A New Synthetic Method for the Preparation of Indenones from Aromatic Imines. Ru3(CO)12-Catalyzed Carbonylation at an ortho C-H Bond in the Aromatic Imines

Full text of DOI:10.1021/jo970697f

J . Org. Chem. 1997, 62, 5647-5650
5647
Ru3(CO)12-catalyzed reaction of aromatic imines with CO
and olefins. The initial concept was based on the
regioselective propionylation of an aromatic imine. If the
propionylation occurred ortho to an imino group in a
manner similar to the reaction of pyridylbenzenes,9 the
product would possess an 1-imino-4-keto structure which
should undergo intramolecular aldol cyclization to a five-
membered ring.11,12 Fortunately this took place readily.
We now report a new, simple synthetic method for the
preparation of indenones by the Ru3(CO)12-catalyzed
reaction of aromatic imines with CO and olefins. Some
of 2-substituted indenones, which were prepared by the
present method, are new compounds and, thus, have not
been reported thus far.
The reaction of N-(2-methylbenzylidene)-tert-butyl-
amine (1) (2 mmol) with CO (5 atm at room temperature)
and ethylene (7 atm at room temperature in a 50-mL
stainless steel autoclave) in the presence of Ru3(CO)12 (0.1
mmol) was run in toluene (6 mL) at 160 °C for 12 h. After
the solution was cooled to room temperature, silica gel
(chromatography grade, 70-230 mesh, 5 g) (vide infra)
was added to the solution and the mixture stirred at 25
°C for 1 d. The silica gel was filtered off and the residue
subjected to column chromatography on silica gel (hex-
ane/C6H6 ) 1/1) to give 2,4-dimethyl-1H-inden-1-one (2)
in 82% isolated yield based on 1 (eq 1). Increasing the
A New Syn th etic Meth od for th e
P r ep a r a tion of In d en on es fr om Ar om a tic
Im in es. Ru 3(CO)12-Ca ta lyzed
Ca r bon yla tion a t a n or th o C-H Bon d in th e
Ar om a tic Im in es
Takahide Fukuyama, Naoto Chatani,
Fumitoshi Kakiuchi, and Shinji Murai*
Department of Applied Chemistry, Faculty of Engineering,
Osaka University, Suita, Osaka 565, J apan
Received April 18, 1997
Indenones are important substructures in natural
products and their related biologically active counter-
parts.1 As a result, a variety of synthetic methods have
been developed and remain the subject of study. The
most straightforward synthetic method for the prepara-
tion of indenones is the R-bromination of 1-indanones,
followed by dehydrobromination.2 Other common meth-
ods include the AlCl3-catalyzed addition of benzoyl
chlorides to acetylenes3 and the intramolecular Friedel-
Crafts acylation of â-chloro-â-arylpropionyl chlorides4 or
variations of this approach.5 A number of 2,3-disubsti-
tuted indenones have been prepared by the Pd-catalyzed
reaction of o-bromo- or o-iodobenzaldehyde with various
internal acetylenes,6 as well as the Rh-catalyzed reaction
of aroyl chlorides with internal acetylenes.7 Although
other methods for the preparation of indenones are
known,8 all have some drawbacks in terms of substrate
limitation, yield, or reaction conditions. The present
study was initiated in order to develop a more efficient
method that would allow the preparation of some of
indenones that cannot be prepared by previously reported
methodology.
Recently, we reported the Ru3(CO)12-catalyzed reaction
of pyridylbenzenes with CO and ethylene in which
propionylation occurs selectively at an ortho position in
the phenyl ring.9 The reaction involves the effective
carbonylation at a C-H bond9,10 in the benzene ring. To
explore some new aspects of this direct carbonylation
reaction in organic synthesis, we have examined the
CO pressure (20 atm) resulted in a decreased product
yield (50% yield), even after a 20 h reaction.13 On the
basis of studies of the Ru3(CO)12-catalyzed reaction of
pyridylbenzenes with CO and ethylene,9 a keto imine,
such as 3, would be expected as the primary product.
