Regioselective arylation and alkynylation of 2,3-dibromo-1h-inden-1-one by Suzukii-Miyaura and Sonogashira cross-coupling reactions

Article abstract of DOI:10.1002/hlca.201100315

Suzukii-Miyaura reactions of 2,3-dibromo-1H-inden-1-one afforded a wide range of arylated 1H-inden-1-ones. Sonogashira cross-coupling reactions gave alkynylated indenones. The reactions proceeded with very good regioselectivity in the less sterically hind

Full text of DOI:10.1002/hlca.201100315

Helvetica Chimica Acta – Vol. 95 (2012)
469
Regioselective Arylation and Alkynylation of 2,3-Dibromo-1H-inden-1-one
by SuzukiꢀMiyaura and Sonogashira Cross-Coupling Reactions
by Rasheed Ahmad Kheraa)b), Munawar Hussaina), Nguyen Thai Hunga), Nadi Eleyaa),
Holger Feista), Alexander Villingera), and Peter Langer*a)c)
a) Institut fꢀr Chemie, Universitꢁt Rostock, Albert Einstein Strasse 3a, D-18059 Rostock
(phone: þ 49-381-4986410; fax: þ 49-381-4986412; e-mail: peter.langer@uni-rostock.de)
b) Department of Chemistry, Government College University Faisalabad, Pakistan
c) Leibniz-Institut fꢀr Katalyse an der Universitꢁt Rostock e.V., Albert Einstein Strasse 29a,
D-18059 Rostock
SuzukiꢀMiyaura reactions of 2,3-dibromo-1H-inden-1-one afforded a wide range of arylated 1H-
inden-1-ones. Sonogashira cross-coupling reactions gave alkynylated indenones. The reactions proceeded
with very good regioselectivity in the less sterically hindered and more electron-deficient position 3.
Introduction. – Functionalized indenones exhibit a wide spectrum of pharmaco-
logical applications [1]. Indenone-containing compounds constitute a novel and
interesting chemical class for the treatment of diabetes type 2. For example, compound
A has been reported to have a very good agonistic activity with an EC50 value of 50 nm
and shows a new binding mode in the co-crystal structure. Furthermore, nitrated
indenoisoquinolines have been revealed as potent topoisomerase I (Top1) inhibitors
[1][2].
Indenones have been synthetically available for many decades by intramolecular
FriedelꢀCrafts acylations and by various other established procedures [3]. Recently,
novel syntheses of indenones based on Pd-catalyzed cyclizations have been developed
[4]. An alternative approach involves regioselective functionalization reactions of
polybrominated indenones. For example, the reaction of 2,3-dibromo-1H-inden-1-one
with amines and C-nucleophiles was reported already many years ago [5]. Regiose-
lective Pd-catalyzed cross-coupling reactions have increasingly gained importance in
the last decade1). The selectivity of these reactions is generally influenced by electronic
and steric factors. Recently, we have reported the synthesis of 2,3-diaryl-1H-inden-1-
ones by regioselective SuzukiꢀMiyaura reactions of 2,3-dibromo-1H-inden-1-one [7].
Here, we report full details of these studies. With regard to our preliminary
1
)
For reviews of cross-coupling reactions of polyhalogenated heterocycles, see [6].
ꢂ 2012 Verlag Helvetica Chimica Acta AG, Zꢀrich

470
Helvetica Chimica Acta – Vol. 95 (2012)
communication, we have considerably extended the scope, and report, for the first time,
Sonogashira reactions which also proceed with excellent regioselectivity.
Results and Discussion. – The SuzukiꢀMiyaura reaction of 2,3-dibromo-1H-inden-
1-one (1) with arylboronic acids 2a – 2g (2.2 equiv.) afforded the 2,3-diaryl-1H-inden-1-
ones 3a – 3g, respectively, in 86 – 98% yield (Scheme 1 and Table 1). The reactions were
carried out by with Pd(PPh3)4 (5 mol-%) as the catalyst and K2CO3 (2m aq. soln.) as the
base. 1,4-Dioxane was used as the solvent, and the reactions were performed at 708 for
6 h. The reactions could be successfully carried out with both electron-rich and
electron-poor arylboronic acids. The yields were all excellent (> 95%). The presence of
a substituent in the ortho-position of the arylboronic acid resulted in a minor decrease
of the yield (e.g., 3d).
Scheme 1. Synthesis of 3a – 3g
i) 2 (2.2 equiv.), Pd(PPh3)4 (5 mol-%), 2m aq. K2CO3, dioxane, 708, 6 h.
Table 1. Synthesis of 3a – 3g
2,3
Ar
Yield [%] of the isolated product 3
a
b
c
d
e
f
Ph
97
98
95
86
98
97
96
4-MeꢀC6H4
4-FꢀC6H4
2-MeOꢀC6H4
3-MeOꢀC6H4
4-MeOꢀC6H4
3-FꢀC6H4
g
The SuzukiꢀMiyaura reaction of 1 with 1 equiv. of arylboronic acids 2b and 2e – 2l
afforded the 3-aryl-2-bromo-1H-inden-1-ones 4a – 4i, respectively, in excellent yields
and with very good regioselectivity (Scheme 2 and Table 2). The first attack occurred at
C(3) of 1. The temperature played an important role during the optimization, as a good
selectivity was achieved only at 458. At higher temperatures, the formation of a mixture
of starting material, and mono- and disubstituted products was observed. The reactions
of the highly reactive (electron rich) MeO-substituted arylboronic acids had to be
carried out at 408 instead of 458.
The structure of compound 4i was established by means of 1D- and 2D-NMR
(HMQC, NOESY, and HMBC) data (Fig. 1). The H-atoms of the 4-MeOꢀC6H4
moiety, HꢀC(2’,6’) (d(H) 7.60) showed a clear HMBC correlation with C(3) (d(C)
155.5) of the indenone part, but no correlation appeared with C(2) (d(C) 115.6),
indicating the connectivity of C(3) with C(1’). A key NOESY correlation of
HꢀC((2’,6’) (d(H) 7.60) with HꢀC(4) (d(H) 7.11) further established the position of

Helvetica Chimica Acta – Vol. 95 (2012)
Scheme 2. Synthesis of 4a – 4i
471
i) 2b, 2e – 2l (1.0 equiv.), Pd(PPh3)4 (3 mol-%), 2m aq. K2CO3, dioxane, 458, 4 h.
Table 2. Synthesis of 3-Aryl-2-bromo1H-inden-1-ones 4a – 4i
4
2
Ar
Yield [%] of the isolated product 4
a
b
c
d
e
f
g
h
i
b
h
i
g
j
k
l
e
f
4-MeꢀC6H4
4-EtꢀC6H4
98
93
89
83
4-tBuꢀC6H4
3-FꢀC6H4
4-CF3ꢀC6H4
2,6-(MeO)2C6H3
3,5-Me2C6H3
3-MeOꢀC6H4
4-MeOꢀC6H4
88
83a)
88
95a)
93a)
a) Reaction temperature: 408.
Fig. 1. HMQC (H-- ! C), NOESY (H $ H), and HMBC (H ! C)
correlations of 4i
the 4-MeOꢀC6H4 moiety at C(3). The structure of 4f was confirmed by an X-ray
crystal-structure analysis [7].
The one-pot reaction of 1 with two different arylboronic acids afforded the
unsymmetrically substituted 2,3-diaryl-1H-inden-1-ones 5a – 5i (Scheme 3 and Ta-
ble 3). The boronic acids were added in a sequential manner. The first step was carried
out at 458 (or at 408 in case of 2k, 2n, and 2o), and the second step was performed out at
708. All reactions proceeded in excellent yields.
The structures of 5d and 5i were independently confirmed by X-ray crystal-
structure analyses (Figs. 2 and 3)2).
The Sonogashira reaction of 1 with alkynes 6a – 6d (2.2 equiv.) gave the 2,3-
bis(alkynyl-alkynyl)-1H-inden-1-ones 7a – d in 89 – 94% yield (Scheme 4 and Table 4).
2
)
CCDC-869743 and -869744 contain all crystallographic details for 5d and 5i, respectively, which are
available free of charge via www.ccdc.cam.ac.uk/data_request/cif.

472
Helvetica Chimica Acta – Vol. 95 (2012)
Scheme 3. Synthesis of 5a – 5i
i) 1) Ar1B(OH)2 (1.0 equiv.), Pd(PPh3)4 (3 mol-%), 2m aq. K2CO3, dioxane, 458, 4 h. 2) Ar2B(OH)2
(1.1 equiv.), Pd(PPh3)4 (3 mol-%), 708, 6 h.
Table 3. Synthesis of 5a – 5i
5
2
Ar1
Ar2
Yield [%] of the isolated product 5
a
b
c
d
e
f
g
h
i
b,f
4-MeꢀC6H4
4-MeꢀC6H4
2,6-(MeO)2C6H3
4-MeꢀC6H4
2-MeOꢀC6H4
4-EtꢀC6H4
4-MeOꢀC6H4
3-ClꢀC6H4
4-FꢀC6H4
93
89
b,m
k,c
b,k
d,b
h,n
m,b
h,f
86a)
90
2,6-(MeO)2C6H3
4-MeꢀC6H4
4-ClꢀC6H4
4-MeC6H4
4-MeOꢀC6H4
Ph
85a)
83
3-ClꢀC6H4
79
93
87
4-EtꢀC6H4
j,a
4-CF3ꢀC6H4
a) Reaction temperature: 408.
Fig. 2. Crystal structure of 5d (50% probability level)

Helvetica Chimica Acta – Vol. 95 (2012)
473
Fig. 3. Crystal structure of 5i (50% probability level)
Scheme 4. Synthesis of 7a – 7d
i) 6a – 6d (2.2 equiv.), (i-Pr)2NH (1.5 equiv.), CuI (20 mol-%), [Pd(PPh3)2Cl2] (6 mol-%), DMF, 208,
30 min.
Table 4. Synthesis of 7a – 7d
7
6
R
Yield [%] of the isolated product 7
a
b
c
a
b
c
Ph
89
93
94
92
4-MeꢀC6H4
4-tBuꢀC6H4
Me(CH2)7
d
d
The reaction was carried out by using catalytic amounts of CuI (10 mol-%) and
[Pd(PPh3)2Cl2] (3 mol-%), and proceeded smoothly at room temperature, needing
only 30 min to completion. In the reaction, (i-Pr)2NH (1.5 equiv.) was used as the base.
The Sonogashira reaction of 1 with 1 equiv. of alkynes proved to be unsuccessful as
regioisomeric mixtures were formed.

