Efficient synthesis of β-substituted α-haloenones by rhodium(II)-catalyzed and thermal reactions of iodonium ylides

Article abstract of DOI:10.1039/b111206f

Rhodium(II)catalyzed and thermal reaction of iodonium ylides are described. Rhodium(II)-catalyzed reactions of iodonium ylides with benzyl halides and acid halides afforded α-chloro-α,β-enones and α-bromo-α,β-enones in good yields, whereas thermal reactions of iodonium ylides in a solvent such as benzene afforded α-iodo-α,β-enones in good yields.

Full text of DOI:10.1039/b111206f

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Efficient synthesis of ꢀ-substituted ꢁ-haloenones by rhodium(II)-
catalyzed and thermal reactions of iodonium ylides
Yong Rok Lee* and Yong Ug Jung
1
School of Chemical Engineering and Technology, College of Engineering, Yeungnam University,
Kyongsan 712-749, Korea
Received (in Cambridge, UK) 7th December 2001, Accepted 4th April 2002
First published as an Advance Article on the web 16th April 2002
Rhodium()-catalyzed and thermal reaction of iodonium ylides are described. Rhodium()-catalyzed reactions
of iodonium ylides with benzyl halides and acid halides afforded α-chloro-α,β-enones and α-bromo-α,β-enones in
good yields, whereas thermal reactions of iodonium ylides in a solvent such as benzene afforded α-iodo-α,β-enones
in good yields.
The strategy that we have developed begins with the reaction
Introduction
of iodonium ylides and halides (10-fold excess), which serve
as a solvent and a reactant, in the presence of 1 mol% of
Rh2(OAc)4. Reaction of iodonium ylides with benzyl halides
was examined first (Chart 1). When iodonium ylide 1 was
α-Haloenones are valuable and versatile intermediates in the
synthesis of α-carbon substituted enones1 and biologically
active natural products.2 α-Haloenones are typically prepared
by a halogenation–dehydrohalogenation reaction,3 an addition–
elimination reaction,4 and a halohydrin–dehydration reaction.5
Although many methods for the preparation of these com-
pounds have been developed, their synthetic exploitation has
been limited due to difficulty in handling and controlling
the regioselectivity, the strong acidic conditions, and the side
reactions involving over-oxidation.6 The necessity to overcome
these serious problems has prompted further research into
new methods for the preparation of α-haloenones. We have
discovered a facile method for the preparation of β-substituted
α-chloroenones starting from diazodicarbonyl compounds.7
We found that these reactions sometimes afforded β-substituted
α-chloroenones in low yields. Therefore, we have tried develop-
ing a more useful and efficient method for the preparation of
β-substituted α-haloenones.
Iodonium ylides are attractive and important reagents
in organic synthesis.8 Photochemical and metal-mediated
reactions of iodonium ylides with several substrates have
been widely studied by many groups.9 However, the rhodium-
catalyzed reaction of iodonium ylides with halides to prepare
β-substituted α-haloenones has not been investigated. We
report herein a new and efficient synthesis of β-substituted
α-haloenones starting from the corresponding iodonium ylides
with a variety of halides.
Chart 1
treated with benzyl chloride at room temperature for 12 h,
3-benzyloxy-2-chlorocyclohex-2-enone (5) was obtained as a
single compound in 81% yield. Support for the structural
assignment was obtained from spectroscopic analysis. α-Chloro-
enone 5 is identified by the IR carbonyl absorption of the enone
at 1657 cmϪ1 and the H NMR peak of the methylene group
1
of benzyl ether as a singlet at δ 5.24. Similarly, reaction
of iodonium ylides 2–4 with benzyl chloride afforded
α-chloroenones 6–8 in 92, 55, and 59% yields, respectively.
Under the same conditions, 4-methylbenzyl chloride afforded
α-chloroenone 9 in 50% yield, whereas 4-methoxybenzyl
chloride gave 10 and 11 in 85 and 75% yields, respectively.
When benzyl bromide was used, the expected 3-benzyloxy-2-
bromocyclohex-2-enones (12 and 13) were produced in 51 and
52% yields, respectively. The results are summarized in Fig. 1.
