was verified by the obtention
of suitable crystals for the X-ray determination of 7b.
Contrary to Thompson’s preliminary work on sulfox-
ylates, we have found that 4-substituted benzyl sulfox-
ylates 7a -e could be isolated and were not that prone
to readily rearrange to their corresponding sulfinates
8a -e. Thermal isomerization studies have shown that
Resu lts a n d Discu ssion
Sulfoxylates 7a -e were prepared by adding a solution
of sulfur dichloride, SCl2 (1 equiv), to a solution of the
corresponding benzyl alcohol (2 equiv) in the presence of
triethylamine, Et3N (2 equiv), at -78 °C. However, SCl2
is prone to decomposition and gives sulfur monochloride,
S2Cl2, even at low temperature (eq 2). In the present
(1) (a) Braverman S. The Chemistry of Sulfones and Sulfoxides;
Patai, S., Rappoport, Z., Sterling, C. J . M., Eds.; Wiley: Chichester,
1988; Chapter 14. (b) Kice J . L. Adv. Phys. Org. Chem. 1980, 100.
(2) Thompson Q. E. J . Org. Chem. 1965, 30, 2703.
(3) (a) Kogami H.; Motoki S. J . Org. Chem. 1978, 43, 1262. (b)
Chapman J . S.; Cooper J . W.; Roberts B. P. J . Chem. Soc., Chem.
Commun. 1976, 835. (c) Birkofer L.; Niedrig H. Chem. Ber. 1966, 99,
2070.
10.1021/jo991360b CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/20/2000

4792 J . Org. Chem., Vol. 65, No. 16, 2000
Tardif and Harpp
Ta ble 1. P r od u ct Distr ibu tion a for th e P r ep a r a tion of
Sch em e 2
4-Su bstitu ted Ben zyl Su lfoxyla tes 7a -e
exptl
ROHb RO(SdO)R (RO)2SdO ROSSOR ROSOR conditionsd
11
8
10
9
7
(°C)
0-5
-10
-40
-78
-40
-40
-78
-40
-78
-40
bf
b
b
10
27
50
58
21
e
27
24
46
38
9
15
16
11
23
34
16
25
17
24
26
15
10
18
24
22
26
17
19
b
e
7
4
d c
a
a
c
c
3
a
b
% yield. R ) 4-X-C6H4CH2: 11a , X ) H; b, X ) NO2; c,
X ) Cl; d , X ) OMe; e, X ) Me. c NMR yields otherwise isolated
d
yields using column chromatography.
2 h, solvent CH2Cl2.
e Compound was formed (NMR) but does not withstand column
chromatography on silica gel. f Product precipitated from the
mixture in the fridge.
preparation, the decomposition to S2Cl2 was minimized
due to the low temperature used for the reaction.
However, the product distribution reported in Table 1
shows formation of the corresponding dialkoxy disulfides
9a -e,4 sulfites 10a -e,4 sulfinates 8a -e, and unreacted
alcohols 11a -e.
The formation of 7b was enhanced at the expense of
the formation 9b as the reaction temperature was
lowered. This is attributed to the slowing of the rate of
disproportionation of SCl2 to S2Cl2. The formation of
sulfite 10b can be rationalized considering the “oxy-
chloro-sulfide and disulfide” types of intermediates 12
and 13; they are known to decompose to the sulfite at
-78 °C (eqs 3-5).5 Intermediate 12 may also be gener-
(1 equiv) under the same experimental conditions (-78
°C followed by workup at 0 °C). A potential rationale for
their formation could follow Scheme 2, since 9b and 10b
were formed and detected during the course of the
reaction prior to the workup. Although 4-nitrobenzyl
chloride was not detected, it is of interest that the
formation of the sulfite in this reaction has, to our
knowledge, not been previously rationalized.
Sulfoxylates 7 could be isolated and were stable to
rearrangement to the corresponding sulfinates 8 when
purified. It seems that the presence of HCl and interme-
diates 12 and 13 generated in the reaction mixture are
responsible for the wide product distribution observed.
