Acyl iodides in organic synthesis: VI. Reactions with vinyl ethers

Article abstract of DOI:10.1023/B:RUJO.0000036063.58577.17

Reactions of acetyl iodide with butyl vinyl ether, 1,2-divinyloxyethane, phenyl vinyl ether, 1,4-di-vinyloxybenzene, and divinyl ether were studied. Vinyl ethers derived from aliphatic alcohols (butyl vinyl ether and 1,2-divinyloxyethane) react with acetyl iodide in a way similar to ethyl vinyl ether, i.e., with cleavage of both O-Csp2 and Alk-O ether bonds. From butyl vinyl ether, a mixture of vinyl iodide, butyl acetate, vinyl acetate, and butyl iodide is formed, while 1,2-divinyloxyethane gives rise to vinyl iodide, vinyl acetate, and 2-iodoethyl acetate. The reaction of acetyl iodide with divinyl ether involves cleavage of only one O-Csp2 bond, yielding vinyl acetate and vinyl iodide. In the reactions of acetyl iodide with phenyl vinyl ether and 1,4-divinyloxybenzene, only the O-CVin bond is cleaved, whereas the O-CAr bond remains intact.

Full text of DOI:10.1023/B:RUJO.0000036063.58577.17

Russian Journal of Organic Chemistry, Vol. 40, No. 4, 2004, pp. 467–469. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 4, 2004,
pp. 498–500.
Original Russian Text Copyright © 2004 by Voronkov, Trukhina, Vlasova.
Acyl Iodides in Organic Synthesis: VI.* Reactions
with Vinyl Ethers
M. G. Voronkov, A. A. Trukhina, and N. N. Vlasova
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: voronkov@irioch.irk.ru
Received June 27, 2003
Abstract—Reactions of acetyl iodide with butyl vinyl ether, 1,2-divinyloxyethane, phenyl vinyl ether, 1,4-di-
vinyloxybenzene, and divinyl ether were studied. Vinyl ethers derived from aliphatic alcohols (butyl vinyl ether
and 1,2-divinyloxyethane) react with acetyl iodide in a way similar to ethyl vinyl ether, i.e., with cleavage of
both O–Csp2 and Alk–O ether bonds. From butyl vinyl ether, a mixture of vinyl iodide, butyl acetate, vinyl
acetate, and butyl iodide is formed, while 1,2-divinyloxyethane gives rise to vinyl iodide, vinyl acetate, and
2-iodoethyl acetate. The reaction of acetyl iodide with divinyl ether involves cleavage of only one O–Csp2 bond,
yielding vinyl acetate and vinyl iodide. In the reactions of acetyl iodide with phenyl vinyl ether and 1,4-
divinyloxybenzene, only the O–CVin bond is cleaved, whereas the O–CAr bond remains intact.
We previously studied reactions of acyl iodides
with acyclic and cyclic ethers [1] and found that in the
reaction of acetyl iodide with ethyl vinyl ether both
ether bonds, Et–O and O–CH=CH2 are cleaved. Later
(2) the reaction of acyl chlorides with alkyl vinyl
ethers in acetonitrile, catalyzed by CoCl2 [7]
(Scheme 3). In the presence of (Ph3P)2CoCl2 as
catalyst, only addition of acyl chlorides at the double
C=C bond occurs [7].
on, an analogous cleavage of the O–Csp bond was
2
observed in the reaction of acetyl iodide with vinyl
acetate [2]. Both these reactions occurred under mild
conditions in the absence of a catalyst.
Scheme 2.
PhSiCl3
+
CH2=CHOR
It is known that in most reactions of vinyl ethers
R–O–CH=CH2 with electrophilic reagents the latter
adds to the β-carbon of the vinyl group with
subsequent cleavage of only the O–R bond [3, 4].
Likewise, the reaction of benzoyl chloride with alkyl
vinyl ethers in the presence of palladium catalyst and
triethylamine results in benzoylation exclusively of the
β-carbon atom [5] (Scheme 1).
CoCl2
PhSi(OR)Cl2
+
CH2=CHCl
Scheme 3.
R'COCl
+
CH2=CHOR
CoCl2
R'C(O)OR CH2=CHCl
+
In continuation of our studies on cleavage of
acyclic and cyclic ethers [1], we examined reactions of
acetyl iodide with butyl vinyl ether, 1,2-divinyloxy-
ethane, phenyl vinyl ether, 1,4-divinyloxybenzene, and
divinyl ether. The reactions were carried out in
methylene chloride at 10°C, and in all cases the
process was accompanied by heat evolution. Vinyl
ethers derived from aliphatic alcohols, namely butyl
vinyl ether and 1,2-divinyloxyethane, reacted with
acetyl iodide in a way similar to the reaction with ethyl
vinyl ether. As a result, both ether bonds, O–Csp2 and
Alk–O were cleaved. In the two cases, the products
Scheme 1.
PhCOCl
+
CH2=CHOR
Pd, Et3N
PhC(O)CH=CHOR
+
Et3N·HCl
Prior to our studies, only two examples of cleavage
of the O–Csp bond in vinyl alkyl ethers have been
2
reported. These are (1) the reaction of alkyl vinyl
ethers with trichloro(phenyl)silane [6] (Scheme 2) and
* For communication V, see [1].
1070-4280/04/4004-0467 © 2004 MAIK “Nauka/Interperiodica”

