Preparation, structure, and oxidative reactivity of (dichloroiodo)pyridines: Recyclable hypervalent iodine reagents

Article abstract of DOI:10.24820/ark.5550190.p010.279

New pyridine-based hypervalent iodine reagents, (dichloroiodo)pyridines, were prepared by chlorination of 2-, 3-, or 4-iodopyridines with NaOCl-HCl at room temperature. Structures of 2-(dichloroiodo)pyridine and 2-(dichloroiodo)-3-propoxypyridine were established by X-ray crystallography. The new (dichloroiodo)pyridines can be used as efficient reagents for oxidation of alcohols to carbonyl compounds and also as chlorinating reagents. The reduced form of the reagents such as 2-iodo-3-propoxypyridine, can be recovered from the reaction mixture in good yields by an acid-base liquid-liquid biphasic protocol.

Full text of DOI:10.24820/ark.5550190.p010.279

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Arkivoc 2018, part ii, 40-49
Organic Chemistry
Preparation, structure, and oxidative reactivity of (dichloroiodo)pyridines:
recyclable hypervalent iodine reagents
a,b
b
c
a,b
Akira Yoshimura,* Khiem C. Nguyen, Victor N. Nemykin, and Viktor V. Zhdankin*
a
The Tomsk Polytechnic University, 634050 Tomsk, Russia
b
Department of Chemistry and Biochemistry, University of Minnesota Duluth,
Duluth, Minnesota, 55812, USA
c
Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
Emails: ayoshimu@d.umn.edu vzhdanki@d.umn.edu
Dedicated to Prof. Kenneth K. Laali on the occasion of his 65th birthday
Received 07-26-2017
Accepted 09-22-2017
Published on line 10-11-2017
Abstract
New pyridine-based hypervalent iodine reagents, (dichloroiodo)pyridines, were prepared by chlorination of 2-,
-, or 4-iodopyridines with NaOCl-HCl at room temperature. Structures of 2-(dichloroiodo)pyridine and 2-
dichloroiodo)-3-propoxypyridine were established by X-ray crystallography. The new (dichloroiodo)pyridines
3
(
can be used as efficient reagents for oxidation of alcohols to carbonyl compounds and also as chlorinating
reagents. The reduced form of the reagents such as 2-iodo-3-propoxypyridine, can be recovered from the
reaction mixture in good yields by an acid-base liquid-liquid biphasic protocol.
Keywords: Hypervalent iodine, iodopyridine, (dichloroiodo)arenes, oxidation, recyclable reagents
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Introduction
Organohypervalent iodine compounds are widely used in organic synthesis as versatile and environmentally
1
-7
friendly reagents for various oxidative transformations. In particular, (dichloroiodo)arenes, ArICl , are
2
8
commonly applied as efficient oxidants or chlorinating reagents. (Dichloroiodo)benzene 1 is one of the most
9
common reagents that can be conveniently prepared by direct chlorination of iodobenzene. Numerous
alternative procedures for oxidative chlorination of iodobenzene are also known, and a particularly useful
1
0-13
method employs the combination of hydrochloric acid and inorganic oxidants such as NaClO or NaClO2.
Numerous (dichloroiodo)arenes and other organic iododichlorides (e.g., compounds 2-5 shown in Scheme 1)
1
4-17
have been prepared by chlorination of the corresponding iodides using similar procedures.
Scheme 1. Representative examples of organic iododichlorides.
1
8-23
Recently, several pyridine-based hypervalent iodine compounds have been prepared and investigated.
Most of these compounds are pyridine-derived iodonium salts, which can be used as effective electrophilic
pyridine transfer reagents toward various organic substrates. The chemistry of pyridine-based hypervalent
iodine compounds of general type PyIX remains undeveloped. Previously, our group reported the preparation
2
of pyridine-based pentavalent iodine reagents, 2-iodylpyridines, by oxidation of corresponding 2-iodopyridines
using 3,3-dimethyldioxirane. We have demonstrated that 2-iodylpyridines are useful oxidizing reagents
2
4
towards alcohols or sulfides. However, to the best our knowledge, the pyridine based trivalent iodine
reagents such as 2-(dichloroiodo)pyridine have not been reported. In the present paper, we report the
synthesis, structural characterization, and reactivity of several (dichloroiodo)pyridine derivatives. These
compounds can be used as efficient recyclable oxidants towards alcohols or chlorinating reagents towards
electron-rich organic substrates.