However, 3 was not detected by GC. The keto imine 3
would readily undergo intramolecular aldol-type conden-
sation to give 4 in situ. Although 4 could be isolated by
bulb-to-bulb distillation, the formation of 2 was also
observed, to a greater or lesser extent.14 The elimination
of tert-butylamine from 4 to give 2 proceeded smoothly
on treatment of the crude reaction mixture with silica
gel. No ortho-ethylation took place under CO, which is
(1) Sengupta, P.; Sen, M.; Niyogi, S. K.; Pakrashi, S. C.; Ali, E.
Phytochemistry 1976, 15, 995. Tanaka, N.; Satake, T.; Takahashi, A.;
Mochizuki, M.; Murakami, T.; Saiki, Y.; Yang, J .-Z.; Chen, C.-M. Chem.
Pharm. Bull. 1982, 30, 3640. Ng, K.-M. E.; McMorris, T. C. Can. J .
Chem. 1984, 62, 1945. Anstead, G. M.; Altenbach, R. J .; Wilson, S.
R.; Katzenellenbogen, J . A. J . Med. Chem. 1988, 31, 1316. Anstead,
G. M.; Wilson, S. R.; Katzenellenbogen, J . A. J . Med. Chem. 1989, 32,
2163. Anstead, G. M.; Ensign, J . L.; Peterson, C. S.; Katzenellenbogen,
J . A. J . Org. Chem. 1989, 54, 1485.
(2) Marvel, C. S.; Hinman, C. W. J . Am. Chem. Soc. 1954, 76, 5435.
(3) Martens, H.; Hoornaert, G. Synth. Commun. 1972, 2, 147.
Martens, H.; Hoornaert, G. Tetrahedron 1974, 30, 3641.
(4) Floyd, M. B.; Allen, G. R., J r. J . Org. Chem. 1970, 35, 2647.
(5) Galatsis, P.; Manwell, J . J .; Blackwell, J . M. Can. J . Chem. 1994,
72, 1656.
(6) Tao, W.; Silverberg, L. J .; Rheingold, A. L.; Heck, R. F. Orga-
nometallics 1989, 8, 2550. Larock, R. C.; Doty, M. J .; Cacchi, S. J .
Org. Chem. 1993, 58, 4579.
(7) Kokubo, K.; Matsumasa, K.; Miura, M.; Nomura, M. J . Org.
Chem. 1996, 61, 6941.
(8) Liebeskind, L. S.; South, M. S. J . Org. Chem. 1980, 45, 5426.
Butler, I. R.; Elliot, J . E.; Houde, J ., J r. Can. J . Chem. 1989, 67, 1308.
Keumi, T.; Matsuura, K.; Nakayama, N.; Tsubota, T.; Morita, T.;
Takahashi, I.; Kitajima, H. Tetrahedron 1993, 49, 537. Padwa, A.;
Austin, D. J .; Gareau, Y.; Kassir, J . M.; Xu, S. L. J . Am. Chem. Soc.
1993, 115, 2637.
(11) To our knowledge, only two limited example of the intramo-
lecular aldol condensation of a related compound, o-acylbenzophenone
to 3-hydroxy-1-indanone or indenone, have been reported. Tada, M.;
Maeda, T. Chem. Ind. (London) 1976, 17, 742. Baidossi, W.; Lahav,
M.; Blum, J . J . Org. Chem. 1997, 62, 669.
(12) It was found that 2-acetyl-4,5-dimethoxybenzaldehyde decom-
posed during silica gel column chromatography to give 5,6-dimethoxy-
3-methyl-3H-isobenzofuran-1-one but not the inden-1-one derivative.
Van Broeck, P. I.; Vanderzande, D. J .; Kiekens, E. G.; Hoornaert, G.
J . J . Chem. Soc., Perkin Trans. 1 1991, 639.
(9) Chatani, N.; Ie, Y.; Kakiuchi, F.; Murai, S. J . Org. Chem. 1997,
62, 2604.
(10) Chatani, N.; Fukuyama, T.; Kakiuchi, F.; Murai, S. J . Am.
Chem. Soc. 1996, 118, 493.
(13) Presumably because high pressure of CO inhibits the coordina-
tion of imine nitrogen to a metal center.
(14) Compounds similar to 3 and 4 can be isolated in a particular
case (vide infra).
