Synthesis of 2,3-dihydro-1H-inden-1-one derivatives via Ni-catalyzed intramolecular hydroacylation

Article abstract of DOI:10.1016/j.tet.2012.03.053

An efficient synthetic method for the formation of 2,3-dihydro-1H-inden-1- one derivatives through a Ni-catalyzed intramolecular hydroacylation of 2-(prop-2-ynyl)benzaldehydes has been developed. Examination of various nickel and other transition metal catalysts and phosphine ligands showed that the use of Ni(COD)₂ catalyst combined with P(i-Pr)₃ ligand was the best choice to the success of the present intramolecular hydroacylation. A wide range of functional groups were tolerated, affording the corresponding substituted α-lidene-2,3-dihydro-1H-inden-1-ones in good to high yields with a sole E-selectivity under present reaction conditions.

Full text of DOI:10.1016/j.tet.2012.03.053

Tetrahedron 68 (2012) 5223e5228
Contents lists available at SciVerse ScienceDirect
Tetrahedron
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Synthesis of 2,3-dihydro-1H-inden-1-one derivatives via Ni-catalyzed
intramolecular hydroacylation
,
a,
*
Fan Yang b, Tienan Jin a , Yoshinori Yamamoto
*
a WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
b Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient synthetic method for the formation of 2,3-dihydro-1H-inden-1-one derivatives through a Ni-
catalyzed intramolecular hydroacylation of 2-(prop-2-ynyl)benzaldehydes has been developed. Exami-
nation of various nickel and other transition metal catalysts and phosphine ligands showed that the use
of Ni(COD)2 catalyst combined with P(i-Pr)3 ligand was the best choice to the success of the present
intramolecular hydroacylation. A wide range of functional groups were tolerated, affording the corre-
Received 3 February 2012
Received in revised form 7 March 2012
Accepted 15 March 2012
Available online 21 March 2012
sponding substituted
tivity under present reaction conditions.
a-lidene-2,3-dihydro-1H-inden-1-ones in good to high yields with a sole E-selec-
Keywords:
Nickel catalysts
Intramolecular hydroacylation
2-(Prop-2-ynyl)benzaldehydes
2,3-Dihydro-1H-inden-1-ones
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
intermolecular alkyne hydroacylation reactions.5 Other transition
metal catalysts were also applied to the alkyne hydroacylations.
For examples, Krische group demonstrated that alkyne hydro-
acylation could be applied to the ruthenium catalyzed transfer
hydrogenation-based method,6 and Tusda reported an in-
termolecular hydroacylation of aldehydes and alkynes by using Ni
comlpexes as catalyst forming the corresponding enones with E-
isomers as major products.7 These results indicated that the choice
of catalyst and ligand, and the use of appropriate structure of the
starting substrate should be crucial to the success of these
reactions.
Transition metal-catalyzed hydroacylation of alkenes and al-
kynes is one of attractive atom-economical methodologies for the
formation of new CeC bonds in organic synthesis through func-
tionalization of CeH bonds.1 However, hydroacylation for the
alkene-based process has been well developed, the catalytic
hydroacylation of alkynes has received less attention. Recent ad-
vances on both inter- and intramolecular hydroacylation of al-
kynes proved that the use of rhodium catalysts is one of the best
choices to realize these transformations. For examples, Fu and
Tanaka groups reported the intramolecular hydroacylation of the
alkyl-tethered 4-, 5-, and 6-alkynals using different kinds of cat-
ionic rhodium complexes,2 and Bendorf group developed the S-
chelation-assisted Rh-catalyzed intramolecular alkyne hydro-
In the continuation of our interests in the study of reactivity of
2-(prop-2-ynyl)benzaldehyde derivatives,8 herein, we report an
efficient Ni-catalyzed intramolecular hydroacylation of 2-(prop-2-
ynyl)benzaldehyde derivatives 1 affording a variety of substituted
acylations to give the seven- and eight-membered
a
-alkylidenes in
a
a
-lidene-2,3-dihydro-inden-1-ones 2 in good to high yields [Eq. 1].
