Synthesis of 2,3-dihydro-4H-furo[3,2-c] chromen-4-ones and 2,3-dihydronaphtho[2,3-b]furan-4,9-diones by the radical cyclizations of hydroxyenones with electron-rich alkenes using manganese(III) acetate

Article abstract of DOI:10.1080/00397910701845456

We have obtained dihydrofurans 3a-j in the radical cyclization of 4-hydroxycoumarin 1a and 2-hydroxy-1,4-naphtoquinone 1b with electron rich alkenes 2a-i by manganese(III) acetate. Methods A and B, which have different molar ratios were studied comparatively in these reactions, and we observed that method B (molar ratio 2:1:3) gave the best results. Treatment of 4-hydroxycoumarin 1a and electron rich alkenes 2a-e gave 2,3-dihydro-4H-furo[3, 2-c]chromen-4-ones 3a-e in 36-86% yields by the method B. Under the same conditions, the reactions of 2-hydroxy-1,4-naphtaquinone 1b with conjugated alkenes 2b and 2f-i afforded 2,3-dihydronaphtho[2,3-b]furan-4,9-diones 3f-j in an excellent yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701845456

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Synthesis of 2,3‐Dihydro‐4H‐furo[3,2‐c]
chromen‐4‐ones and
2,3‐Dihydronaphtho[2,3‐b]furan‐4,9‐diones
by the Radical Cyclizations of Hydroxyenones
with Electron-Rich Alkenes using
Manganese(III) Acetate
Mehmet Yılmaz a , Mehtap Yakut b & A. Tarık Pekel b
a Faculty of Arts and Sciences, Department of Chemistry, Kocaeli University,
Umuttepe Kocaeli, Turkey
b Science Faculty, Department of Chemistry, Ankara University, Ankara,
Turkey
Version of record first published: 22 Feb 2008.
To cite this article: Mehmet Yılmaz , Mehtap Yakut & A. Tarık Pekel (2008): Synthesis of
2,3‐Dihydro‐4H‐furo[3,2‐c] chromen‐4‐ones and 2,3‐Dihydronaphtho[2,3‐b]furan‐4,9‐diones by the
Radical Cyclizations of Hydroxyenones with Electron-Rich Alkenes using Manganese(III) Acetate, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 38:6,
914-927
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Synthetic Communicationsw, 38: 914–927, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701845456
Synthesis of 2,3-Dihydro-4H-furo[3,2-c]
chromen-4-ones and 2,3-
Dihydronaphtho[2,3-b]furan-4,9-diones by
the Radical Cyclizations of Hydroxyenones
with Electron-Rich Alkenes using
Manganese(III) Acetate
Mehmet Yılmaz,1 Mehtap Yakut,2 and A. Tarık Pekel2
1Faculty of Arts and Sciences, Department of Chemistry, Kocaeli
University, Kocaeli Turkey
2Science Faculty, Department of Chemistry, Ankara University, Ankara,
Turkey
Abstract: We have obtained dihydrofurans 3a–j in the radical cyclization of 4-hydro-
xycoumarin 1a and 2-hydroxy-1,4-naphtoquinone 1b with electron rich alkenes 2a–i
by manganese(III) acetate. Methods A and B, which have different molar ratios were
studied comparatively in these reactions, and we observed that method B (molar
ratio 2:1:3) gave the best results. Treatment of 4-hydroxycoumarin 1a and electron
rich alkenes 2a–e gave 2,3-dihydro-4H-furo[3,2-c]chromen-4-ones 3a–e in 36–86%
yields by the method B. Under the same conditions, the reactions of 2-hydroxy-1,4-
naphtaquinone 1b with conjugated alkenes 2b and 2f–i afforded 2,3-dihydro-
naphtho[2,3-b]furan-4,9-diones 3f–j in an excellent yields.
Keywords: 2,3-dihydronaphtho[2,3-b]furan-4,9-dione, hydroxyenone 2,3-dihydro-
4H-furo[3,2-c]chromen-4-one, manganese(III) acetate, oxidative addition, radical
cyclization
In the past two decades, the synthetic opportunities offered by high-
valent transition metal salt (Mn3þ, Ce4þ, Co3þ, Agþ, etc.) oxidation of 1,3-
Received in Poland 27, June 2007
Address correspondence to Mehmet Yılmaz, Faculty of Arts and Sciences,
Department of Chemistry, Kocaeli University, 41380 Umuttepe Kocaeli, Turkey.
E-mail: mehmet.yilmaz@kou.edu.tr
914