Nevertheless, the low temperature is a key factor for the
preparation of the 4-substituted benzyl sulfoxylates. Once
purified, 7b and 7c could be recrystallized. In the case
of 7b, the crystals were suitable for X-ray analysis at
room temperature and a full determination was obtained
(see Experimental Section). Sulfoxylates 7a and 7e were
able to withstand column chromatography conditions,
and samples were isolated and found to isomerize in an
hour once purified at ambient temperature. Where 7d
was only detected by NMR in the reaction mixture, 7b
and 7c were stable enough, once purified, to be kept at
-30 °C under N2 in the freezer over a period of 2 months.
Sulfoxylate 7b and 7c were found to rearrange slowly
in CDCl3 over a period of time not exceeding 24 and 35
h, respectively (for 7b: Figure 2). The isomerization
process for 7b and 7c was studied in solution (0.13-0.14
M) at temperatures close to room temperature. The
kinetic runs, in deuterated solvent, were found to obey
first-order kinetics. The process was monitored in three
different solvents at different temperatures (7c in toluene-
d8 at 19.9, 25.0, and 27.3 °C; 7b in toluene-d8 at 19.9,
25.0, 27.3, and 35.3 °C; 7b in CDCl3 at 19.9, 20.3, 25.0,
27.2, and 35.3 °C; 7b in CD3CN at 19.9, 25.0, 27.3, and
35.2 °C) and each run was duplicated; in certain cases,
3-4 repetitions were carried out. The kinetics of the
ated at very low temperature (eq 6) and leads to the
formation of sulfite 10 following Scheme 2. The formation
of dialkoxy disulfide 9b seems to be unavoidable consid-
ering the multiple sources of S2Cl2 (eqs 4 and 5 and
Scheme 2) even at low temperature.
Interestingly, 9b and 10b were detected in a separate
experiment where sulfoxylate 7b was treated with SCl2
(4) (a) Tardif S. L.; Rys A.; Abrams C. B.; Abu-Yousef, I. A.; Leste´-
Lasserre, P. B. F.; Schultz, E. K. V.; Harpp, D. N. Tetrahedron 1997,
53, 12225. (b) Tardif, S. L.; Williams, C. R.; Harpp, D. N. J . Am. Chem.
Soc. 1995, 117, 9067. (c) Thompson, Q. E.; Crutchfield, M. M.; Dietrich,
M. M.; Pierron, E. J . Org. Chem. 1965, 30, 2692.
(5) Schmidt H.; Steudel R. Z. Naturforsch. 1990, 45B, 557: R ) i-Pr;
ROSSOR reacts with SCl2 at -78 °C to give intermediates 12 and 13
that decompose to give the sulfite (eq 3). While the intermediate 12
decomposes rapidly at -78 °C, the intermediate 13 was detected and
analysed at -20 °C.

Preparation of 4-Substituted Benzyl Sulfoxylates
J . Org. Chem., Vol. 65, No. 16, 2000 4793
Ta ble 3. Rela tive Ra tes a n d Activa tion P a r a m eter sa ,b for
Isom er iza tion 7b,c to 8b,c
k × 10-6 a
∆Sq
(eu)
7
solvent
(s-1
)
krel
Ea
ln A ∆Gq
b
toluene-d8
CDCl3
CD3CN
toluene-d8
CDCl3
43.0
57.8
52.9
14.5
24.4
19.1
1.0 21.1 ( 0.3 26.1 23.4 -10.1 ( 0.9
1.3 19.9 ( 0.2 24.4 23.0 -12.6 ( 0.8
1.2 25.1 ( 0.5 33.2 22.8
5.7 ( 0.9
6.8 ( 1.1
c
1.0 26.2 ( 0.7 33.9 23.6
1.7
1.3
CD3CN
a
At 19.9 °C; Ea and ∆Gq are expressed in kcal mol-1, and error
b
limits represent the standard deviation. Temperature depen-
dence of k for 7b was not studied in CDCl3 and CD3CN.
rangement. The entropy factor, at least for 7b in toluene-
d8 and in CDCl3, is interpreted in terms of restricted
internal rotation to achieve the activated complex in the
transition state. The activation parameters can be quali-
tatively interpreted. The activation energy of 7b was
increased in CD3CN from the less polar solvents CDCl3
and toluene-d8, likely due to an increase of solute-solvent
interaction and the polar interaction between the nitro
group of 7b and the cyano group of acetonitrile.6 The
entropy of activation for these reactions is generally
consistent with transition states for unimolecular process.