474
Helvetica Chimica Acta – Vol. 95 (2012)
The reaction of 4e and 4i with 1 equiv. aliphatic or aromatic alkynes, 6a, 6c – 6e,
afforded the 2-(alkynyl)-3-aryl-1H-inden-1-ones 8a – 8d in 78 – 94% yield (Scheme 5
and Table 5).
Scheme 5. Synthesis of 8a – 8d
i) 6a, 6c – 6e (1.0 equiv.), (i-Pr)2NH (1.5 equiv.), CuI (10 mol-%), [Pd(PPh3)2Cl2] (3 mol-%), 208, 2 h.
Table 5. Synthesis of 8a – 8d
8
4
Ar
R
Yield [%] of the isolated product 8
a
b
c
e
i
e
i
4-CF3ꢀC6H4
4-MeOꢀC6H4
4-CF3ꢀC6H4
4-MeOꢀC6H4
Ph
93
94
92
78
4-tBuꢀC6H4
Me(CH2)7
6-Methoxynaphthalen-2-yl
d
Conclusions. – We have reported an efficient method for the synthesis of substituted
indenones by regioselective SuzukiꢀMiyaura reactions of 2,3-dibromo-1H-inden-1-
one (1). The regioselective formation of 4a – 4i and 5a – 5i can be explained by the
finding that the first attack in the Pd0-catalyzed cross-coupling reactions generally
occurs at the more electron-deficient and sterically less hindered position (Fig. 4).
Fig. 4. Possible explanation for the site-selectivity of
cross-coupling reactions of 1
Financial support from the State of Pakistan (HEC scholarships for R. A. K. and M. H.), from the
DAAD (scholarships for R. A. K. and N. T. H. ), from the State of Mecklenburg-Vorpommern
(scholarships for M. H.), from the Friedrich-Irmgard-Harms-Stiftung (scholarships for R. A. K.), and
from State of Vietnam (MOET scholarship for N. T. H.) is gratefully acknowledged.
Experimental Part
General. See [8].
General Procedure for the Synthesis of 3a – 3e and 4a – 4e (GP A). The reaction was carried out in a
pressure tube. To a suspension of 1 (144 mg, 0.5 mmol), Pd(PPh3)4 (2.5 – 3.0 mol-% per cross-coupling),
and boronic acid 2 (0.5 – 0.55 mmol per cross-coupling) in dioxane (5 ml), a 2m aq. K2CO3 soln. (1 ml)

Helvetica Chimica Acta – Vol. 95 (2012)
475
was added. The mixture was heated at the indicated temp. (40 – 708) under Ar for 4 – 6 h. The mixture was
diluted with H2O and extracted with CH2Cl2 (3 ꢁ 25 ml). The combined org. layers were dried (Na2SO4),
filtered, and the filtrate was concentrated in vacuo. The resulting residue was purified by column
chromatography (CC; silica gel, AcOEt/heptanes).
2,3-Diphenyl-1H-inden-1-one (3a). From 1 (144 mg, 0.50 mmol), Pd(PPh3)4 (29 mg, 5 mol-%),
dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and PhB(OH)2 (2a; 134 mg, 1.1 mmol), according to GP A;
reaction temp./time: 708/6 h. Yield: 137 mg (97%). Brownish yellow solid. M.p. 154 – 1558. IR (KBr):
1700, 1604, 1455, 1444, 1348, 1178, 1157, 1149, 999, 929, 858, 840, 807w, 780, 760, 751, 723, 699, 675, 637,
612, 587, 549s, 537m. 1H-NMR (300 MHz, CDCl3): 7.04 – 7.07 (m, 1 arom. H); 7.16 – 7.22 (m, 6 arom. H);
7.30 – 7.34 (m, 6 arom. H); 7.45 – 7.51 (m, 1 arom. H). 13C-NMR (62.9 MHz, CDCl3): 121.3, 123.0, 127.7,
128.1, 128.5, 128.8, 129.0, 129.3, 130.0 (CH); 130.8, 132.4, 132.7 (C); 133.4 (CH); 141.3, 145.2, 155.3 (C);
196.0 (C¼O). GC/EI-MS (70 eV): 282 (100, Mþ), 281 (82), 265 (16), 253 (39), 252 (47), 250 (18), 126
(12). HR-EI-MS (70 eV): 282.103409 (Mþ, C21H14Oþ; calc. 282.10392).
2,3-Bis(4-methylphenyl)-1H-inden-1-one (3b). From 1 (144 mg, 0.50 mmol), Pd(PPh3)4 (29 mg,
5 mol-%), dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and (4-MeꢀC6H4)B(OH)2 (2b; 150 mg, 1.1 mmol),
according to GP A; reaction temp./time: 708/6 h. Yield: 152mg (98%). Brownish yellow solid. M.p. 147 –
1488. IR (KBr): 3032, 2921w, 1706s, 1595, 1502, 1454, 1386, 1342, 1283, 1175, 1150, 973, 922, 851m, 806,
794s, 783m, 763, 727, 708s, 689, 644, 638, 623, 573, 540m. 1H-NMR (300 MHz, CDCl3): 2.23 (s, Me); 2.32
(s, Me); 6.98 – 7.29 (m, 11 arom. H); 7.46 – 7.49 (m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 21.3, 21.5
(Me); 121.1, 122.8 (CH); 128.0 (C); 128.5, 128.7, 128.9, 129.5, 129.9 (CH); 130.0, 131.0, 132.1 (C); 133.3
(CH); 137.5, 139.4, 145.5, 154.8 (C); 196.8 (C¼O). GC/EI-MS (70 eV): 310 (100, Mþ), 309 (21), 296 (15),
295 (61), 293 (9), 266 (11), 265 (20), 263 (10), 252 (18). HR-EI-MS (70 eV): 310.135147 (Mþ, C23H18Oþ;
calc. 310.13522).
2,3-Bis(4-fluorophenyl)-1H-inden-1-one (3c). From 1 (144 mg, 0.50 mmol), Pd(PPh3)4 (29 mg,
5 mol-%), dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and (4-FꢀC6H4)B(OH)2 (2c; 154 mg, 1.1 mmol),
according to GP A; reaction temp./time: 708/6 h. Yield: 151 mg (95%). Brownish yellow solid. M.p. 134 –
1358. IR (KBr): 1705, 1592, 1575, 1512m, 1498s, 1455, 1409, 1344, 1303m, 1220s, 1159, 1149, 1071, 924, 860,
838m, 824, 794, 768, 733, 708s, 680, 658, 630, 572m, 541s. 1H-NMR (300 MHz, CDCl3): 6.85 – 6.94 (m, 2
arom. H); 7.01 – 7.08 (m, 3 arom. H); 7.13 – 7.34 (m, 6 arom. H); 7.49 – 7.52 (m, 1 arom. H). 13C-NMR
(75.5 MHz, CDCl3): 115.3 (d, J(C,F) ¼ 21.5, CH); 116.2 (d, J(C,F) ¼ 21.5, CH); 121.1, 123.2 (CH); 126.6
(d, J(C,F) ¼ 3.4, C); 128.5 (d, J(C,F) ¼ 3.6, C); 129.2 (CH); 130.5 (d, J(C,F) ¼ 8.3, CH); 131.5 (C); 131.8
(d, J(C,F) ¼ 8.3, CH); 133.6 (CH); 144.9, 154.1 (C); 162.4 (d, J(C,F) ¼ 48.4, CF); 163.2 (d, J(C,F) ¼ 250.3,
CF); 196.2 (C¼O). 19F-NMR (282.4 MHz, CDCl3): ꢀ 113.0, ꢀ 158.4 (ArF). GC/EI-MS (70 eV): 318
(100, Mþ), 317 (53), 301 (14), 289 (19), 288 (36), 270 (6), 268 (9). HR-EI-MS (70 eV): 318.085333 (Mþ;
C21H12F2Oþ; calc. 318.08507).
2,3-Bis(2-methoxyphenyl)-1H-inden-1-one (3d). From 1 (144 mg, 0.50 mmol), Pd(PPh3)4 (29 mg,
5 mol-%), dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and (4-MeOꢀC6H4)B(OH)2 (2d; 167 mg,
1.1 mmol), according to GP A; reaction temp./time: 708/6 h. Yield: 149 mg (86%). Brownish yellow
solid. M.p. 121 – 1228. IR (KBr): 3078, 3012, 2938, 2843, 1707s, 1606m, 1571s, 1475m, 1429s, 1333m, 1280,
1231s, 1177m, 1127, 1045s, 953, 877, 790m, 768, 726, 707, 695, 683s, 598, 560m. 1H-NMR (300 MHz,
CDCl3): 3.42 (s, MeO); 3.54 (s, MeO); 6.72 – 6.91 (m, 5 arom. H); 7.01 – 7.28 (m, 6 arom. H); 7.44 – 7.48
(m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 55.1, 55.2 (MeO); 111.0, 111.1, 120.3, 120.5 (CH); 120.2
(C); 121.5, 122.5 (CH); 123.0 (C); 128.3, 129.1, 129.2, 130.3 (CH); 131.0 (C); 131.1 (CH); 132.5 (C); 133.1
(CH); 145.6, 154.8, 156.8, 157.4 (C); 196.2 (C¼O). GC/EI-MS (70 eV): 342 (100, Mþ), 312 (18), 311 (12),
281 (9), 255 (16), 252 (9), 239 (15), 234 (16), 226 (58), 207 (58). HR-EI-MS (70 eV): 342.125581 (Mþ,
C23H18Oþ3 ; calc. 342.12559).
2,3-Bis(3-methoxyphenyl)-1H-inden-1-one (3e). From 1 (144 mg, 0.50 mmol), Pd(PPh3)4 (29 mg,
5 mol-%), dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and (3-MeOꢀC6H4)B(OH)2 (2e; 167 mg,
1.1 mmol), according to GP A; reaction temp./time: 708/6 h. Yield: 167 mg, (98%). Brownish yellow
solid. M.p. 141 – 1428. IR (KBr): 3079, 3012, 2960, 2939, 2916, 2843, 2831w, 1708s, 1606, 1595m, 1572s,
1476, 1454, 1446m, 1429s, 1333, 1290m, 1280, 1231s, 1194, 1178, 1162m, 1128s, 995, 969, 954, 903, 887, 878,
872, 846, 791m, 769s, 726, 708, 695, 683, 675s, 626, 639, 599, 560, 542m. 1H-NMR (300 MHz, CDCl3): 3.57
(s, MeO); 3.63 (s, MeO); 6.69 – 6.90 (m, 7 arom. H); 7.05 – 7.30 (m, 4 arom. H); 7.46 – 7.50 (m, 1 arom. H).

