Synthesis of iodinated naphthoquinones using morpholine-iodine complex

Article abstract of DOI:10.1081/SCC-200030621

The efficient synthesis of 2-hydroxy-3-iodo-1,4-naphthoquinone (3), 2-amino-3-iodo-1,4-naphthoquinone (4), and 2-iodo-1,4-naphthoquinone (5) have been developed using the parent naphthoquinone in combination with the charge-transfer complex between iodine and morpholine.

Full text of DOI:10.1081/SCC-200030621

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Synthesis of Iodinated
Naphthoquinones Using
Morpholine‐Iodine Complex
Dr. Alice L. Perez a , G. Lamoureux a & A. Herrera
a
a Centro de Investigaciones en Productos Naturales
(CIPRONA) and Escuela de Química , Universidad
de Costa Rica , 2060, San Pedro, San José, Costa
Rica
Published online: 10 Jan 2011.
To cite this article: Dr. Alice L. Perez , G. Lamoureux & A. Herrera (2004) Synthesis
of Iodinated Naphthoquinones Using Morpholine‐Iodine Complex, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 34:18, 3389-3397, DOI: 10.1081/SCC-200030621
To link to this article: http://dx.doi.org/10.1081/SCC-200030621
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 18, pp. 3389–3397, 2004
Synthesis of Iodinated Naphthoquinones
Using Morpholine-Iodine Complex
*
Alice L. Perez, G. Lamoureux, and A. Herrera
Centro de Investigaciones en Productos Naturales (CIPRONA) and
´
Escuela de Quımica, Universidad de Costa Rica, Costa Rica
ABSTRACT
The efficient synthesis of 2-hydroxy-3-iodo-1,4-naphthoquinone (3),
2-amino-3-iodo-1,4-naphthoquinone (4), and 2-iodo-1,4-naphthoquinone
(5) have been developed using the parent naphthoquinone in combination
with the charge-transfer complex between iodine and morpholine.
Key Words: Iodination; Lawsone; Morpholine-iodine complex;
Naphthoquinones.
INTRODUCTION
Recently, iodinated arenes or heteroarenes have become some of the most
important intermediates in the synthesis of natural products or pharmaceutical
*
´
Correspondence: Dr. A. L. Perez, Escuela de Quımica, Universidad de Costa Rica,
´
2060, San Pedro, San Jose, Costa Rica; E-mail: alperez@cariari.ucr.ac.cr.
3389
DOI: 10.1081/SCC-200030621
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

3390
Perez, Lamoureux, and Herrera
drugs; for a review on the preparation and uses of iodoarenes, see Ref.[1]. For
example, iodobenzene derivatives can undergo carbon-carbon cross-coupling
reactions such as the Sonogashira,[2] Heck,[3] Stille,[4] and Suzuki[5] reactions
catalyzed by palladium. In these reactions, the presence of iodine facilitates
the palladium insertion into the C-X bond to a greater degree than bromine
or chlorine. However, the availability of iodinated arenes is limited by the
lower electrophilicity of iodine compared to the other halogens. Furthermore,
the preparation of iodinated compounds frequently requires the use of strong
acids (e.g., HNO3),[6] oxidizing agents (e.g., NaOCl),[7] or heavy metals salts
(e.g., Hg2þ),[8] which can create problems with sensitive substrates and com-
plicate the conditions of the reaction and during isolation of the product. More
expensive (and highly water-sensitive) reagents such as ICI,[9] diiodine pent-
oxide (I2O5),[10] and N-iodosuccinimide[11] have been developed for specific
iodinations.
We are interested in the synthesis of naphthoquinone compounds and have
been exploring the various carbon-carbon cross-coupling reactions to form
alkylated derivatives. Of the various iodination methods utilized for arenes,
several procedures were applied to the formation of halogenated naphtho-
quinones.a One reagent seemingly forgotten for this type of transformation is
the charge-transfer complex between morpholine and iodine.[12] In this report,
we present our results using this morpholine-iodine complex (2) for the efficient
and practical preparation of various iodinated naphthoquinones.
RESULTS AND DISCUSSION
The morpholine-iodine complex (prepared as an isolable solid[12a] or
in situ[12b,12d]) is known to react with activated arenes (phenols and aryl-
amines) to perform successful iodinations where other reagents fail.
However, only anhydrous organic solvents (alcohols, ether, benzene) have
been investigated up to this point due to the known instability of the
charge-transfer complex in the presence of water.[12a] We have discovered
that the reaction between lawsone (2-hydroxy-l,4-naphthoquinone, 1) and
the complex provides in good yield 2-hydroxy-3-iodo-l,4-naphthoquinone
(For previous synthesis of compound 3 (in lower field) see Ref.[13]), in a
variety of solvents (e.g., methanol, ethyl acetate, benzene). More interesting
is that the complex, if added in small portions over time, can be used in
aWe have found that naphthoquinones cannot be halogenated in high yields under
oxidative conditions (decomposition) nor in the presence of metal ions (formation of
chelates). The iodination does not go to completion using only elemental iodine
(even in large excess).

