2-Phenylthioallylation of aldehydes with allyl phenyl sulfides via dibromination, followed by dehydrobromination

Article abstract of DOI:10.1246/bcsj.76.1679

2-Phenylthioallyl bromides, derived from allyl phenyl sulfides via dibromination, followed by dehydrobromination, cause the 2-phenylthioallylation of aldehydes with tin(II) iodide, tetrabutylammonium iodide and sodium iodide in 1,3-dimethylimidazolidin-2-

Full text of DOI:10.1246/bcsj.76.1679

Short Articles
Bull. Chem. Soc. Jpn., 76, 1679–1680 (2003) 1679
2-Phenylthioallylation of Aldehydes
with Allyl Phenyl Sulfides via
Dibromination, Followed by
Dehydrobromination
ꢀ
Michihito Oshima, and Yasuhiko Kurusu
Yoshiro Masuyama, Takehiro Sano,
Department of Chemistry,
Faculty of Science and Technology, Sophia University,
7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554
ð1Þ
Carbonyl allylation by 3-bromo-2-phenylthio-1-propene
(2a), derived from allyl phenyl sulfide (1a) via dibromination,
followed by dehydrobromination, was investigated with SnI2,
TBAI, and NaI under the same conditions as those for the usu-
al allylic halides.4 The reactivity of the carbonyl allylations by
allylic trihalotins is usually affected by the bulkiness of ꢁ-sub-
stituents of the allylic trihalotins.2 The reactivity of 2a in the
allylation of benzaldehyde is almost the same as that of 3-bro-
mo-1-propene, in contrast to the low reactivity of 3-bromo-2-
methyl-1-propene (Eq. 2). The results of carbonyl allylations
with 2a are summarized in Table 1. Aromatic aldehydes bear-
ing an electron-donating or electron-withdrawing group, ꢂ; ꢁ-
unsaturated aldehydes, and aliphatic aldehydes can be em-
ployed for carbonyl allylations.
(Received April 3, 2003)
2-Phenylthioallyl bromides, derived from allyl phenyl
sulfides via dibromination, followed by dehydrobromination,
cause the 2-phenylthioallylation of aldehydes with tin(b) io-
dide, tetrabutylammonium iodide and sodium iodide in 1,3-
dimethylimidazolidin-2-one to produce the corresponding
1-substituted 3-phenylthiohomoallyl alcohols.
Barbier-type carbonyl allylation is one of the most conven-
ient methods for introducing allylic functions.1 (E)-2-Butenyl-
metals, prepared from (E)-1-halo-2-butene under Barbier con-
ditions, usually cause ꢀ-anti-selective addition to aldehydes.
Our (E)-2-butenyltrichlorotin, derived from (E)-2-buten-1-ol
with palladium catalysts and tin(b) chloride in 1,3-dimethyl-
imidazolidin-2-one (DMI), also exhibits ꢀ-anti-selectivity.2
We recently found that tin(b) iodide–tetrabutylammonium io-
dide (TBAI) combo-reagent functions effectively without pal-
ladium catalysts for Barbier-type carbonyl allylations by allyl
alcohols or chlorides.3,4 Carbonyl allylation by (E)-2-butenyl-
polyiodotin, derived from either (E)-2-buten-1-ol or (E)-1-
chloro-2-butene with SnI2–TBAI/NaI in DMI–H2O, leads to
ꢀ-syn-selection, which is unprecedented under Barbier
conditions. The difference of diastereoselection between
(E)-2-butenyltrichlorotin and (E)-2-butenylpolyiodotin can be
explained by the Lewis acidity of tin in these 2-butenyltins.
The Lewis acidity of tin in (E)-2-butenylpolyiodotin is proba-
bly low because of the low electronegativity value of the io-
dide ligand. Therefore, (E)-2-butenylpolyiodotin may disfavor
the formation of a usual six-membered cyclic transition state
with aldehyde, and may slowly make a nucleophilic attack
on aldehyde via an acyclic antiperiplanar transition state with-
out Lewis acids, to exhibit ꢀ-syn-selectivity. We hoped that
an enhancement of the electron density on the ꢀ-carbon of al-
lyltins would promote carbonyl allylation via the acyclic anti-
periplanar transition state. We report on the influence of the 2-
phenylthio group on the reactivity and diastereoselectivity for
carbonyl allylation by 2-phenylthioallyl bromides 2, derived
from allyl phenyl sulfides 1 via dibromination, followed by de-
hydrobromination, under Barbier conditions using SnI2–TBAI
(Eq. 1).
ð2Þ
Regioselection and diastereoselection in carbonyl allylation
by 1-bromo-2-phenylthio-2-butene (2b),5 derived from 2-bu-
tenyl phenyl sulfide (1b) via dibromination, followed by dehy-
drobromination, were investigated under the same conditions
Table 1. Carbonyl Allylation by 2a with SnI2, TBAI, and
NaIaÞ
R2
Time/h
Product
Yield/%bÞ
Ph
4
13
11
16
13
24
16
46
3a
3b
3c
3d
3e
3f
79
67
83
86
64
60
53
33
4-MeC6H4
4-ClC6H4
2-Furyl
PhCH=CH
PhCH2CH2
n-C6H13
3g
3h
c-C6H11
a) The allylation of aldehydes (1.0 mmol) by 2a (1.5 mmol) was
carried out with SnI2 (1.5 mmol), TBAI (0.2 mmol), and NaI
(1.5 mmol) at room temperature in DMI (3 mL). b) Isolated
yields.
Published on the web August 15, 2003; DOI 10.1246/bcsj.76.1679

