Acyl iodides in organic synthesis: II. Reactions with acyclic and cyclic ethers

Article abstract of DOI:10.1023/A:1022545630736

Reaction of acyl iodides RCOI (R = Me, Ph) was studied with acyclic and cyclic ethers (Et₂O, MeCHCH₂(O), ClCH₂CHCH ₂(O), THF, O(CH₂CH₂)₂O, EtOCH ₂CH₂OH, EtOCH=CH₂, PhOEt]. The reaction occurred with the rupture of one or two CO bonds furnishing the corresponding iodides and esters.

Full text of DOI:10.1023/A:1022545630736

Russian Journal of Organic Chemistry, Vol. 38, No. 11, 2002, pp. 1579 1581. Translated from Zhurnal Organicheskoi Khimii, Vol. 38, No. 11, 2002,
pp. 1633 1635.
Original Russian Text Copyright
2002 by Voronkov, Trukhina, Vlasova.
Acyl Iodides in Organic Synthesis: II. Reactions with Acyclic
and Cyclic Ethers
M. G. Voronkov, A. A. Trukhina, and N. N. Vlasova
Faworsky Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, 664033 Russia
Received September 27, 2001
Abstract Reaction of acyl iodides RCOI (R = Me, Ph) was studied with acyclic and cyclic ethers (Et2O,
MeCHCH2(O), ClCH2CHCH2(O), THF, O(CH2CH2)2O, EtOCH2CH2OH, EtOCH=CH2, PhOEt]. The
reaction occurred with the rupture of one or two CO bonds furnishing the corresponding iodides and esters.
In extension of the study on reactivity of acyl
iodides RCOI [R = Me (I), Ph (II)] as compared with
that of trimethyliodosilane we investigated their
reaction with acyclic and cyclic ethers. The reaction
of trialkyliodosilanes with ethers is known [1 4] to
proceed with a rupture of C O C bonds [Scheme (1)].
iodine failed [1]. Unlike acyclic ethers the ethylene
oxide reacts both with acetyl chloride and acetyl
iodide at 25 C within 45 days and 24 days respectively
[5] [Scheme (4)].
(4)
R3SiI + R OR
R OSiR3
+
R I
(1)
By examples of propylene oxide and epichloro-
hydrin we established that acyl iodides I and II
readily cleaved the oxirane ring. The process is
exothermic, occurs within 1 1.5 h, and same as with
Me3SiI follows Krasusky rule [10] [Scheme (5)].
Already in [5, 6] the acyl iodides RCOI were
shown to react with ethers along Scheme (2).
RCOI + R OR
RCOOR
+
R I
(2)
(5)
These processes were carried out at 80 120 C
within 80 240 h. We confirmed that reaction of
RCOI (R = Me, Ph) with ethyl ether at 1: 1 and 2: 1
ratio followed Scheme (2). However unlike previous-
ly published data [5, 6] we established that the reac-
tion proceeded already in boiling ether (at 36 C) and
completed within 1.5 2 h. Therewith formed ethyl
iodide and ethyl acetate or ethyl benzoate respectively.
R
= CH3, ClCH2.
In the same way as trimethyliodosilane [3] the
studied acyl iodides reacted also with tetrahydrofuran
at 100 110 C in 2 h with the cleavage of C O bond
and formation of 4-iodobutyl acetate [Scheme (6)].
In contrast the analogous reaction of acyl chlorides
or bromides RCOX (X = Cl, Br) with aliphatic
ethers occurs cleanly only in the presence of a large
quantity of catalyst [ZnCl2, FeCl3, SnBr2, CoCl2,
Mo(CO)6, metallic Zn, Pd complexes and even
graphite] [7 9] [Scheme (3)].
(6)
We succeeded in performing reaction between
1,4-dioxane and benzoyl iodide, as in the case of tri-
methyliodosilane [3], only at the double excess of
PhCOI. As a result a crystalline 1,2-dibenzoyloxy-
ethane was isolated [Scheme (7)]. The other reaction
product, 1,2-diiodoethane, we failed to isolate due to
its instability: it decomposed at distillation into
ethylene and elemental iodine.
Cat
RCOCl + R OR
R Cl + RCOOR
(3)
This route to esters is not interesting from the
preparative viewpoint for the yields of the target
products often are no more than 15 40% due to
formation of side products of polymeric and other
nature. The attempt to carry out the acetyl chloride
reaction with ethers in the presence of elemental
(7)
1070-4280/02/3811-1579$27.00 2002 MAIK Nauka/Interperiodica