Synthesis of Iodinated Naphthoquinones
3391
water on the benchtop with no particular precautions to exclude oxygen from
the reaction flask. The iodination proceeds without concomitant decompo-
sition of the complex if the pH of the solution is basic. Since these conditions
are illustrative of “green chemistry,” we foresee the wide use of this reagent on
an industrial scale. The use of water appears to accelerate the reaction and pro-
vides the advantage of easy isolation: after acidification, the product precipi-
tates from the aqueous solution and can be filtered off. The importance of
2-hydroxy-3-iodo-l,4-naphthoquinone in the synthesis of naphtha[2,3-
b]furan-4,9-dione natural products has been demonstrated by Kobayashi
(see Fig. 1).[14]
The same procedure can be applied to the preparation in good yield of
2-amino-3-iodo1,4-naphthoquinone from aminonaphthoquinone. In this
case, the reaction is more heterogeneous due to the low solubility of amino-
naphthoquinones in aqueous solution. However, the work-up procedure is
equally facile: acidification of the aqueous solution allows the easy filtration
of the product away from the impurities (see Fig. 2).
We believe that in the charge-transfer complex the central iodine atom is
activated to nucleophilic attack. The pi-nucleophile (lawsone or amino-
naphthoquinone) attacks the activated electrophilic iodine faster than sigma-
nucleophiles, such as water (see Fig. 3).[15]
We were curious if the electrophilic nature of the iodine complex
extended to deactivated alkenes i.e., unsubstituted naphthoquinones (see
literature for the iodination of enones: (a) I2/ceric ammonium nitrate,[16a]
(b) I2/pyridine,[16b] (c) I2/bis(tetra-n, butylammmonium peroxydisulpha-
te,[16c] (d) I2/PhI(OCOCF3)2.[16d]). The morpholine-iodine complex has
been used with enones to form a,b-dimorpholinyl ketones, but naphtho-
quinones were not studied. See Ref.[17]. Specifically, the reaction between
1,4-naphthoquinone and the morpholine-iodine complex did not form any
iodination product in most solvents, including water. However, when an
excess of reagent (.2 equivalents) was used in refluxing dichloroethane,
the substrate was completely consumed and two products were formed:
2-morpholinyl-1,4-naphthoquinone and 2-iodo-1,4-naphthoquinone. (For pre-
vious syntheses of compound 5 (in lower yield), see Ref.[18]) (see Fig. 4).
Figure 1.

