Ytterbium metal promoted allylation of disulfides with allyl bromide

Article abstract of DOI:10.1081/SCC-120005416

In the presence of a catalytic amount of methyliodide, ytterbium metal can promote the reductive cleavage of the S-S bond in disufides 1 to give ytterbium thiolates 2 which then react with allyl bromide to form the corresponding allylic sulfides 3 in good yields under mild and neutral conditions.

Full text of DOI:10.1081/SCC-120005416

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YTTERBIUM METAL PROMOTED ALLYLATION OF
DISULFIDES WITH ALLYL BROMIDE
Weike Su a b , Yongshu Li a & Yongmin Zhang b
a College of Pharmaceutical Sciences , Zhejiang University of Technology , Hangzhou,
310014, China
b Department of Chemistry , Zhejiang University at Xi Xi Campus , Hangzhou, 310028, China
Published online: 18 Oct 2011.
To cite this article: Weike Su , Yongshu Li & Yongmin Zhang (2002) YTTERBIUM METAL PROMOTED ALLYLATION OF DISULFIDES
WITH ALLYL BROMIDE, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 32:14, 2101-2106, DOI: 10.1081/SCC-120005416
To link to this article: http://dx.doi.org/10.1081/SCC-120005416
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 14, pp. 2101–2106, 2002
YTTERBIUM METAL PROMOTED
ALLYLATION OF DISULFIDES WITH
ALLYL BROMIDE
2
Weike Su,1,2, Yongshu Li,1 andYongmin Zhang
*
1College of Pharmaceutical Sciences, Zhejiang
University of Technology, Hangzhou, 310014, China
2Department of Chemistry, Zhejiang University at
Xi Xi Campus, Hangzhou, 310028, China
ABSTRACT
In the presence of a catalytic amount of methyliodide,
ytterbium metal can promote the reductive cleavage of the
S–S bond in disufides 1 to give ytterbium thiolates 2 which
then react with allyl bromide to form the corresponding allylic
sulfides 3 in good yields under mild and neutral conditions.
Chemistry of lanthanoid in organic synthesis has received more and
more attention in the last decade.[1] Especially, the application of samarium
reagents in organic synthesis has been recently achieved.[2–6] However, rela-
tively few studies on ytterbium reagents have been reported. Nevertheless, it
was shown that ytterbium reagents have the potential to serve as selective
nucleophiles in C–X ꢀ-bond addition reactions and eventually will take their
place among the other lanthanide reagents with a unique role in organic
synthesis.[7] As a Grignard-type reagent, PhYbI can react with many kinds
*Corresponding author. E-mail: suweike@zjut.edu.cn
2101
DOI: 10.1081/SCC-120005416
Copyright & 2002 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

2102
SU, LI, AND ZHANG
of electrophilic reagents, such as with aldehydes or ketones to afford the
corresponding alcohols in moderate yields,[8–10] with ꢁ,ꢂ-unsaturated alde-
hydes or ketones to provide higher selectivity of 1,2-addition than their
Grignard counterparts,[11–13] with carboxylic acid derivatives to give benzo-
phenone,[14–15] with chlorotrimethylsilane to give trimethylphenylsilane in
70% yield,[10] with isocyanatobenzene to give benzanilide.[10] MeYbI reacted
with chlorodimethylphenylsilane to give trimethylphenylsilane in 73%
yield.[10] Our group has studied the allylation of imines, aldehydes, ketones,
diselenides and disulfides with allylytterbium bromide. Taniguchi and his
workers[16] reported the formation of Lanthanoid(III) thiolates from
benzophenone-catalyzed. There are no reports on the formation of ytter-
bium thiolated from methyl iodide-catalyzed. In our series of working with
ytterbium metal in organic synthesis, we have been interested in reductive
cleavage of the S–S bond in symmetrical disulfides by ytterbium metal
activated by methyliodide. Most conventional reducing agents for symme-
trical disulfides are strong bases, but ytterbium metal is an efficient, mild and
neutral reducing agent.
Allylic sulfides are a class of useful synthetic intermediates, and many
synthetic methods have been reported for the preparation of allylic sulfides
in the last decade. For example, the alkylation of thiols,[17] the reaction of
alkyl halide with sodium sulfide, addition of thiophol with alkene,[18] reduc-
tion of disulfides with copper in the presence of halide, reduction of sulph-
oxides with titanium(II) chloride, deoxygenation of sulfoxides with
triphenylphosphine/iodine/sodium idodide,[19] synthesis of allylthioethers
via allyldialkyltelluronium salts. Our group has studied the synthesis of
allylic sulfides by disulfides with allylsamarium bromide.[20] We now
report the preparation of ytterbium thiolates via disulfides and ytterbium
activated by CH3I, which is not reported in literature. The thiolates are
active intermediates for the synthesis of allylic sulfides upon treatment
with allyl bromide under mild and neutral conditions.
In our experimental work, it was found that without activation ytter-
bium metal not only does not react with allyl bromide to form allylytter-
bium bromide as does samarium, but also does not promote the allylation of
disulfides with allyl bromide directly. Surprisingly in the presence of a cat-
alytic amount of CH3I, ytterbium can be activated, and then promote the
allylation of disulfides with allyl bromide easily. We investigated firstly
whether the S–S bond in disulfides 1 would be cleaved by ytterbium metal
in the presence of methyl iodide to give ytterbium thiolates 2, and the latter
thus formed in situ, react with allyl bromide to give allylsulfides 3 (Scheme 1).
The results are summarized in Table 1.
Taniguchi[16] and his co-workers reported that ytterbium metal
activated by benzophenone cleaved the S–S bond in disulfides to afford