Results and Discussion
In our initial experiments, we have found that the reaction of 2-iodopyridine 6 with the HCl-NaOCl
combination for 2 hours at room temperature yields 2-(dichloroiodo)pyridine 7 in 89% yield (Scheme 2, eq. 1).
The solid-state structure of 7 was established by single crystal X-ray crystallography (Figure 1). According to
the X-ray crystallographic data, compound 7 has a T-shaped geometry of the iodine(III) center (the Cl1-I1-Cl2
o
bond angle is 177.21(4) ), and the bond distances between iodine and chlorine atoms are 2.4488(13) Å (I1-Cl1)
and 2.5274(12) Å (I1-Cl2). This molecular arrangement is similar to the previous reported structure of PhICl
2
2
5
o
1
. The ICl fragment in 7 is significantly rotated out of the pyridine plane (50.14(11) ). There are no close
2
intermolecular contacts in the structure of 7 (the closest intermolecular I-Cl contact is 3.627 Å). The analogous
reaction of 2-iodo-3-propoxypyridine 8 under similar conditions gave the expected product 9 in 95% yield
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Yoshimura, A. et al.
(
Scheme 2, eq. 2). A single-crystal X-ray study of 9 revealed that this compound also has T-shaped geometry
o
with the Cl1-I1-Cl2 angle of 170.12(5) . Compound 9 has a pseudocyclic structure with an intramolecular
2
4,26-29
interaction of 3.084(8) Å between the iodine center and the alkoxy group oxygen atom (Figure 1).
to 7, the ICl fragment is rotated out of the pyridine plane (85.46(9)). Two intermolecular I-Cl contacts at about
Similar
2
3
.5 Å are present in the X-ray structure of 9 forming a trigonal-bipyramidal motif.
The chlorination of 3-iodopyridine 10 under similar conditions afforded 3-(dichloroiodo)pyridine 11 in 90%
yield (Scheme 2, eq. 3), and the reaction of 4-iodopyridine 12 produced the expected dichloride 13 in 49%
yield (Scheme 2, eq. 4).
Scheme 2. Preparation of (dichloroiodo)pyridines.
Cl2 I1
Cl1
Cl1
N1
C5
C1
O1
C1
C2
N1
C5
C6
C8
I1
C7
C4
C3
C2
Cl2
C4
C3
Figure 1. X-ray crystal structures of 2-(dichloroiodo)pyridines 7 and 9.
In general, dichloroiodoarene compounds, ArICl , can serve as useful oxidants or efficient chlorinating
2
1
1,30
reagents towards various organic substrates.
We have investigated the oxidation of alcohols and oxidative
chlorination of electron-rich organic substrates using (dichloroiodo)pyridines as reagents. The reaction of
benzyl alcohol 14a with 2-iodopyridine dichloride 7 in acetonitrile solution at room temperature gave
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benzaldehyde 15a, isolated from reaction mixture as the 2,4-dinitrophenylhydrazone derivative in good yield
Table 1). As expected, the oxidation of benzyl alcohol 14a using other dichloroiodopyridines also produced
(
benzaldehyde in good yields. In the reactions of para-chloro- 14b or para-nitro-benzyl alcohol 14c under
similar conditions, the respective products were obtained in low to moderate yields. When the reaction of
cycloheptanol 14d was performed using dichloroiodopyridines under these conditions, the expected ketone
was obtained in moderate yields. Compared to the reactions of (dichloroiodo)benzene 1 under the same
conditions, the new (dichloroiodo)pyridines afforded respective carbonyl compounds in comparable or better
yields.
In the reaction of benzyl alcohol 14a with PhICl (1) in the presence of 2-iodopyridine (6) as additive, the
2
yield of benzaldehyde was improved up to 81%. This result implies that the pyridine moiety present in
iodopyridines or (dichloroiodo)pyridines is facilitating the oxidation. Previously, Wicha and co-workers
3
1
reported that the addition of pyridine resulted in increased reactivity of PhICl (1).
2
a
Table 1. Oxidation of alcohols 14 using (dichloroiodo)pyridines
b
Product 15 (%)
ArICl2
C H CHO 15a
p-ClC H CHO 15b
p-NO C H CHO 15c
Cyc-C H O 15d
7 12
6
5
6
4
2
6
4
7
9
98%
84%
87%
84%
62%
69%
97%
61%
66%
30%
19%
39%
13%
24%
52%
37%
41%
30%
29%
1
1
1
3
c
1
57% (81%)
a
Reaction conditions: ArICl (0.300 mmol) and alcohol 14 (0.250 mmol) stirred in acetonitrile (2.0 mL)
2
b
at room temperature for 24 hours. Isolated yields as 2,4-dinitrophenylhydrazone derivatives of 15.
c
In the presence of 2-iodopyridine 6 (1.2 equiv).