S0022-3263(97)00697-X CCC: $14.00 © 1997 American Chemical Society

5648 J . Org. Chem., Vol. 62, No. 16, 1997
Notes
Ta ble 1. Ru 3(CO)12-Ca ta lyzed Rea ction of Ar om a tic
in contrast to the Ru3(CO)12-catalyzed ortho-ethylation
of aromatic imines with ethylene under N2.15
Im in es w ith CO a n d Eth ylen ea
We examined the Ru3(CO)12-catalyzed reaction of 1
with a variety of olefins. It was found that 1 did not react
with olefins such as 1-hexene, styrene, and methyl
acrylate, but reaction with tert-butylethylene (4 equiv)
gave the corresponding indenone 5 in 41% yield (eq 2).
A similar limitation with respect to olefin reactivity was
observed in the reaction of pyridylbenzenes.9
The reaction of 1 with trimethylvinylsilane (4 equiv)
afforded 4-methyl-2-[(trimethylsilyl)methyl]-1H-inden-1-
one (7) in 64% yield, along with 2 as a byproduct in 14%
yield (eq 3). It is likely that byproduct 2 arises from
ethylene, which is generated in situ from the vinylsi-
lane.16 Without treatment of the reaction mixture with
silica gel, compound 6 was isolated in 60% yield in pure
form, by bulb-to-bulb distillation.
a
Reaction conditions: imine (2 mmol), ethylene (initial pressure
The reaction of N-benzylidene-tert-butylamine (8) gave
two products, 2-methyl-1H-inden-1-one (9) and 2-methyl-
4-propionyl-1H-inden-1-one (10) (eq 4). The formation
of 10 clearly indicates that the second acylation proceeds
more rapidly than cyclization (aldol type condensation).
Once cyclized, 9 does not undergo further acylation to
10 under the reaction conditions employed.
7 atm at rt in a 50-mL stainless steel autoclave), CO (initial
pressure 5 atm at rt in a 50-mL stainless steel autoclave), toluene
b
(6 mL), 160 °C, and silica gel at rt for 1 day. Isolated yields based
on the imine. c Reaction run under 20 atm of CO.
Some selected results of the reaction of aromatic imines
with CO and ethylene are summarized in Table 1. The
reaction of o-methoxy-substituted imine 11 gave, after
deamination by treatment with silica gel, the correspond-
ing indenone 12 in high yield (entry 1). A CF3 group as
in 13 resulted in a decrease in the product yield, and a
small amount (3% yield) of ortho-ethylation product15
(structure not shown) was obtained as a byproduct (entry
2). A high degree of regioselectivity was observed in the
case of the m-methyl-substituted imine 17. Carbonyla-
tion took place at a sterically less hindered C-H bond to
selectively give 18 (entry 4), indicating the importance
of steric factors. The present reaction provides an
efficient method for the construction of a benz[f]indenone
structure (entry 5).17 Most of the synthetic methods for
the preparation of indenones reported thus far involve
electrophilic substitution as a key step (cyclization step).3-7
In contrast, the present transformation involves a regio-
selective acylation and an intramolecular aldol-type
reaction of the resulting keto imines, providing a comple-
(15) Kakiuchi, F.; Yamauchi, M.; Chatani, N.; Murai, S. Chem. Lett.
1996, 111.
(16) The ruthenium-catalyzed conversion of vinylsilanes to ethylene
and disilylethylene is known. Wakatuki, Y.; Yamazaki, H.; Nakano,
M.; Yamamoto, Y. J . Chem. Soc., Chem. Commun. 1991, 703. Mar-
ciniec, B.; Pietraszuk, C. J . Organomet. Chem. 1991, 412, C1. See
also: Seki, Y.; Takeshita, K.; Kawamoto, K. J . Organomet. Chem. 1989,
369, 117.
(17) Mal, D.; Hazra, N. K.; Murty, K. V. S. N.; Majumdar, G. Synlett
1995, 1239.

Notes
J . Org. Chem., Vol. 62, No. 16, 1997 5649
mentary method to conventional electrophilic substituted
methods. For example, indenones having an electron-
withdrawing group at the 4-position, such as 14 and 16,
cannot be obtained by literature methods based on
Friedel-Crafts acylation,3-5 which are the most useful
and reliable methods for the preparation of 2-methyl-1H-
inden-1-one derivatives, but which involve electrophilic
cyclization.18 Indeed, prior to this report, these were
unknown compounds. The present transformation is a
synthetically useful method, as well as a new type of
transformation.
