2
C. Mi et al. / Tetrahedron xxx (2016) 1e6
2
.3. Synthesis of 1-methoxy-4-vinylbenzene
-Methoxy-4-vinylbenzene was prepared according to liter-
reaction.28 Although some studies on oxidation of olefins to al-
dehydes or ketones with PhI(OAc) have been reported in the
the disadvantages of slow reaction rate, ad-
ditional oxidants, and low selectivity still exist. In this work, five
oxidants were employed to carry out the oxidation reaction. As
seen in Table 2, the substrates styrene, trans-stilbene, and 1,2-
2
2
2,29
1
past few years,
16e18
atures.
It was characterized by ESI-MS: m/z 135.08 (Calcd for
þ
1
[
5
6
M þ1]: 135.07); H NMR (400 MHz, CDCl
3
) d 3.85 (s, 3H),
.16e5.19 (dd, J¼10.8 8.0 Hz, 1H), 5.64e5.68 (dd, J¼17.6 8.0 Hz, 1H),
13
.67e6.75 (m, 1H), 6.90e6.92 (m, 2H), 7.38e7.41 (m, 2H). C NMR
159.36, 136.23, 130.42, 127.41, 113.91, 111.60,
diphenylethyne can’t be oxidized by oxidants
Fe (SO under the same conditions. However the oxidants m-
CPBA, NaIO , and PhI(OAc) were efficient, and best results could
be achieved with PhI(OAc) as oxidant. RuCl is one of the
commonly used reagent for the oxidation reactions of olefins to
H
2
O
2
and
(
100 MHz, CDCl
3
)
d
2
4 3
)
5
5.31. The NMR spectra in the ESI.
4
2
2
3
3
3
. Results and discussion
.1. Effect of solvent
19,30,31
aldehydes.
oxidation cleavage of styrene by PhI(OAc)
metal salts was comparatively investigated (Table S2 in the ESI).
As seen in Table S2, for RuCl catalyzed system, the reaction was
satisfactory that the conversion of styrene achieved 100% after
.5 h, and the yield of benzaldehyde achieved 99.8% at a low
To examine the catalytic activity of catalyst,
2
catalyzed by various
Solvent displayed important influence on many oxidation
3
reactions.1
9e21
To investigate the solvent effect, styrene, trans-stil-
1
bene, 1-octene, and 1,2-diphenylethyne were chosen as substrates
to carry out oxidation reaction by using oxidant PhI(OAc) and
catalyst RuCl in four kinds of two-phase systems dichloro-
methane/water, acetonitrile/water, acetone/water, and benzene/
water, respectively. The experimental results were listed in Table 1.
It can be seen that the oxidation of these substrates afforded small
amount of products when acetonitrile/water, acetone/water, and
benzene/water were used as solvent systems. Dichloromethane/
water was the best solvent system to afford desired product alde-
hyde or diketone with good yield in relatively short time. It can be
catalyst load of 0.1 mol %. It can be observed that other metal
halides showed low catalytic activity for both conversion of
styrene and yield of benzaldehyde. It should be noted that only
2
3
12.7% conversion of styrene and 10.8% yield of benzaldehyde
could be obtained after 4 h in the absence of catalyst.
3.3. Oxidative cleavage of terminal olefins
Under the optimum conditions, various aryl- and alkyl-
substituted terminal olefins were investigated and the experi-
mental results were listed in Table 3. As observed from Table 3, the
3 2 2 2 2
RuCl ePhI(OAc) eCH Cl eH O system showed excellent catalytic
2 2 2
further found that the volume ratio of CH Cl to H O had great
influence on the oxidation reaction of styrene (Table S1 in the ESI).
From Table S1, it can be observed that the two-phase system of 4:1
ratio of CH
2 2 2
Cl to H O gave the best results of 100% conversion of
ability for the oxidative cleavage of terminal olefins to aldehydes.
The aromatic terminal olefins with electron-rich and electron-poor
substituted group in the para position (2ae6a) were oxidized to the
corresponding aldehydes in high yields (76.2e92.1%, Table 3, en-
tries 2e6). Styrene (1a) and 2-vinylnaphthalene (7a) were con-
verted to benzaldehyde and 2-vinylnaphthaldehyde in 99.8% and
57.5% yields, respectively (Table 3, entries 1 and 7). The GC profiles
of styrene oxidation reaction solution were shown in Figs. 1Se2S.
However, when aliphatic alkene was employed, this catalysis re-
action showed slow reaction rate. For the oxidation of 1-octene
(8a), although the selectivity of the product heptanal (8b) was
high (97.5%), only 22.6% yield was obtained after 1.5 h reaction.
styrene and 99.8% yield of benzaldehyde.
3
.2. Effect of oxidant
The chemistry of polyvalent iodine compounds has experi-
enced an unprecedented, explosive development during the
past few decades. This increasing interest is mainly due to the
very useful oxidizing properties of polyvalent iodine reagents
combined with their benign environmental nature and com-
mercial availability.2
2,23
2
PhI(OAc) was used as an oxidant for
2
4,25
26,27
the oxidation of alcohols,
phenol,
and olefin aziridination
Table 1
a
The yields of carbonyl compounds for the oxidation of unsaturated hydrocarbon in various solvent systems
Substrate
Product
Time (h)
Yield (%)
Dichloro-methaneb
Acetonitrile
14.5
Acetone
56.0
Benzene
52.5
1
1
.5
.5
99.8
99.7
21.4
58.1
7.3
31.6
3.2
1.5
22.6
d
2.0
89.6
24.6
63.0
32.5
a
The reactions were carried out by using oxidant PhI(OAc)
2
and catalyst RuCl
3
in 5 mL solvent (organic solvent:H
2
O¼4:1, v/v), GC yields are given. d represent for no
reaction.
b
Isolated yields are given, see ESI for details.