1680 Bull. Chem. Soc. Jpn., 76, No. 8 (2003)
Ó 2003 The Chemical Society of Japan
Table 2. syn-Diastereoselective Carbonyl Allylation by 2baÞ
R2
Time/h Product Yield/%bÞ syn:anticÞ
Ph
4-MeC6H4
4-ClC6H4
PhCH=CH
PhCH2CH2
n-C6H13
11
20
19
21
46
20
20
39
4a
4b
4c
4d
4e
4f
43
42
60
46
46
31
32
43
93:7
95:5
93:7
94:6
99:1
82:18
93:7
91:9
H2C=CH(CH2)8
c-C6H11
4g
4h
a) The allylation of aldehydes (1.0 mmol) by 2b (2.0 mmol)
was carried out with SnI2 (2.0 mmol), TBAI (0.25 mmol),
and NaI (2.0 mmol) at room temperature in DMI (3 mL).
b) Isolated yields. c) The ratio was determined by 500
1
MHz H NMR (JEOL ꢄ-500). See Ref. 6.
as those of 2a (Eq. 1). The results are summarized in Table 2.
The allylation of any used aldehyde occurred at the ꢀ-position
to the bromo group of 2b accompanying syn-diastereoselectiv-
ity6 (ꢀ-syn-selection), which is higher than that in carbonyl al-
lylation by 1-chloro-2-butene or 2-buten-1-ol with SnI2 and
TBAI.3,4
A plausible mechanism that explains the ꢀ-syn-selection in
the carbonyl allylation by 2b derived from 1b is shown in
Scheme 1. 1-Bromo-2-phenylthio-2-butene (2b) may be
formed via the formation of episulfonium bromide (A) after
the bromination of 1b, followed by the isomerization of 2b0 af-
ter the dehydrobromination of A. The allylic bromide 2b may
react with SnI2, TBAI and NaI to produce 2-phenylthio-2-bu-
tenylpolyiodotin (B), which may cause ꢀ-syn-addition to alde-
hyde via an acyclic antiperiplanar transition state (C).
Scheme 1. A plausible mechanism.
References
1
2
Y. Yamamoto and N. Asao, Chem. Rev., 93, 2207 (1993).
Y. Masuyama, J. Synth. Org. Chem., Jpn., 50, 202 (1992);
Y. Masuyama, in ‘‘Advances in Metal-Organic Chemistry,’’ ed by
L. S. Liebeskind, JAI Press, Greenwich (1994), Vol. 3, p. 255.
Experimental
The Carbonyl Allylation by 3-Bromo-2-phenylthio-1-pro-
pene (2a), Derived from Allyl Phenyl Sulfide (1a) via Dibromi-
nation Followed by Dehydrobromination: 3-Bromo-2-phenyl-
thio-1-propene (2a), which was prepared by the dibromination of
allyl phenyl sulfide (1a) with bromine in CCl4, followed by dehy-
drobromination of the resulting dibromide with DBU in acetoni-
trile, was roughly purified by column chromatography (silica
gel, hexane:ethyl acetate = 15:1); 76–78% yields; 500 MHz
1H NMR (CDCl3): ꢃ 4.02 (d, J ¼ 0:92 Hz, 2H), 5.26 (s, 1H),