476
Helvetica Chimica Acta – Vol. 95 (2012)
13C-NMR (75.5 MHz, CDCl3): 55.1, 55.3 (MeO); 113.7, 114.1, 115.0, 115.1, 120.8, 121.4, 122.5, 123.0, 129.0,
1291, 130.0 (CH); 130.7, 132.0, 132.3 (C); 133.5 (CH); 134.0, 145.2, 155.4, 159.2, 159.8 (C); 196.3 (C¼O).
GC/EI-MS (70 eV): 342 (100, Mþ), 327 (11), 311 (20), 284 (10), 268 (12), 239 (16), 226 (14), 207 (10).
HR-EI-MS (70 eV): 342.124291 (Mþ, C23H18O3þ ; calc. 342.12505).
2,3-Bis(4-methoxyphenyl)-1H-inden-1-one (3f). From with 1 (144 mg, 0.50 mmol), Pd(PPh3)4
(29 mg, 5 mol-%), dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and (4-MeOꢀC6H4)B(OH)2 (2f;
167 mg, 1.1 mmol), according to GP A; reaction temp./time: 708/6 h. Yield: 166 mg (97%). Brownish
yellow solid. M.p. 94 – 958. IR (KBr): 3000, 2955, 2835w, 1697, 1603, 1500s, 1454, 1342, 1291m, 1243, 1172s,
1
1071m, 1026s, 907, 854, 818, 797, 765m, 732s, 682, 647, 581, 531m. H-NMR (300 MHz, CDCl3): 3.69 (s,
MeO); 3.75 (s, MeO); 6.72 (d, J ¼ 8.9, 2 arom. H); 6.84 (d, J ¼ 8.9, 2 arom. H); 7.06 (d, J ¼ 7.2, 1 arom. H);
7.12 – 7.18 (m, 3 arom. H); 7.22 – 7.28 (m, 3 arom. H); 7.42 – 7.46 (m, 1 arom. H). 13C-NMR (62.9 MHz,
CDCl3): 55.2, 55.3 (MeO); 113.7, 114.2, 121.0, 122.7 (CH); 123.4, 125.1 (C); 128.6, 130.2 (CH); 131.0,
131.2 (C); 131.3, 133.3 (CH); 145.5, 153.8, 159.1, 160.3 (C); 196.9 (C¼O). GC/EI-MS (70 eV): 342 (100,
Mþ), 327 (14), 239 (9), 226 (10). HR-EI-MS (70 eV): 342.125095 (Mþ, C23H18Oþ3 ; calc. 342.12559).
2,3-Bis(3-fluorophenyl)-1H-inden-1-one (3g). From 1 (144 mg, 0.50 mmol), Pd(PPh3)4 (29 mg,
5 mol-%), dioxane (5 ml), 2m aq. K2CO3 soln. (1 ml), and (3-FꢀC6H4)B(OH)2 (2g; 154 mg, 1.1 mmol),
according to GP A; reaction temp./time: 708/6 h. Yield: 152 mg (96%). Brownish yellow solid. M.p. 124 –
1258. IR (KBr): 3065, 2961w, 1702, 1610m, 1580, 1475, 1455, 1437, 1339, 1266, 1243, 1220, 1184, 1170, 1157,
1
1125, 973, 930, 890, 859, 797m, 776, 763, 725, 706, 690s, 682, 639, 596, 583, 559m. H-NMR (300 MHz,
CDCl3): 6.83 – 7.08 (m, 7 arom. H), 7.58 – 7.36 (m, 4 arom. H), 7.49 – 7.52 (m, 1 arom. H). 13C-NMR
(75.5 MHz, CDCl3): 114.1 (d, J(C,F) ¼ 21.3, CH); 114.4 (d, J(C,F) ¼ 22.3, CH); 115.5 (d, J(C,F) ¼ 21.1,
CH); 115.8 (d, J(C,F) ¼ 22.2, CH); 120.4, 122.4 (CH); 123.2 (d, J(C,F) ¼ 3.3, CH); 124.7 (d, J(C,F) ¼ 3.0,
CH); 128.5 (CH); 129.3 (C); 128.7 (d, J(C,F) ¼ 8.4, CH); 130.6 (d, J(C,F) ¼ 2.2, C); 129.8 (d, J(C,F) ¼
8.4, CH); 131.4 (d, J(C,F) ¼ 8.3, C); 132.8 (CH); 133.4 (d, J(C,F) ¼ 8.0, C); 143.5 (C); 153.6 (d, J(C,F) ¼
1.9, C); 161.6 (d, J(C,F) ¼ 245.2, CꢀF); 161.9 (d, J(C,F) ¼ 247.5, CꢀF); 194.5 (C¼O). 19F-NMR
(282.4 MHz, CDCl3): ꢀ 112.8, ꢀ 111.3. GC/EI-MS (70 eV): 318 (100, Mþ), 317 (49), 301 (14), 289 (30),
288 (36), 270 (11), 268 (12). HR-EI-MS (70 eV): 318.085575 (Mþ, C21H12F2Oþ; calc. 318.08507).
2-Bromo-3-(4-methylphenyl)-1H-inden-1-one (4a). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4 (18 mg,
3 mol-%), and 2b (68 mg, 0.5 mmol), according to GP A; reaction temp.: 458. Yield: 146 mg (98%).
White yellow solid. M.p. 119 – 1208. IR (KBr): 3022, 2919, 2855w, 1711s, 1599, 1504, 1450, 1362, 1284,
1182, 1099, 1020, 918, 832, 797m, 755, 701s, 669, 629, 569. 1H-NMR (300 MHz, CDCl3): 2.37 (s, Me); 7.08
(dt, J ¼ 7.2, 1.0, 1 arom. H); 7.18 (td, J ¼ 7.9, 1.1, 1 arom. H); 7.24 – 7.29 (m, 3 arom. H); 7.45 – 7.51 (m, 3
arom. H). 13C-NMR (75.5 MHz, CDCl3): 21.6 (Me); 117.4 (C); 121.3, 123.6 (CH); 128.2 (C); 128.3, 128.9,
129.5 (CH); 130.1 (C); 133.7 (CH); 140.8, 144.6, 157.0 (C); 189.9 (C¼O). GC/EI-MS (70 eV): 298 (100,
Mþ), 219 (36), 191 (21), 190 (18), 189 (50), 176 (13), 165 (9). HR-EI-MS (70 eV): 297.998324 (Mþ;
C16H11BrOþ; calc. 297.99878).
2-Bromo-3-(4-ethylphenyl)-1H-inden-1-one (4b). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4 (18 mg,
3 mol-%), and (4-EtꢀC6H4)B(OH)2 (2h; 75 mg, 0.5 mmol), according to GP A; reaction temp.: 458.
Yield: 145 mg (93%). Colorless crystalline solid. IR (KBr): 3066w, 2962m, 2928, 2871w, 1712s, 1606, 1596,
1503, 1455, 1284, 1183, 1101, 1018, 918, 843, 759m, 704s, 627, 545m. 1H-NMR (300 MHz, CDCl3): 0.72 (t,
J ¼ 7.8, Me); 2.16 (q, J ¼ 7.5, CH2); 6.57 – 6.55 (m, 1 arom. H); 6.63 – 6.68 (m, 2 arom. H); 6.78 (d, J ¼ 7.9, 2
arom. H); 6.95 – 6.97 (m, 1 arom. H); 7.01 (d, J ¼ 7.9, 2 arom. H). 13C-NMR (75.5 MHz, CDCl3): 15.2
(Me); 28.9 (CH2); 117.4 (C); 121.3, 123.5, 128.2, 128.3, 128.4 (CH); 128.8, 130.1 (C); 133.6 (CH); 144.6,
147.0, 156.9 (C); 189.9 (C¼O). GC/EI-MS (70 eV): 314 (100, [M(81Br)]þ), 312 (99, [M(79Br)]þ), 299
(58), 297 (56), 202 (14), 190 (16), 189 (43), 176 (10), 109 (12), 95 (10). HR-EI-MS (70 eV): 312.013869
([M(81Br)]þ, C17H13BrOþ; calc. 312.01443).
2-Bromo-3-[4-(tert-butyl)phenyl]-1H-inden-1-one (4c). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4
(18 mg, 3 mol-%), and (4-tBuꢀC6H4)B(OH)2 (2i; 89 mg, 0.5 mmol), according to GP A; reaction temp.:
458. Yield: 151 mg (89%). Colorless crystalline solid. IR (KBr): 3066w, 2959m, 2902, 2865w, 1713s, 1606,
1556, 1407, 1362, 1267, 1099, 1015, 919, 800, 764m, 704s, 626, 533m. 1H-NMR (300 MHz, CDCl3): 1.31 (s, 3
Me); 7.10 – 7.13 (m, 1 arom. H); 7.15 – 7.20 (m, 1 arom. H); 7.24 – 7.30 (m, 2 arom. H); 7.47 (d, J ¼ 8.5, 2
arom. H); 7.55 (d, J ¼ 8.5, 2 arom. H). 13C-NMR (75.5 MHz, CDCl3): 31.2 (Me); 35.0, 117.4 (C); 121.4,
123.5, 125.6, 128.1 (CH); 128.2 (C); 128.8 (CH); 130.1 (C); 133.6 (CH); 144.5, 153.8, 156.8 (C); 189.9