This protocol was applied to heteroaromaic compounds.
Interestingly, the reaction of furfural imines 21 with CO
and ethylene gave keto imine 22 in 63% GC yield (eq 5).
GC analysis of the crude reaction mixture did not show
the formation of further reaction products, such as 5,6-
dihydro-6-amino-4H-cyclopenta[b]furan-4-one (23) and
4H-cyclopenta[b]furan-4-one derivative (24). In compari-
son with benzaldehyde imines, the two substituents, the
keto and imino groups, in 22 are located too far from one
another to undergo an intramolecular aldol-type reaction.
The reaction of 25 also afforded keto imine 26 in high
yield (eq 6).
condensation) for the synthesis of 2-substituted inden-
1-ones from aromatic imines. The reaction involves
carbonylation at an ortho C-H bond in the benzene ring.
The isolation of keto imines, in some particular cases,
clearly indicates that the transformation of aromatic
imines to indenones involves keto imines as primary
intermediate.
Exp er im en ta l Section
Gen er a l P r oced u r es. In a 50-mL stainless autoclave were
placed Ru3(CO)12 (64 mg, 0.1 mmol), aromatic imine (2 mmol),
and toluene (6 mL). The autoclave was charged with ethylene
to 7 atm at 25 °C and carbon monoxide to 5 atm at 25 °C and
then heated in an oil bath at 160 °C for 12 h. The autoclave
was cooled to room temperature and the pressure released. To
the reaction mixture was added ca. 5 g of SiO2 (usual chroma-
tography grade, 70-230 mesh), and the resulting mixture was
stirred at room temperature for 1 day. After SiO2 was filtered,
the filtrate was evaporated in vacuo and the coupling product
was isolated by column chromatography on silica gel with
hexane/benzene as eluent. An analytical sample was obtained
by bulb-to-bulb distillation or recrystallization.
2,3-Dih yd r o-2,4-d im eth yl-3-[(1,1-d im eth yleth yl)a m in o]-
1H-in d en -1-on e (4). After the reaction of 1 with CO and
ethylene, bulb-to-bulb distillation gave a mixture of 2 and 4
(trans and cis). Spectral data were obtained from the mixture.
4-m a jor : 1H NMR (CDCl3) δ 1.17 (d, J ) 7.6 Hz, 3H), 1.24 (s,
9H), 2.63 (s, 3H), 2.75-2.92 (m, 1H), 4.62 (d, J ) 6.2 Hz, 1H),
7.18-7.60 (m, 3H); MS, m/ z (rel intensity) 231 (M+, 10), 216
(26), 58 (100). 4-m in or : 1H NMR (CDCl3) δ 1.23 (s, 9H), 1.27
(d, J ) 8.1 Hz), 2.48 (s, 3H), 2.56 (q, J ) 8.1 Hz, 1H), 4.09 (s,
1H), 7.18-7.60 (m, 3H); MS, m/ z (rel intensity) 231 (M+, 8),
216 (16), 58 (100).
2-(2,2-Dim eth ylp r op yl)-4-m eth yl-1H-in d en -1-on e (5): yel-
low oil; Rf ) 0.23 (hexane/benzene ) 2/1); 1H NMR (CDCl3) δ
0.93 (s, 9H), 2.17 (s, 2H), 2.28 (s, 3H), 7.03 (t, J ) 7.2 Hz, 1H),
7.10 (d, J ) 7.2 Hz, 1H), 7.21 (d, J ) 7.2 Hz, 1H), 7.26 (s, 1H);
13C NMR (CDCl3) δ 16.9, 29.4, 31.6, 37.6, 120.3, 127.8, 130.3,
130.3, 135.5, 137.5, 142.6, 143.2, 199.0; IR (neat) 1709, 1604;
MS, m/ z (rel intensity) 214 (M+, 3), 158 (100). Anal. Calcd for
C
15H18O: C, 84.07; H, 8.47. Found: C, 84.01; H, 8.46.