5.65 (t, J ¼ 0:92 Hz, 1H), 7.31–7.39 (m, 3H), 7.45–7.48 (m,
2H). And then to the solution of benzaldehyde (1.0 mmol), SnI2
(1.5 mmol), TBAI (0.2 mmol), and NaI (1.5 mmol) in DMI (3 mL)
was immediately added 2a (1.5 mmol) in DMI (1 mL). The solu-
tion was stirred at room temperature for 4 h. After the mixture
had been worked up as usual, purification by column chromatog-
raphy (Merck silica gel 60, hexane:ethyl acetate = 7:1) afforded
1-phenyl-3-phenylthio-3-buten-1-ol (3a, 0.20 g, 78%). IR (neat)
3
Y. Masuyama, T. Ito, K. Tachi, A. Ito, and Y. Kurusu,
Chem. Commun., 1999, 1261.
A. Ito, M. Kishida, Y. Kurusu, and Y. Masuyama, J. Org.
Chem., 65, 494 (2000).
4
5
E:Z = ca. 1:1, 500 MHz 1H NMR (CDCl3): ꢃ 1.68 (2d,
J ¼ 6:5 Hz, 3H), 3.83 (2s, 2H), 5.80 (2q, J ¼ 6:5 Hz, 1H). This
crude 2b includes 4.7% of 3-bromo-2-phenylthio-1-butene (2b0)
[ꢃ 1.91 (d, J ¼ 7:0 Hz, 3H), 4.71 (q, J ¼ 7:0 Hz, 1H), 5.06 (s,
1H), 5.64 (s, 1H)] and 22% of 3-bromo-1-phenylthio-2-butene
[ꢃ 2.28 (s, 3H), 3.66 (d, J ¼ 7:0 Hz, 2H), 5.75 (t, J ¼ 7:0 Hz,
1H)].
6
The diastereomer ratio of 4 was determined by 500 MHz
1H NMR (JEOL ꢄ-500). The syn structure of 4a was confirmed
by the transformation into syn-2-methyl-1-phenyl-3-buten-1-ol;
its 1H NMR spectrum was consistent with that of an authentic
sample.7 See: J. P. Takahara, Y. Masuyama, and Y. Kurusu, J.
Am. Chem. Soc., 114, 2577 (1992). On the basis of the syn-diaster-
eoselection for benzaldehyde, other aldehydes are presumed to un-
dergo syn-allylation by 2b with SnI2–TBAI.
3421, 2924, 1607, 1583, 1475, 1439, 1024, 874, 748, 700 cmꢁ1
.
1H NMR (500 MHz, CDCl3) ꢃ 2.31 (br, 1H), 2.56–2.64 (m,
2H), 4.98 (dd, 1H, J ¼ 8:0, 5.5 Hz), 5.02 (s, 1H), 5.23 (br, 1H),
7.23–7.26 (m, 1H), 7.28–7.36 (m, 7H), 7.44–7.47 (m, 2H). Anal.
Found: C, 74.44; H, 6.31%. Calcd for C16H16OS: C, 74.96; H,
6.29%.
7
The transformation (reductive desulfurization) of 4a into 2-
methyl-1-phenyl-3-buten-1-ol was carried out with EtMgBr in the
presence of a catalytic amount of NiCl2(PPh3)2 in THF/Et2O at
room temperature. No exchange of phenylthio group with ethyl
group occurred, in contrast with PhMgBr and BuMgBr. See: H.
Okamura, M. Miura, and H. Takei, Tetrahedron Lett., 1979, 43.
The structure of all other products was determined by IR,
1H NMR, and elemental analysis (or HRMS for 3d and 3g). These
materials for characterizations are available.