Radical Cyclizations of Hydroxyenones
915
dicarbonyl compounds in the presence of unsaturated systems have attracted
attention.[1,2] Among these metal salts, manganese(III) acetate[3–10] and
cerium(IV) ammonium nitrate (CAN)[11–13] have a prominent place and
have been used efficiently in the synthesis of new organic molecules by
forming a C-C bond.
We have reported the formation of dihydrofuran and furan derivatives as a
result of oxidative cyclizations of 1,3-dicarbonyl compounds with alkenes and
alkynes,[5,7] and the synthesis of 4,5-dihydrofuran and naphthalene derivatives
included carboxamide because of the reaction of 1,3-dicarbonyls with a,b-
unsaturated-amide[4]-mediated Mn(OAc)3. Previously, we described the
synthesis of 3-trifluoroacetyl-4,5-dihydrofurans and 3-[dihydrofuran-2(3H)-
ylidene]-1,1,1-trifluoroacetones by the treatment of trifluoromethyl-1,3-dicar-
bonyl compounds with conjugated alkenes.[8] We have also reported oxidative
cyclization of 3-oxopropanenitriles with alkenes, which gave 4,5-dihydro-
furan-3-carbonitriles containing heterocycles.[9]
2,3-Dihydro-4H-furo[3,2-c]chromen-4-ones such as fercoprolone,[14]
cyclobrachycoumarin,[15] and isoerlangefusciol[16] and 2,3-dihydronaphtho
[2,3-b]furan-4,9-dione as dehydroiso-a-lapachone[17] showed selective
activity toward DNA-repair-deficient yeast mutants widely distributed in
nature. Moreover, it is well known that many compounds containing these
skeleton structures show biological activities such as anticoagulant, insectici-
dal, anthelmintic, antifungal, and HIV protease inhibition activities.[18,19]
Thus, obtaining these compounds with high yields and improving new
synthetic methods are very important. Manganese (III) acetate (MAH),
which is a very good radical oxidant and which can be easily synthesized,
have not been used efficiently in the synthesis of these compounds.
Here, we have studied radical cyclization of various conjugated alkenes
using manganese (III) acetate obtained by electrochemical methods[20] with
4-hydroxycoumarin (1a) and 2-hydroxy-1,4-naphthoquinone (1b) in detail.
We have optimized reaction conditions such as temperature and different
molar ratios of reagents. As a result, we have obtained 2,3-dihydro-4H-
furo[3,2-c]chromen-4-ones (3a–e) and 2,3-dihydronaphtho[2,3-b]furan-4,9-
diones (3f–j) in very good yields, and these compounds were characterized
by spectroscopic techniques.
The radical cyclization of 4-hydroxycoumarin (1a) and 2-hydroxy-1,4-
naphthoquinone (1b) with electron-rich alkenes (2a–i) were performed
using methods A (1:1.5:2) and B (2:1:3) with different molar ratio
[1:2:Mn(OAc)3, respectively] under nitrogen at 1008C, in HOAc. All new
compounds purified by column chromatography or preparative thin-layer
1
chromatography (TLC) were characterized by infrared spectra (IR), H and
13C NMR, mass spectra (MS), and microanalysis, and the other products
1
were characterized by H NMR and MS.
The results of the reactions of 1a with 2a–e are given in Table 1. The
oxidative cyclization of 4-hydroxycoumarin (1a) with 1-phenylpropene (2a)
afforded 2,3-dihydro-4H-furo[3,2-c]chromen-4-one (3a) in 32% yield by

Table 1. Radical cyclization of 4-hydroxycoumarin 1a with electron-rich alkenes 2a–e
Product and yield (%)
Method Aa Method Bb
Entry
1
4-Hydroxycoumarin
Alkene
Dihydrofurocoumarin
3a, 32
3b, 65
3c, 71
50
81
86
2a
2
3
1a
1a
2b
2c

4
5
1a
1a
3d, 23
36
54
2d
3e, 45
2e
aMolar ratio is 1:1.5:2 [1:2:Mn(OAc)3, respectively], and yield of product is based on 1a.
bMolar ratio is 2:1:3 [1:2:Mn(OAc)3, respectively], and yield of product is based on the alkene.

918
M. Yılmaz, M. Yakut, and A. T. Pekel
method A. On the other hand, we obtained this product in 50% yield by
1
method B (in 30% yield by Agþ/Celite[21]). The H NMR spectra of 3a
show that the methyl and phenyl groups are in trans position because the
coupling constants between H-2 and H-3 protons of this compound are
Jtrans ¼ 7.3 Hz. It is reported that the coupling constants between these
protons in same structures are Jcis ¼ 8–9 Hz, in the literature.[22,23]
We got the best results in the reactions of 1a with the other alkenes by
manganese(III) acetate using method B. We obtained 3b in 81% yield in
the radical cylization of 2-phenyl-1-propene 1a with 2b by manganese(III)
acetate. Product 3b was obtained in lower yield (37%[21] and 46%[24] by
Ag/Celite and 62%[12] and 70%[25] by CAN in the different reaction
conditions).
The reaction of 1a with 1,1-diphenyl substituted (2c) and 1,2-diphenyl
substituted alkene 2d gave 2,3-dihydro-4H-furo[3,2-c]chromen-4-ones 3c
(86%) and 3d (36%) by method B. Treatment of 1a with isopropenyl
acetate (2e) gave 2-acetoxy-dihydrofurocoumarin derivative 3e in 54%
yield. Yet, this compound was obtained in 21% yield by CAN.[12]
The proposed reaction mechanism of 1a and 1b with alkenes is given in
Scheme 1. According to this mechanism, Mn(OAc)3 (MnL3) and hydroxy-
enone give manganese(III)–enolate complex A, and an a-carbon radical B
Scheme 1. Mechanism for the radical cyclizations of 1a and 1b with electron rich
alkenes.