The formation of 8 can be explained in terms of a nucleo-
philic attack by the chloride of benzyl chloride. A plausible
mechanism is shown in Scheme 1. The iodonium ylide 4 first
gives a carbenoid 14 (or a carbene) by displacement of iodo-
benzene by Rh2(OAc)4.The intermediate 14 is attacked by the
chloride of benzyl chloride to give 15, which subsequently
undergoes intramolecular substitution to give product 8.
Results and discussion
Iodonium ylides 1–4 were prepared by reaction of the
corresponding 1,3-dicarbonyl compounds with iodobenzene
diacetate according to Koser’s method in 81, 86, 80, and 91%
yields.10 Iodonium ylides 1–4 are fairly stable and can be stored
in a refrigerator for a long time without any decomposition.
Reactions with acid halides were also examined (Chart 2).
Treatment of iodonium ylide 1 with AcCl at room temperature
DOI: 10.1039/b111206f
J. Chem. Soc., Perkin Trans. 1, 2002, 1309–1313
This journal is © The Royal Society of Chemistry 2002
1309

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Fig. 2
for 12 h afforded 3-acetoxy-2-bromo-5,5-dimethylcyclohex-2-
enone (24) in 40% yield. The results are summarized in Fig. 2.
Although the exact mechanism for the formation of 19 is still
not clear, it is best described as shown in Scheme 2. Two possible
intermediates 25 (chloronium ylide) and 27 (carbonyl ylide) can
be formed by the competitive nucleophilic attack of chloride
(path a) or oxygen (path b) on the electrophilic metal carbenoid
14. However, only compound 19 has been observed experi-
mentally, with no formation of the other possible product
28 being observed. A mechanism involving formation of a
chloronium ylide (path a) explains the formation of 19 from
metal carbenoid 14. Nucleophilic attack of the chloride on the
electrophilic carbenoid 14 yields intermediate 25, which under-
goes fast intramolecular nucleophilic addition of oxygen to the
carbonyl group with the cleavage of the C–Cl bond to give
product 19.
Fig. 1
Finally, thermal reactions of iodonium ylides in the absence
of Rh2(OAc)4, were investigated (Chart 3). Some evidence of
Scheme 1
Chart 3
this thermal rearrangement to give α-iodoenone is available
in the literature.11 We surveyed these reactions by using several
solvents such as THF, acetonitrile, and benzene for the
production of α-iodoenones. Tetrahydrofuran (reflux, 3 h) gave
only a low yield (20%) of 2-iodo-3-phenoxycyclohex-2-enone
(29), whereas acetonitrile (reflux, 3 h) and benzene (reflux, 3 h)
afforded 29 in 72 and 89% yields, respectively. We found that
benzene as a nonpolar solvent was more efficient than polar
solvents such as acetonitrile or THF for the preparation of
α-iodoenones. Other results from reactions in refluxing benzene
are summarized in Fig. 3.
Chart 2
for 12 h in the presence of 1 mol% of Rh2(OAc)4 gave
3-acetoxy-2-chlorocyclohex-2-enone (16) in 94% yield. The
structure of 16 is easily identified by the two IR carbonyl
absorptions at 1777 and 1693 cmϪ1 associated with a vinyl ester
and a ketone. The 1H NMR spectrum shows the peak of
the methyl group of the vinyl acetate at 2.26 ppm as a singlet.
Similarly, reaction of iodonium ylides 2–4 with AcCl afforded
the expected α-chloroenones 17–19 in 90, 91, and 92% yields,
respectively. In these cases, only a single product was seen and
no other products were found. When propionyl chloride was
used, α-chloroenones 20–23 were produced in 91–97% yields.
Extension of the reaction with AcBr was also successful.
Treatment of 2 with acetyl bromide at room temperature
Fig. 3
1310
J. Chem. Soc., Perkin Trans. 1, 2002, 1309–1313

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Scheme 2
In conclusion, rhodium-catalyzed reactions and thermal
1252, 1171, 1152, 1053, 1011, 943, 918, 900, 842; δH (300 MHz,
reactions of iodonium ylides offer a simple and facile method
for the synthesis of α-halo-α,β-unsaturated enones in good
yields. Further applications of these reactions are currently
being investigated in our laboratory.
CDCl3) 7.40–7.32 (5H, m, ArH), 5.23 (2H, s, CH2Ph), 2.51 (2H,
s, CH2), 2.34 (2H, s, CH2), 1.02 (6H, s, 2 × CH3).