That there appears to be a more ordered transition state
required (more negative ∆Sq) for the less polar solvents
is reasonable. The values of krel indicate that the change
of solvent polarity has a very small effect on the rate of
the reaction and that the charge distribution in the
activated complex of 7b is very similar to 7b itself
(isopolar activated complex).7
Although the concerted mechanism of isomerization is
reasonable, an intimate or tight ion-pair, as well as
radical-pair, cannot be completely ruled out in the
transition state. The stability and reactivity observed
among the sulfoxylates 7a -e can be qualitatively ex-
plained in terms of valence bond structures leading to a
tight ion-pair in the transition state (Scheme 4). Sulfox-
ylates 7b,c are more stable in comparison to 7a ,d -e
presumably because 7b,c have an electronegative group
in the para position causing the ring to be electron
deficient and to the extreme formation of a tight ion-pair
containing the cation R′OS+(dO) (Scheme 4, path a). The
isomerization of 7 via the concerted process or the tight
ion-pair where the sulfur from the O-S-O functionality
acts as a donor would be predicted to be slowed when
the electron withdrawing groups are attached at the para
position. This also rationalizes why 7a ,d -e were found
to isomerize at room temperature in a matter of an hour
and less. In 7d , the resonance electron-donating effect
outweighs the possible inductive electron-withdrawal
effect of the moderate electronegative oxygen atom of the
methoxy group leading to the possible formation of a tight
ion-pair containing the more favorable anion R′OS-(dO)
that undergoes rapid recombination (Scheme 4, path b).
The contribution of the more stable anion R′OS-(dO)
over the cation R′OS+(dO) might favor a dissociative
mechanism for 7a ,d ,e. Similar mechanistic consider-
ations were reported to be substrate-dependent. The
thermal sulfenate-sulfoxide rearrangement of allyl and
F igu r e 2. Isomerization of 7b to 8b in CDCl3 at 20.3 °C; from
bottom to top 1.9, 5.6, 9.3, 13.0, 16.8, and 22.4 h, respectively.
Ta ble 2. 13C NMR Ch em ica l Sh iftsa for 7b,c a n d 8b,c
δ
CR (CH2)d
δ
CR′ (CH2)d
solventb,c
µ (D)
ꢀ
δC (CH2)
7b
7c
8b
8c
toluene-d8
0.36
2.38
chloroform-d
1.01
4.81
80.37
80.33
81.61
81.07
67.81
63.31
68.47
63.58
81.06
81.88
68.90
63.26
69.71
63.55
acetonitrile-d3
3.92
69.62
63.49
69.93
63.40
35.94
a
b
In ppm at 19.6-20.3 °C. Dipole moment µ (Debye) and
dielectric constant ꢀ at 25 °C. c Reference 6. CR and CR′ are on
the left and right hand side of O(SdO) functionality, respectively.
d
Sch em e 3
intensity change of the 13C NMR signal of the benzylic
methylene carbon were followed. The average correlation
coefficient for all the rate constant plots is 0.994. 13C
chemical shifts for the sulfoxylates 7b,c and sulfinates
8b,c in these different solvents are reported in Table 2.
The isomerization process is unimolecular; the central
sulfur atom acts as an electron donor, interacting with
the adjacent benzylic carbon as this atom is loosening
its CH2-O interaction to the profit of the forming sulfonyl
group (SdO) (Scheme 3). This concerted three-membered
ring transition state is in reasonable agreement with both
kinetic and thermodynamic parameters correlated in
Table 3: the positive activation enthalpies and the
negative entropies (except for 7b in CD3CN, vide infra)
are comparable to other pericyclic concerted processes7c
such as the Diels-Alder reactions and the Cope rear-
(7) (a) Pacey, P. D. J . Chem. Educ. 1981, 58, 612. (b) Moore, J . W.;
Pearson, R. G. Kinetics and Mechanism, 3rd ed.; Wiley: New York,
1981. (c) Snyder, J . P.; Harpp, D. N. J . Am. Chem. Soc. 1976, 98, 7821.
(d) Benson, S. W. Thermochemical Kinetics; Wiley: New York, 1968.
(e) Breslow, R. Organic Reaction Mechanism An Introduction; W. A.