2,3-Dih yd r o-3-[(1,1-d im et h ylet h yl)a m in o]-4-m et h yl-2-
[(tr im eth ylsilyl)m eth yl]-1H-in d en -1-on e (6). The stereo-
chemistry of 6 was not determined, but a single isomer was
obtained: brown oil; bp 170 °C (1 mmHg); 1H NMR (CDCl3) δ
0.00 (s, 9H), 0.81 (dd, J ) 14.9, 10.3 Hz, 1H), 1.03 (dd, J ) 14.9,
4.6 Hz, 1H), 1.22 (s, 9H), 2.45 (s, 3H), 2.67 (dd, J ) 10.3, 4.6 Hz,
1H), 4.10 (s, 1H), 7.33 (t, J ) 7.3 Hz, 1H), 7.40 (d, J ) 7.3 Hz,
1H), 7.55 (d, J ) 7.3 Hz, 1H); 13C NMR (CDCl3) δ -0.5, 17.9,
20.4, 30.1, 50.6, 55.2, 60.7, 121.3, 128.9, 135.8, 136.1, 136.3,
153.9, 209.8; IR (neat) 1711, 1645, 1607, 1591; MS, m/ z (rel
intensity) 303 (M+, 0), 288 (M+ - 15, 7), 73 (100); HRMS calcd
for C18H29NOSi (M+) 303.2018, found 303.2005.
4-Me t h yl-2-[(t r im e t h ylsilyl)m e t h yl]-1H -in d e n -1-on e
(7): brown oil; bp 150 °C (1 mmHg); Rf ) 0.23 (hexane/benzene
) 2/1); 1H NMR (CDCl3) δ 0.04 (s, 9H), 1.74 (d, J ) 1.4 Hz, 2H),
2.24 (s, 3H), 6.96 (t, J ) 7.6 Hz, 1H), 6.97 (m, 1H), 7.06 (d, J )
7.6 Hz, 1H), 7.18 (d, J ) 7.6 Hz, 1H); 13C NMR (CDCl3) δ -1.7,
15.1, 16.9, 120.2, 126.9, 129.4, 130.2, 135.7, 138.2, 143.6, 137.3,
198.7; IR (neat) 1711, 1604; MS, m/ z (rel intensity) 230 (M+,
12), 215 (16), 73 (100); HRMS calcd for C14H18OSi (M+) 230.1127,
found 230.1130.
On the other hand, the reaction of thiophenecarbox-
aldehyde imine 27 gave a mixture of keto imine 28 and
aldol-type product 29 in favor of 28 (eq 7).
2-Meth yl-4-p r op ion yl-1H-in d en -1-on e (10): yellow solid;
mp 81-83 °C (hexane); Rf ) 0.20 (benzene); 1H NMR (CDCl3) δ
1.22 (t, J ) 7.3 Hz, 3H), 1.92 (d, J ) 1.6 Hz, 3H), 2.96 (q, J )
7.3 Hz, 2H), 7.22 (t, J ) 7.6 Hz, 1H), 7.50 (d, J ) 7.6 Hz, 1H),
7.72 (d, J ) 7.6 Hz, 1H), 7.98-8.03 (m, 1H); 13C NMR (CDCl3)
δ 8.0, 10.1, 33.3, 125.0, 127.8, 129.7, 131.7, 132.7, 138.4, 144.9,
143.7, 197.8, 201.5; IR (KBr) 1726, 1683, 1603, 1577; MS, m/ z
(rel intensity) 200 (M+, 36), 171 (17), 143 (100). Anal. Calcd
for C13H12O2: C, 77.98; H, 6.04. Found: C, 78.32; H, 6.07.
4-Meth oxy-2-m eth yl-1H-in d en -1-on e (12): orange solid;
mp 86-88 °C (EtOH); Rf ) 0.23 (hexane/benzene ) 1/2); 1H NMR
(CDCl3) δ 1.85 (d, J ) 1.6 Hz, 3H), 3.85 (s, 3H), 6.91 (d, J ) 7.4
Hz, 1H), 7.03 (d, J ) 7.4 Hz, 1H), 7.11 (t, J ) 7.4 Hz, 1H), 7.30-
7.35 (m, 1H); 13C NMR (CDCl3) δ 9.9, 55.7, 115.6, 118.3, 129.5,
In summary, we have developed a two-step procedure
(carbonylation at a C-H bond and intramolecular aldol
(18) 2-Methyl-4-nitro-1H-inden-1-one was prepared by the bromi-
nation-dehydrobromination of the corresponding indanone derivative.
Murray, R. J .; Cromwell, N. H. J . Org. Chem. 1976, 41, 3540.