Radical Cyclizations of Hydroxyenones
919
is formed on this structure while Mnþ3 is reduced to Mnþ2. A radical
intermediate product C is obtained in the addition of the a-carbon radical to
alkene. This product is oxidized to carbocation D with equivalent of
Mn(OAc)3. The intramolecular cyclization of D can produce angular
products H and I, and similarly the cyclization of E (the other enolic form
of D) can lead to lineer products F and G. 2,3-Dihydro-4H-furo[3,2-
c]chromen-4-one H and/or 2,3-dihydro-4H-furo[2,3-b]chromen-4-one F can
occur in the reaction of 1a with alkenes. These compounds were characterized
according to the chemical shift values of carbonyl groups in their 13C NMR
spectra. The chemical shift values of the carbonyl groups were found at
dC¼O 160–161 ppm as lactone carbonyls, so that isolated compounds are
2,3-dihydro-4H-furo[3,2-c]chromen-4-one H (3a–e). 2,3-Dihydro-4H-furo
[2,3-b]chromen-4-ones F were not obtained in the radical cyclization
of 1a with alkenes (2a–e). On the other hand, we obtained only 2,3-dihydro-
naphtho[2,3-b]furan-4,9-diones G (3f–j) in the treatment of 2-hydroxy-1,
4-naphthoquinone (1b) and alkenes, but 2,3-dihydronaphtho[1,2-b]furan-
4,5-diones I were not formed. As it is described in the literature, the structures
of G and I were determined on the basis of chemical shift values of carbonyl
groups.[11] Linear products are lemon yellow, and angular products are
orange.[26] Although angular products 3a–e were obtained in the reactions
of 1a with alkenes, linear products 3f–j were obtained in the treatments of
1b with alkenes. This situation can be explained in that the intramoleculer
cyclization of intermediate products D and E is carried out on the more
stable enolic form of hydroxyenones 1a and 1b.
As a result of the reaction of 2-hydroxy-1,4-naphthoquinone 1b with 2b
by CAN, it was occurred with both linear product 2-methyl-2-phenyl-2,3-dihy-
dronaphtho[2,3-b]furan-4,9-dione (3f, 38%) and angular product 2-methyl-2-
phenyl-2,3-dihydronaphtho[1,2-b]furan-4,5-dione (48%).[26] However, in this
study we obtained only linear products regioselectively in the radical cyclization
of 1b with alkenes by manganese(III) acetate, and all results are given in
Table 2. Product 3f was obtained using methods A and B in 69 and 93%
yields respectively in the treatment of 1b and 2b. The reactions of 1b and
alkenes of 1a and alkenes gave better results using method B.
For instance, 3g was formed in 95% yield in the treatment of 1b and 1, 1-
diphenylethylene 2f, and 2,3-dihydronaphtho[1,2-b]furan-4,5-diones 3h
and 3i were obtained in 98% yields in the reaction of 1b and both
2g and 2h. Compound 3j was obtained in 66% yield in the treatment of
1b and 1-phenylcyclohexene 2i, which are more sterically hindered than
2f–h.
In conclusion, we comparatively studied methods A and B in different
molar ratios in treatments of 4-hydroxycoumarin 1a and 2-hydroxy-1,4-
naphthoquinone 1b with electron-rich alkenes by Mn(OAc)3. As a result,
2,3-dihydro-4H-furo[3,2-c]chromen-4-ones 3a–e and 2,3-dihydronaphtho
[2,3-b]furan-4,9-diones 3f–j were obtained in very good yields by
method B.

Table 2. Radical cyclization of 2-hydroxy-1,4-naphthoquinone 1b with conjugated alkenes
Yield (%)
2-Hydroxy-1,4-
naphtoquinone
Entry
1
Alkene
Dihydrofuronaphthoquinone
Method Aa
Method Bb
93
3f, 69
2b
1b
1b
2
3
3 g, 73
3 h, 77
95
98
2f
1b
2g

4
1b
3i, 86
98
2h
2i
5
1b
3j, 54
66
aMolar ratio is 1:1.5:2 [1:2:Mn(OAc)3, respectively], and yield of product is based on 1b.
bMolar ratio is 2:1:3 [1:2:Mn(OAc)3, respectively], and yield of product is based on the alkene.