-Lidene-2,3-dihydro-1H-inden-1-one is important framework
good yields,3 Jun has selectively synthesized the branched
a,b-
enones by applying Rh/picoline catalyst system to intermolecular
hydroacylation of alkynes,4 and some interesting Rh-catalyzed O-
and S-chelating systems have also been applied to the
found in pharmaceutically active compounds and used as valuable
intermediates in organic synthesis.9 To date, Aldol condensation of
1H-inden-1-ones with aldehydes is still the most common ap-
proach for synthesis of
a
-lidene-2,3-dihydro-inden-1-ones.10 Re-
cently, new synthetic method of this framework has been reported,
for example, a Pd-catalyzed carbonylation of arynes with allyl ac-
etates or carbonates.11 Our methodology for synthesizing inden-
ones with a wide range of functional groups provides a new entry
for this important framework.
* Corresponding authors. Tel.: þ81 22 217 5130; fax: þ81 22 795 6784; e-mail
addresses: tjin@m.tohoku.ac.jp (T. Jin), yoshi@m.tohoku.ac.jp (Y. Yamamoto).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.03.053

5224
F. Yang et al. / Tetrahedron 68 (2012) 5223e5228
2. Results and discussion
reactions of substrates bearing an alkyl groups, such as ethyl (1b)
and n-hexyl (1c) at the alkynyl terminus (R1) produced the corre-
sponding 1H-inden-1-ones 2b and 2c in 83% and 78% yield, re-
spectively (entries 1 and 2, condition A). In contrast, the reaction of
substrate 1d having a phenyl substituent at R1 dramatically de-
creased the yield of 2a under same conditions even though the
higher loadings of Ni and phosphine catalysts were used (entries 3
and 4). We thought that the lower yield might be due to the de-
composition of 2d in the presence of a trace amount of water. Thus,
In the preliminary studies, we investigated metal catalysts and
phosphine ligands on the intramolecular hydroacylation of 2-(but-
2-ynyl)benzaldehyde 1a for the formation of the (E)-2-ethylidene-
2,3-dihydro-1H-inden-1-one 2a in toluene at 100 ꢀC under Ar at-
mosphere (Table 1). The use of Ni(COD)2 catalyst without phos-
phine ligand, the reaction did not proceed at all (entry 1). The use of
triarylphosphine ligand, PPh3 showed a lower reactivity, producing
2a in 14% yield (entry 2). Among the trialkylphosphine ligands
tested, the sterically less hindered or bulky phosphine ligands, such
as PMe3 (28%), P(n-Pr)3 (70%), P(t-Bu)3 (35%), and PCy3 (8%),
exhibited lower reactivity compared to that of P(i-Pr)3 (86% isolated
yield), indicating that phosphine ligand both having a strong
electron donating property and adequate bulkiness was the best
choice in the present hydroacylation (entries 3e5, 8, and 9). It
should be noted that the decrease or increase of the amount of P(i-
Pr)3 ligand resulted in lower yields of 2a (entries 6 and 7). The use
of bidentate phosphine ligand, dppe did not show obvious in-
fluence on the catalytic activity (entry 10). Other catalysts, such as
Ni(CO)2(PPh3)2, [Ir(COD)Cl]2, RuHCl(CO)PPh3 combined with P(i-
Pr)3 ligand gave lower yields of 2a (entries 11e13). It was noted that
the use of cationic rodium catalyst [Rh(binap)]BF4, which was
employed by Tanaka group2b gave 2a in 40% yield (entry 14). It was
noteworthy that the corresponding product 2a was obtained as
a sole E-selectivity, which was determined by the reported au-
thentic compound.10a
ꢀ
the reaction was carried out in the presence of molecular sieves 4 A
under a higher catalyst loading, affording 2a in 78% yield (entry 5,
condition B). Under this reaction condition B, various aryl groups at