In the next step, we have investigated the reactivity of (dichloroiodo)pyridines as chlorine atom transfer
reagents towards organic substrates. The reaction of dibenzoylmethane 16 with 2-(dichloroiodo)pyridine 7
gave the corresponding α-mono chloride 17 in good yield. As expected, the reactions of dibenzoylmethane 16
with other (dichloroiodo)pyridine reagents also produced product 17 in moderate yield. In the reactions of
1
,4-dimethoxybenzene 18 with (dichloroiodo)pyridines, the corresponding product of monochlorination 19
was obtained in moderate yield. Compared to the reactions of (dichloroiodo)benzene 1 or analogous
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(
dichloroiodo)arenes under similar conditions, the (dichloroiodo)pyridine reagents showed better reactivity
3
2-34
and higher yields.
Among the chlorination reactions, the reactions of 4-(dichloroiodo)pyridine 13 gave the
lowest yields because of the low solubility of this reagent in methylene chloride.
ArICl2:
7
9
11
13
1
Yield of 17 (%)
97%
78%
85%
57%
70%
ArICl2
7
9
11
13
1
1
9 (%)
78%
81%
84%
47%
68%
Scheme 2. Oxidative chlorination using (dichloroiodo)pyridine reagents.
Finally, we have demonstrated that 2-(dichloroiodo)-3-propoxypyridine 9 can be used as a recyclable
reagent. The reduced form of reagent 9, 2-iodo-3-propoxypyridine 8, can be easily recovered from the
reaction mixture in over 85% yield by a simple acid-base liquid-liquid biphasic protocol. The recovered
24
compound 8 can be converted to 2-(dichloroiodo)-3-propoxypyridine 9 using standard procedure.
Conclusions
In summary, we have prepared new (dichloroiodo)pyridines from respective iodopyridines by chlorination
with the HCl/NaOCl combination. Structures of 2-(dichloroiodo)pyridine 7 and 2-(dichloroiodo)-3-
propoxypyridine 9 were established by X-ray crystallography. According to the crystal data, both compounds
have the typical for hypervalent iodine T-shape structure. Compound 9 has a pseudocyclic structure with a
short intramolecular interaction between oxygen atom and iodine center. The new (dichloroiodo)pyridines can
be used as efficient reagents for oxidation of alcohols to carbonyl compounds and also as chlorinating
reagents. The reduced form of the reagents, in particular, 2-iodo-3-propoxypyridine, can be recovered from
the reaction mixture in good yields by an acid-base liquid-liquid biphasic protocol.
Experimental Section
General. All reactions were performed under dry argon atmosphere with flame-dried glassware.
Dichloromethane and acetonitrile were distilled from CaH immediately prior to use. All commercial reagents
2
were ACS reagent grade and used without further purification. Melting points were determined in an open
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capillary tube with a Mel-temp II melting point apparatus. NMR spectra were recorded on a Varian Inova 500
1
MHz ( H NMR). Chemical shifts are reported in parts per million (ppm) and referenced relative to the
24
9
tetramethylsilane. The known compounds, 3-propoxy-2-iodopyridine (8) and dichloroiodobenzene (1) were
prepared according to the reported procedures.
General Procedure for preparation of (dichloroiodo)pyridines
Aqueous 12M HCl solution (1.5 mL) was added to a mixture of iodoarene (1.4 to 2.0 mmol) with 5.85%
aqueous NaOCl (8.0 mL). The reaction was stirred at room temperature for 2 h (reaction completion was
controlled by TLC), and the reaction mixture changed from a light yellow solution to a yellow suspension. After
completion of the reaction, the resulting yellow precipitate was separated by filtration. The precipitate was
washed with hexane and dried in vacuum to afford analytically pure (dichloroiodo)pyridine product.