4-Benzyloxy-3-chlorochromen-2-one (7). Reaction of 3 (364
mg, 1.0 mmol) and benzyl chloride (1.26 g, 10.0 mmol) afforded
7 (158 mg, 55%) as a liquid (Found: C, 66.70; H, 3.92.
C16H11ClO3 requires C, 67.03; H, 3.87%); νmax (neat)/cmϪ1 3067,
Experimental
3036, 1732 (C᎐O, ester), 1609, 1557, 1487, 1454, 1389, 1333,
᎐
All experiments were carried out under a nitrogen atmosphere.
Merck precoated silica gel plates (Art. 5554) with fluorescent
indicator were used for analytical TLC. Flash column chrom-
atography was performed using silica gel 9385 (Merck). Melting
points were determined with microcover glasses on a Fisher–
1275, 1206, 1161, 1098, 1036, 1003, 914, 860; δH (300 MHz,
CDCl3) 7.71–7.24 (9H, m, ArH), 5.54 (2H, s, CH2Ph).
3-Benzyloxy-2-chlorophenalen-1-one (8). Reaction of 4 (398
mg, 1.0 mmol) and benzyl chloride (1.26 g, 10.0 mmol) afforded
8 (189 mg, 59%) as a solid, mp 95–96 ЊC (from hexane–ethyl
acetate) (Found: C, 74.52; H, 4.39.C20H13ClO2 requires C,
1
Johns apparatus and are uncorrected. H NMR spectra were
recorded on a Bruker Model ARX (300 MHz) spectrometer.
13C NMR spectra were recorded on a Bruker Model ARX
(75 MHz) spectrometer in CDCl3 using 77.0 ppm as the solvent
chemical shift. IR spectra were recorded on a JASCO FTIR
5300 spectrophotometer. Elemental analyses and mass spectra
were carried out by Korea Basic Science Institute.
74.89; H, 4.08%); νmax (KBr)/cmϪ1 3030, 1647 (C᎐O, enone),
᎐
1561, 1453, 1406, 1372, 1310, 1221, 1204, 1144, 1094, 1026, 965,
937, 903, 864, 839; δH (300 MHz, CDCl3) 8.69 (1H, d, J 7.3,
ArH), 8.20 (1H, d, J 8.1, ArH), 8.06 (2H, dd, J 8.1, 7.3, ArH),
7.76 (1H, dd, J 7.8, 7.6, ArH), 7.60–7.52 (3H, m, ArH), 7.44–
7.34 (3H, m, ArH), 5.40 (2H, s, CH2Ph); m/z (EI) 320 (Mϩ, 9%),
285 (20), 284 (10), 230 (8), 201 (7), 173 (11), 164 (11), 146 (30),
129 (15), 91 (100), 71 (7), 65 (11).
General procedure for the synthesis of ꢁ-chloro- and
ꢁ-bromoenones
To a solution of iodonium ylide (1.0 mmol) and alkyl or acyl
halide (10.0 mmol) was added rhodium acetate (4.4 mg, 0.01
mmol) at room temperature under a N2 atmosphere. The reac-
tion mixture was stirred at room temperature for 12 h. The
excess alkyl or acyl halide was evaporated under reduced pres-
sure to give a residue. The residue was purified by flash column
chromatography on silica gel to give the product.
2-Chloro-5,5-dimethyl-3-(4-methylbenzyloxy)cyclohex-2-enone
(9). Reaction of 2 (342 mg, 1.0 mmol) and 4-methylbenzyl
chloride (1.41g, 10.0 mmol) afforded 9 (139 mg, 50%) as a solid,
mp 101–102 ЊC (from hexane–ethyl acetate) (Found: C, 69.15;
H, 6.99. C16H19ClO2 requires C, 68.93; H, 6.87%); νmax (KBr)/
cmϪ1 3032, 2959, 2932, 2890, 1649 (C᎐O, enone), 1586, 1460,
᎐
1408, 1362, 1306, 1248, 1221, 1173, 1049, 1015, 947, 918;
δH (300 MHz, CDCl3) 7.23 (2H, d, J 8.1, ArH), 7.18 (2H, d,
J 8.1, ArH), 5.19 (2H, s, CH2Ph ), 2.51 (2H, s, CH2), 2.34 (5H, s,
CH2 and CH3), 1.03 (6H, s, 2 × CH3); m/z (EI) 278 (Mϩ, 1%),
244 (2), 174 (3), 149 (5), 129 (8), 118 (8), 105 (100), 103 (16), 77
(22).