Benjamin Inc.: New York, 1965.
(6) Reichardt C. Solvents and Solvent Effects in Organic Chemistry,
2nd revised Ed.; VCH: Weinheim, 1990.

4794 J . Org. Chem., Vol. 65, No. 16, 2000
Tardif and Harpp
Exp er im en ta l Section
Sch em e 4
1H NMR and 13C NMR spectra were recorded at 200 and
300 MHz in the deuterated solvents indicated. Low-resolution
electron impact (EI) and chemical ionization (CI) mass spectra
were obtained using a 70 eV ionizing energy source and used
in direct-inlet mode. Chemical reagents were obtained from
Aldrich Chemical Co. and the purity was always verified.
Sulfur dichloride, SCl2, was distilled twice from 0.1% phos-
phorus pentachloride, PCl5, and the red fraction boiling from
58 to 60 °C was collected and stored in the freezer under N2.8
Column chromatography was carried out on Merck Kieselgel
60 (230-400 mesh). The X-ray structure of 7b has been
deposited at the Cambridge Crystallographic Data Center.
Diben zyl Su lfoxyla te 7a . To a solution of benzyl alcohol
(1.0 g, 9.3 mmol) and Et3N (1.4 mL, 9.3 mmol) in CH2Cl2 (25
mL) cooled at -78 °C was added dropwise a solution of SCl2
(314 µL, 4.65 mmol) in CH2Cl2 (4 mL), and the resulting
mixture was stirred for 2 h at -40 °C. The mixture was
allowed to reach 0 °C, transferred to a separatory funnel, and
washed with water (3 × 10 mL), and dried over anhydrous
MgSO4, and the solvent evaporated under reduced pressure.
Column chromatography of the crude mixture (hexanes-CH2-
Cl2-toluene in 2:1:1) gave 9a as an off-white solid: mp
(hexanes-t-BuOH) 50-51 °C (lit.2 58-59 °C); (276 mg, 22%);
Rf 0.49; 1H NMR (200 MHz, CDCl3) δ 4.70, 4.90 (ABq, J )
11.67 Hz, 2H), 7.34 (s, 5H); 13C NMR (75.4 MHz, CDCl3) δ
76.74 (CH2), 128.48, 128.53, 128.65, 136.54 (Ar); MS (EI, direct
inlet, 1.6 V) m/z 278 (M•+, 38), 230 (M•+ - SdO, 100), 180
propargyl sulfenates is reported to proceed by a facile
[2,3]-sigmatropic shift;9a p-methoxybenzyl trichlorometh-
anesulfenate is believed to undergo thermal rearrange-
ment to the corresponding sulfoxide, in hexane, via a
dissociative mechanism (k ) 3.4 × 10-4 s-1 at 77 °C,
∆Hq ) 28 kcal/mol, ∆Sq ) 5 eu).9b The rearrangement of
benzyl p-toluenesulfenate to the corresponding sulfoxide,
in benzene, is established to proceed by a concerted
intramolecular mechanism (k ) 8.7 × 10-5 s-1 at 120 °C,
∆Hq ) 29.7 kcal/mol, ∆Sq ) -2 eu).9c The transition state
calculations for the concerted conversion of dimethyl
sulfenate to dimethyl sulfoxide is expected to be about
21 kcal/mol above the radical-pair pathway.9d
(M•+ - H2S2O2, 33), 105 (C6H5-(CH2)2+, 30), 91 (C6H5-CH2
,
+
100), 77 (Ph+, 14); 7a (305 mg, 27%) Rf 0.44; 1H NMR (200
MHz, CDCl3) δ 5.11 (s, 2H), 7.39 (s, 5H); 13C NMR (75.4 MHz,
CDCl3) δ 81.86 (CH2), 128.44, 128.48, 128.61, 136.92 (Ar); 10a
1
as a clear colorless oil (195 mg, 16%) Rf 0.15; H NMR (200
MHz, CDCl3) δ 4.93, 5.05 (ABq, J ) 11.75 Hz, 2H), 7.36 (s,
5H); 13C NMR (75.4 MHz, CDCl3) δ 64.07 (CH2), 128.49, 128.59,
128.64, 135.04 (Ar); MS (CI, direct inlet, 100 °C) m/z 280
+
(M + NH4+, 100), 216 (M + NH4 - SO2, 40).