Helvetica Chimica Acta – Vol. 95 (2012)
477
(C¼O). GC/EI-MS (70 eV): 340 (51, Mþ), 327 (96), 325 (100), 299 (16), 297 (15), 231 (12), 202 (23), 189
(12), 176 (14), 109 (29), 95 (16). HR-EI-MS (70 eV): 340.045511 (Mþ, C19H17BrOþ; calc. 340.04573).
2-Bromo-3-(3-fluorophenyl)-1H-inden-1-one (4d). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4 (18 mg,
3 mol-%), and 2g (70 mg, 0.5 mmol), according to GP A; reaction temp.: 458. Yield: 125 mg (83%).
White-yellow solid. M.p. 116 – 1178. IR (KBr): 1714s, 1596, 1579, 1564, 1484, 1427, 1418, 1354, 1298, 1284,
1209, 1178, 1134, 965, 893, 824, 787m, 758, 700, 670s, 657, 614, 599, 555m. 1H-NMR (300 MHz, CDCl3):
7.04 – 7.07 (m, 1 arom. H); 7.11 – 7.23 (m, 2 arom. H); 7.27 – 7.38 (m, 3 arom. H); 7.42 – 7.51 (m, 2 arom. H).
13C-NMR (75.5 MHz, CDCl3): 115.3 (d, J(C,F) ¼ 22.8, CH); 117.3 (d, J(C,F) ¼ 21.8, CH); 118.8 (C);
121.1, 123.9 (CH); 124.1 (d, J(C,F) ¼ 3.1, CH); 129.1 (CH); 129.7 (C); 130.6 (d, J(C,F) ¼ 8.3, CH); 133.1
(d, J(C,F) ¼ 8.2, C); 134.0 (CH); 144.2 (C); 155.5 (d, J(C,F) ¼ 2.5, C); 163.1 (d, J(C,F) ¼ 247.5, CꢀF);
189.5 (C¼O). 19F-NMR (282.4 MHz, CDCl3): ꢀ 111.3. GC/EI-MS (70 eV): 302 (100, Mþ), 224 (10), 223
(64), 195 (28), 194 (63), 175 (24), 169 (13), 168 (16), 112 (11), 97 (14). HR-EI-MS (70 eV): 302.982201
([M þ H]þ, C15H8BrFOþ; calc. 301.98153).
2-Bromo-3-[4-(trifluoromethyl)phenyl]-1H-inden-1-one (4e). From
1 (144 mg, 0.5 mmol),
Pd(PPh3)4 (18 mg, 3 mol-%), and (4-CF3ꢀC6H4)B(OH)2 (2j; 95 mg, 0.5 mmol), according to GP A;
reaction temp.: 458. Yield: 155 mg (88%). Colorless crystalline solid. IR (KBr): 3080, 2929w, 1718s, 1598,
1407m, 1318s, 1156m, 1109, 1099, 1064s, 1014, 850, 761m, 704s, 622m. 1H-NMR (300 MHz, CDCl3): 6.24
(d, J ¼ 7.2, 1 arom. H); 6.41 – 6.47 (m, 1 arom. H); 6.51 – 6.56 (m, 1 arom. H); 6.74 (d, J ¼ 7.0, 1 arom. H);
6.91 – 6.93 (m, 2 arom. H); 6.96 – 6.99 (m, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 120.2, 118.8, 119.5
(CH); 120.2 (q, J ¼ 275.0, CF3); 122.4 (C); 126.7 (q, J ¼ 1.0, C); 128.9 (CH); 132.6 (q, J ¼ 8.0, CH); 135.2
(C); 138.1 (CH); 152.5 (q, J ¼ 36.1, C); 157.8, 165.7 (C); 196.7 (C¼O). 19F-NMR (282 MHz, CDCl3):
ꢀ 63.4. GC/EI-MS (70 eV): 354 (100, [M(81Br)]þ), 352 (99, [M(79Br)]þ), 274 (11), 274 (61), 245 (28), 225
(27), 176 (34), 112 (10). HR-EI-MS (70 eV): 351.970583 ([M(79Br)]þ, C16H8BrOþ; calc. 351.97051).
2-Bromo-3-(2,6-dimethoxyphenyl)-1H-inden-1-one (4f). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4
(18 mg, 3 mol-%), and (2,6-(MeO)2C6H3)B(OH)2 (2k; 91 mg, 0.5 mmol), according to GP A; reaction
temp.: 408. Yield: 143 mg (83%). Brown crystalline solid. M.p. 189 – 1908. IR (KBr): 3009, 2965, 2933,
2836w, 1729, 1594, 1583, 1470, 1423s, 1358, 1300w, 1290m, 1249s, 1169w, 1101s, 1027m, 952, 942, 903, 873,
845w, 817, 771m, 756, 703s, 650, 633, 595, 577m. 1H-NMR (250 MHz, CDCl3): 3.71 (s, 2 MeO); 6.58 – 6.68
(m, 3 arom. H); 7.05 – 7.18 (m, 2 arom. H); 7.22 – 7.34 (m, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 54.8
(MeO); 104.0 (CH); 107.8 (C); 120.1 (CH); 120.6 (C); 121.8, 127.1 (CH); 128.3 (C); 129.8, 132.7 (CH);
144.3, 153.3, 156.7 (C); 189.1 (C¼O). GC/EI-MS (70 eV): 344 (Mþ, 44), 265 (13), 251 (18), 250 (100), 237
(16), 235 (17), 234 (16), 221 (9), 207 (14), 165 (14), 163 (12), 151 (10). HR-EI-MS (70 eV): 345.0121
([M þ H]þ, C17H14BrOþ3 ; calc. 345.0127).
2-Bromo-3-(3,5-dimethylphenyl)-1H-inden-1-one (4g). From 1 (144 mg, 0.5 mmol), (PPh3)4Pd
(18 mg, 3 mol-%), and (3,5-Me2C6H3)B(OH)2 (2l; 75 mg, 0.5 mmol), according to GP A; reaction
temp.: 458. Yield: 138 mg (88%). White-yellow solid. M.p. 136 – 1378. IR (KBr): 3072, 2959, 2913, 2856w,
1713s, 1600, 1553, 1455, 1374, 1309, 1227, 1103, 1080, 949, 859, 819, 801, 756, 731m, 705s, 668, 621, 547m.
1H-NMR (300 MHz, CDCl3): 2.32 (s, 2 Me); 7.03 – 7.29 (m, 5 arom. H); 7.43 – 7.46 (m, 1 arom. H).
13C-NMR (75.4 MHz, CDCl3): 21.4 (2 Me); 117.6 (C); 121.4, 123.5, 125.8, 128.9 (CH); 130.0, 131.0 (C);
132.1, 133.7 (CH); 138.4, 144.7, 157.3 (C); 190.0 (C¼O). GC/EI-MS (70 eV): 312 (100, Mþ), 233 (36), 203
(14), 202 (19), 190 (14), 189 (43). HR-EI-MS (70 eV): 312.014774 (Mþ, C17H13BrOþ; calc. 312.01443).
2-Bromo-3-(3-methoxyphenyl)-1H-inden-1-one (4h). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4 (18 mg,
3 mol-%), and 2e (76 mg, 0.5 mmol), according to GP A; reaction temp.: 458. Yield: 133 mg (85%).
White-yellow solid. M.p. 218 – 2198. IR (KBr): 3069, 3005, 2839w, 1714s, 1593, 1563, 1483, 1453, 1365,
1304, 1287m, 1234s, 1172, 957, 837, 822m, 793, 758, 707, 673s, 659, 614, 548m. 1H-NMR (300 MHz, CDCl3):
3.80 (s, MeO); 6.96 – 7.00 (m, 1 arom. H); 7.07 – 7.21 (m, 4 arom. H); 7.25 – 7.30 (m, 1 arom. H); 7.38 (t, J ¼
7.9, 1 arom. H); 7.46 – 7.49 (m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 55.4 (MeO); 113.7, 116.0 (CH);
118.1 (C); 120.5, 121.3, 123.7, 128.9, 129.9 (CH); 132.4 (C); 133.8 (CH); 144.5, 156.8, 159.7 (C); 189.8
(C¼O). GC/EI-MS (70 eV): 314 (100, Mþ), 235 (30), 192 (10), 176 (12), 164 (27), 163 (38), 117 (10).
HR-EI-MS (70 eV): 313.993841 (Mþ, C16H11 BrOþ2 ; calc. 313.99369).
2-Bromo-3-(4-methoxyphenyl)-1H-inden-1-one (4i). From 1 (144 mg, 0.5 mmol), Pd(PPh3)4 (18 mg,
3 mol-%), and 2f (76 mg, 0.5 mmol), according to GP A; reaction temp.: 408. Yield: 139 mg (88%).
White-yellow solid. M.p. 80 – 818. IR (KBr): 3412, 3080, 3043, 3016, 2968, 2917, 2841,1747w, 1715, 1607s,