VORONKOV et al.
468
Scheme 8.
were vinyl iodide and vinyl acetate. In the reaction
with butyl vinyl ether, butyl acetate (39.8%) and butyl
iodide (12.5%) were also isolated (Scheme 4). Thus,
unlike ethyl vinyl ether [1], cleavage of the O–Csp2
bond predominates over cleavage of the O–Csp3 bond.
2MeCOI
+
CH2=CHOC6H4OCH=CH2
[MeC(O)OC6H4OCH=CH2]
–CH2=CHI
MeCOI
2CH2=CHI
+
MeC(O)OC6H4OC(O)Me
Scheme 4.
iodide and 1,4-diacetoxybenzene (Scheme 8; a pos-
sible intermediate product, 4-vinyloxyphenyl acetate,
was not detected).
MeCOI
+
CH2=CHOBu
MeC(O)OBu
BuI
+
CH2=CHI MeC(O)OCH=CH2
+
+
Despite very low basicity and nucleophilicity of the
oxygen atom in alkyl vinyl ethers (which was noted for
the first time as early as 1947 [9]), their reaction with
strongly electrophilic acetyl iodide possessing a readily
departing iodine atom (as iodide ion) begins with elec-
trophilic attack on the oxygen atom with formation of
intermediate oxonium complex, i.e., according to the
mechanism proposed by us previously and substan-
tiated by theoretical calculations [2, 10] (Scheme 9).
Acetyl iodide reacted with 1,2-divinyloxyethane to
afford approximately equal amounts of vinyl iodide
and vinyl acetate (40.5 and 42.8%, respectively)
together with 2-iodoethyl acetate (Scheme 5). These
results indicate that the probabilities for cleavage of
the O–Csp2 and O–Csp3 bonds in 1,2-divinyloxyethane
are almost equal.
Scheme 5.
2MeCOI
+
CH2=CHOC2H4OCH=CH2
CH2=CHI MeC(O)OCH=CH2
MeC(O)OC2H4I
Scheme 9.
R
CH CH2
+
O
C
I–
MeCOI
+
CH2=CHOR
+
Me
O
According to early data [8], the reaction of acetyl
iodide with divinyl ether resulted in explosion. Under
our conditions, the reaction occurred smoothly and
involved cleavage of only one ether bond even in
the presence of excess acetyl iodide (Scheme 6). The
yield of vinyl iodide and vinyl acetate was greater
than 80% (GLC).
MeC(O)OR
+
CH2=CHI
We previously found that the reaction of acetyl
iodide with phenyl acetate leads to cleavage of only
the ester O–C=O bond [2]. Likewise, acetyl iodide
reacts with aryl vinyl ethers selectively at the
O–CH=CH2 bond [2]. This is explained by very high
stability of the O–CAr bond due to n–π conjugation
between the oxygen lone electron pair and aromatic
π-electron system. The same factor is responsible for
our failure to effect cleavage of diphenyl ether and
dibenzofuran by the action of acetyl iodide (contrary
to published data [11] which were not confirmed
subsequently).
Scheme 6.
MeCOI
+
CH2=CHOCH=CH2
MeC(O)OCH=CH2
+
CH2=CHI
The formation of vinyl acetate (which is readily
cleaved by acetyl iodide [2]) in the presence of excess
acetyl iodide may be explained by very mild reaction
conditions and the presence of vinyl iodide in the
mixture. The reactions of acetyl iodide with phenyl
vinyl ether and 1,4-divinyloxybenzene involve only
the O–CVin bond, while the O–CAr bond remains intact.
In the first case, the products are vinyl iodide and
phenyl acetate (Scheme 7), and in the second, vinyl
EXPERIMENTAL
The IR spectra were recorded on a UR-20 spec-
trometer from samples prepared as thin films. GLC
analysis was performed on an LKhM-8M chromatog-
raph equipped with a thermal conductivity detector;
carrier gas helium; 2-m×4-mm column; oven tem-
perature programming mode. Initial acetyl iodide was
synthesized by reaction of acetyl chloride with
anhydrous sodium iodide following the known
procedure [7].
Scheme 7.
MeCOI
+
CH2=CHOPh
MeC(O)OPh CH2=CHI
+
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