1580
VORONKOV et al.
In the acetyl iodide reaction with 2-ethoxyethanol
EXPERIMENTAL
the Et O bond is subject to rupture resulting in
formation of EtI and 2-hydroxyethyl acetate. Interest-
IR spectra were recorded on a spectrometer UR-20
1
ingly the hydroxy group remained intact [Scheme (8)]. from thin films. H NMR spectra were registered on
Bruker DPX-400 instrument (400 MHz) in deutero-
RCOI + C2H5OCH2CH2OH
chloroform, internal reference TMS. The initial acyl
iodides were obtained by reaction between the cor-
responding acyl chlorides with anhydrous sodium
iodide by the known procedure [11]. The chromato-
graphic analysis was carried out on LKhM-8M
instrument, detector katharometer, carrier gas
helium, column 2000 4 mm, operation in a program-
med mode.
RCOOCH2CH2OH + C2H5I
(8)
Similarly to reaction with oxiranes this process is
exothermal and does not depend on the ratio of the
initial reagents (1: 1 or 2: 1).
Among the product of reaction between acetyl
iodide and ethyl vinyl ether vinyl iodide, vinyl
acetate, ethyl acetate, and ethyl iodide were identified.
This fact evidences the rupture of both ether bonds
Et O and O CH=CH2; the latter process is un-
common [Scheme (9)].
Acetyl iodide reaction with ethyl ether. A mix-
ture of 10.6 g of acetyl iodide and 4.6 g of ethyl ether
was boiled for 1.5 h. By common distillation 3.21 g
(34%) of ethyl iodide, bp 72 C, and 1.22 g (23%) of
ethyl acetate, bp 77 C, was isolated. The products
were identified by GLC comparison with standards.
(9)
Benzyl iodide reaction with ethyl ether. A mix-
ture of 11 g of benzyl iodide and 3.5 g of ethyl ether
was boiled for 2 h. From the reaction mixture 3.15 g
(43%) of ethyl iodide, bp 72 C, was separated and
identified by GLC. The residue after distillation of
ethyl iodide was distilled in a vacuum to obtain 1.35g
(19%) of ethyl benzoate, bp 90 C (10 mm Hg).
Found, %: C 71.86; H 6.92. C9H10O2. Calculated,%:
C 72.00; H 6.66.
In view of extremely high heat liberation in this
reaction and because vinyl ethyl ether is prone to
polymerization the reaction has been performed in
CH2Cl2 solution. The process occurs virtually at once.
The products ratio in the reaction mixture (ethyl
iodide: vinyl acetate: ethyl acetate = 1: 1.2 : 1.05;
identification and quantitative analysis by GLC)
suggests that the reaction occurs with approximately
equal probability in both directions.
Benzyl iodide reaction with propylene oxide. At
mixing of 11 g of benzyl iodide and 2.75 g of propyl-
ene oxide the reaction mixture self-heated. The
separated dark-brown precipitate was several times
washed with ethanol and dried in a vacuum desiccator
over P2O5. 2-Iodoisopropyl benzoate (1,54 g; 11%)
was isolated as brown powder, mp 94 C. Found I, %:
43.29. C10H12IO2. Calculated I, %: 43.64.
On the contrary in reaction of acetyl iodide with
phenyl ethyl ether only the Et O bond is ruptured to
afford as final products phenyl acetate and ethyl
iodide [Scheme (10)].
PhOC2H5 + CH3COI
C2H5I + PhOCOCH3 (10)
Acetyl iodide reaction with epichlorohydrin. At
room temperature 10.6 g of acetyl iodide was mixed
with 5.8 g of epichlorohydrin. The vacuum distilla-
tion afforded 9.54 g (61%) of 1-iodo-3-chloroiso-
propyl acetate, bp 100 110 C (10mm Hg). Found, %:
C 22.84; H 3.36; Cl + I 60.65. C5H8ClIO2. Cal-
culated, %: C 22.85; H 3.04; Cl + I 61.9.
The similar reactivity exhibited by acyl iodides and
trimethyliodosilane with respect to organic com-
pounds containing a C O C group suggests that the
mechanism of C O bond cleavage is analogous to that
observed for (CH3)3SiI [3] and consists in formation
and decomposition of the corresponding acyloxonium
iodides [Scheme(11)].
Acetyl iodide reaction with tetrahydrofuran.
A mixture of 10.6 g of acetyl iodide and 4.5 g of
tetrahydrofuran was heated to boiling for 2 h. By
vacuum distillation was separated 10.55 g (73%) of
4-iodobutyl acetate, bp 110 C (10 mm Hg). IR
(11)
1
spectrum, , cm : 2900 2850s (CH), 1745s (C=O),
Thus the studied acyl iodides are as reagents
identic to trimethyliodosilane and as such may be
used for synthons in the organic synthesis.
1
1275, 1050, v.s (COC), 500 m (C I). H NMR spec-
trum, , ppm: 4.1 (2H, CCH2O), 3.2 (2H, CCH2I),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 11 2002