YTTERBIUM METAL PROMOTED DISULFIDE ALLYLATION
2103
Scheme 1.
Table 1. Reaction Conditions and Yields
Time
(h)
Temperature
(ꢀC)
Yield*
(%)
Product
R
3a
3b
3c
3d
3e
3f
3g
3h
3i
C6H5
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
25
25
25
25
25
25
25
25
25
25
85
81
82
88
87
78
77
80
87
86
p-CH3C6H4
o-CH3C6H4
p-ClC6H4
o-ClC6H4
p-CH3OC6H4
o-CH3OC6H4
m-CH3OC6H4
o-BrC6H4
3j
m-BrC6H4
*Yields of isolated products based on disulfides.
ytterbium thiolates 2 at room temperature in 3 h. But, in our study, we
found that in the presence of a catalytic amount of CH3I. Ytterbium
metal cleaves the S–S bond within 0.5 h.
As shown in Table 1, we found that the substituents on the aromatic
rings may effect the reaction yields. If the substituents are electron-
withdrawing groups, the yields of products are higher than those of
electron-donating groups. We can also find that the yield for electron-
withdrawing groups in ortho-position or para-position are higher than
that in meta-position, and for electron-donating groups the yield is higher
in meta-position than in ortho- or para-position.
Another evidence is that if we cleaved diaryl disulfides with SmI2, we
only use one electron of samarium, and two electrons of samarium are
wasted during the preparation of SmI2. The substitution products
would not be obtained if ytterbium was replaced by Samarium whereas
the reaction conditions remain the same.

2104
SU, LI, AND ZHANG
EXPERIMENTAL
1H NMR spectra were recorded with a Bruker AC-80 MHz instru-
ment, with CDCl3 used as the solvent and tetramethylsilane as an internal
standard. IR spectra were determined on a PE-683 spectrometer. Mass
spectra were recorded on HP 5989B MS spectrometers. Microanalysis was
carried out on a Carlo-Erba 1160 instrument.
Tetrahydrofuran was freshly distilled from sodium/benzophenone
ketyl before use. Ytterbium metal was obtained from Sigma-Aldrich Co.
The reaction was preformed in a Schlenk type glass apparatus and under a
nitrogen atmosphere.
GENERAL PROCEDURE
Ytterbium powder (0.173 g, 1 mmol) and a catalytic amount of CH3I
(1 drop) were added to a three-necked flask at room temperature under a
nitrogen atmosphere. The metal was then warmed slightly to activate for
about 15 min, and then cooled to room temperature. Disulfide (1.5 mmol) in
18 mL of anhydrous THF and 0.363 g (3 mmol) of freshly distilled allyl
bromide were added by a syringe. The mixture was stirred at 25ꢀC for a
given time (Table 1), the reaction was monitored by TLC, and quenched
with dilute HCl (0.1 mol/L, 5 mL). Then the mixture was extracted with
ether (3 ꢁ30 mL). The crude product was isolated with usual ways and
purified by preparative thin layer chromatogrophy using cyclohexane as
eluent. All products were identified by IR,1H NMR and MS spectra.
3a: Oil,[4] 1H NMR (CDCl3) ꢃ: 3.48 (2H, d, J ¼ 6 Hz), 4.85–5.25 (2H,
m), 5.45–6.15 (1H, m), 7.00–7.50 (5H, m); IR ꢄmax: 3100, 2950, 1650, 1600,
1490, 1095, 920, 740, 695 cmÀ1
.
3b: Oil,[4] 1H NMR (CDCl3) ꢃ: 2.25 (3H, s), 3.40 (2H, d, J ¼ 6Hz),
4.85–5.20 (2H, m), 5.46–6.10 (1H, m), 6.98–7.30 (4H, m); IR ꢄmax: 3100,
2970, 1650, 1520, 1400, 990, 920, 830; MS (m/z, %) 164(M þ, 39), 123 (100),
91 (12), 77 (22) cmÀ1
.
3c: Oil, 1H NMR (CDCl3) ꢃ: 2.36 (3H, s), 3.41 (2H, d, J ¼ 6 Hz),
4.99–5.24 (2H, m), 5.73–5.91 (1H, m), 6.96–7.28 (4H, m); IR ꢄmax: 3060,
2920, 1630, 1589, 1468, 1379, 986, 919, 744 cmÀ1; MS (m/z, %): 165 (M þ 1,
29), 164(M þ, 100), 149 (28), 123 (67), 91 (22), 77 (13); Anal. calcd for
C10H12S: C, 73.12; H, 7.36. Found: C, 73.28; H, 7.45.
3d: Oil,[4] 1H NMR (CDCl3) ꢃ: 3.54(2H, d, J ¼ 6 Hz), 5.00–5.25
(2H, m), 5.65–5.95 (1H, m), 7.18–7.51 (4H, m); IR ꢄmax: 3110, 2955, 1650,
1480, 1095, 930, 695 cmÀ1
.