922
M. Yılmaz, M. Yakut, and A. T. Pekel
EXPERIMENTAL
Melting points were determined on a Gallencamp capillary melting-point
apparatus. IR spectra (KBr disc) were obtained with a Matson 1000 IR in
1
the 400–4000 cm21 range with 4 cm21 resolution. H NMR (400 MHz) and
13C NMR (100 MHz) spectra were recorded on a Bruker Avance DPX-
400 MHz and Varian Mercury-400 high-performance digital FT-NMR spec-
trophotometers. Mass spectra were measured on Shimadzu GC-17A/GC-
MS-QP5000 (EIMS, 70 eV) spectrophotometers. Elemental analyses were
performed on a Leco 932 CHNS-O instrument. TLC was performed on
Merck aluminium-packed silica-gel plates. Purification of products was
performed by column chromatography on silica gel (Merck silica gel 60,
40–63 mm) or preparative TLC on Merck silica gel (PF254–366nm). All
solvents and reagents were purchased from Merck.
General Procedure
Method A
A solution of manganese(III) acetate dihydrate (4 mmol, 1.10 g) in 20 mL in
glacial acetic acid was heated under a nitrogen atmosphere at 808C until it
dissolved. After Mn(OAc)3 dissolved completely, a solution of 1a–c
(2 mmol) and alkene (3 mmol) in 5 mL of acetic acid was added to this
mixture and the temperature was warmed to 1008C. The reaction was
complete when the dark brown color of the solution disappeared. Acetic
acid was evaporated under reduced pressure. Water was added to the
residue, and extraction was performed with CHCl3 (3 ꢀ 20 mL). The
combined organic extracts were neutralized with satd. NaHCO3 solution,
dried over anhydrous Na2SO4, and evaporated. Products were purified by
column chromatography on silica gel or preparative TLC (20 ꢀ 20-cm
plates, 2 mm thick) using n-hexane/EtOAc (1:1) as eluent.
Method B
The only difference with method A is that a 2:1:3 molar ratio [1:2:Mn(OAc)3,
respectively] was used.
Data
3-Methyl-2-phenyl-2,3-dihydro-4H-furo[3,2-c]chromen-4-one (3a).
Colorless solid, mp 73–748C (n-hexane–EtOAc), lit: 738C;[21] dH
(400 MHz, CDCl3) 7.63 (1H, dd, J ¼ 6.3, 1.5 Hz, ArH), 7.48 (1H, td,
J ¼ 8.6, 1.6 Hz, ArH), 7.35 (6H, m, ArH), 7.2 (1H, td, J ¼ 6.0, 0.9 Hz,
ArH), 5.54 (1H, d, J ¼ 7.3 Hz, H-2), 3.49 (1H, m H-3), 1.47 (3H, d,

Radical Cyclizations of Hydroxyenones
923
J ¼ 6.8 Hz, Me); m/z (EI, 70 eV) 279 (MHþ, 17), 278 (Mþ, 100), 263
(Mþ -CH3, 44), 187 (Mþ -PhCH2, 24), 158 (Mþ -PhCOCH2, 54), 121
(PhOCOþ, 54), 91 (PhCH2þ, 12), 77 (C6Hþ5 , 10), 65 (C5Hþ5 , 11).
2-Methyl-2-phenyl-2,3-dihydro-4H-furo[3,2-c]chromen-4-one (3b).
Colorless solid, mp 114–1168C (n-hexane–EtOAc), lit: 1058C (Et2O-
hexane);[12] dH (400 MHz, CDCl3) 7.71 (1H, dd, J ¼ 6.3, 1.5 Hz, ArH), 7.5
(1H, td, J ¼ 8.65, 1.59 Hz, ArH), 7.37–7.26 (7H, m, ArH), 3.35 (1H, d,
J ¼ 15.4 Hz, -CH2), 3.26 (1H, d, J ¼ 15.1 Hz, -CH2), 1.83 (3 H, s, Me); m/z
(EI, 70 eV) 279 (MHþ, 13), 278 (Mþ, 55), 263 (Mþ -CH3, 16), 184 (Mþ
PhOH, 40), 158 (Mþ -CH3COPh, 74), 121 (C7H5O2þ, 100), 91 (PhCHþ2 , 36),
77 (C6Hþ5 , 56), 65 (C5Hþ5 , 46).
3-Ethyl-2,2-diphenyl-2,3-dihydro-4H-furo[3,2-c]chromen-4-one (3c).
Colorless solid, mp 179–1818C (n-hexane–EtOAc), Found: C, 81.67; H,
5.31. C25H20O3 requires C, 81.50; H, 5.47%. nmax (KBr disc): 1729 (C55O),
1646 (C55C), 1201 (C-O-C), 995, 895, 756, cm21; dH (400 MHz, CDCl3)
7.9 (1H, dd, J ¼ 6.3, 1.5 Hz, H-9), 7.64 (2 H, dd, J ¼ 2.3, 1.5 Hz), 7.59
(1H, m, H-6), 7.40–7.28 (10H, m, ArH), 4.02 (1H, t, J ¼ 6.65 Hz, H-3),
1.65 (1H, m, -CH2), 1.49 (1H, m, -CH2), 0.75 (3H, t, J ¼ 7.4 Hz, Me); dC
(100 MHz, CDCl3) 165.5 (C-9b), 161.4 (C ¼ O, C-4), 144.5, 133.2 (C-7),
129.2, 128.7, 128.6, 127.6, 127.3, 124.7 (C-8), 123.5 (C-9), 117.6 (C-6),
113.5 (C-9a), 107.7 (C-3a), 100.9 (C-2), 49.6 (C-3), 24.8 (-CH2), 11.5
(Me); m/z (EI, 70 eV) 369 (MHþ, 20), 368 (Mþ, 78), 339 (Mþ -C2H5, 24),
325 (Mþ -CO2, 51), 290 (Mþ -C6H5, 3), 277 (Mþ -PhCH2, 7), 263 (Mþ
-
PhCO, 11), 206 (MHþ -C9H6O3, 18), 165 (Ph2Cþ, 100), 120 (C7H5Oþ2 , 78),
105 (PhCOþ, 33), 91 (PhCH2þ, 19), 77 (C6Hþ5 , 14), 65 (C5Hþ5 , 8).
2,3-Diphenyl-2-propyl-dihydro-4H-furo[3,2-c]chromen-4-one (3d). Pale
yellow oil. Found: C, 81.79; H, 5.66. C26H22O3 requires C, 81.65; H, 5.80%.
nmax (KBr disc, CHCl3): 1729 (C55O), 1648 (C55C), 1606, 1030 (C-O-C),
970 cm21; dH (400 MHz, CDCl3) 7.71 (1H, dd, J ¼ 8.8, 0.8 Hz, H-9), 7.63
(1H, td, J ¼ 8.0, 1.6 Hz, ArH), 7.43–7.25 (10 H, m, ArH), 4.72 (1H, s, H-3),
1.57 (2 H, m, -CH2), 1.38 (1H, m, -CH2), 0.97 (1H, m, -CH2), 0.69 (3 H, t,
J ¼ 7.2 Hz, Me); dC (100 MHz, CDCl3) 166.2 (C-9b), 160.0 (C55O, C-4),
155.6 (C-5a), 144.8, 136.7, 132.9 (C-7), 129.1, 128.9, 128.2, 127.8, 124.4,
124.3 (C-8), 123.1 (C-9), 117.4 (C-6), 112.8 (C-9a), 105.0 (C-3a), 100.0 (C-
2), 58.9 (C-3), 40.4 (-CH2), 17.6 (-CH2), 14.4 (Me); m/z (EI, 70 eV) 383
(MHþ, 15), 382 (Mþ, 31), 339 (Mþ -C3H7, 19), 291 (Mþ -PhCHþ2 , 26), 288
(Mþ -PhOHþ, 18), 262 (Mþ -PhOCOþ, 15), 251 (Mþ -C9H7O, 33), 189
(C11H9Oþ3 , 26), 131 (C9H7Oþ, 46), 121 (PhOCOþ, 86), 105 (PhCOþ, 45), 91
(PhCH2, 100), 77 (C6Hþ5 , 88), 65 (C5Hþ5 , 33), 43 (C3Hþ7 , 49).
2-Methyl-4-oxo-2,3-dihydro-4H-furo[3,2-c]chromen-2-yl acetate (3e).
Colorless solid, mp 170–1728C (n-hexane–EtOAc), lit: 177–1798C