3-Benzyloxy-2-chlorocyclohex-2-enone (5). Reaction of 1
(314 mg, 1.0 mmol) and benzyl chloride (1.26 g, 10.0 mmol)
afforded 5 (192 mg, 81%) as a solid, mp 98–99 ЊC (from hexane–
ethyl acetate) (Found: C, 65.58; H, 5.20. C13H13ClO2 requires C,
65.97; H, 5.54%); νmax (KBr)/cmϪ1 3036, 2945, 2889, 1657 (C᎐O,
᎐
enone), 1589, 1458, 1368, 1294, 1262, 1192, 1154, 1080, 1026,
1007, 922, 905, 817; δH (300 MHz, CDCl3) 7.41–7.33 (5H, m,
ArH), 5.24 (2H, s, CH2Ph), 2.67 (2H, dd, J 6.2, 6.1, CH2), 2.48
(2H, dd, J 7.0, 6.2, CH2), 1.98 (2H, m, CH2); δC (75 MHz,
CDCl ) 191.88 (C᎐O), 171.14, 135.86, 129.33, 128.98, 128.05,
2-Chloro-3-(4-methoxybenzyloxy)cyclohex-2-enone
(10).
Reaction of 1 (314 mg, 1.0 mmol) and 4-methoxybenzyl
chloride (1.57 g, 10.0 mmol) afforded 10 (227 mg, 85%) as a
solid, mp 139–140 ЊC (from hexane–ethyl acetate) (Found: C,
62.72; H, 5.91. C14H15ClO3 requires C, 63.04; H, 5.67%); νmax
᎐
3
127.41, 127.13, 112.99, 71.03 (CH2Ph), 37.09 (CH2), 29.07
(CH2). 20.66 (CH2); m/z (EI) 236 (Mϩ, 10%), 146 (53), 120 (31),
118 (92), 91 (100), 89 (16), 65 (59).
(KBr)/cmϪ1 2957, 1649 (C᎐O, enone), 1582, 1514, 1453, 1416,
᎐
1368, 1327, 1294, 1260, 1173, 1071, 1011, 897; δH (300 MHz,
CDCl3) 7.27 (2H, d, J 8.6, ArH), 6.91 (2H, d, J 8.6, ArH), 5.16
(2H, s, CH2Ph), 3.80 (3H, s, OCH3), 2.68 (2H, m, CH2 ), 2.47
(2H, m, CH2), 2.00 (2H, m, CH2).
3-Benzyloxy-2-chloro-5,5-dimethylcyclohex-2-enone
(6).
Reaction of 2 (342 mg, 1.0 mmol) and benzyl chloride (1.26 g,
10.0 mmol) afforded 6 (244 mg, 92%) as a solid, mp 92–93 ЊC
(from hexane–ethyl acetate) (Found: C, 67.94; H, 6.72. C15H17-
ClO2 requires C, 68.05; H, 6.47%); νmax (KBr)/cmϪ1 3038, 2963,
2-Chloro-3-(4-methoxybenzyloxy)-5,5-dimethylcyclohex-2-
enone (11). Reaction of 2 (342 mg, 1.0 mmol) and 4-
methoxybenzyl chloride (1.57 g, 10.0 mmol) afforded 11 (221
2934, 2880, 1649 (C᎐O, enone), 1586, 1460, 1400, 1358, 1302,
᎐
J. Chem. Soc., Perkin Trans. 1, 2002, 1309–1313
1311

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mg, 75%) as a solid, mp 142–143 ЊC (from hexane–ethyl acetate)
8.73 (1H, dd, J 7.4, 1.2, ArH), 8. 25 (1H, dd, J 8.0, 1.1, ArH),
8.10 (1H, dd, J 8.2, 1.2, ArH), 7. 89 (1H, dd, J 7.4, 1.1, ArH),
7.80 (1H, dd, J 8.0, 7.4, ArH), 7.64 (1H, dd, J 8.2, 7.4, ArH),
(Found: C, 65.36; H, 6.82. C16H19ClO3 requires C, 65.19; H,
6.50%); νmax (KBr)/cmϪ1 2957, 1649 (C᎐O, enone), 1586, 1514,
᎐
1462, 1304, 1246, 1175, 1032, 945; δH (300 MHz, CDCl3) 7.27
(2H, d, J 8.6, ArH), 6.89 (2H, d, J 8.6, ArH), 5.16 (2H, s,
CH2Ph), 3.79 (3H, s, OCH3), 2.52 (2H, s, CH2), 2.35 (2H, s,
CH2), 1.03 (6H, s, 2 × CH3).