2
-(Dichloroiodo)pyridine (7). Chlorination of 2-iodopyridine 6 (410 mg, 2.00 mmol) according to the general
o
procedure afforded 490 mg (89%) of product 7, isolated as a yellow solid: mp 79.5-81.1 C (from methylene
-
1
1
chloride); IR (KBr) cm 3077, 1556, 1444, 1412; H NMR (500 MHz, CDCl ): δ 8.53 (dd, J 4.9 Hz, 1.8 Hz, 1H),
8
3
1
3
.19 (dd, J 8.3 Hz, 0.5 Hz, 1H), 7.84 (ddd, J 8.3 Hz, 7.4 Hz, 1.8 Hz, 1H), 7.59 (ddd, J 7.4 Hz, 4.9 Hz, 0.5 Hz, 1H); C
NMR (125 MHz, CDCl ): δ 150.8,144.8, 141.5, 129.9, 127.6; Anal. Calcd forC H Cl IN: C, 21.77; H, 1.46; N, 5.08.
3
5
4
2
Found: C, 22.04; H,1.30; N, 5.08%.
Single crystals of product 7 suitable for X-ray crystallographic analysis were obtained by slow evaporation of
MeCN-CH Cl solution. For details on crystal structure of compound 7 see the CIF file in Supporting
2
2
Information. Selected crystallographic data for 7: Triclinic P-1 a 4.0281(3) Å, b 8.6219(6) Å, c 11.7755(11) Å, α =
o
o
o
3
7
3.583(5) , β = 88.270(6) , γ = 80.810(6) , V = 387.20(5) Å , Z = 2, R (I>2.0/σ(I)) = 0.0204, R (all) = 0.0640,
w
CCDC 1563656
.
2
-(Dichloroiodo)-3-propoxypyridine (9). Chlorination of 2-iodo-3-propoxypyridine 8 (375 mg, 1.43 mmol)
according to the general procedure afforded 452 mg (95 %) of product 9, isolated as a yellow solid: mp 89.1-
o
-1
1
9
0.5 C (from methylene chloride); IR (KBr) cm 3071, 2964, 2877, 1559, 1443, 1411, 1290, 1043; H NMR (500
MHz, CDCl ): δ 8.05 (dd, J 4.4 Hz, 1.4 Hz, 1H), 7.53 (dd, J 8.3 Hz, 4.4 Hz, 1H), 7.41 (dd, J 8.3 Hz, 1.4 Hz, 1H), 4.21
3
1
3
(
t, J 6.3 Hz, 2H), 2.06-1.93 (m, 2H), 1.16 (t, J 7.5 Hz, 3H); C NMR (125 MHz, CDCl ): δ 149.5, 141.4, 139.2,
3
1
4
28.9, 121.8, 72.2, 22.3, 10.5; Anal. Calcd forC H INCl : C, 28.77; H, 3.02; N, 4.19. Found: C, 28.77; H,2.89; N,
8 10 2
.15.
Single crystals of product 9 suitable for X-ray crystallographic analysis were obtained by slow evaporation of
MeCN-CH Cl solution. For details on crystal structure of compound 9 see the CIF file in Supporting
2
2
Information. Selected crystallographic data for 9: Orthorhombic, P2 2 2 , a = 8.0475(5) Å, b = 10.3684(5) Å, c =
1
1 1
3
1
3.9105(9) Å, V = 1160.69(12) Å , Z = 4, R (I>2.0/σ(I)) = 0.0379, R (all) = 0.0659, CCDC 1563657.
w
3
5
3
-(Dichloroiodo)pyridine (11) : Chlorination of 3-iodopyridine 10 (410 mg, 2.00 mmol) according to the
o
general procedure afforded 498 mg (90%) of product 11, isolated as a yellow solid: mp 130.5-132.0 C (from
3
5
o
-1
1
methylene chloride) (lit, mp 128-129 C); IR (neat) cm 3007, 2986, 2921, 1568, 1459; H NMR (500 MHz,
1
3
DMSO-d ): δ 9.10 (s, 1H), 8.87-8.78 (m, 1H), 8.73 (d, J 7.0 Hz, 1H), 7.75-7.63 (m, 1H); C NMR (75 MHz, DMSO-
d ): δ 151.8, 149.5, 142.9, 128.1, 96.3; HRMS (APCI-positive ionization): calcd for C H Cl IN ([M+H] ):
6
3
5
+
6
5
5
2
2
75.8844, found: 275.8860.
4
-(Dichloroiodo)pyridine (13): Chlorination of 4-iodopyridine 12 (410 mg, 2.00 mmol) according to the general
o
procedure afforded 270 mg (49%) of product 10, isolated as yellow solid: mp 109.5-110.1 C (from methylene
-
1
1
chloride); IR (neat) cm ; 3103, 2915, 2846, 1617, 1481; H NMR (500 MHz, DMSO-d ): δ 8.49 (d, J 5.0 Hz, 2H),
6
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Yoshimura, A. et al.