R1 were tested. The reactions of substrates bearing an electron-
withdrawing (1e) and an electron-donating (1f and 1g) aromatic
group at R1 produced the corresponding products 1eeg in 75e63%
yields (entries 6e8). Substrates 1h and 1i having a naphthyl and
conjugated cyclohexenyl group afforded the desired products in
moderate yields (entries 9 and 10). Substrates 1j and 1k having
heteroaromatic rings at R1, such as furanyl and thienyl, showed
a high compatibility with the present reaction conditions, pro-
ducing 2j and 2k in high yields (entries 11 and 12). The electronic
characteristics of the benzaldehyde moiety of 1 exert obvious in-
fluence on the yields of products 2. For examples, substrates 1l and
1m having an electron-withdrawing group (eF, or eCl) at R2 de-
creased the yields of 2l and 2m, while the reaction worked well
with the substrates 1n and 1o, substituted with an electron-
donating group (dimethoxy, eMe) at R2, furnishing the expected
Table 1
Optimization of reaction conditions for the intramolecular hydroacylation of 2-(but-2-ynyl)benzaldehyde 1aa
Entry
Catalyst (10 mol %)
P ligand (20 mol %)
2ab (%)
1
2
Ni(COD)2
Ni(COD)2
None
PPh3
0
14
3
Ni(COD)2
PMe3
28
4
5
6
7
8
9
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
P(n-Pr)3
P(i-Pr)3
P(i-Pr)3 (10 mol %)
P(i-Pr)3 (40 mol %)
P(t-Bu)3
PCy3
70
92 (86)
61
64
35
8
10
11
12c
13
14
Ni(COD)2
dppe
34
74
7
19
Ni(CO)2(PPh3)2
[Ir(COD)Cl]2
RuHCl(CO)PPh3
[Rh(binap)]BF4
P(i-Pr)3
P(i-Pr)3
P(i-Pr)3
None
40
a
Reaction conditions: 1a (0.2 mmol), anhydrous toluene (0.1 M), 100 ꢀC, 18 h under Ar atmosphere.
b
c
1H NMR yield determined using CH2Br2 as an internal standard. Isolated yield is shown in parentheses.
Catalyst (5 mol %) was used.
The scope and limitations of Ni(COD)2/P(i-Pr)3-catalyzed intra-
molecular hydroacylation of various 2-(prop-2-ynyl)benzaldehydes
1 in toluene under Ar atmosphere were summarized in Table 2. The
products 2n and 2o in high yields (entries 13e16). When substrate
1p having a methoxy group at R3 was used, the reaction proceeded
smoothly, furnishing the multisubstituted inden-1-one product 2p

F. Yang et al. / Tetrahedron 68 (2012) 5223e5228
5225
Table 2
Ni-catalyzed hydroacylation of various 2-(prop-2-ynyl)benzaldehydesa
Entry
Substrate
1
Conditions
2
Yieldb (%)
1
2
3
4
5
6
7
8
R1¼Et, R2¼H
1b
1c
1d
1d
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
A
A
A
Bd
B
B
B
B
B
B
B
B
B
B
B
B
2b
2c
2d
2d
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2o
83
78
12c
45
78
75
63
70
43
45
90
88
64
58
80
82
R1¼n-Hexyl, R2¼H
R1¼C6H5, R2¼H
R1¼C6H5, R2¼H
R1¼C6H5, R2¼H
R1¼4-CleC6H4, R2¼H
R1¼4-MeOeC6H4, R2¼H
R1¼4-MeeC6H4, R2¼H
R1¼1-Naphthyl, R2¼H
R1¼1-Cyclohexenyl, R2¼H
R1¼3-Furanyl, R2¼H
R1¼2-Thienyl, R2¼H
R1¼Me, R2¼5-F
9
10
11
12
13
14
15
16
R1¼Me, R2¼5-Cl
R1¼Me, R2¼4,5-(MeO)2
R1¼Me, R2¼4-Me
a
Reaction condition: 1 (0.2 mmol), anhydrous toluene (0.1 M), 100 ꢀC, 8e12 h under Ar atmosphere; condition A: 10 mol % Ni(COD)2, 20 mol % P(i-Pr)3; condition B:
ꢀ
20 mol % Ni(COD)2, 40 mol % P(i-Pr)3, MS 4 A (64 mg).
b
Isolated yield.
c
1H NMR yield determined using CH2Br2 as an internal standard.
d
ꢀ
Without MS 4 A.
in good yield (Eq. 2). It should be noted that under the standard
reaction conditions other aldehydes, such as 2-(4-phenylbut-3-yn-
1-yl)benzaldehyde was completely inactive without producing any
six-membered ring products, aliphatic aldehyde, such as 6-
phenylhex-5-ynal resulted in decomposition of the aldehyde, and
the aldehyde having a terminal alkyne moiety (R1¼H) did not un-
dergo the present hydroacylation.