2.52 (3H, s, CH3); δC (75 MHz, CDCl ) 179.20 (C᎐O, enone),
᎐
3
167.05 (C᎐O, ester), 154.93, 136.37, 133.69, 132.48, 132.37,
᎐
128.61, 127.86, 127.58, 126.99, 125.63, 125.48, 124.40, 21.04
(CH3); m/z (EI) 272 (Mϩ, 10%), 230 (100), 292 (15), 196 (15),
173 (22), 155 (30), 138 (34), 129 (22), 105 (9), 87 (5), 71 (6), 57
(7).
3-Benzyloxy-2-bromocyclohex-2-enone (12). Reaction of 1
(314 mg, 1.0 mmol) and benzyl bromide (1.71 g, 10.0 mmol)
afforded 12 (143 mg, 51%) as a solid, mp 104–105 ЊC (from
hexane–ethyl acetate) (Found: C, 55.48; H, 4.85. C13H13BrO2
requires C, 55.54; H, 4.66%); νmax (KBr)/cmϪ1 3063, 3036, 2949,
2-Chloro-3-propanoyloxycyclohex-2-enone (20). Reaction of
1 (314 mg, 1.0 mmol) and propionyl chloride (925 mg,
10.0 mmol) afforded 20 (197 mg, 97%) as a liquid (Found: C,
53.22; H, 5.54. C9H11ClO3 requires C, 53.35; H, 5.47%);
2887, 1655 (C᎐O, enone), 1585, 1499, 1458, 1368, 1287, 1260,
᎐
νmax (neat)/cmϪ1 2946, 2888, 1770 (C᎐O, vinylic ester), 1694
1192, 1154, 1080, 1026, 987, 920, 904; δH (300 MHz, CDCl3)
7.38–7.33 (5H, m, ArH), 5.25 (2H, s, CH2Ph), 2.66 (2H, dd,
J 6.3, 6.1, CH2), 2.51 (2H, dd, J 6.8, 6.3, CH2), 1.99 (2H, m,
CH2).
᎐
(C᎐O, enone), 1628, 1460, 1424, 1345, 1277, 1167, 1115,
᎐
1076, 1017, 986, 841; δH (300 MHz, CDCl3) 2.64 (2H, t, J 5.9,
CH2), 2.57–2.48 (4H, m, 2 × CH2), 2.03 (2H, m, CH2),
1.19 (3H, t, J 6.0, CH3); δC (75 MHz, CDCl ) 191.33 (C᎐O,
᎐
3
enone), 169.78 (C᎐O, ester), 164.49, 121.85, 37.23, 29.91, 27.42,
20.15, 8.75.
᎐
3-Benzyloxy-2-bromo-5,5-dimethylcyclohex-2-enone
(13).
Reaction of 2 (342 mg, 1.0 mmol) and benzyl bromide (1.71 g,
10.0 mmol) afforded 13 (161 mg, 52%) as a solid, mp 102–103
ЊC (from hexane–ethyl acetate) (Found: C, 58.57; H, 5.91.
C15H17BrO2 requires C, 58.24; H, 5.54%); νmax (KBr)/cmϪ1 3063,
2-Chloro-5,5-dimethyl-3-propanoyloxycyclohex-2-enone (21).
Reaction of 2 (342 mg, 1.0 mmol) and propionyl chloride (925
mg, 10.0 mmol) afforded 21 (224 mg, 97%) as a liquid (Found:
C, 57.54; H, 6.44. C11H15ClO3 requires C, 57.27; H, 6.55%); νmax
(neat)/cmϪ1 2962, 2878, 1771 (C᎐O, vinylic ester), 1694 (C᎐O,
2957, 2872, 1667 (C᎐O, enone), 1589, 1462, 1352, 1292, 1244,
᎐
1171, 1038, 1001, 910; δH (300 MHz, CDCl3) 9.38–7.35 (5H, m,
ArH), 5.24 (2H, s, CH2Ph), 2.50 (2H, s, CH2), 2.38 (2H, s, CH2),
1.02 (6H, s, 2 × CH3).