3392
Perez, Lamoureux, and Herrera
Figure 2.
The mechanism of this reaction is different from the reaction with acti-
vated naphthoquinones; we believe that the complex dissociates under the
conditions of the reaction, the morpholine reacts with the 1,4-naphthoquinone
in a Michael-like attack, and the enolate formed reacts with free iodine. From
this intermediate, a second equivalent of morpholine deprotonates either of the
a-protons to eliminate morpholine or iodide to provide either product.
Although a mixture is formed, the two products are easily separated by
column chromatography to provide both compounds in a pure state. We are
continuing to investigate this reaction to search for conditions that lead to a
higher selectivity. Albeit the limitations, at this point the indicated trans-
formations are the most direct and economical preparations of iodinated
naphthoquinones (see Fig. 5).
EXPERIMENTAL
The morpholine-iodine complex was prepared according to Ref.[12a] and
was stored in a desiccator protected from light. Lawsone and 1,4-naphthoqui-
none are commercial compounds and are used as received. 2-Amino-1,4-
naphthoquinone was prepared by the procedure of Couladouros.[19] NMR
spectra were recorded on a Varian 400-MHz spectrometer in CDCl3. All IR
spectra were recorded on a Perkin-Elmer Spectrum 1000.
Figure 3.

Synthesis of Iodinated Naphthoquinones
3393
Figure 4.
2-Hydroxy-3-iodo-1,4-naphthoquinone (3): To a mixture of lawsone
(174 mg, 1.00 mmol) and K2CO3 (420 mg, 3.00 mmol) in an Erlenmeyer
flask was added distilled water (10 mL). The dark red solution was stirred
at room temperature while the morpholine-iodine complex (425 mg,
1.25 mmol) was added in small portions every 15 min during 2 hr. The reaction
was stirred at room temperature for an additional hour and then the mixture
was filtered to remove any solids present. The filtrate was cooled in an ice
bath and then acidified with 25% H3PO4 until the pH was approximately 2.
At this point, the mixture was allowed to age (10–60 min) to eliminate any
complex remaining and to form a bright yellow precipitate. The solid was
filtered off and washed with cold H2O. The product was dried under
vacuum overnight to provide the desired hydroxyiodo product 3 (261 mg,
1
87%). This product was pure (.98%) by analysis of the H NMR spectrum
but can be recrystallized in glacial acetic acid and then dried to form analyti-
cally pure crystals. m.p. 1778C–1798C (lit. m.p.[13d] 1778C–1798C) UV
(EtOH): l 202, 252 (max), 285 (sh), 330, 404 nm IR: 3196 (br), 1671,
1646, 1621, 1579, 1293, 1258 (s), 1212, 1120, 999, 778, 718, 678 cm21
.
Figure 5.