The plausible Ni-catalyzed hydroacylation mechanism is shown
in Scheme 1. Initially, oxidative insertion of the strong electron rich
Ni(0) catalyst into CeH bond of aldehyde 1a forms nickel acyl
Scheme 1. A plausible mechanism of Ni-catalyzed hydroacylation.

5226
F. Yang et al. / Tetrahedron 68 (2012) 5223e5228
hydride A. The cis addition of nickel hydride to the metal-bound
alkyne moiety affords the six-membered nickel acyl intermediate
B. Reductive elimination of B produces the corresponding hydro-
acylation product 2a as an E-isomer.
Condition B: synthesis of (E)-2-benzylidene-2,3-dihydro-1H-
inden-1-one (2d): to a toluene (2 ml, 0.1 M) solution of 1d (44 mg,
0.2 mmol), Ni(COD)2 (6 mg, 20 mol %), and P(i-Pr)3 (20.6 mg,
40 mol %), and MS 4 A (64 mg) was stirred at 100 ꢀC under Ar at-
ꢀ
mosphere for 8 h. After consumption of 1d, which was monitored
by TLC, the reaction mixture was filtered through a short florisil pad
using diethyl ether as an eluent. After concentration, the residue
was purified with silica gel chromatography to afford 2d (34 mg,
78%) as a yellow solid.
3. Conclusion
In conclusion, we have developed a new and efficient synthetic
method for the formation of 2,3-dihydro-1H-inden-1-one de-
rivatives through the Ni-catalyzed intramolecular hydroacylation
of 2-(prop-2-ynyl)benzaldehydes. A wide range of functional
groups are tolerated in the present catalytic hydroacylation. The
use of Ni(COD)2/P(i-Pr)3 catalyst system is crucial for the efficient
formation of the corresponding hydroacylation products. Further
extension of this method to the synthesis of important fused ar-
omatic compounds and application to organic electronics are in
progress.
4.4. Analytical data of products 2
4.4.1. (E)-2-Ethylidene-2,3-dihydro-1H-inden-1-one
solid; 1H NMR (400 MHz, CDCl3)
(2a). Yellow
7.85 (d, J¼7.6 Hz, 1H), 7.59 (t,
d
J¼7.6 Hz, 1H), 7.50 (d, J¼7.6 Hz, 1H), 7.39 (t, J¼7.6 Hz, 1H), 6.95 (qt,
J¼7.6, 2.4 Hz, 1H), 3.66 (s, 2H), 1.97 (dt, J¼7.6, 1.1 Hz, 3H); 13C NMR
(100 MHz, CDCl3)
d 15.32, 29.78, 124.3, 126.28, 127.41, 133.00,
134.34, 137.48, 138.86, 149.23, 193.13; IR (neat): 671, 741, 901, 1093,
1264, 1607, 1649, 1700, 2335, 2903 cmꢁ1; HRMS (ESI): [MþNa]þ
calcd for C11H11O, 181.0624; found, 181.0623.