ACYL IODIDES IN ORGANIC SYNTHESIS: VI.
469
br (C–O–C). Found, %: C 71.81; H 6.15. C8H8O2.
Calculated, %: C 70.58; H 5.88.
Reaction of butyl vinyl ether with acetyl iodide.
Acetyl iodide, 5.3 g, was added dropwise to a solution
of 3.1 g of butyl vinyl ether in 15 ml of methylene
chloride, cooled to 10°C. Immediately after mixing the
reactants, GLC analysis of the reaction mixture (using
authentic samples) showed the presence of vinyl iodide
(35.8%), vinyl acetate (11.8%), butyl iodide (12.8%),
and butyl acetate (39.8%).
Reaction of acetyl iodide with 1,4-divinyloxy-
benzene. Following a similar procedure, distillation of
the reaction mixture obtained from 5.06 g of 1,4-di-
vinyloxybenzene and 10.6 g of acetyl iodide in 30 ml
of methylene chloride gave 3.78 g (78.6%) of vinyl
iodide. By recrystallization of the residue from ethanol
we isolated 1.12 g (19.4%) of 1,4-diacetoxybenzene
with mp 121°C; published data [12]: mp 121°C, 123–
124°C. Found, %: C 61.04; H 4.8. C10H10O4. Calcu-
lated, %: C 61.85; H 5.15.
Reaction of acetyl iodide with 1,2-divinyloxy-
ethane. Acetyl iodide, 10.6 g, was slowly added to
a solution of 3.6 g of 1,2-divinyloxyethane in 30 ml of
methylene chloride, cooled to 10°C. Distillation of the
mixture gave 1.95 g (40.5%) of vinyl iodide, bp 54–
55°C, nD23 = 1.537 (published data [12]: bp 56–56.5°C,
nD20 = 1.5385); 1.15 g (42.8%) of vinyl acetate, bp 75–
80°C, n2D3 = 1.391 (published data [12]: bp 73°C, nD20 =
1.3958); and 5.15 g (54.9%) of 2-iodoethyl acetate,
bp 80°C (20 mm). IR spectrum, ν, cm–1: 2962 s
(C–Hasym), 2872 s (C–Hsym), 1745 s (C=O), 1050 s
(C–O–C), 510 m (C–I). Found, %: C 22.41; H 3.39;
I 62.75. C4H7O2. Calculated, %: C 22.42; H 3.27;
I 59.34.
This study was performed under financial support
by the Council for Grants of the President of the
Russian Federation (project no. NSh-1129.2003.3).
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Reaction of acetyl iodide with divinyl ether.
Divinyl ether, 2.2 g, was added dropwise to a solution
of 5.31 g of acetyl iodide in 15 ml of methylene
chloride, cooled to 10°C. The solvent was distilled off,
and the residue was analyzed by GLC. Only vinyl
iodide and vinyl acetate were identified (using
authentic samples). Likewise, GLC analysis of the
reaction mixture obtained from 10.6 g of acetyl iodide
and 2.2 g of divinyl ether showed the presence of vinyl
iodide, vinyl acetate, and unreacted acetyl iodide.
Reaction of acetyl iodide with phenyl vinyl ether.
Phenyl vinyl ether, 3.75 g, was added dropwise to
a solution of 5.31 g of acetyl iodide in 15 ml of dry
methylene chloride, cooled to 10°C. Distillation of
the mixture gave 1.54 g (32%) of vinyl iodide, bp 53–
56°C, which was identified by GLC using an authentic
sample. The residue was distilled under reduced
pressure to isolate 2.53 g (59.5%) of phenyl acetate,
bp 90–92°C (20 mm), nD20 = 1.4990. IR spectrum, ν,
cm–1: 1760 s (C=O); 1580, 1450 (C=Carom); 1210 v.s,
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004