3394
Perez, Lamoureux, and Herrera
1H-NMR: 8.14 (1H, dd, J ¼ 8.0, 2.0 Hz) H5/H8, 8.08 (1H, dd, J ¼ 8.0,
2.0 Hz) H5/H8, 8.04 (1H, bs) OH; 7.78 (1H, td, J ¼ 8.0, 2.0 Hz) H6/H7,
7.74 (1H, td, J ¼ 8.0, 2.0 Hz) H6/H7 13C-NMR: 178.75 (C4), 177.26 (C1),
159.51 (C2), 142.25 (C3), 135.12 (C6/C7), 133.44 (C6/C7), 131.77 (C4a/
C8a), 128.77 (C4a/C8a), 128.15 (CS/C8), 127.01 (CS/C8).
2-Amino-3-iodo-1,4-naphthoquinone (4): To a mixture of 2-amino-1,4-
naphthoquinone (246 mg, 2.00 mmol) and K2CO3 (829 mg, 6.00 mmol) in an
Erlenmeyer flask was added distilled water (20 mL). The orange suspension
was stirred at room temperature while the morpholine-iodine complex
(820 mg, 2.4 mmol) was added in small portions every 15 min during 2 hr.
The reaction was stirred at room temperature for an additional hour. The reac-
tion mixture was cooled in an ice bath and then acidified with 25% H3PO4
until the pH was approximately 4. The solid was filtered off, washed with
cold dilute NaHSO3 solution to remove any residual iodine, and finally
washed with cold H2O. The product was dried under vacuum overnight to
provide the desired aminoiodo product 4 (508 mg, 85%). This product was
pure (. 98%) by analysis of the 1H NMR spectrum but can be recrystallized
in distilled water and then dried to form analytically pure orange crystals. m.p.
2018C–2028C. UV (EtOH): l 202, 215, 230, 264 (max), 322 (sh), 456 nm IR:
3450, 3346, 1676, 1604 (s), 1577 (s), 1365, 1270 (s), 721, 677 cm21 1H-NMR:
8.16 (1 H, dd, J ¼ 2.4, 8.8 Hz) H5/H8, 8.07 (1 H, dd, J ¼ 2.4, 8.8 Hz) H5/H8,
7.71 (ddd, J ¼ 2.4, 8.8, 9.6 Hz) H6/H7, 7.66 (1 H, ddd, J ¼ 2.4, 8.8, 9.6 Hz)
H6/H7, 5.2 (2H, brs) NH2 13C-NMR: 177.44 (C4), 177.18 (C1), 151.20 (C2),
134.74 (C6/C7), 132.68 (C6/C7), 132.01 (C4a/C8a), 129.54 (C4a/C8a),
127.61 (C5/C8), 126.83 (C5/C8), 85.76 (C3).
2-Iodo-1,4-naphthoquinone (5): A solution of 1,4-naphthoquinone
(158 mg, 1.00 mmol) and dichloroethane (10 mL) in a round-bottomed
flask was heated to 608C under a nitrogen atmosphere to form a yellow
solution. The morpholine-iodine complex (1.02 g, 3.00 mmol) was added
and the red reaction mixture was heated to reflux for 1 hr. At this time,
analysis of the thin layer chromatography (TLC) indicated that there was
no naphthoquinone remaining. The reaction mixture was concentrated in
vacuo and the resulting residue was applied to the top of a silica chromato-
graphy column. Elution with toluene provided fractions of the iodo product
5 and then elution with toluene-ethyl acetate (4 : 1) provided fractions of the
morpholine product 6. The fractions containing 5 were combined and the
dissolvent was removed in vacuo to provide product contaminated by a
dark residue. Recrystallization from hexane provided analytically pure
iodonaphthoquinone (100 mg, 35%) as bright-orange crystals. m.p.
1198C–1208C (lit. m.p.[18a] 1198C–1208C) UV (EtOH): l 210 (max),
244, 288, 333 nm IR: 3048, 1651 (s), 1586 (s), 1567 (s), 1327, 1299 (s),
1247 (s), 1223, 1118, 910, 808, 777, 691, 666 cm21
.

Synthesis of Iodinated Naphthoquinones
3395
1H-NMR: 8.16–8.19 (1H, dd, J ¼ 8.0, 2.0 Hz) H5/H8, 8.07–8.10 (1H,
dd, J ¼ 8.0, 2.0 Hz) H5/H8, 7.79 (1H, td, J ¼ 8.0, 2.0 Hz) H6/H7, 7.75 (1
H, td, J ¼ 8.0, 2.0 Hz) H6/H7, 7.95 (1H, s) H3.
13C-NMR: 181.77 (C4), 178.52 (C1), 148.23 (C3), 134.17 (C6/C7),
133.82 (C6/C7), 131.59 (C4a/C8a), 129.54 (C4a/C8a), 128.05 (C5/C8),
126.88 (C5/C8), 122.91 (C2).
ACKNOWLEDGMENTS
´ ´
We are grateful to the Vicerrectorıa de Investigacion (UCR Project 809-
´
98-231) for financial support and to Ms. L. Hernandez (CIPRONA) for her
technical assistance.
REFERENCES
1. Merkushev, E.B. Advances in the synthesis of iodoaromatic compounds.
Synthesis 1988, 923–937.
2. (a) Sonogashira, K. Comprehensive Organic Synthesis; Trost, B.M.,
Fleming, L., Eds.; Pergamon Press: New York, 1991; Vol. 3, 521–549;
(b) Sonogashira, K. Metal-Catalyzed Cross-Coupling Reactions;
Diederich, F., Stang, P.J., Eds.; Wiley-VCH: Weinheim, Germany,
1998; 203–229.
3. Beletskaya, I.P.; Cheprakov, A.V. The heck reaction as a sharpening
stone of palladium catalysis. Chem. Rev. 2000, 100, 3009–3066.
4. Stille, J.K. The Stille Reaction. Farina V.; Krrshr Scott, W.J., Eds.; John
Wiley & Sons: New York, 1998.
5. Miyaura, N.; Suzuki, A. Palladium-catalyzed cross-coupling reactions of
organoboron compounds. Chem. Rev. 1995, 95, 2457–2483.
6. Dains, F.B.; Brewster, R.Q. Iodobenzene. In Organic Synthesis Collected,
Vol. 1; John Wiley and Sons: New York, 1932, 323–324.
7. Edgar, K.J.; Falling, S.N. An efficient and selective method for the prep-
aration of iodophenols. J. Org. Chem. 1990, 55, 5287–5291.
8. Orito, K.; Hatakeyama, T.; Takeo, M.; Suginome, H. Iodination of alkyl
aryl ethers by mercury(II) oxide-iodine reagent in dichloromethane.
Synthesis 1995, 1273–1277.
9. (a) Wariishi, K.; Morishima, S.; Inagaki, I. Facile synthesis of 1,4-
dialkoxy-2,5-diiodobenzenes: reaction of dialkoxybenzenes with iodine
monochloride in alcoholic solvent. Org. Process Res. Dev. 2003, 7,
98–100; (b) Hubig, S.M.; Jung, W.; Kochi, J.K. Cation radicals as inter-
mediates in aromatic halogenation with iodine monochloride: solvent and