478
Helvetica Chimica Acta – Vol. 95 (2012)
1577m, 1505s, 1468, 1445, 1417, 1367, 1352, 1301m, 1258, 1178s, 1113, 918, 830, 858, 791m, 769s, 724m, 704s,
667, 652, 624, 576, 546m. 1H-NMR (300 MHz, CDCl3): 3.81 (s, MeO); 6.97 (d, J ¼ 8.8, 2 arom. H); 7.09 –
7.19 (m, 2 arom. H); 6.26 (td, J ¼ 7.7, 1.3, 1 arom. H); 7.44 – 7.47 (m, 1 arom. H); 7.59 (d, J ¼ 8.9, 2 arom.
H). 13C-NMR (62.9 MHz, CDCl3): 54.4 (MeO); 113.1 (CH); 115.6 (C); 120.3 (CH); 122.3 (C); 122.4,
127.8, 129.1 (CH); 129.2 (C); 132.5 (CH); 143.4, 155.5, 160.2 (C); 188.9 (C¼O). GC/EI-MS (70 eV): 314
(100, Mþ), 235 (15), 164 (24), 163 (38), 118 (58). HR-EI-MS (70 eV): 313.99354 (Mþ, C16H11BrOþ2 ; calc.
313.99369).
General Procedure for the One-Pot Synthesis of 5a – 5j (GP B) The reaction was carried out in a
pressure tube. To a suspension of 1 (1.0 mmol), Pd(PPh3)4 (35 mg, 3 mol-%), and Ar1B(OH)2
(1.0 mmol) in dioxane (5 ml) was added a 2m aq. K2CO3 soln. (1 ml). The mixture was heated at 40 –
458 under Ar for 6 h. The mixture was cooled to 208, and Ar2B(OH)2 (1.1 mmol) and an additional
amount of Pd(PPh3)4 (35 mg, 3 mol-%) were added. The mixture was heated under Ar for 6 h at 708.
After cooling to 208, the mixture was diluted with H2O and extracted with CH2Cl2 (3 ꢁ 25 ml). The
combined org. layers were dried (Na2SO4) and concentrated in vacuo. The residue was purified by CC
(AcOEt/heptanes).
2-(4-Methoxyphenyl)-3-(4-methylphenyl)-1H-inden-1-one (5a). From 1 (288 mg, 1.0 mmol), 2b
(136 mg, 1.0 mmol), and 2f (167 mg, 1.1 mmol), resp., according to GP B; reaction temp.: 45 and 708,
resp. Yield: 303 mg (93%). Brown crystalline solid. M.p. 154 – 1558. IR (KBr): 3387, 3042, 2999, 2937,
2843, 2548, 2368, 2335w, 1704, 1699s, 1596, 1515, 1501, 1453, 1417, 1380, 1340, 1295m, 1251, 1176s, 1151,
1114, 922, 850m, 831, 806, 798s, 775m, 764, 733s, 713, 631, 575m, 555, 533s. 1H-NMR (250 MHz, CDCl3):
2.41 (s, Me); 3.80 (s, MeO); 6.81 (d, J ¼ 8.52, 2 arom. H); 7.12 – 7.21 (m, 1 arom. H); 7.14 – 7.28 (m, 8 arom.
H); 7.52 – 57 (m, 1 arom. H). 13C-NMR (62.9 MHz, CDCl3): 21.5 (Me); 55.2 (MeO); 113.6, 121.0, 127.7
(CH); 123.3 (C); 128.5, 128.6, 129.5 (CH); 130.0, 130.9 (C); 131.3 (CH); 131.6 (C) 133.3 (CH); 139.3,
145.6, 154.0, 159.1 (C); 197.0 (C¼O). GC/EI-MS (70 eV): 326 (100, Mþ), 311 (20), 268 (11), 239 (19).
HR-EI-MS (70 eV): 326.130187 (Mþ, C23H18O2þ ; calc. 326.13013).
2-(3-Chlorophenyl)-3-(4-methylphenyl)-1H-inden-1-one (5b). From 1 (288 mg, 1.0 mmol), 2b
(136 mg, 1.0 mmol), and (3-ClꢀC6H4)B(OH2) (2m; 172 mg, 1.1 mmol), resp., according to GP B;
reaction temp.: 45 and 708, resp. Yield: 294 mg (89%). White-yellow solid. M.p. 147 – 1488. IR (KBr):
3382, 3057, 3043, 2917, 2854, 2354, 2138, 2001, 1938w, 1702s, 1606, 1595, 1575, 1563, 1509, 1454, 1403, 1340,
1300, 1284, 1184, 1148, 1115, 998, 959, 921, 885, 854, 824, 788m, 776, 767, 731, 726s, 716m, 693, 678s, 662,
1
601, 567, 558m. H-NMR (300 MHz, CDCl3): 2.32 (s, Me); 7.00 – 7.32 (m, 11 arom. H); 7.50 (dd, J ¼ 7.1,
0.6, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 21.6 (Me); 121.6, 123.0, 127.7, 128.1, 128.4, 129.2 (CH);
129.2 (C); 129.3, 129.6, 129.9 (CH); 130.6, 130.8, 132.9 (C); 133.5 (CH); 133.9, 139.9, 144.9, 156.6 (C);
195.9 (C¼O). GC/EI-MS (70 eV): 330 (100, Mþ), 315 (19), 295 (33), 280 (12), 265 (18), 263 (13). HR-
ESI-MS (pos.): 331.0883 ([M þ H]þ, C22H16ClOþ; calc. 331.0884).
3-(2,6-Dimethoxyphenyl)-2-(4-fluorophenyl)-1H-inden-1-one (5c). From 1 (288 mg, 1.0 mmol), 2k
(182 mg, 1.0 mmol), and 2c (154 mg, 1.1 mmol), resp., according to GP B; reaction temp.: 40 and 708,
resp. Yield: 309 mg, (86%). Brownish yellow solid. M.p. 206 – 2078. IR (KBr): 3046, 2963, 2838w, 1696,
1591, 1574, 1504, 1462, 1432m, 1359, 1296w, 1255, 1222, 1156m, 974, 941, 903w, 853, 825, 794, 781m, 761,
721, 709s, 684, 643, 626w, 585, 542m, 528s. 1H-NMR (300 MHz, CDCl3): 3.51 (s, 2 MeO); 6.53 (d, J ¼ 8.4, 2
arom. H); 6.68 (dt, J ¼ 7.1, 0.8, 1 arom. H); 6.70 – 6.87 (m, 3 arom. H); 7.58 – 7.31 (m, 5 arom. H); 7.43 –
7.46 (m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 55.7 (2 MeO); 108.3 (CH); 114.7 (d, J(C,F) ¼ 21.4,
CH); 121.2, 121.3, 128.3 (CH); 128.5 (d, J(C,F) ¼ 3.3, C); 1130.3 (d, J(C,F) ¼ 8.0, CH); 130.4 (C); 130.9,
133.5 (CH); 145.8, 150.6, 157.8, 158.5 (C),162.1 (d, J(C,F) ¼ 247.4, CF); 196.8 (C¼O). 19F-NMR
(282.4 MHz, CDCl3): ꢀ 114.2. GC/EI-MS (70 eV): 360 (100, Mþ), 273 (10), 257 (9), 172 (8). HR-EI-MS
(70 eV): 360.11556 (Mþ, C23H17FO3þ ; calc. 360.11562).
2-(2,6-Dimethoxyphenyl)-3-(4-methylphenyl)-1H-inden-1-one (5d). From 1 (288 mg, 1.0 mmol), 2b
(136 mg, 1.0 mmol), and 2k (200 mg, 1.1 mmol), resp., according to GP B; reaction temp.: 45 and 708,
resp. Yield: 320 mg (90%). White-yellow solid. M.p. 207 – 2088. IR (KBr): 3077, 2996, 2971, 2941, 2918,
2837w, 1704s, 1470, 1455, 1445, 1430, 1360, 1332m, 1250s, 1180m, 1105s, 1061, 1030, 924, 855, 817m, 765,
724s, 677, 645, 604, 545m. 1H-NMR (300 MHz, CDCl3): 2.26 (s, Me); 3.49 (s, 2 MeO); 6.44 (d, J ¼ 8.3, 2
arom. H); 7.05 (d, J ¼ 7.9, 2 arom. H); 7.12 – 7.29 (m, 6 arom. H); 7.45 – 7.48 (m, 1 arom. H). 13C-NMR
(75.5 MHz, CDCl3): 21.1 (Me); 55.8 (2 MeO); 104.3 (CH); 109.8 (C); 120.9, 122.6, 127.4, 128.4 (CH);