5650 J . Org. Chem., Vol. 62, No. 16, 1997
Notes
131.0, 132.0, 133.8, 140.3, 151.6, 198.9; IR (Kbr) 1709, 1660,
1622, 1602; MS, m/ z (rel intensity) 174 (M+, 100), 159 (64). Anal.
Calcd for C11H10O2: C, 75.85; H, 5.79. Found: C, 75.59; H, 5.81.
2-Meth yl-4-(tr iflu or om eth yl)-1H-in d en -1-on e (14): yellow
(CDCl3) δ 1.20 (t, J ) 7.3 Hz, 3H), 1.33 (s, 9H), 2.85 (q, J ) 7.3
Hz, 2H), 6.74 (d, J ) 2.0 Hz, 1H), 7.48 (d, J ) 2.0 Hz, 1H), 8.74
(s, 1H); 13C NMR (CDCl3) δ 7.4, 29.4, 34.7, 58.4, 110.7, 125.5,
143.6, 146.2, 153.2, 196.9; IR (neat) 1680, 1632; MS, m/ z (rel
intensity) 207 (M+, 7), 151 (44), 57 (100); HRMS calcd for
1
oil; bp 120 °C (1 mmHg); Rf ) 0.26 (hexane/benzene ) 3/1); H
NMR (CDCl3) δ 1.94 (d, J ) 1.6 Hz, 3H), 7.20-7.31 (m, 1H),
7.37-7.45 (m, 1H), 7.46-7.57 (m, 2H, 5-H); 13C NMR (CDCl3) δ
9.9, 122.8 (q, J ) 32.7 Hz), 123.5 (q, J ) 271.8 Hz), 124.9, 128.9,
129.5 (q, J ) 3.6 Hz), 131.3, 138.3, 140.5, 142.6 (q, J ) 2.4 Hz),
196.5; IR (neat) 1723, 1681, 1606; MS, m/ z (rel intensity) 212
(M+, 37), 115 (100). Anal. Calcd for C11H7F3O: C, 62.27; H,
3.33. Found: C, 62.24; H, 3.39.
C
12H17NO2 (M+) 207.1259, found 207.1258.
1-[3-[[(1,1-Dim et h ylet h yl)im in o]m et h yl]-2-fu r a n yl]-1-
p r op a n on e (26): yellow solid; mp 51-55 °C, bp 105 °C (5
mmHg); 1H NMR (CDCl3) δ 1.20 (t, J ) 7.3 Hz, 3H), 1.29 (s,
9H), 2.94 (q, J ) 7.3 Hz, 2H), 7.06 (brs, 1H), 7.42 (d, J ) 1.7 Hz,
1H), 8.89 (s, 1H); 13C NMR (CDCl3) δ 7.4, 29.5, 32.5, 58.0, 110.8,
130.9, 144.3, 149.1, 149.9, 192.5; IR (KBr) 1675, 1639; MS, m/ z
(rel intensity) 207 (M+, 1), 151 (56), 136 (100); HRMS calcd for
4-F lu or o-2-m eth yl-1H-in d en -1-on e (16): yellow solid; mp
1
C
12H17NO2 (M+) 207.1259, found 207.1249.
64-65 °C (EtOH); Rf ) 0.20 (hexane/benzene ) 2/1); H NMR
(CDCl3) δ 1.90 (d, J ) 1.6 Hz, 3H), 7.01 (t, J ) 8.1 Hz, 1H), 7.12
(dt, J ) 4.6, 8.1 Hz, 1H), 7.21 (d, J ) 8.1 Hz, 1H), 7.28-7.35 (m,
1H); 13C NMR (CDCl3) δ 10.0, 118.7 (d, J ) 2.4 Hz), 122.2 (d, J
) 21.8 Hz), 129.5 (d, J ) 15.8 Hz), 123.0 (d, J ) 6.1 Hz), 132.9
(d, J ) 3.6 Hz), 136.2 (d, J ) 2.4 Hz), 138.0, 154.5 (d, J ) 251.56
Hz), 197.2; IR (KBr) 1710, 1627, 1614, 1596; MS, m/ z (rel
intensity) 162 (M+, 56), 133 (100); HRMS calcd for C10H7OF (M+)
162.0481, found 162.0470.