4. Experimental section
4.1. General information
4.4.2. (E)-2-Propylidene-2,3-dihydro-1H-inden-1-one (2b). Yellow
solid; 1H NMR (400 MHz, CDCl3)
d
7.85 (d, J¼7.6 Hz, 1H), 7.58 (t,
1H NMR and 13C NMR spectra were recorded on JEOL JNM AL
300 (300 MHz), JEOL JNM AL 400 (400 MHz), and JEOL JNM
(500 MHz) spectrometers. 1H NMR spectra are reported as follows:
chemical shift in parts per million ( ) relative to the chemical shift
of CDCl3 at 7.26 ppm, integration, multiplicities (s¼singlet,
d¼doublet, t¼triplet, q¼quartet, m¼multiplet, and br¼broad-
ened), and coupling constants (hertz). 13C NMR spectra were
recorded on JEOL JNM AL 300 (75.45 MHz), JEOL JNM AL 400
J¼7.6 Hz, 1H), 7.49 (d, J¼7.6 Hz, 1H), 7.39 (t, J¼7.6 Hz, 1H), 6.85 (tt,
J¼7.6, 2.0 Hz,1H), 3.66 (s, 2H), 2.34 (t, J¼7.6 Hz, 2H),1.15 (t, J¼7.6 Hz,
a-500
3H); 13C NMR (100.50 MHz, CDCl3)
d 12.93, 23.22, 29.78, 124.33,
d
126.30, 127.43, 134.39, 135.75, 138.91, 139.56, 149.36, 193.57; IR
(neat): 666, 726, 748, 880, 1093, 1258, 1606, 1645, 1693, 2342, 2891,
2933, 2975 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for C12H12O,
195.0780; found, 195.0781.
(100.5 MHz), and JEOL JNM
with complete proton decoupling, and chemical shift reported in
ppm ( ) relative to the central line of triplet for CDCl3 at 77 ppm.
IR spectra were recorded on JASCO FT/IR-4100 spectrometer; ab-
sorptions are reported in cmꢁ1. High-resolution mass spectra were
obtained on a BRUKER APEXIII spectrometer and JEOL JMS-700
MStation operator. Column chromatography was carried out
a-500 (125.65 MHz) spectrometers
4.4.3. (E)-2-Hexylidene-2,3-dihydro-1H-inden-1-one (2c). Colorless
oil; 1H NMR (500 MHz, CDCl3)
d
7.84 (d, J¼7.5 Hz, 1H), 7.56 (t,
d
J¼7.5 Hz, 1H), 7.47 (d, J¼7.5 Hz, 1H), 7.37 (t, J¼7.5 Hz, 1H), 6.87 (t,
J¼7.5 Hz, 1H), 3.64 (s, 2H), 2.29 (t, J¼7.5 Hz, 2H), 1.54e1.52 (m, 2H),
1.33e1.31 (m, 4H), 0.88 (t, J¼6.5 Hz, 3H), 1.15 (t, J¼7.6 Hz, 3H); 13C
NMR (125.65 MHz, CDCl3) d 13.96, 22.48, 28.12, 29.85, 29.96, 31.59,
124.34, 126.28,127.42,134.34, 136.33,138.42,138.96,149.37, 193.41;
IR (neat): 671, 734, 923, 1262, 1466, 1610, 1650, 1703, 2327, 2343,
2856, 2926, 2955 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for C15H18O,
237.1250; found, 237.1250.
employing silica gel 60
N (spherical, neutral, 40e100 mm,
KANTO Chemical Co.). Analytical thin-layer chromatography (TLC)
was performed on 0.2 mm precoated plate Kieselgel 60 F254
(Merck).
4.4.4. (E)-2-Benzylidene-2,3-dihydro-1H-inden-1-one (2d). Yellow
solid; 1H NMR (300 MHz, CDCl3)
d
7.91 (d, J¼7.2 Hz, 1H), 7.69e7.66
(m, 3H), 7.62e7.56 (m, 2H), 7.46e7.40 (m, 4H), 4.04 (s, 2H); 13C NMR
(75.45 MHz, CDCl3) 32.40, 124.38, 126.13, 127.62, 128.88, 129.61,
4.2. Materials
Anhydrous toluene, o-xylene, benzene, octane, dioxane (WAKO),
Ni(COD)2 (STREM), (WAKO), Ni(CO)2(PPh3)2 (FLUKA), [Ir(COD)Cl]2,
RuHCl(CO)PPh3, P(t-Bu)3 (TCI), P(n-Pr)3, P(i-Pr)3, PCy3, PMe3, deep
(ALDRICH) were purchased and used as received. 2-(Prop-2-ynyl)
benzaldehydes 1 were prepared according to the literature pro-
cedure.12 The structures of new products were determined by 1H,
13C NMR, high-resolution mass and comparing with the reported
authentic compounds.10a
d
130.67, 133.87, 134.57, 134.68, 135.35, 137.97, 149.59, 194.29; IR
(neat): 737, 761, 949, 1092, 1294, 1580, 1606, 1622, 1691, 2325, 2851,
2915 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for C16H12O, 243.0780;
found, 243.0780.