3396
Perez, Lamoureux, and Herrera
salt effects on the competition between chlorination and iodination. J. Org.
Chem. 1994, 59, 6233–6244.
10. Brazdil, L.C.; Cutler, C.J. Selective production of diiodobenzene and
iodobenzene from benzene. J. Org. Chem. 1996, 61, 9621–9622.
11. (a) Castanet, A.-S.; Colobert, F.; Broutin, P.-E. Mild and regioselec-
tive iodination of electro-rich aromatics with N-iodosuccinimide and
catalytic trifluoroacetic acid. Tetrahedron Lett. 2002, 43, 5047–5048;
(b) Carren˜o, M.C.; Garcia Ruano, J.L.; Sanz, G.; Toledo, M.A.;
Urbano, A. Mild and regiospecific nuclear iodination of methoxybenzenes
and naphthalenes with N-iodosuccinimide in acetonitrile. Tetrahedron
Lett. 1996, 37, 4081–4084; (c) Olah, G.A.; Wang, Q.; Sandford, G.;
Prakash, G.K.S. Iodination of deactivated aromatics with N-iodosuccini-
mide in trifluoromethanesulfonic acid (NIS-CF3SO3H) via in situ gener-
ated superelectrophilic iodine(I) trifluoromethanesulfonate. J. Org.
Chem. 1993, 58, 3194–3195.
12. (a) Rice, R.V.; Beal, G.D. Morpholine periodide. US Patent 2,290,710,
July 21, 1942. (b) Chabrier, P.; Seyden-Penne, J.; Fouace, A.-M.
Compt. Rend. Acad. Sci. 1957, 245, 174; (c) Southwick, P.L.;
Kirchner, J.R. The morpholine-iodophenylacetylene adduct or charge-
transfer complex. Formation and conversion to N-styrylmorpholine.
J. Org. Chem. 1962, 27, 3305–3308; (d) Giza, C.A.; Hinman, R.L.
New thyroxine analogs. Halogen derivatives of 3-carbethoxy-5-
hydroxy-2-methylbenzofuran. J. Org. Chem. 1964, 29, 1453–1461.
13. (a) Kehrmann, R.; Mascioni, B. Ber. Dtsch. Chem. Ges. 1895, 28, 345;
(b) Courseille, C.; Geoffre, S.; Schvoerer, M. Crystal structure of
2-hydroxy-3-iodo-1,4 naphthoquinone. Compt. Rend. Acad. Sci. 1971,
273, 1633–1634; (c) Sharma, J.; Singh, P.K.; Singh, K.P.; Khanna, R.N.
Iodination of naphthoquinones and coumarin catalyzed by ceric
ammonium and mercuric nitrates. Org. Prep. Proced. Int. 1995, 27,
84–86; (d) Hatzigrigoriou, E.; Spyroudis, S.; Varvoglis, A. Derivatives
of 1,4-naphthoquinone via 3-(phenyliodonio)-1,2,4-trioxo-1,2,3,4-tetra-
hydronaphthalenide. Liebigs Ann. Chem. 1989, 167–170.
14. Kobayashi, K.; Uneda, T.; Kawakita, M.; Morikawa, O.; Konishi, H. One-
pot synthesis of naphtho[2,3-b]furan-4,9-diones by sequential coupling/
ring closure reactions. Tetrahedron Lett. 1997, 38, 837–840.
15. Mayr, H.; Kempf, B.; Ofial, A.R. p-Nucleophilicity in carbon–carbon
bond-forming reactions. Acc. Chem. Res. 2003, 36, 66–77.
16. (a) Zhang, F.; Li, Y. A new and efficient synthesis of 3-iodo derivatives of
flavones, thioflavones, and thiochromones. Chin. Chem. Lett. 1991, 2,
763–764; (b) Johnson, C.R.; Adams, J.P.; Braun, M.P.;
Senanayake, C.B.W.; Wovkulich, P.M.; Uskokovic, M.R. Direct
a-iodination of cycloalkenones. Tetrahedron Lett. 1992, 33, 917–918;