924
M. Yılmaz, M. Yakut, and A. T. Pekel
(Et2O-DCM);[12] dH (400 MHz, CDCl3) 7.6 (1H, dd, J ¼ 9.4, 1.5 Hz, H-9), 7.5
(1H, td, J ¼ 8.7, 1.6 Hz, H-8), 7.3 (1H, d, J ¼ 8.2, H-7), 7.2 (1H, td, J ¼ 7.78,
1.0 Hz, H-6), 3.45 (1H, d, J ¼ 16.8 Hz, Ha-3), 3.1 (1H, d, J ¼ 16.8, Hb-3),
2.03 (3 H, s, Me), 1.88 (3 H, s, Me); m/z (EI, 70 eV) 261 (MHþ, 2), 260
(Mþ, 11), 219 (Mþ -CH3CO, 22), 201 (Mþ -Ac, 13), 200 (Mþ -HOAc, 49),
176 (Mþ -C4H6O2, 76), 121 (C7H5O2þ, 23), 91 (PhCHþ2 , 7), 77 (C6Hþ5 , 10),
43 (CH3COþ, 100).
2-Methyl-2-phenyl-2,3-dihydronaphto[2,3-b]furan-4,9-dione
(3f).
A
lemon-yellow solid, mp 166–1688C (n-hexane–EtOAc), lit: 112–1138C
(hexane);[26] dH (400 MHz, CDCl3) 8.13 (1H, dd, J ¼ 7.81, 1.95 Hz, C-8),
8.07 (1H, dd, J ¼ 7.42, 1.56 Hz, C-5), 7.71 (2H, m, ArH), 7.47 (2H, dt,
J ¼ 7.43, 1.56 Hz, ArH), 7.39 (2H, td, J ¼ 7.03, 1.09 Hz, ArH), 7.31 (1H,
tt, J ¼ 7.42, 1.18 Hz, ArH), 3.48 (1H, d, J ¼ 17.2 Hz, -CH2), 3.38 (1H, d,
J ¼ 17.2 Hz, -CH2), 1.88 (3 H, s, -Me).
2,2-Diphenyl-2,3-dihydronaphto[2,3-b]furan-4,9-dione (3g). A lemon-
yellow solid, mp 194–1968C (n-hexane–EtOAc). Found: C, 81.90; H, 4.42.
C24H16O3 requires C, 81.80; H, 4.58%. nmax (KBr disc): 1671 (C55O), 1641
(C55O), 1589, 1247 (C-O-C), 1197, 962, 700 cm21; dH (400 MHz, CDCl3)
8.13 (1H, dd, J ¼ 7.05, 1.39 Hz, C-8), 8.07 (1H, dd, J ¼ 7.6, 1.85 Hz, C-5),
7.73 (1H, td, J ¼ 7.43, 1.64 Hz, ArH), 7.71 (4H, td, J ¼ 7.18, 1.57 Hz,
ArH), 7.48 (4H, dd, J ¼ 8.47, 3.27 Hz, ArH), 7.38 (4H, td, J ¼ 8.2,
1.39 Hz, ArH), 7.28 (2H, m, ArH), 3.96 (2H, s, H-3); dc (100 MHz, CDCl3)
183.8 (C ¼ O, C-4), 178.7 (C55O, C-9), 159.6 (C-9a), 144.4, 135.0,
133.9 (C-6), 133.8 (C-4a), 132.5 (C-7), 129.4 (C-8a), 129.2, 129.1, 129.0,
127.2, 126.8, 126.5 (C-5), 126.2 (C-8), 124.5 (C-3a), 97.0 (C-2), 41.9 (C-3);
m/z (EI, 70 eV) 353 (MHþ, 1), 352 (Mþ, 5), 324 (Mþ -CO, 22), 307 (MHþ
-CO2, 17), 275 (Mþ -C6H5, 3), 247 (Mþ -PhCO, 5), 218 (C8H6Oþ2 , 3),
165 (Ph2Cþ, 100), 105 (PhCOþ, 62), 91 (PhCHþ2 , 5), 77 (C6Hþ5 , 78), 65
(C5Hþ5 , 7).
2,2-Bis(4-methylphenyl)-2,3-dihydronaphto[2,3-b]furan-4,9dione (3h). A
lemon-yellow solid, mp 163–1658C (n-hexane–EtOAc). Found: C, 81.81;
H, 5.18. C26H20O3 requires C, 82.08; H, 5.30%. nmax (KBr disc): 1683
(C55O), 1629 (C55O), 1247 (C-O-C), 1197, 955, 812, 719 cm21; dH
(400 MHz, CDCl3) 8.1 (2H, dd, J ¼ 10.92, 1.76 Hz, ArH), 7.74–7.67 (2H,
m, ArH), 7.35 (4H, td, J ¼ 8.28, 1.80 Hz, ArH), 7.17 (4H, d, J ¼ 7.96 Hz,
ArH), 3.91 (2H, s, -CH2), 2.35 (6H, s, Me); dc (100 MHz, CDCl3) 182.5
(C55O, C-4), 177.9 (C ¼ O, C-9), 158.9 (C-9a), 141.0, 138.2, 134.3 (C-6),
133.3 (C-7), 133.2 (C-4a), 132.0 (C-8a), 129.4, 126.5, 126.2 (C-5), 125.9
(C-8), 123.9 (C-3a), 96.8 (C-2), 41.7 (C-3), 21.2 (Me); m/z (EI, 70 eV) 381
(MHþ, 5), 380 (Mþ, 21), 352 (Mþ -CO, 29), 337 (MHþ -CO2, 19), 289
(Mþ -PhCH2, 7), 165 (Ph2Cþ, 24), 133 (C9H4O2þ, 18), 105 (PhCOþ, 60), 91
(PhCHþ2 , 51), 77 (C6H5þ, 50), 65 (C5Hþ5 , 31).