4.4.5. (E)-2-(4-Chlorobenzylidene)-2,3-dihydro-1H-inden-1-one
(2e). Yellow solid; 1H NMR (300 MHz, CDCl3)
d
7.91 (d, J¼7.5 Hz,
1H), 7.63e7.55 (m, 5H), 7.46e7.41 (m, 3H), 4.02 (s, 2H); 13C NMR
(75.45 MHz, CDCl3) 32.34, 124.49, 126.16, 127.78, 129.20, 131.77,
4.3. General procedure of Ni-catalyzed intramolecular
hydroacylation
d
132.45, 133.85, 134.76, 135.15, 135.65, 137.87, 149.40, 194.09; IR
(neat): 728, 819, 1092, 1269, 1584, 1623, 1693, 2328, 2851,
2926 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for C16H11ClO, 277.0391;
found, 277.0390.
Condition A: synthesis of (E)-2-ethylidene-2,3-dihydro-1H-
inden-1-one (2a): to a toluene (2 ml, 0.1 M) solution of 1a (32 mg,
0.2 mmol), Ni(COD)2 (3 mg, 10 mol %), and P(i-Pr)3 (10.3 mg,
20 mol %) was stirred at 100 ꢀC under Ar atmosphere for 18 h. After
consumption of 1a, which was monitored by TLC, the reaction
mixture was filtered through a short florisil pad using diethyl ether
as an eluent. After concentration, the residue was purified with
silica gel chromatography to afford 2a (27 mg, 86%) as a yellow
solid.
4.4.6. (E)-2-(4-Methoxybenzylidene)-2,3-dihydro-1H-inden-1-one
(2f). Yellow solid; 1H NMR (300 MHz, CDCl3)
d
7.89 (d, J¼7.5 Hz,
1H), 7.64e7.53 (m, 5H), 7.41 (t, J¼7.5 Hz, 1H), 6.97 (d, J¼8.7 Hz, 2H),
3.99 (s, 2H), 3.85 (s,1H); 13C NMR (75.45 MHz, CDCl3)
32.42, 55.34,
d
114.41, 124.23, 126.05, 127.52, 128.10, 132.35, 132.51, 133.74, 134.28,
138.20, 149.44, 160.80, 194.31; IR (neat): 734, 822, 1023, 1255, 1514,

F. Yang et al. / Tetrahedron 68 (2012) 5223e5228
5227
1600, 1691, 2318, 2343, 2840, 2926 cmꢁ1; HRMS (ESI): [MþNa]þ
2851, 2918 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for C11H9ClO,
calcd for C17H14O2, 273.0886; found, 273.0885.
215.0234; found, 215.0234.
4.4.7. (E)-2-(4-Methylbenzylidene)-2,3-dihydro-1H-inden-1-one
4.4.14. (E)-2-Ethylidene-5,6-dimethoxy-2,3-dihydro-1H-inden-1-one
(2g). Yellow solid; 1H NMR (300 MHz, CDCl3)
d
7.89 (d, J¼7.5 Hz,
1H), 7.65e7.54 (m, 5H), 7.40 (t, J¼7.5 Hz, 1H), 7.26e7.23 (m, 2H),
4.01 (s, 2H), 2.93 (s, 3H); 13C NMR (75.45 MHz, CDCl3)
21.49, 32.47,
(2n). Pale yellow solid; 1H NMR (300 MHz, CDCl3)
d 7.27 (s, 1H),
6.91 (s,1H), 6.84 (qt, J¼7.2, 2.1 Hz,1H), 3.97 (s, 3H), 3.92 (s, 3H), 3.55
d
(s, 2H), 1.93 (d, J¼7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3)
d 15.24,
124.34, 126.11, 127.58, 129.68, 130.76, 132.59, 133.72, 133.99, 134.45,
138.10, 140.14, 149.56, 194.41; IR (neat): 739, 817, 954, 1098, 1581,
1602, 1620, 1686, 2332, 2855, 2922 cmꢁ1; HRMS (ESI): [MþNa]þ
calcd for C17H14O, 257.0937; found, 257.0937.