Helvetica Chimica Acta – Vol. 95 (2012)
479
128.6 (C); 128.9, 129.7 (CH); 130.9, 132.0 (C); 132.8 (CH); 139.0, 145.5, 157.4, 158.8 (C); 196.0 (C¼O).
GC/EI-MS (70 eV): 356 (100, Mþ), 326 (27), 311 (17), 252 (10), 239 (12), 233 (34), 226 (9), 119 (9). HR-
EI-MS (70 eV): 356.139956 (Mþ, C24H20Oþ3 ; calc. 356.14070).
3-(2-Methoxyphenyl)-2-(4-methylphenyl)-1H-inden-1-one (5e). From 1 (288 mg, 1.0 mmol), 2d
(152 mg, 1.0 mmol), and 2b (150 mg, 1.1 mmol), resp., according to GP B; reaction temp.: 40 and 708,
resp. Yield: 277 mg (85%) White-yellow solid.. M.p. 157 – 1588. IR (KBr): 3042, 2998, 2937, 2843w, 1698,
1596, 1514, 1453, 1416, 1340, 1295m, 1250, 1176s, 1068m, 1029s, 922, 850, 830m, 798s, 764m, 733s, 680, 665,
555m. 1H-NMR (300 MHz, CDCl3): 2.21 (s, Me); 3.52 (s, MeO); 6.80 (dt, J ¼ 7.2, 0.8, 1 arom. H); 6.87 –
6.97 (m, 4 arom. H); 7.09 – 7.34 (m, 6 arom. H); 7.44 – 7.47 (m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3):
21.3 (Me); 55.3 (MeO); 111.6, 120.9, 121.3 (CH); 122.4 (C); 128.4, 128.7, 129.1 (CH); 129.8 (C); 130.5
(CH); 130.6, 133.2 (C); 133.4 (CH); 137.4, 145.8, 152.8, 157.0 (C); 196.9 (C¼O). GC/EI-MS (70 eV): 326
(100, Mþ), 311 (19), 268 (10), 239 (18). HR-EI-MS (70 eV): 326.130186 (Mþ, C23H18Oþ2 ; calc.
326.13013).
2-(4-Chlorophenyl)-3-(4-ethylphenyl)-1H-inden-1-one (5f). From 1 (288 mg, 1.0 mmol), 2h (150 mg,
1.0 mmol), and (4-ClꢀC6H4)B(OH)2 (2n; 171 mg, 1.1 mmol), resp., according to GP B; reaction temp.:
45 and 708, resp. Yield: 285 mg (83%). Brown solid. M.p. 94 – 958. IR (KBr): 3393, 3026, 2963, 2930, 2872,
2676, 1704s, 1607, 1579m, 1487, 1455, 1340, 1181s, 1068, 1013m, 814, 794, 764, 727, 708s, 679, 628, 574m.
1H-NMR (300 MHz, CDCl3): 1.21 (t, J ¼ 7.6, Me); 2.64 (q, J ¼ 7.8, CH2); 7.12 – 7.33 (m, 11 arom. H); 7.48 –
7.51 (m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 15.2 (Me); 28.8 (CH2); 121.5, 123.0, 128.3, 128.4,
128.5, 129.1 (CH); 129.5, 129.6, 130.8 (C); 131.3, 133.5 (CH); 133.6, 136.3, 145.1, 146.0, 156.0 (C) 196.3
(C¼O). GC/EI-MS (70 eV): 344 (100, Mþ), 317 (12), 315 (33), 309 (11), 280 (15), 265 (19), 263 (13), 252
(16), 131 (9). HR-EI-MS (70 eV): 344.095128 (Mþ, C23H17ClOþ; calc. 344.09624).
3-(3-Chlorophenyl)-2-(4-methylphenyl)-1H-inden-1-one (5g). From 1 (288 mg, 1.0 mmol), (3-
ClꢀC6H4)B(OH)2 (2m; 156 mg, 1.1 mmol), and 2b (150 mg, 1.1 mmol), resp., according to GP B;
reaction temp.: 45 and 708, resp. Yield: 260 mg (79%). Brown solid. M.p. 147 – 1488. IR (KBr): 3057,
3028, 2916w, 1701s, 1595, 1558, 1453, 1403, 1340, 1299, 1263, 1183, 1148, 1115, 998, 921, 885m, 766, 731,
692, 677s, 600, 556m. 1H-NMR (300 MHz, CDCl3): 2.22 (s, Me); 6.96 – 7.00 (m, 3 arom. H); 7.05 – 7.32 (m,
8 arom. H); 7.46 – 7.49 (m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 21.4 (Me); 120.9, 123.2, 126.9
(CH); 127.3 (C); 128.3, 129.0, 129.3, 129.8, 130.3 (CH); 130.5, 133.0 (C); 133.6 (CH); 134.7, 134.8, 137.7,
145.1, 152.8 (C); 196.4 (C¼O). GC/EI-MS (70 eV): 330 (100, Mþ), 329 (13), 317 (10), 315 (31), 295 (42),
280 (14), 265 (19), 263 (13), 252 (27), 250 (12), 131 (10). HR-ESI-MS (pos.): 330.080183 (Mþ,
C22H15ClOþ; calc. 330.08004).
3-(4-Ethylphenyl)-2-(4-methoxyphenyl)-1H-inden-1-one (5h). From 1 (288 mg, 1.0 mmol), 2h
(150 mg, 1.0 mmol), and 2f (167 mg, 1.1 mmol), resp., according to GP B; reaction temp.: 45 and 708,
resp. Yield: 316 mg (93%). Brown solid. M.p. 143 – 1448. IR (KBr): 3000, 2956, 2927, 2840w, 1695s, 1605,
1497, 1456, 1339, 1289, 1240, 1171s, 1032, 952, 922, 854, 802, 734, 680, 581m. 1H-NMR (300 MHz, CDCl3):
1.14 (t, J ¼ 7.8, Me); 2.54 (q, J ¼ 7.8, CH2); 3.77 (s, MeO); 6.86 (d, J ¼ 7.9, 2 arom. H); 7.03 (d, J ¼ 8.2, 2
arom. H); 7.10 (d, J ¼ 8.3, 2 arom. H); 7.13 – 7.23 (m, 3 arom. H); 7.28 (d, J ¼ 8.4, 2 arom. H); 7.47 – 7.50
(m, 1 arom. H). 13C-NMR (75.5 MHz, CDCl3): 15.2 (Me); 28.6 (CH2); 55.3 (MeO); 114.1, 121.0, 122.7
(CH); 125.0 (C); 127.6 (CH); 128.3 (C); 128.7, 129.9, 130.2 (CH); 131.0, 131.7 (C); 133.2 (CH); 143.7,
145.4, 154.5, 160.3 (C); 196.7 (C¼O). GC/EI-MS (70 eV): 340 (100, Mþ), 325 (26), 311 (23), 252 (12), 239
(12). HR-EI-MS (70 eV): 340.145705 (Mþ, C24H20O2þ ; calc. 340.14578).
2-Phenyl-3-[4-(trifluoromethyl)phenyl]-1H-inden-1-one (5i). From 1 (288 mg, 1.0 mmol), 2j
(150 mg, 1.0 mmol), and 2a (134 mg, 1.10 mmol), resp., according to GP B; reaction temp.: 45 and
708, resp. Yield: 304 mg (87%). Brown solid. M.p. 153 – 1548. IR (KBr): 3070, 2961, 2855w, 1707s, 1596,
1455, 1408m, 1318s, 1165m, 1108, 1063, 1013s, 858, 801m, 752, 699s, 656, 599m. 1H-NMR (300 MHz,
CDCl3): 7.01 – 7.21 (m, 6 arom. H); 7.28 – 7.33 (m, 2 arom. H); 7.42 (d, J ¼ 8.0, 2 arom. H); 7.51 – 7.54 (m, 1
arom. H); 7.59 (d, J ¼ 7.4, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 120.9 (CH); 122.7 (q, J(C,F) ¼
274.5, C); 123.3, 125.8 (q, J(C,F) ¼ 3.8, CH); 128.1, 128.2, 128.9 (CH); 129.2 (C); 129.9 (q, J(C,F) ¼ 8,
CH); 130.1 (q, J(C,F) ¼ 33.5, C); 132.4, 132.6, 135.5 (C); 133.6 (CH); 143.7, 152.3 (C); 194.9 (C¼O). 19F-
NMR (282 MHz, CDCl3): ꢀ 62.7. GC/EI-MS (70 eV): 350 (100, Mþ), 333 (10), 281 (38), 252 (39), 126
(13). HR-EI-MS (70 eV): 350.091245 (Mþ, C22H13F3Oþ; calc. 350.09130).