᎐
᎐
enone), 1634, 1464, 1372, 1345, 1290, 1267, 1155, 1113, 1074,
1026, 947, 918, 850; δH (300 MHz, CDCl3) 2.55 (2H, q, J 6.0,
CH2), 2.54 (2H, s, CH2), 2.45 (2H, s, CH2), 1.22 (3H, t, J 6.0,
CH3), 1.11 (6H, s, 2 × CH3).
3-Acetoxy-2-chlorocyclohex-2-enone (16). Reaction of
1
(314 mg, 1.0 mmol) and acetyl chloride (785 mg, 10.0 mmol)
afforded 16 (177 mg, 94%) as a liquid (Found: C, 50.82; H, 5.14.
C8H9ClO3 requires C, 50.94; H, 4.81%); νmax (neat)/cmϪ1 2959,
3-Chloro-4-propanoyloxychromen-2-one (22). Reaction of 3
(364 mg, 1.0 mmol) and propionyl chloride (925 mg, 10.0
mmol) afforded 22 (243 mg, 96%) as a solid, mp 112 ЊC (from
hexane–ethyl acetate) (Found: C, 57.18; H, 3.69. C12H9ClO4
requires C, 57.05; H, 3.59%); νmax (KBr)/cmϪ1 3046, 2948, 1780
1777 (C᎐O, vinylic ester), 1693 (C᎐O, enone), 1630, 1427, 1371,
᎐
᎐
1352, 1281, 1169, 1065, 1007, 968, 912, 873, 845; δH (300 MHz,
CDCl3) 2.67 (2H, dd, J 6.2, 6.1, CH2), 2.59 (2H, dd, J 6.1, 5.1,
CH2), 2.26 (3H, s, CH3), 2.06 (2H, m, CH2); δC (75 MHz,
(C᎐O, vinylic ester), 1730 (C᎐O, ester), 1618, 1566, 1451, 1348,
᎐
᎐
CDCl ) 191.31 (C᎐O, enone), 166.15 (C᎐O, vinylic ester),
᎐
᎐
3
1283, 1262, 1105, 1065, 1015, 997, 877; δH (300 MHz, CDCl3)
7.58 (1H, dd, J 7.9, 7.7, ArH), 7.47 (1H, d, J 7.7, ArH),
7.39–7.28 (2H, m, ArH), 2.78 (2H, q, J 7.5, CH2), 1.35 (3H, t,
J 7.5, CH3); m/z (EI) 252 (Mϩ, 16%), 196 (31), 167 (5), 121 (37),
120 (21), 92 (13), 75 (6), 57 (100).
164.31, 121.97, 37.21, 29.84, 20.58, 20.13.
3-Acetoxy-2-chloro-5,5-dimethylcyclohex-2-enone
(17).
Reaction of 2 (342 mg, 1.0 mmol) and acetyl chloride (785 mg,
10.0 mmol) afforded 17 (195 mg, 90%) as a liquid (Found: C,
55.43; H, 6.24. C10H13ClO3 requires C, 55.54; H, 6.05%);
2-Chloro-3-propanoyloxyphenalen-1-one (23).7 Reaction of 4
(398 mg, 1.0 mmol) and propionyl chloride (925 mg, 10.0
mmol) afforded 23 (261 mg, 91%) as a solid, mp 146–147 ЊC
(from hexane–ethyl acetate); νmax (KBr)/cmϪ1 2963, 2932, 2874,
νmax (neat)/cmϪ1 2963, 2876, 1777 (C᎐O, vinylic ester), 1694
᎐
(C᎐O, enone), 1634, 1470, 1416, 1372, 1348, 1294, 1181, 1026,
᎐
947, 920, 856; δH (300 MHz, CDCl3) 2.54 (2H, s, CH2), 2.44
(2H, s, CH2), 2.25 (3H, s, CH3), 1.10 (6H, s, 2 × CH3); m/z
(EI) 216 (Mϩ, 5%), 174 (96), 159 (21), 149 (15), 129 (6), 118
(100), 103 (12), 83 (22), 55 (16).