29.48, 56.08, 56.19, 104.96, 107.26, 131.22, 131.82, 137.92, 144.36,
149.39, 155.15, 192.11; IR (neat): 753, 785, 837, 905, 1068, 1301,
1603, 1649, 1695, 2309, 2924 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for
C13H14O3, 241.0835; found, 241.0836.
4.4.8. (E)-2-(Naphthalen-1-ylmethylene)-2,3-dihydro-1H-inden-1-
4.4.15. (E)-2-Ethylidene-5-methyl-2,3-dihydro-1H-inden-1-one
one (2h). Yellow solid; 1H NMR (300 MHz, CDCl3)
d
8.46 (s, 1H),
(2o). Yellow solid; 1H NMR (400 MHz, CDCl3)
d
7.71 (d, J¼7.6 Hz,
8.23 (d, J¼7.5 Hz, 1H), 7.97 (d, J¼7.5 Hz, 1H), 7.91 (d, J¼7.5 Hz, 2H),
1H), 7.23 (s, 1H), 7.17 (d, J¼7.6 Hz, 1H), 6.88 (qt, J¼7.2, 2.0 Hz, 1H),
7.80 (d, J¼7.5 Hz, 1H), 7.62e7.44 (m, 6H), 4.01 (s, 2H); 13C NMR
3.57 (s, 2H), 2.42 (s, 3H), 1.92 (d, J¼7.2 Hz, 3H); 13C NMR (100 MHz,
(125.65 MHz, CDCl3)
d
32.03, 124.09, 124.56, 125.21, 126.18, 126.31,
CDCl3) d 15.28, 22.14, 29.64, 124.16, 126.63, 128.65, 132.39, 136.62,
126.81, 126.94, 127.66, 128.73, 129.87, 130.93, 132.29, 132.35, 133.69,
134.64, 137.21, 138.28, 150.00, 193.90; IR (neat): 733, 768, 949, 1089,
1295, 1613, 1692, 2334, 2851, 2926, 3052 cmꢁ1; HRMS (ESI):
[MþNa]þ calcd for C20H14O, 293.0937; found, 293.0936.
137.80, 145.51, 149.71, 192.80; IR (neat): 669, 755, 891, 1113, 1322,
1609, 1646, 1698, 2318, 2851, 2922 cmꢁ1; HRMS (ESI): [MþNa]þ
calcd for C12H12O, 195.0799; found, 195.0799.
4.4.16. (E)-2-Ethylidene-3-methoxy-2,3-dihydro-1H-inden-1-one
4.4.9. (E)-2-(Cyclohexenylmethylene)-2,3-dihydro-1H-inden-1-one
(2p). Colorless oil; 1H NMR (400 MHz, CDCl3)
d
7.84 (d, J¼7.6 Hz,
(2i). Yellow solid; 1H NMR (500 MHz, CDCl3)
7.57 (t, J¼7.5 Hz,1H), 7.49 (d, J¼7.5 Hz,1H), 7.40 (t, J¼7.5 Hz,1H), 7.24
(s, 1H), 6.38 (s, 1H), 3.95 (s, 2H), 2.49 (s, 2H), 2.27e2.26 (m, 2H),
1.76e1.73 (m, 2H), 1.65e1.63 (m, 2H); 13C NMR (125.65 MHz, CDCl3)
d
7.87 (d, J¼7.5 Hz,1H),
1H), 7.73e7.67 (m, 2H), 7.52 (t, J¼7.6 Hz, 1H), 7.18 (q, J¼7.6 Hz, 1H),
5.75 (s, 1H), 3.01 (s, 3H), 2.11 (d, J¼7.6 Hz, 3H); 13C NMR (100 MHz,
CDCl3)
d 14.84, 51.17, 74.86, 123.86, 126.23, 129.68, 134.92, 136.65,
138.42, 138.91, 148.47, 191.23; IR (neat): 746, 888, 903, 1073, 1255,
1604, 1656, 1705, 2309, 2821, 2931 cmꢁ1; HRMS (ESI): [MþNa]þ
calcd for C12H12O2, 211.0730; found, 211.0729.