Radical Cyclizations of Hydroxyenones
925
2,2-Bis(4-fluorphenyl)-2,3-dihydronaphto[2,3-b]furan-4,9dione (3i). A
lemon-yellow solid, mp 143–1448C (n-hexane–EtOAc). Found: C, 74.05; H,
3.58. C24H14F2O3 requires C, 74.22; H, 3.63%. nmax (KBr disc): 1683
(C55O), 1643 (C55O), 1596, 1508, 1246 (C-O-C), 946, 839, 714, 571 cm21
;
dH (400 MHz, CDCl3) 8.04 (1H, dd, J ¼ 7.11, 1.29 Hz, H-8), 7.99 (1H, dd,
J ¼ 7.55, 1.76 Hz, H-5), 7.66 (1H, td, J ¼ 7.32, 1.55 Hz, ArH), 7.62 (1H, td,
J ¼ 7.36, 2.02 Hz, ArH), 7.35 (4H, dd, J ¼ 7.49, 1.43 Hz, ArH), 6.98 (4H,
td, J ¼ 7.2, 1.85 Hz, ArH), 3.81 (2H, s, H-3); dc (100 MHz, CDCl3) 183.2
1
(C ¼ O, C-4), 178.6 (C55O, C-9), 164.7–162.2 (d, JC-F ¼ 248.2 Hz), 159.3
4
(C-9a), 140.0 (d, JC-F ¼ 3.1 Hz), 135.1 (C-6), 134.0 (C-7), 133.7 (C-4a),
3
132.4 (C-8a), 128.5 (d, JC-F ¼ 8.3 Hz), 127.2 (C-5), 126.9 (C-8), 124.2 (C-
2
3a), 116.3 (d, JC-F ¼ 21.0 Hz), 96.6 (C-2), 42.1 (C-3); m/z (EI, 70 eV) 389
(MHþ, 2), 388 (Mþ, 8), 360 (Mþ -CO, 29), 216 (C14H10Fþ2 , 89), 201
(C13H9Fþ2 , 100), 120 (PhCOCH3þ, 8), 105 (PhCOþ, 78), 77 (C6Hþ5 , 26).
4a-Phenyl-1,2,3,4,4a,11b-hexahydro[b]naphtho[3,2-a]furan-6,11-dione (3j).
A lemon-yellow solid, mp 132–1348C (n-hexane–EtOAc). Found C, 79.75;
H, 5.64. C22H18O3 requires C, 79.98; H, 5.49%. nmax (KBr disc): 1677
(C55O), 1623 (C55O), 1592, 1201 (C-O-C), 947, 754, 719, 694 cm21; dH
(400 MHz, CDCl3) 8.12 (1H, dd, J ¼ 7.06, 2.18 Hz, H-6), 8.03 (1H, dd,
J ¼ 6.77, 1.83 Hz, H-7), 7.71 (1H, td, J ¼ 7.41, 1.63 Hz, ArH), 7.68 (1H,
td, J ¼ 7.13, 2.06 Hz, ArH), 7.5 (2H, dd, J ¼ 7.49, 1.43 Hz, ArH),
7.37 (2H, td, J ¼ 7.2, 1.85 Hz, ArH), 7.29 (1H, m, ArH), 3.77 (1H, t,
J ¼ 6.17 Hz, H-6), 2.29 (1H, m), 2.02 (2H, m, -CH2), 1.66 (4H, m, -CH2);
dc (100 MHz, CDCl3) 183.5 (C55O, C-6), 179.4 (C55O, C-11), 160.1
(C-11a), 146.0, 134.9 (C-8), 134.0 (C-6a), 133.7 (C-9), 132.4 (C-10a),
129.3, 129.1, 128.5, 127.0 (C-7), 126.7 (C-10), 125.2 (C-5b), 95.5 (C-1a), 45.9
(C-5a), 34.6 (-CH2), 25.7 (-CH2), 19.1 (-CH2), 18.9 (-CH2); m/z (EI, 70 eV)
331 (MHþ, 7), 330 (Mþ, 31), 302 (Mþ -CO, 13), 285 (Mþ-CO2, 13), 239 (Mþ
-PhCH2, 13), 226 (MHþ -PhCO, 7), 188 (C13H16Oþ, 23), 143 (Mþ -C13H16O,
45), 105 (PhCOþ, 57), 91 (PhCH2þ, 60), 77 (C6Hþ5 , 100), 65 (C5Hþ5 , 21), 55
(C4Hþ7 , 31), 43 (C3Hþ7 , 17).
ACKNOWLEDGMENT
This work was supported by a research grant from the Scientific and Technical
Research Council of Turkey (TBAG-2380, 103T124).
REFERENCES
1. Iqbal, J.; Bhatia, B.; Nayyar, N. K. Transition metal–promoted free-radical
reactions in organic synthesis: The formation of carbon–carbon bonds. Chem.
Rev. 1994, 94, 519–564.