Bis(4-n itr oben zyl) Su lfoxyla te 7b . According to the
procedure described for 7a , starting with 4-nitrobenzyl alcohol
(1.0 g, 6.5 mmol), Et3N (910 µL, 6.53 mmol), and SCl2 (207
µL, 3.27 mmol) in CH2Cl2 (3 mL), we obtained a crude that
was taken up in CH2Cl2 until almost completed dissolution
and filtered once more. The filtered solution was left overnight
at -30 °C under N2. Light orange crystals were collected to
give 7b (530 mg, 50%): 1H NMR (200 MHz, CDCl3) δ 5.17 (s,
2H), 7.46 (d, J ) 8.79 Hz, 2H), 8.18 (d, J ) 8.54 Hz, 2H); 13C
NMR (75.4 MHz, CDCl3) δ 80.33 (CH2), 123.71, 128.50, 143.73,
Con clu sion
Some 4-substituted benzyl sulfoxylates 7 were pre-
pared and isolated. The yields are optimized through low-
temperature control during the reaction. The isomeriza-
tion process of 7b,c to the corresponding sulfinates 8b,c
follows first-order kinetics, in C7D8, CDCl3, and CD3CN,
and is likely achieved via a three-membered ring acti-
vated complex in the transition state where the sulfur
from the O-S-O functionality acts as an electron donor
on the adjacent benzylic carbon. The solvent polarity has
little effect on the rate constant and can be interpreted
in terms of solvation of the para substitutent on the
benzene ring of 7b instead of solvation of the activated
complex. The inductive effects for 7b,c as well as the
resonance effect for 7b transmitted through the aromatic
ring are believed to be responsible for their stability
compared to 7a ,d ,e. The nature of the para substituent
is probably very important in the overall stability of
sulfoxylates 7 and the mechanism of the isomerization
process.
1
147.91 (Ar); the corresponding sulfinate 8b H NMR (200 MHz,
CDCl3) δ 4.18 (d, J ) 1.46 Hz, 2H), 5.08, 5.13 (ABq, J ) 13.13
Hz, 2H), 7.38-7.53 (m, Ar H, 4H) 8.16-8.31 (m, Ar H, 4H);
13C NMR (74.5 MHz, CDCl3) δ 63.25, 68.89, 123.72, 123.82,
128.51, 131.59, 135.34, 143.73, 147.76, 147.91; the remaining
was chromatographed (20% CH2Cl2 in hexanes) to give 9b as
a off-white powder, mp 95-97 °C (acetone-hexanes) (179 mg,
15%); 1H NMR (200 MHz, CDCl3) δ 4.88, 4.99 (ABq, J ) 12.18
Hz, 2H), 7.48 (d, J ) 8.82 Hz, 2H) 8.20 (d, J ) 8.71 Hz, 2H);
13C NMR (75.4 MHz, CDCl3) δ 75.05 (CH2), 123.70, 128.61,
143.55, 147.77 (Ar); MS (EI, direct inlet, 423 mV) m/z 320
(M•+ - SdO, 8), (M•+ - SO2, 15), 151 (HONO-C6H4-CdO+, 47),
136 (O2N-C6H4-CH2+, 100), 106 (136+ - NO, 35), 89 (136+
-
HONO, 27), 77 (Ph+, 63). Anal. Calcd for C14H12O6N2S2: C,
45.62; H, 3.28; N, 7.61. Found: C, 45.53; H, 3.07; N, 7.23. Rf:
0.67. 10b as a yellow solid, mp 81-82 °C (180 mg, 16%); Rf
0.27; 1H NMR (200 MHz, CDCl3) δ 5.03, 5.17 (ABq, J ) 12.40
Hz, 2H), 7.50 (d, J ) 8.50 Hz, 2H) 8.21 (d, J ) 8.50 Hz, 2H);
13C NMR (75.4 MHz, CDCl3) δ 62.93 (CH2), 124.27, 128.91,
142.34, 148.32 (Ar); MS (CI, direct inlet, 300 °C) m/z 354
(M + NH4+, 4), 272 (M•+ - SO2, 6); MS (EI, direct inlet, 3.9 V)
m/z 353 (M - H•+, 1). Anal. Calcd for C14H12O7N2S: C, 47.71;
H, 3.43; N, 7.96. Found: C, 47.71; H, 3.23; N, 7.81.