d
21.57, 22.56, 26.81, 27.15, 32.06, 124.18, 125.97, 127.36, 131.02,
134.08, 135.85, 138.11, 138.31, 140.80, 149.73, 194.68; IR (neat): 734,
930, 1092, 1266, 1579, 1605, 1686, 2321, 2851, 2926 cmꢁ1; HRMS
(ESI): [MþNa]þ calcd for C16H16O, 247.1093; found, 247.1093.
Acknowledgements
4.4.10. (E)-2-(Furan-3-ylmethylene)-2,3-dihydro-1H-inden-1-one
This work was supported by World Premier International Re-
search Center Initiative (WPI), MEXT, Japan.
(2j). Yellow solid; 1H NMR (300 MHz, CDCl3)
d
7.88 (d, J¼7.5 Hz,
1H), 7.81 (s, 1H), 7.63e7.51 (m, 4H), 7.44e7.39 (m, 1H), 6.72 (d,
J¼1.8 Hz, 1H), 3.87 (d, J¼1.8 Hz, 1H); 13C NMR (75.45 MHz, CDCl3)
Supplementary data
d
31.97, 110.00, 122.50, 123.99, 124.29, 126.18, 127.62, 133.95, 134.48,
138.45, 144.31, 145.75, 148.97, 193.81; IR (neat): 735, 810, 869, 1020,
1082, 1156, 1631, 1692, 2318, 2851, 2926, 3129 cmꢁ1; HRMS (ESI):
[MþNa]þ calcd for C14H10O2, 233.0572; found, 233.0572.
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2012.03.053. These data include MOL files and
InChIKeys of the most important compounds described in this
article.
4.4.11. (E)-2-(Thiophen-2-ylmethylene)-2,3-dihydro-1H-inden-1-one
(2k). Yellow solid; 1H NMR (300 MHz, CDCl3)
d
7.89e7.87 (m, 2H),
7.61e7.56 (m, 3H), 7.43e7.39 (m, 2H), 7.17e7.15 (m,1H), 3.91 (s, 2H);
13C NMR (100 MHz, CDCl3)
32.27, 124.24, 126.19, 126.51, 127.61,
References and notes
d
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128.15, 130.51, 132.69, 133.07, 134.50, 138.47, 139.84, 149.00, 193.77;
IR (neat): 708, 734, 941, 1094, 1268, 1579, 1617, 1690, 2318, 2851,
2922 cmꢁ1; HRMS (ESI): [MþNa]þ calcd for C14H10OS, 249.0345;
found, 249.0345.
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(2l). Yellow solid; 1H NMR (300 MHz, CDCl3)
d 7.51e7.45 (m, 2H),
7.33e7.26 (m, 1H), 6.97 (qt, J¼7.5, 2.7 Hz, 1H), 3.63 (s, 2H), 1.97 (dt,
J¼7.5, 2.7 Hz, 3H); 13C NMR (100.5 MHz, CDCl3)
d 15.40, 29.26, 110.2
(d, J2¼21.4 Hz), 122.0 (d, J3¼13.9 Hz), 127.7 (d, J5¼7.0 Hz), 133.96,
137.8 (d, J7¼1.6 Hz), 140.6 (d, J4¼7.4 Hz), 144.6 (d, J8¼1.4 Hz), 162.5
(d, J1¼245.8 Hz), 192.2 (d, J1¼3.3 Hz); IR (neat): 757, 825, 1177, 1274,
1484, 1609, 1652, 1697, 2318, 2932, 3048 cmꢁ1; HRMS (ESI):
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4.4.13. (E)-6-Chloro-2-ethylidene-2,3-dihydro-1H-inden-1-one
(2m). Yellow solid; 1H NMR (300 MHz, CDCl3)
d 7.80 (s, 1H),
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d
15.45, 29.43, 124.19, 127.56, 133.82, 134.17, 134.34, 137.36, 140.34,
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