926
M. Yılmaz, M. Yakut, and A. T. Pekel
2. Snider, B. B. Manganese(III)-based oxidative free-radical cyclizations. Chem. Rev.
1996, 96, 339–363.
3. Gregory, B.; Parsons, A. F.; Thomas, C. B. Manganese(III) acetate–mediated
radical reactions leading to araliopsine and related quinoline alkaloids. Tetrahe-
dron 2001, 57, 4719–4728.
4. Yilmaz, M.; Pekel, A. T. Regioselective synthesis of 5-carbamoyl-dihydrofurans
mediated manganese(III) acetate in acetic acid. Synth. Commun. 2001, 31,
2189–2194.
5. Yilmaz, M.; Pekel, A. T. Synthesis of benzofuran derivatives using manganese(III)
acetate mediated addition of b-dicarbonyl compounds to alkyne and alkenes—a
comparative study. Synth. Commun. 2001, 31, 3871–3876.
6. Yilmaz, M.; Bicer, E.; Pekel, A. T. Manganese(III) acetate–mediated free radical
cyclization of 1,3-dicarbonyl compounds with sterically hindered olefins. Turk. J.
Chem. 2005, 29, 579–587.
7. Alagoz, O.; Yilmaz, M.; Pekel, A. T. Free radical cyclization of 1,3-dicarbonyl
compounds mediated by manganese(III) acetate with alkynes and synthesis of tet-
rahydrobenzofurans, naphthalene and trifluoroacetyl substituted aromatic
compounds. Synth. Commun. 2006, 36, 1005–1013.
8. Yilmaz, M.; Pekel, A. T. Manganese(III) acetate mediated synthesis of 3-trifluor-
oacetyl-4,5-dihydrofurans and 3-(dihydrofuran-2(3H)- ylidene)-1,1,1-trifluoroace-
tones by free radical cyclization, part 1. J. Fluorine Chem. 2005, 126, 401–414.
9. Yilmaz, M.; Uzunalioglu, N.; Pekel, A. T. Manganese(III) acetate–based
oxidative cyclizations of 3-oxopropanenitriles with conjugated alkenes and
synthesis of 4,5-dihydrofuran-3-carbonitriles containing heterocycles. Tetrahe-
dron 2005, 61, 8860–8867.
¨
10. Burgaz, E. V.; Yilmaz, M.; Pekel, A. T.; Oktemer, A. Oxidative cyclization of
3-oxopropanenitriles with a,b-unsaturated amides by manganese(III) acetate.
Regio- and stereoselective synthesis of 4-cyano-2,3-dihydrofuran-3-carboxa-
mides. Tetrahedron 2007, 63, 7229–7239.
11. Nair, V.; Treesa, P. M.; Maliakal, D.; Rath, N. P. CAN Mediated oxidative
addition of 2-hydroxynaphthoquinone to dienes: a facile synthesis of naphthofur-
andiones. Tetrahedron 2001, 57, 7705–7710.
12. Kobayashi, K.; Sakashita, K.; Akamatsu, H.; Tanaka, K.; Uchida, M.; Uneda, T.;
Kitamura, T.; Morikawa, O.; Konishi, H. CAN Mediated formation of furopyra-
nones and furoquinolinones. Heterocycles 1999, 51, 2881–2892.
13. Kajikawa, S.; Nishino, H.; Kurosawa, K. Convenient construction of hexahydro-
benzo-[b]furan keleton containing heteroatoms: Choice of Mn(III)- and Ce(IV)-
based radical cyclization. Heterocycles 2001, 54, 171–183.
14. Miski, M.; Jakupovic, J. Cyclic and farnesyl-chromone derivatives from Ferula
communis subsp. Communis. J. Phytochemistry 1990, 29, 1995–1998.
15. Zdero, C.; Bohlmann, F.; King, R. M.; Robinson, H. Further 5-methyl coumarins
and other constituents from the subtribe mutisiinae. Phytochemistry 1986, 25,
509–516.
16. Rustalyan, A.; Nazarians, L.; Bohlmann, F. Two new 5-methyl coumarins from
Erlangea Fusca. Phytochemistry 1980, 19, 1254–1255.
17. Hoffmann, G.; Johnson, R. K. Bioactive furanonaphthoquinones from Crescentia
cujete. J. Nat. Prod. 1993, 56, 1500–1505.
18. Feuer, G In Progress in Medicinal Chemistry; Ellis, G. P., West, G. B. (Eds.);
North Holland Publishing Co.: North New York, 1974.
19. Deana, A. A. 2-(Aminomethyl)phenols, a new class of saluretic agents, 5: Fused-
ring analogues. J. Med. Chem. 1983, 26, 580–585.