YTTERBIUM METAL PROMOTED DISULFIDE ALLYLATION
2105
3e: Oil, 1H-NMR (CDCl3) ꢃ: 3.51 (2H, d, J ¼ 6 Hz), 4.97–5.24 (2H, m),
5.67–5.88 (1H, m), 6.98–7.35 (4H, m); IR ꢄmax: 3080, 3061, 2979, 2920, 1637,
1576, 1453, 1431, 1115, 1035, 744 cmÀ1; MS (m/z, %) 186 (M þ 2, 24), 184
(Mþ, 74), 143 (31), 108 (100), 77 (23); Anal. calcd for C9H9ClS: C, 58.53; H,
4.91. Found: C, 58.65; H, 4.92.
1
3f: Light yellow oil, H NMR (CDCl3) ꢃ: 3.56 (2H, d, J ¼ 6 Hz), 3.76
(3H, s), 4.85–5.07 (2H, m), 5.69–6.03 (1H, m), 6.72–7.39 (4H, m); IR ꢄmax
:
3018, 2943, 2830, 1593, 1494, 1285, 1245, 1035, 920, 825 cmÀ1; MS (m/z, %):
180 (Mþ, 98), 139 (100), 77 (7); Anal. calcd for C10H12OS: C, 66.63; H, 6.71.
Found: C, 66.79; H, 6.75.
1
3g: Light yellow oil, H NMR (CDCl3) ꢃ: 3.53 (2H, d, J ¼ 6 Hz), 3.87
(3H, s), 4.98–5.22 (2H, m), 5.72–5.93 (1H, m), 6.78–7.32 (4H, m); IR ꢄmax
:
2933, 2850, 1588, 1478, 1244, 1028, 786 cmÀ1; MS (m/z, %): 181 (M þ 1, 26),
180 (Mþ, 100), 165 (11), 154(2), 139 (8), 77 (8); Anal. calcd for C 10H12OS:
C, 66.63; H, 6.71. Found: C, 66.82; H, 6.80.
1
3h: Light yellow oil, H NMR (CDCl3) ꢃ: 3.35 (2H, d, J ¼ 6 Hz), 3.60
(3H, s), 4.85–5.15 (2H, m), 5.45–6.05 (1H, m), 6.45–7.10 (4H, m); IR ꢄmax
:
;
2930, 1250, 2850, 1230, 1590, 1045, 1480, 860, 1425, 760, 1285, 680 cmÀ1
MS (m/z, %): 180 (Mþ, 98), 165 (29), 154 (100), 77 (14), 41 (13); Anal. calcd
for C10H12OS: C, 66.63; H, 6.71. Found: C, 66.85; H, 6.75.
3i: Light yellow oil, 1H NMR (CDCl3)ꢃ: 3.54(2H, d, J ¼ 6 Hz),
5.04–5.29 (2H, m), 5.71–5.83 (1H, m), 6.91–7.54 (4H, m); IR ꢄmax: 3060,
2921, 1651, 1589, 1468, 1065, 987, 919, 743 cmÀ1; MS (m/z, %): 230 (M þ 1,
72), 229 (Mþ, 20), 228 (M-1, 68), 149 (100), 108 (36), 77 (17); Anal. calcd for
C9H9BrS: C, 47.18; H, 3.96. Found: C, 47.42; H, 4.13.
3j: Light yellow oil, 1H NMR (CDCl3)ꢃ: 3.52 (2H, d, J ¼ 6 Hz),
5.01–5.16 (2H, m), 5.23–5.69 (1H, m), 7.06–7.44 (4H, m); IR ꢄmax: 3056,
2923, 1651, 1575, 1556, 1459, 1402, 1068, 992, 922, 865, 770, 753 cmÀ1; MS
(m/z, %): 231 (Mþ2, 18), 230 (M þ 1, 100), 229 (Mþ, 21), 228 (96), 188 (12),
149 (34), 108 (62); Anal. calcd for C9H9BrS: C, 47.18; H, 3.96. Found: C,
47.37; H, 4.08.
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Received in the UK March 15, 2001