(8) Fieser, M.; Fieser, L. Reagents for Organic Synthesis; Wiley: New
York, 1967; Vol. 1, p 1122.
(9) (a) Braverman, S. Reactions Involving Sulfenic Acids and Their
Derivatives; Patai S., Ed.; J ohn Wiley & Sons: Toronto, 1990; Chapter
8. (b) Braverman, S.; Sredni, B. Tetrahedron 1974, 30, 2379. (c) Miller,
E. G.; Rayner, D. R.; Thomas, H. J .; Mislow, K. J . Am. Chem. Soc.
1968, 90, 4861. (d) Gregory, D. D.; J enks, W. S. J . Org. Chem. 1998,
63, 3859.
Bis(4-ch lor oben zyl) Su lfoxyla te 7c. Starting with 4-chlo-
robenzyl alcohol (1.0 g, 7.0 mmol), Et3N (978 µL, 7.02 mmol),
and SCl2 (238 µL, 3.50 mmol) in CH2Cl2 (3 mL), we obtained
a crude that was chromatographed (60% CH2Cl2 in hexanes)

Preparation of 4-Substituted Benzyl Sulfoxylates
J . Org. Chem., Vol. 65, No. 16, 2000 4795
very quickly to give fractions as mixture of 9c and 7c: Rf 0.68;
the sulfite 10c (195 mg, 17%). The mixed fractions were
chromatographed in hexanes-CH2Cl2-toluene (2:1:1) very
quickly to give 9c as clear shiny pellets, mp (pentane) 46-48
°C (204 mg, 17%): Rf 0.60; 1H NMR (200 MHz, CDCl3) δ 4.76,
4.86 (ABq, J ) 10.41 Hz, 2H) 7.24-7.36 (m, 4H); 13C NMR
(75.4 MHz, CDCl3) δ 75.76 (CH2), 128.72, 129.91, 134.40,
134.93 (Ar); the sulfoxylate 7c (500 mg, 46%) Rf 0.56; 1H NMR
(200 MHz, CDCl3) δ 5.00 (s, 2H), 7.28 (d, J ) 10.28 Hz, 2H),
7.32 (d, J ) 7.21 Hz, 2H); 13C NMR (75.4 MHz, CDCl3) δ 81.05
(CH2), 128.71, 129.81, 129.91, 135.34 (Ar).
Isom er iza tion of Bis(4-ch lor oben zyl) Su lfoxyla te 7c to
th e Su lfin a te 8c. The isomerization to the sulfinate was
observed: 1H NMR (200 MHz, CDCl3) δ 3.98, 4.02 (ABq, J )
12.94 Hz, 2H), 4.90, 5.01 (ABq, J ) 11.96 Hz, 2H), 7.11-7.38
(m, H Ar, 8H); 13C NMR (75.4 MHz, CDCl3) δ 63.54, 69.71,
128.70, 128.82, 128.96, 129.62, 129.80, 131.79, 133.95, 134.54;
MS (EI, direct inlet, 30 °C) m/z 266/268 (M•+ Cl cluster 0.15/
0.15), 142/144 (4-Cl-C6H4-CH2OH•+ Cl cluster, 83/27), 107
(142•+ - Cl, 100), 77 (Ph+, 96).
X-r a y Cr ysta llogr a p h ic An a lysis of 7b. Pure colorless
crystals were obtained from CH2Cl2. The principal crystal-
lographic parameters of compound 7b are as follows: M )
336.32; triclinic; space group P1; a ) 7.728(2) Å, b ) 8.011(2)
Å, c ) 12.553 Å; R ) 89.13(2)°, â ) 79.74(2)°, γ ) 73.73(2)°;
V ) 733.6(3) Å3; Z ) 2; Dc ) 1.523 g/cm3; Mo KR; λ ) 0.70930
Å; µ ) 0.255 mm-1; F(000) ) 348. The structure was refined
to a final R ) 0.0704, Rw ) 0.1132 for 2588 reflections, I >
2σ(I).