1765 (C᎐O, vinylic ester), 1647 (C᎐O, enone), 1577, 1404, 1377,
᎐
᎐
1323, 1300, 1211, 1182, 1148, 1122, 1063, 965, 842, 820, 777;
δH (300 MHz, CDCl3) 8.69 (1H, d, J 7.5, ArH), 8.21 (1H, d,
J 8.0, ArH), 8.31 (1H, d, J 8.3, ArH), 7.84 (1H, d, J 7.4, ArH),
7.76 (1H, dd, J 8.0, 7.6, ArH), 7.61 (1H, dd, J 8.3, 7.4, ArH),
2.83 (2H, q, J 7.5, CH2), 1.38 (3H, t, J 7.5, CH3); m/z (EI) 286
(Mϩ, 12%), 230 (100), 196 (22), 173 (14), 155 (14), 129 (32), 112
(9), 71 (8), 57 (32).
4-Acetoxy-3-chlorochromen-2-one (18).7 Reaction of
(364 mg, 1.0 mmol) and acetyl chloride (785 mg, 10.0 mmol)
afforded 18 (217 mg, 91%) as a solid, mp 167–168 ЊC (from
hexane–ethyl acetate); νmax (KBr)/cmϪ1 3109, 3071, 3045, 1784
3
(C᎐O, vinylic ester), 1730 (C᎐O, ester), 1620, 1566, 1493, 1453,
᎐
᎐
1356, 1281, 1200, 1173, 1138, 1090, 1038, 1015, 1001, 903, 777,
734; δH (300 MHz, CDCl3) 7.59 (1H, dd, J 8.2, 7.5, ArH), 7.49
(1H, d, J 7.8, ArH), 7.39 (1H, d, J 8.2, ArH), 7.34 (1H, dd,
J 7.8, 7.5, ArH), 2.49 (3H, s, CH3); m/z (EI) 238 (Mϩ, 17%), 196
(100), 162 (9), 121 (71), 92 (13), 63 (6).
3-Acetoxy-2-bromo-5,5-dimethylcyclohex-2-enone (24). Reac-
tion of 2 (342 mg, 1.0 mmol) and acetyl bromide (1.23 g, 10.0
mmol) afforded 24 (104 mg, 40%) as a liquid (Found: C, 45.79;
H, 5.21. C10H13BrO3 requires C, 46.00; H, 5.02%); νmax (neat)/
cmϪ1 2965, 2874, 1777 (C᎐O, vinylic ester), 1690 (C᎐O, enone),
᎐
᎐
1626, 1470, 1416, 1370, 1290, 1179, 1123, 1013, 934, 912, 856;
δH (300 MHz, CDCl3) 2.51 (2H, s, CH2), 2.45 (2H, s, CH2), 2.24
(3H, s, CH2), 1.07 (6H, s, CH3).
3-Acetoxy-2-chlorophenalen-1-one (19). Reaction of 4 (398
mg, 1.0 mmol) and acetyl chloride (785 mg, 10.0 mmol)
afforded 19 (251 mg, 92%) as a solid, mp 195–198 ЊC (from
hexane–ethyl acetate) (Found: C, 65.95; H, 3.39. C15H9ClO3
General procedure for the synthesis of ꢁ-iodoenones
requires C, 66.07; H, 3.33%); νmax (KBr)/cmϪ1 2926, 1775 (C᎐O,
᎐
vinylic ester), 1640 (C᎐O, enone), 1574, 1404, 1368, 1323, 1225,
The iodonium ylide (1.0 mmol) was refluxed in benzene
᎐
1215, 1182, 1157, 1088, 1028, 1001, 960; δH (300 MHz, CDCl3)
(10 mL) for 3 h. After evaporation of the solvent, the residue
1312
J. Chem. Soc., Perkin Trans. 1, 2002, 1309–1313

View Article Online
was purified by flash column chromatography on silica gel to
give the product.
Acknowledgements
This work was supported by the Korea Research Foundation
Grant (KRF-2001–041–D00145). Dr Ronald Tepper is greatly
appreciated for his discussions on this work.