ACYL IODIDES IN ORGANIC SYNTHESIS: II.
1581
2.1 s (CH3COO). Found, %: C 30.34; H4.57; I52.76.
C6H11 IO2. Calculated, %: C 29.75; H 4.54; I 52.47.
mixed with 5.8 g of phenyl ethyl ether. From the
mixture was separated by distillation 2.5 g (53%) of
ethyl iodide, bp 70 72 C, nD27 1.5022 (publ. [12]: bp
72 C, nD20 1.5137), and 2.3 g (71%) of phenyl acetate,
bp 75 C (10 mm Hg) {publ. [12]: bp 195.5 C
(760 mm Hg.)}. Found, %: C 70.1; H 5.52. C8H8O2.
Calculated, %: C 70.58; H 5.92.
Benzyl iodide reaction with 1,4-dioxane. At mix-
ing of 11 g of benzyl iodide and 2.05 g of 1,4-di-
oxane a precipitate immediately separated. The latter
was filtered off, dissolved in ethanol, reprecipitated
with water, and dried in a vacuum desiccator over
P2O5. Thus was isolated 1.43 g (23%) of 1,2-dibenzo-
yloxyethane, bp 73 C (publ. [12]: bp 73 74 C].
Found, %: C 70.66; H 5.27. C16H14O4. Calculated,
%: C 71.1; H 5.18.
REFERENCES
1. Voronkov, M.G., Trukhina, A.A., and Vlasova, N.N.,
Zh. Org. Khim., 2002, vol. 38, no. 11, pp. 1630 1632.
2. Voronkov, M.G.and Khudobin, A.Yu., Izv. Akad.
Nauk SSSR, Ser. Khim., 1956, no. 6, p. 713.
3. Voronkov, M.G. and Dubinskaya, E.I., J. Organo-
metal. Chem., 1991, vol. 410, no. 3, p. 1.
4. Olah, G.A. and Narang, S.C., Tetrahedron, 1982,
vol. 38, no. 130, p. 2225.
5. Kizhner, N., Zh. Russian Fed. Khim. Obshch.,
1909, vol. 41, no. 5, p. 651.
6. Gustus, E.L. and Stevens, Ph.G., J. Am. Chem. Soc.,
1933, vol. 55, no. 1, p. 378.
Acetyl iodide reaction with 2-ethoxyethanol. At
mixing of 10.6 g of acetyl iodide and 5.6 g of 2-eth-
oxyethanol the reaction mixture self-heated. By
distillation of the reaction mixture at the atmo-
spheric pressure we separated 4.21 g of ethyl iodide,
bp 67 72 C, nD25 1.5011 (publ. [12]: bp 72 C, nD20
1.5137), and 4.92 g (79%) of 2-hydroxy ethyl
acetate, bp 80 85 C (25 mm Hg.) {publ. [12]: bp
1
182 C (760 mm Hg.)}. IR spectrum, , cm : 3450
(OH), 2962 s, 2872 s (CH), 1750 s (C=O), 1275,
1050 s (COC). Found, %: C 46.86; H 8.31. C4H8O3.
Calculated, %: C 46.15; H 7.69.
7. Sonntag, N.O.V., Chem. Rev., 1953, vol. 52, no. 2,
p. 238.
Acetyl iodide reaction with vinyl ethyl ether.
To a solution of 5.3 g of acetyl iodide in 20 ml of
dichloromethane at 10 C was added 2.25 g of vinyl
ethyl ether. After mixing by a common distillation of
the reaction mixture was isolated 0.45 g (10%) of
vinyl iodide, bp 56 C, nD18 1.541 (publ. [12]: bp
56 56.5 C, nD20 1.5385). In the second fraction ethyl
iodide, vinyl acetate, and ethyl acetate were identified
by GLC.
8. Patai, S., The Chemistry of Acyl Halides, London,
1972, p. 177.
9. Suzuki, Y. and Matsushima, M., Chem. Lett., 1998,
no. 4, p. 319.
10. Krasusky, K.A., J. Rus. Phis. Soc., 1907, vol. 39,
p. 520.
11. Teobald, D.W. and Smith, J.C., Chem. Ind., 1958,
no. 32, p. 1007.
12. Spravochnik khimika (Chemist,s Handbook), Nikol,-
skii, B.P., Ed., Moscow: Khimiya, 1953, vol. 2,
p. 398.
Acetyl iodide reaction with phenyl ethyl ether.
At room temperature 5.31 g of acetyl iodide was
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 11 2002