Synthesis of Iodinated Naphthoquinones
3397
(c) Bovonsombat, P.; Angara, G.J.; McNelis, E. Concerning the for-
mations of a-iodoenones. Tetrahedron Lett. 1994, 35, 6787–6790;
(d) Djuardi, E.; Bovonsombat, P.; McNelis, E. Formations of a-iodo-
enones by iodine and catalytic amounts of amines. Syn. Commun.
1997, 27, 2497–2503; (e) Whang, J.P.; Yang, S.G.; Kim, Y.H. Novel
a-iodination of functionalized ketones with iodine mediated by bis
(tetra-n-butylammonium) peroxydisulfate. J. Chem. Soc., Chem.
Commun. 1997, 1355–1356; (f) Benhida, R.; Blanchard, P.; Fourrey,
J.-L. A mild and effective iodination method using iodine in the presence
of bis-(trifluoroacetoxy)iodobenzene. Tetrahedron Lett. 1998, 39,
6849–6852.
17. (a) Southwick, P.L.; Christman, D.R. Reactions of unsaturated com-
pounds with iodine–amine complexes. I. Reactions of benzalaceto-
phenone and benzalacetone. J. Am. Chem. Soc. 1952, 74, 1886–1891;
(b) Southwick, P.L.; Christman, D.R. Reactions of iodine–amine com-
plexes with unsaturated compounds. II. An investigation of the scope of
the reaction with the iodine–morpholine complex. J. Am. Chem. Soc.
1953, 75, 629–632.
18. (a) Hodgson, H.H.; Elliott, R.L. J. Chem. Soc. 1935, 1850–1854;
(b) Gautier, J.; Hauw, C.; Housty, J.; Schvoerer, M. Molecular crystal
structure of 2-iodo-1,4-naphthoquinone. Compt. Rend. Acad. Sci. 1971,
273, 956–958; (c) Sharma, J.; Singh, P.K.; Singh, K.P.; Khanna, R.N.
Iodination of naphthoquinones and coumarin catalyzed by ceric
ammonium and mercuric nitrates. Org. Prep. Proced. Int. 1995, 27,
84–86.
19. Couladouros, E.A.; Plyta, Z.F.; Haroutounian, S.A.; Papageorgiou, V.
Efficient synthesis of aminonaphthoquinones and azidobenzohydro-
quinones: mechanistic considerations of the reaction of hydrazoic acid
with quinones. an overview. J. Org. Chem. 1997, 62, 6–10.
Received in the USA June 2, 2004