2-Iodo-3-phenoxycyclohex-2-enone (29).11 Reaction of 1 (314
mg, 1.0 mmol) in benzene afforded 29 (280 mg, 89%) as a solid,
mp 107–109 ЊC (from hexane–ethyl acetate); νmax (KBr)/cmϪ1
2953, 1655 (C᎐O, enone), 1568, 1487, 1418, 1316, 1233, 1186,
᎐
References
1142, 1069, 1022, 982, 966, 916; δH (300 MHz, CDCl3) 7.36 (2H,
dd, J 8.2, 7.4, ArH), 7.23 (1H, t, J 7.4, ArH), 7.04 (2H, d, J 8.2,
ArH), 2.58 (2H, dd, J 6.2, 6.1, CH2), 2.40 (2H, dd, J 6.1, 5.1,
CH2), 1.94 (2H, m, CH2); m/z (EI) 314 (Mϩ, 76%), 254 (13), 238
(100), 210 (82), 187 (25), 159 (22), 149 (6), 131 (25), 112 (42), 94
(34), 84 (53), 83 (51), 55 (77).
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2-Iodo-5,5-dimethyl-3-phenoxycyclohex-2-enone (30).12 Reac-
tion of 2 (342 mg, 1.0 mmol) in benzene afforded 30 (308 mg,
90%) as a solid, mp 158–162 ЊC (from hexane–ethyl acetate);
νmax (KBr)/cmϪ1 2963, 2932, 1661 (C᎐O, enone), 1580, 1487,
᎐
1454, 1372, 1343, 1294, 1229, 1192, 1138, 1073, 1024, 1001, 897;
δH (300 MHz, CDCl3) 7.39 (2H, dd, J 8.2, 7.4, ArH), 7.25 (1H,
t, J 7.4, ArH), 7.02 (2H, d, J 8.2, ArH), 2.47 (2H, s, CH2), 2.28
(2H, s, CH2), 1.03 (6H, s, 2 × CH3); m/z (EI) 342 (Mϩ, 100%),
286 (8), 215 (29), 193 (38), 159 (33), 131 (19), 122 (6), 103 (5), 94
(20), 77 (21), 67 (8), 51 (6).
3-Iodo-4-phenoxychromen-2-one (31). Reaction of 3 (364 mg,
1.0 mmol) in benzene afforded 31 (333 mg, 92%) as a solid, mp
124–126 ЊC (from hexane–ethyl acetate) (Found: C, 49.21; H,
2.56. C15H9IO3 requires C, 49.48; H, 2.49%); νmax (KBr)/cmϪ1
3074, 1736 (C᎐O, ester), 1591, 1555, 1483, 1447, 1337, 1246,
᎐
1209, 1161, 1082, 1034, 970, 889; δH (300 MHz, CDCl3)
7.58 (1H, dd, J 8.3, 7.2, ArH), 7.52 (1H, d, J 7.2, ArH),
7.42 (1H, d, J 8.3, ArH), 7.34 (2H, dd, J 8.1, 7.8, ArH), 7.18
(1H, dd, J 7.8, 7.5, ArH), 7.12 (1H, t, J 7.5, ArH), 6.94 (2H, d,
J 8.1, ArH).
2-Iodo-3-phenoxyphenalen-1-one (32). Reaction of 4 (398 mg,
1.0 mmol) in benzene afforded 32 (350 mg, 88%) as a solid, mp
183–184 ЊC (from hexane–ethyl acetate) (Found: C, 57.42; H,
2.66. C19H11IO2 requires C, 57.31; H, 2.78%); νmax (KBr)/cmϪ1
3065, 1638, 1572, 1553, 1489, 1402, 1312, 1225, 1209, 1165,
1152, 1074, 1024, 947; δH (300 MHz, CDCl3) 8.76 (1H, d, J 7.3
ArH), 8.25 (1H, d, J 8.1, ArH), 8.10 (1H, d, J 8.1, ArH), 7.99
(1H, d, J 7.3, ArH), 7.80 (1H, dd, J 8.0, 7.5, ArH), 7.53 (1H, dd,
J 8.0, 7.5, ArH), 7.31 (2H, dd, J 8.6, 7.5, ArH), 7.07 (1H, t,
J 7.5, ArH), 6.99 (2H, d, J 8.6, ArH); m/z (EI) 398 (Mϩ, 41%),
271 (100), 243 (15), 215 (17), 213 (12), 150 (34), 129 (63), 112
(18), 105 (14), 71 (17), 57 (22).
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J. Chem. Soc., Perkin Trans. 1, 2002, 1309–1313
1313