1
3
8
.40 (d, J 5.0 Hz, 2H); C NMR (75 MHz, DMSO-d ): δ 142.2, 136.3, 120.3; HRMS (APCI-positive ionization):
6
3
5
+
calcd for C H I Cl N ([M+H] ): 275.8844, found: 275.8816.
5
5
2
General procedure for oxidation of alcohols using (dichloroiodo)arenes
Alcohol 14 (0.250 mmol) was added to a solution of (dichloroiodo)arene (0.300 mmol) in acetonitrile (2 mL).
The reaction was stirred at room temperature for 24 h. After completion of the reaction, a standard solution
of 1.5 mL of 2,4-dinitrophenylhydrazine (prepared from 200mg of 2,4-dinitrophenylhydrazine, 1 mL of H SO ,
2
4
1
0 mL of EtOH, and 2 mL of H O) was added. The precipitate of 2,4-dinitrophenylhydrazone derivative 15 was
2
filtered, washed with water, and dried in vacuum.
,4-Dinitrophenylhydrazone of benzaldehyde (15a): Reaction of benzyl alcohol 14a (27 mg, 0.250 mmol)
according to the general procedure afforded 2,4-dinitrophenylhydrazone of 15a (57-98%), isolated as a light
2
4
2
o
24
o
1
orange solid: mp 231.7-233.2 C (from ethanol) (lit, mp 235.8-237.0 C); H NMR (500 MHz, DMSO-d ): δ 11.7
6
(s, 1H), 8.86 (d, J 0.3 Hz, 1H), 8.70 (s, 1H), 8.37 (dd, J 10.0 Hz, 0.3 Hz, 1H), 8.10 (d, J 10.0 Hz, 1H), 7.79 (dd, J 7.5
Hz, 2.0 Hz, 2H), 7.50-7.42 (m, 3H).
3
6
2
,4-Dinitrophenylhydrazone of p-chlorobenzaldehyde (15b): Reaction of p-chlorobenzyl alcohol 14b (36 mg,
0
.250 mmol) according to the general procedure afforded 2,4-dinitrophenylhydrazone of 15b (61-97%),
o
36
o
1
isolated as a light orange solid: mp 256.0-258.7 C (from ethanol) (lit, mp 264.0 C); H NMR (500 MHz,
DMSO-d ): δ 11.7 (s, 1H), 8.86 (d, J 0.3 Hz, 1H), 8.69 (s, 1H), 8.37 (dd, J 9.5 Hz, 0.3 Hz, 1H), 8.10 (d, J 9.5 Hz, 1H),
6
7
2
0
.81 (d, J 8.3 Hz, 2H), 7.55 (d, J 8.3 Hz, 2H).
3
7
,4-Dinitrophenylhydrazone of p-nitrobenzaldehyde (15c): Reaction of p-nitrobenzyl alcohol 14c (38 mg,
.250 mmol) according to the general procedure afforded 2,4-dinitrophenylhydrazone of 15c (13-39%),
o
37
o
1
isolated as a light orange solid: mp 293.5-295.0 C (from ethanol) (lit, mp 278.0-280.0 C); H NMR (500 MHz,
DMSO-d ): δ 11.8 (s, 1H), 8.88 (d, J 0.3 Hz, 1H), 8.81 (s, 1H), 8.42 (dd, J 9.8 Hz, 0.3 Hz, 1H), 8.32 (d, J 8.5 Hz, 2H),
6
8
.17 (d, J 9.8 Hz, 1H), 8.05 (d, J 8.5 Hz, 2H).
,4-Dinitrophenylhydrazone of cycloheptanone (15d): Reaction of cycloheptanol 14d (29 mg, 0.250 mmol)
2
4
2
according to the general procedure afforded 2,4-dinitrophenylhydrazone of 15d (29-52%), isolated as a yellow
o
24
o
1
solid: mp 146.8-148.3 C (from ethanol) (lit, mp 147.0-147.2 C); H NMR (500 MHz, CDCl ): δ 11.0 (s, 1H),
3
9
1
.13 (d, J 2.5 Hz, 1H), 8.30 (dd, J 9.8 Hz, 2.5 Hz, 1H), 7.99 (d, J 9.8 Hz, 1H), 2.68-2.52 (m, 4H), 1.94-1.80 (m, 2H),
.77-1.51 (m, 6H).