480
Helvetica Chimica Acta – Vol. 95 (2012)
General Procedure for Syntheses of Alkynylindenones 7a – 7d and 8a – 8d (GP C). In a pressure tube,
a suspension of [Pd(PPh3)2Cl2] (5 – 15 mol-%), 1 or 4 ( 0.5 mmol), alkyne (0.50 – 1.10 mmol), CuI (10 –
20 mol-%), and (i-Pr)2NH (1.5 equiv.) in DMF (5 ml) was purged with Ar and stirred at 208 for 10 min.
The mixture was stirred at r.t. for 6 – 8 h and then poured into a 1:1 mixture H2O/CH2Cl2 (25 ml each).
After shaking, the aq. layer was separated and extracted with CH2Cl2 (3 ꢁ 25 ml). The combined org.
layers were washed with H2O (3 ꢁ 20 ml), dried (Na2SO4), concentrated in vacuo, and the residue was
purified by flash CC (silica gel, heptanes/AcOEt) to give 7a – 7d and 8a – 8e.
2,3-Bis(phenylethynyl)-1H-inden-1-one (7a). From 1 (144 mg, 0.50 mmol), [Pd(PPh3)2Cl2] (52 mg,
15 mol-%), dry CuI (19 mg, 20 mol-%), (i-Pr)2NH (1 ml/0.10 mmol of 1), and ethynylbenzene (6a;
0.06 ml, 1.10 mmol), according to GP C. Yield: (147 mg, 89%). Colorless oil. IR (KBr): 3050, 2921,
2853w, 1708s, 1596, 1489, 1442, 1358, 1219, 1157, 1069, 915, 868m, 754, 688s, 528m. 1H-NMR (300 MHz,
CDCl3): 7.26 – 7.32 (m, 5 arom. H); 7.35 – 7.39 (m, 3 arom. H); 7.41 – 7.45 (m, 2 arom. H); 7.53 – 7.60 (m, 4
arom. H). 13C-NMR (62.9 MHz, CDCl3): 81.9, 83.1, 103.5, 111.3 (Cꢂ); 121.1 (CH); 121.9, 122.7 (C);
123.0, 128.3, 128.6, 129.0 (CH); 129.3, 129.5 (C); 129.9, 130.1, 132.0, 132.3, 134.3 (CH); 142.9, 143.1 (C);
192.8 (C¼O). GC/EI-MS (70 eV): 330 (100, Mþ), 329 (17), 300 (45), 165 (15), 150 (21), 140 (12). HR-EI-
MS (70 eV): 330.109432 (Mþ, C25H14Oþ; calc. 330.10392).
2,3-Bis[(4-methylphenyl)ethynyl]-1H-inden-1-one (7b). From
1
(144 mg, 0.50 mmol),
[Pd(PPh3)2Cl2] (52 mg, 15 mol-%), dry CuI (19 mg, 20 mol-%), (i-Pr)2NH (1 ml/0.1 mmol of 1), and
1-ethynyl-4-methylbenzene (6b; 0.07 ml, 1.10 mmol) at r.t., according to GP C. Yield: 166 mg (93%).
Colorless oil. IR (KBr): 3083, 2930w, 1714s, 1597, 1406m, 1314s, 1152m, 1106, 1093, 1060s, 1014, 850,
761m, 702s, 599m. 1H-NMR (300 MHz, CDCl3): 2.26 (s, Me); 2.28 (s, Me); 7.06 (d, J ¼ 8.4, 2 arom. H);
7.10 (d, J ¼ 8.2, 2 arom. H); 7.22 (d, J ¼ 8.0, 2 arom. H); 7.30 – 7.39 (m, 4 arom. H); 7.42 (d, J ¼ 8.0, 2 arom.
H). 13C-NMR (62.9 MHz, CDCl3): 20.5, 20.7 (Me); 80.6, 82.0, 102.7, 110.9 (Cꢂ); 117.9, 118.8 (C); 120.0,
121.7 (CH); 122.5 (C); 128.1 (CH); 128.3 (C); 128.4, 128.7, 130.8, 131.3, 133.2 (CH); 138.2, 139.7, 141.7,
142.1 (C); 191.1 (C¼O). GC/EI-MS (70 eV): 358 (100, Mþ), 313 (12), 97 (10), 83 (11), 69 (26), 43 (15).
HR-EI-MS (70 eV): 358.134682 (Mþ, C27H18Oþ; calc. 358.13522).
2,3-Bis{[(4-tert-butyl)phenyl]ethynyl}-1H-inden-1-one (7c). From
1 (144 mg, 0.50 mmol),
[Pd(PPh3)2Cl2] (52 mg, 15 mol-%), dry CuI (19 mg, 20 mol-%), (i-Pr)2NH (1 ml/0.1 mmol of 1), and
1-(tert-butyl)-4-ethynylbenzene (6c; 0.1 ml, 0.55 mmol), according to GP C. Yield: 207 mg (94%).
Colorless oil. IR (KBr): 3082, 2931w, 1720s, 1590, 1405m, 1312s, 1156m, 1109, 1096, 1063s, 1010, 850,
761m, 703s, 621m. 1H-NMR (300 MHz, CDCl3): 1.26 (s, 3 Me); 1.27 (s, 3 Me); 7.24 – 7.27 (m, 2 arom. H);
7.31 (d, J ¼ 8.6, 2 arom. H); 7.37 (d, J ¼ 8.6, 2 arom. H); 7.37 – 7.42 (m, 2 arom. H); 7.47 (d, J ¼ 8.6, 2 arom.
H); 7.52 (d, J ¼ 8.6, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 31.1, 31.2 (3 Me); 34.9, 35.0 (2 CMe3);
81.5, 83.0, 103.8, 111.9 (Cꢂ); 121.7 (CH); 121.9, 122.7 (C); 123.0, 128.3, 128.6, 129.0 (CH); 129.3 (C);
129.9, 130.1, 132.0 (CH); 133.2, 142.9, 143.2, 152.4, 153.8 (C); 193.0 (C¼O). GC/EI-MS (70 eV): 442 (32,
Mþ), 427 (28), 355 (10), 281 (10), 253 (10), 207 (13), 178 (12), 161 (23), 149 (15), 135 (10), 111 (12), 97
(20), 91 (17), 83 (24), 78 (65), 71 (32), 60 (16), 57 (74), 44 (90). HR-EI-MS (70 eV): 442.227998 (Mþ,
C33H30Oþ; calc. 442.22912).
2,3-Di(dec-1-yn-1-yl)-1H-inden-1-one (7d). From 1 (144 mg, 0.50 mmol), [Pd(PPh3)2Cl2] (52 mg,
15 mol-%), dry CuI (19 mg, 20 mol-%), (i-Pr)2NH (1 ml/0.1 mmol of 1), and dec-1-yne (6d; 0.09 ml,
1.10 mmol), according to GP C. Yield: 185 mg (92%). Colorless oil. IR (KBr): 2961, 2932, 2872w, 1708s,
1
1600, 1462, 1359, 1219, 1089, 763, 528m. H-NMR (300 MHz, CDCl3): 0.79 – 0.83 (m, 2 Me); 1.19 –
1.27(m, 10 CH2); 1.36 – 1.46 (m, 2 CH2); 1.53 – 1.64 (m, 2 CH2); 7.11 – 7.16 (m, 1 arom. H); 7.18 – 7.21
(m, 1 arom. H); 7.30 – 7.35 (m, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 14.0 (2 Me); 20.3, 20.4, 20.5,
20.6, 22.6, 28.4, 28.5, 28.8, 29.0, 29.1, 29.2, 31.8, 31.9(CH2); 72.6, 74.7, 104.7, 113.4 (Cꢂ); 120.7, 122.5 (CH);
124.1, 129.1 (C); 129.4, 134.0 (CH); 143.4, 143.6 (C); 192.8 (C¼O). GC/EI-MS (70 eV): 402 (100, Mþ),
265 (12), 137 (13), 128 (26), 114 (19), 29 (15). HR-EI-MS (70 eV): 402.298533 (Mþ, C29H38Oþ; calc.
402.29838).
2-(Phenylethynyl)-3-[4-(trifluoromethyl)phenyl]-1H-inden-1-one (8a). From 4e (176 mg,
0.50 mmol), [Pd(PPh3)2Cl2] (18 mg, 5 mol-%), dry CuI (10 mg, 10 mol-%), (i-Pr)2NH (1 ml/0.1 mmol
of 4e), and 6a (0.06 ml, 0.55 mmol), according to GP C. Yield: 164 mg (88%). Colorless oil. IR (KBr):
3062, 2961w, 1715s, 1595, 1488, 1455, 1409m, 1320s, 1165m, 1122, 1064, 1014s, 925, 855, 795m, 750, 716m,
686s, 591m. 1H-NMR (300 MHz, CDCl3): 7.17 – 7.22 (m, 2 arom. H); 7.24 – 7.29 (m, 4 arom. H); 7.32 – 7.35