1-[2-[[(1,1-Dim eth yleth yl)im in o]m eth yl]-3-th ien yl]-1-pr o-
p a n on e (28) a n d 5,6-Dih yd r o-6-[(1,1-d im eth yleth yl)a m in o]-
5-m eth yl-4H-cyclop en ta [b]th iop h en -4-on e (29). Bulb-to-
bulb distillation gave a 28-enriched fraction and a 29-enriched
fraction. 28: colorless oil; bp 135 °C (1 mmHg); 1H NMR (CDCl3)
δ 1.21 (t, J ) 7.3 Hz, 3H), 1.29 (s, 9H), 2.92 (q, J ) 7.3 Hz, 2H),
7.28 (d, J ) 5.6 Hz, 1H), 7.41 (d, J ) 5.6 Hz, 1H), 9.06 (s, 1H);
13C NMR (CDCl3) δ 7.8, 29.5, 35.1, 57.9, 127.0, 128.4, 138.0,
149.5, 150.2, 197.0; MS, m/ z (rel intensity) 223 (M+, 8), 152
(100); HRMS calcd for C12H17NOS (M+) 223.1030, found 223.1019.
2,5-Dim eth yl-1H-in d en -1-on e (18): yellow oil; bp 130 °C
1
(1 mmHg); Rf ) 0.21 (hexane/benzene ) 1/1); H NMR (CDCl3)
1
δ 1.86 (d, J ) 1.6 Hz, 3H), 2.31 (s, 3H), 6.75 (s, 1H), 6.90 (d, J
29: colorless oil; bp 140 °C (1 mmHg); H NMR (CDCl3) δ 1.25
) 7.3 Hz, 1H), 7.02-7.08 (m, 1H), 7.26 (d, J ) 7.3 Hz, 1H); 13
C
(s, 9H), 1.38 (d, J ) 7.3 Hz, 3H), 2.60-2.75 (m, 1H), 4.07 (d, J
) 3.3 Hz, 1H), 7.11 (d, J ) 5.0 Hz, 1H), 7.35 (d, J ) 5.0 Hz, 1H);
MS, m/ z (rel intensity) 223 (M+, 12), 208 (15), 152 (100); HRMS
calcd for C12H17NOS (M+) 223.1030, found 223.1035.
NMR (CDCl3) δ 9.9, 21.8, 122.3, 122.4, 127.6, 128.2, 136.4, 142.7,
144.5, 145.2, 142.7, 198.3; IR (neat) 1706, 1609; MS, m/ z (rel
intensity) 158 (M+, 93), 129 (73), 115 (100). Anal. Calcd for
C
11H10O: C, 83.52; H, 6.37. Found: C, 83.43; H, 6.16.
2-Meth yl-1H-ben z[f]in d en -1-on e (20): yellow solid; mp
Ack n ow led gm en t. This work was supported, in
part, by grants from the Ministry of Education, Science,
Sports, and Culture, J apan. T.F. acknowledges Re-
search Fellowships of the J apan Society for the Promo-
tion of Science for Young Scientists. Thanks are given
to the Instrumental Analysis Center, Faculty of Engi-
neering, Osaka University, for assistance in obtaining
HRMS and elemental analyses.
181-182 °C (EtOH); Rf ) 0.26 (hexane/benzene ) 1/1); 1H NMR
(CDCl3) δ 1.96 (d, J ) 1.6 Hz, 3H), 7.24 (s, 1H), 7.32-7.36 (m,
1H), 7.37-7.52 (m, 2H), 7.70 (d, J ) 7.9 Hz, 1H), 7.80 (d, J )
7.6 Hz, 1H), 7.84 (s, 1H); 13C NMR (CDCl3) δ 10.4, 119.9, 123.9,
126.6, 128.6, 128.7, 130.3, 130.8, 133.1, 136.4, 139.4, 140.5, 144.6,
197.0; IR (KBr) 1719, 1695, 1626; MS, m/ z (rel intensity) 194
(M+, 72), 165 (100). Anal. Calcd for C14H10O: C, 86.57; H, 5.19.
Found: C, 86.58; H, 5.25.
1-[2-[[(1,1-Dim et h ylet h yl)im in o]m et h yl]-3-fu r a n yl]-1-
p r op a n on e (22): brown oil; bp 100 °C (1 mmHg); 1H NMR
J O970697F