General procedure for chlorination of dibenzoylmethane 16 using (dichloroiodo)arenes
Dibenzoylmethane 16 (0.250 mmol) was added to a solution of ArICl (0.300 mmol) in dichloromethane (2 mL).
2
The reaction was stirred at room temperature for 24 h. After completion of the reaction, 5% aqueous Na S O
2 3
2
(5 mL) was added, and the mixture was extracted with dichloromethane. The organic phase was dried over
anhydrous Na SO and concentrated under reduced pressure. Purification by short column chromatography
2
4
(
hexane-ethyl acetate = 5 : 1) afforded analytically pure mono-chlorination product 17.
3
8
2
-Chloro-1,3-diphenylpropane-1,3-dione (17): Reaction of dibenzoylmethane 16 (56 mg, 0.250 mmol)
o
according to the general procedure afforded product 17 (57-97%), isolated as a yellow solid: mp 77.1-79.5 C
3
8
o
1
(from methylene chloride) (lit, mp 86.0-87.0 C); H NMR (500 MHz, CDCl ): δ 7.99 (d, J 8.0 Hz, 4H), 7.63-7.58
3
(m, 2H), 7.47 (t, J 7.8 Hz, 4H), 6.41 (s, 1H).
General procedure for chlorination of 1,4-dimethoxybenzene 18 using (dichloroiodo)arenes
,4-Dimethoxybenzene 18 (0.250 mmol) was added to a solution of (dichloroiodo)arene (0.300 mmol) in
1
dichloromethane (2 mL). The reaction was stirred at room temperature for 24 h. After completion of the
reaction, 5% aqueous Na S O (5 mL) was added, and the mixture was extracted with dichloromethane. The
2
2 3
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organic phase was dried over anhydrous Na SO and concentrated under reduced pressure. Purification by
2
4
short column chromatography (hexane-ethyl acetate = 10 : 1) afforded analytically pure mono-chlorination
product 19.
3
9
2
-Chloro-1,4-dimethoxybenzene (19): Reaction of 1,4-dimethoxybenzene 18 (35 mg, 0.250 mmol) according
1
to the general procedure afforded product 19 (47-84%), isolated as a yellow oil; H NMR (500 MHz, CDCl ): δ
3
6
.96 (d, J 3.0 Hz, 1H), 6.86 (d, J 9.0 Hz, 1H), 6.77 (dd, J 9.0 Hz, 3.0 Hz, 1H), 3.85 (s, 3H), 3.76 (s, 3H).
Recovery of 2-iodo-3-propoxypyridine 8
After completion of the reaction of benzyl alcohol 14a with reagent 9, 20% H SO (3.0-5.0 mL) was added. The
2
4
mixture was extracted with dichloromethane. Treatment of the organic layer according to general procedures
for oxidation of benzyl alcohol or chlorination afforded product 15a. To the aqueous layer 20% NaOH (5.0-7.0
mL) was added, and then the mixture was extracted with dichloromethane. The organic solution was dried
over anhydrous Na SO and concentrated in vacuum to give 2-iodo-3-propoxypyridine 8 (70 mg, 89%).
2
4
After completion of the reaction of 1,4-dimethoxybenzene 18 with reagent 9, 20% H SO (3.0-5.0 mL) was
2
4
added. The mixture was extracted with dichloromethane. Treatment of the organic layer according to general
procedures for chlorination of 1,4-dimethoxybenzene afforded product 19. To the aqueous layer 20% NaOH
(5.0-7.0 mL) was added, and then the mixture was extracted with dichloromethane. The organic solution was
dried over anhydrous Na SO and concentrated in vacuum to give 2-iodo-3-propoxypyridine 8 (67 mg, 85%).
2
4
Acknowledgements
This work was supported by a research grant from the NSF (CHE-1262479) and Tomsk Polytechnic University
VIU-316/2017).
(
Supplementary Material
NMR spectra of all reagents and products are given in the associated Supplementary Data File. The crystal data
files can be retrieved from the Cambridge Crystallography Data Center as CCDC numbers 1563656 (compound
7
) and 1563657 (compound 9).
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2
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Wirth, T.; Ed. Top. Curr. Chem. 2016, 373.
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Yoshimura, A.; Zhdankin, V. V. Chem. Rev. 2016, 116, 3328-3435.
https://doi.org/10.1021/acs.chemrev.5b00547
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Dohi, T.; Kita, Y. Curr. Org. Chem. 2016, 20, 580-615.
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