Bis(4-m eth oxyben zyl) Su lfoxyla te 7d . Starting with
4-methoxybenzyl alcohol (1.0 g, 7.2 mmol), Et3N (1.0 mL, 7.2
mmol), and SCl2 (246 µL, 3.60 mmol), we obtained the results
reported in Table 1.
Bis(4-m eth ylben zyl) Su lfoxyla te 7e. Starting with 4-
methylbenzyl alcohol (1.0 g, 8.2 mmol), triethylamine (1.14 mL,
8.18 mmol), and SCl2 (278 µL, 4.10 mmol) in CH2Cl2 (3 mL),
we obtained a semisolid residue that was chromatographed
(50% CH2Cl2 in hexanes) to give the dialkoxy disulfide 9e as
an off-white clear liquid (225 mg, 18%): Rf 0.55; 1H NMR (200
MHz, CDCl3) δ 2.38 (s, 3H), 4.80, 4.90 (ABq, J ) 10.78 Hz,
2H), 7.20 (d, J ) 7.86 Hz, 2H), 7.28 (d, J ) 7.93 Hz, 2H); 13C
NMR (75.4 MHz, CDCl3) δ 21.23, 76.59 (CH2), 128.77, 129.18,
133.55, 138.31 (Ar); MS (EI, direct inlet, 150 °C) m/z 258
(M•+ - SdO, 0.1), 242 (M•+ - SO2, 0.2), 210 (M•+ - H2S2O2,
0.5), 105 (CH3-C6H4-CH2+, 100), 91 (C6H4-CH2+, 36), 77 (Ph+,
Ack n ow led gm en t. We thank the FCAR (Que´bec)
and the Natural Sciences and Engineering Research
Council of Canada for financial support. We thank also
Mr. Nadim Saade for the low-resolution MS (McGill),
Dr. Charles Larsen for the elemental analyses and the
low-resolution MS of 9a , 9b, and 10b (Kemisk Labora-
torium, University of Copenhagen, Denmark), and Dr.
Anne-Marie Lebuis for the X-ray (McGill). We are
grateful to two referees for helpful suggestions concern-
ing the mechanistic interpretations.
1
16); the sulfoxylate 7e (236 mg, 21%) Rf 0.47; H NMR (200
MHz, CDCl3) δ 2.40 (s, 3H), 5.12 (s, 2H), 7.25-7.32 (br, 4H);
13C NMR (75.4 MHz, CDCl3) δ 21.58, 77.30 (CH2), 129.34,
129.70, 134.28, 139.04 (Ar); the sulfite 10e as a light yellow
solid (20% EtOAc in hexanes), mp 40-42 °C (273 mg, 23%) Rf
0.20; 1H NMR (200 MHz, CDCl3) δ 2.32 (s, 3H), 4.84, 4.96 (ABq,
J ) 11.53 Hz, 2H), 7.11-7.22 (m, 4H); 13C NMR (75.4 MHz,
CDCl3) δ 21.22, 64.06 (CH2), 128.67, 129.32, 132.02, 138.53
Su p p or tin g In for m a tion Ava ila ble: An ORTEP presen-
tation for 7b. Time dependence isomerization of 7c to 8c in
CDCl3 at 20.5 °C. Detailed 1H NMR and 13C NMR data (7a -
c,e; 8b,e; 10a -c,e) and MS data for 10a ,e. Note that analyti-
cal data including 1H NMR and 13C NMR for 9a -e and MS
for 9a ,b were previously submitted as Supporting Information
(ref 4b). This material is available free of charge via the
Internet at http://pubs.acs.org.
(Ar); MS (EI, direct inlet, 30 °C) m/z: 290 (M•+, 1), 226 (M•+
-
SO2, 0.1), 105 (CH3-C6H4-CH2•+, 100); the corresponding
sulfinate 8e (oil, 79 mg, 7%) Rf 0.04; 1H NMR (200 MHz,
CDCl3) δ 2.33 (s, 3H), 3.93, 4.02 (ABq, J ) 13.18 Hz, 2H), 4.89,
4.99 (ABq, J ) 11.48 Hz, 2H), 7.12, 7.13 (two singlets, 8H);
13C NMR (74.5 MHz, CDCl3) δ 21.18, 21.23, 64.10, 70.31,
125.64, 128.43, 129.25, 129.46, 130.36, 132.64, 138.08, 138.46.
J O991360B