Helvetica Chimica Acta – Vol. 95 (2012)
481
(m, 1 arom. H); 7.37 – 7.41 (m, 1 arom. H); 7.50 – 7.53 (m, 1 arom. H); 7.73 (d, J ¼ 8.3, 2 arom. H); 7.90 (d,
J ¼ 8.3, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 80.4, 99.8 (Cꢂ); 120.7 (CH); 121.4 (C); 122.6 (q,
J(C,F) ¼ 273, C); 122.8 (C); 124.5 (q, J(C,F) ¼ 3.9, CH); 127.3, 127.6, 128.0, 128.4, 128.8 (CH); 129.3 (C);
129.9 (d, J(C,F) ¼ 32.9, C); 130.9, 132.8 (CH); 134.6, 142.7, 156.9 (C); 191.7 (C¼O). 19F-NMR (282 MHz,
CDCl3): ꢀ 62.7. GC/EI-MS (70 eV): 374 (100, Mþ), 305 (10), 276 (29). HR-EI-MS (70 eV): 374.090996
(Mþ, C24H13F3Oþ; calc. 374.09130).
2-{[(4-tert-Butyl)phenyl]ethynyl}-3-(4-methoxyphenyl)-1H-inden-1-one (8b). From 4i (157 mg,
0.50 mmol), [Pd(PPh3)2Cl2] (18 mg, 5 mol-%), dry CuI (10 mg, 10 mol-%), (i-Pr)2NH (1 ml/0.1 mmol
of 4i), and 6c (0.01 ml, 0.55 mmol), according to GP C. Yield: 157 mg (80%). Colorless oil. IR (KBr):
3080, 2929w, 1718s, 1598, 1407m, 1318s, 1156m, 1109, 1099, 1064s, 1014, 850, 761m, 704s, 622m. 1H-NMR
(300 MHz, CDCl3): 31.1 (Me); 55.4 (MeO) 6.98 (d, J ¼ 9.0, 2 arom. H); 7.20 – 7.32 (m, 4 arom. H); 7.36 (d,
J ¼ 7.9, 2 arom. H); 7.47 (d, J ¼ 9.0, 2 arom. H); 7.85 (d, J ¼ 8.6, 2 arom. H). 13C-NMR (62.9 MHz, CDCl3):
31.4 (Me); 34.8 (C); 55.4 (MeO); 81.9, 99.7 (Cꢂ); 114.0, 116.5, 120.0 (C); 122.0, 123.2, 124.8, 125.3, 129.4,
130.3 (CH); 131.1 (C); 131.5, 133.4 (CH); 144.2, 151.9, 159.5, 161.4 (C); 193.5 (C¼O). GC/EI-MS
(70 eV): 392 (100, Mþ), 377 (77), 207 (26), 144 (13), 32 (18). HR-EI-MS (70 eV): 392.177463 (Mþ,
C28H24Oþ2 ; calc. 392.17708).
2-(Dec-1-yn-1-yl)-3-[4-(trifluoromethyl)phenyl]-1H-inden-1-one (8c). From 4e (176 mg,
0.50 mmol), [Pd(PPh3)2Cl2] (18 mg, 5 mol-%), dry CuI (10 mg, 10 mol-%), (i-Pr)2NH (1 ml/0.1 mmol
of 4e), and 6d (0.01 ml, 0.55 mmol), according to GP C. Yield: 182 mg (89%). Colorless oil. IR (KBr):
2954, 2925, 2855w, 1710s, 1596, 1461, 1410m, 1319s, 1161m, 1125, 1066s, 1016, 926, 827, 761, 717, 681, 601m.
1H-NMR (300 MHz, CDCl3): 0.80 (t, J ¼ 6.9, Me); 1.12 – 1.16 (m, 5 CH2); 1.44 – 1.51 (m, CH2); 2.38 (t, J ¼
7.4, CH2); 7.14 – 7.34 (m, 3 arom. H); 7.46 – 7.50 (m, 1 arom. H); 7.69 (d, J ¼ 7.9, 2 arom. H); 7.82 (d, J ¼ 7.6,
2 arom. H). 13C-NMR (62.9 MHz, CDCl3): 14.0 (Me); 20.1, 22.5, 28.3, 28.8, 29.0, 29.1, 31.8 (CH2); 72.3,
103.3 (Cꢂ); 121.4 (CH); 122.2 (q, J(C,F) ¼ 273.1, C); 123.7 (CH); 125.4 (q, J(C,F) ¼ 3.8, CH); 128.5,
129.5 (CH); 133.7 (q, J(C,F) ¼ 8.1, CH); 135.7 (q, J(C,F) ¼ 36.3, C); 136.5, 143.8, 157.2 (C); 193.3 (C¼O).
19F-NMR (282 MHz, CDCl3): ꢀ 62.8. GC/EI-MS (70 eV): 410 (58, Mþ), 381 (18), 367 (41), 353 (100),
339 (54), 325 (47), 311 (69), 287 (83), 262 (34), 243 (39), 231 (26), 226 (32), 213 (63), 183 (11). HR-EI-
MS (70 eV): 410.185602 (Mþ, C26H25F3Oþ; calc. 410.18520).
2-[(6-Methoxynaphthalen-2-yl)ethynyl]-3-(4-methoxyphenyl)-1H-inden-1-one (8d). From 4i
(157 mg, 0.50 mmol), [Pd(PPh3)2Cl2] (18 mg, 5 mol-%), dry CuI (10 mol-%), (i-Pr)2NH (1 ml/0.1 mmol
of 4i), and 2-ethynyl-6-methoxynaphthalene (6e; 100 mg, 0.55 mmol), according to GP C. Yield: 162 mg
(78%). Colorless oil. IR (KBr): 3014, 2932, 2849w, 1704, 1599s, 1512, 1453, 1388, 1303, 1255s, 1162m,
1025s, 947, 894m, 850s, 811, 728, 710, 661, 585m. 1H-NMR (300 MHz, CDCl3): 3.83 (s, 2 MeO); 6.98 – 7.63
(m, 7 arom. H); 7.83 – 7.96 (m, 3 arom. H). 13C-NMR (62.8 MHz, CDCl3): 55.3, 55.4 (MeO); 82.3, 100.2
(Cꢂ); 105.8, 114.0 (CH); 116.5, 117.9 (C); 119.4, 119.6, 122.0, 123.2 (CH); 124.8 (C); 126.7 (CH); 126.9,
128.4 (C); 129.0, 129.4, 130.3 (CH); 131.2 (C); 131.7, 133.4 (CH); 144.2, 158.4, 159.4, 161.4, 193.5 (C¼O).
GC/EI-MS (70 eV): 416 (100, Mþ), 330 (6), 97 (5), 69 (12), 43 (10). HR-ESI-MS (pos.): 417.1484 ([M þ
H]þ, C29H21Oþ3 ; calc. 417.1485).
REFERENCES
[1] G. M. Anstead, S. R. Wilson, J. A. Katzenellenbogen, J. Med. Chem. 1989, 32, 2163; K. Hajela, R. S.
Kapil, Indian J. Chem., Sect. B 1995, 34, 361; R. E. McDevitt, M. S. Malamas, E. S. Manas, R. J.
Unwalla, Z. B. Xu, C. P. Miller, H. A. Harris, Bioorg. Med. Chem. Lett. 2005, 15, 3137.
[2] J. H. Ahn, M. S. Shin, S. H. Jung, S. K. Kang, K. R. Kim, S. D. Rhee, W. H. Jung, S. D. Yang, S. J. Kim,
J. R. Woo, J. H. Lee, H. G. Cheon, S. S. Kim, J. Med. Chem. 2006, 49, 4781.
[3] E. Weitz, A. Scheffer, Chem. Ber. 1921, 54, 2343; E. D. Bergmann, J. Org. Chem. 1956, 21, 461; R. L.
Frank, H. Eklund, J. W. Richter, C. R. Vanneman, A. N. Wennerberg, J. Am. Chem. Soc. 1944, 66, 1;
F. M. Beringer, P. S. Forgione, M. D. Yudis, Tetrahedron 1960, 8, 49; C. F. Koelsch, J. Am. Chem. Soc.
1932, 54, 2487; J. J. Eisch, W. C. Kaska, J. Am. Chem. Soc. 1966, 88, 2976.
[4] J. L. Jeffrey, R. Sarpong, Org. Lett. 2009, 11, 5450; T.Morimoto, K. Yamasaki, A. Hirano, K.
Tsutsumi, N. Kagawa, K. Kakiuchi, Y. Harada, Y. Fukumoto, N. Chatani, T. Nishioka, Org. Lett.
2009, 11, 1777.

482
Helvetica Chimica Acta – Vol. 95 (2012)
[5] C. Liebermann, Chem. Ber. 1898, 31, 2079; C. Liebermann, 1899, 32, 260; C. Liebermann, Chem. Ber.
1899, 32, 916; C. Liebermann, Chem. Ber. 1900, 33, 566; H. Simonis, C. Kirschten, Chem. Ber. 1912,
45, 567.
[6] S. Schrçter, C. Stock, T. Bach, Tetrahedron 2005, 61, 2245; M. Schnꢀrch, R. Flasik, A. F. Khan, M.
Spina, M. D. Mihovilovic, P. Stanetty, Eur. J. Org. Chem. 2006, 3283; J.-R. Wang, K. Manabe,
Synthesis 2009, 1405.
[7] M. Hussain, N. T. Hung, R. A. Khera, A. Villinger, P. Langer, Tetrahedron Lett. 2011, 52, 184.
[8] V. Karapetyan, S. Mkrtchyan, G. Karapetyan, A. Villinger, A. Saghiyan, T. V. Ghochikyan, P.
Langer, Helv. Chim. Acta 2011, 94, 2045.
Received August 8, 2011