Radical Cyclizations of Hydroxyenones
927
20. Guvenc, A.; Pekel, A. T.; Kockar, O. M. The experimental optimization of the
electrosynthesis of manganese(III) acetate in a bipolar packed-bed reactor.
Chem. Engineering J. 2004, 99, 257–263.
21. Lee, Y. R.; Kim, B. S.; Wang, H. C. Silver(I)/celite promoted oxidative cyclo-
addition of 4-hydroxycoumarin to olefins: A facile synthesis of dihydrofurocou-
marins and furocoumarins. Tetrahedron 1998, 54, 12215–12222.
22. Antonioletti, R.; Malancona, S.; Bovicelli, P. Diastereoselective synthesis of 4,5-
dihydrofurans by iodoenolcyclisation of 2-allyl-1,3-dicarbonyl compounds. Tetra-
hedron 2002, 58, 8825–8831.
23. Wu, A.; Cremer, D. Extension of the karplus relationship for NMR spin–spin
coupling constant to nonplanar ring systems: Pseudorotation of tetrahydrofuran.
Int. J. Mol. Sci. 2003, 4, 158–192.
24. Appendino, G.; Cravotto, G.; Palmisano, G.; Annunziata, R. Oxidative addition of
4-hydroxycoumarin to alkenes: an expeditious entry to 2,3-dihydro-4h-furo-[3,2-
c][1]benzopyran-4-ones. Synth. Commun. 1996, 26, 3359–3351.
25. Bar, G.; Bini, F.; Parsons, F. CAN mediated oxidative free radical reactions in an
ionic liquid. Synth. Commun. 2003, 33, 213–222.
26. Kobayashi, K.; Uneda, T.; Tanaka, K.; Mori, M.; Sakashita, K.; Tanaka, H.;
Morikawa, O.; Konishi, H. One-step synthesis of naphtofurandione benzofuran-
dione and phenalenofuranone derivatives by the CAN-mediated cycloaddition.
Bull. Chem. Soc. Jpn. 1998, 71, 1691–1697.