Rhodium-catalyzed conjugate addition of Sb-aryl-1,5-azastibocines to α,β-unsaturated carbonyl compounds

Article abstract of DOI:10.3987/COM-08-S(F)113

Rhodium-catalyzed conjugate addition of Sb-aryl-1,5-azastibocines to α,β-unsaturated carbonyl compounds is described. The rhodium-catalyzed reaction was carried out in aqueous N-methy-2-pyrrolidinone (NMP) to give 1,4-conjugate adduct exclusively, while t

Full text of DOI:10.3987/COM-08-S(F)113

HETEROCYCLES, Vol. 77, No. 2, 2009
1269
HETEROCYCLES, Vol. 77, No. 2, 2009, pp. 1269 - 1283. © The Japan Institute of Heterocyclic Chemistry
Received, 9th September, 2008, Accepted, 10th November, 2008, Published online, 11th November, 2008
DOI: 10.3987/COM-08-S(F)113
RHODIUM-CATALYZED
CONJUGATE
ADDITION
OF
Sb-ARYL-1,5-AZASTIBOCINES TO α,β-UNSATURATED CARBONYL
COMPOUNDS
Naoki Kakusawa,1 Shuji Yasuike,1,2 and Jyoji Kurita1*
1
Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi
Ho-3, Kanazawa 920-1181, Japan; E-mail: j-kurita@hokuriku-u.ac.jp
2
Organization for Frontier Research in Pharmaceutical Sciences, Hokuriku
University, Kanagawa-machi Ho-3, Kanazawa 920-1181, Japan
This paper is dedicated to Professor Emeritus Keiichiro Fukumoto on the occasion
of his 75th birthday
Abstract – Rhodium-catalyzed conjugate addition of Sb-aryl-1,5-azastibocines to
α,β-unsaturated carbonyl compounds is described ．The rhodium-catalyzed
reaction was carried out in aqueous N-methy-2-pyrrolidinone (NMP) to give
1,4-conjugate adduct exclusively, while the palladium catalyzed reaction gave
only Heck-type adduct. The 1,4-addition of various aryl groups such as
substituted benzenes and thiophenes was achieved with various enones and
enoates.
INTRODUCTION
Recent advancements in metal catalyzed C-C bond formation are remarkable,1 because of the
development of the sophisticated ligands of transition metals,2 elaboration of effective transmetallating
agents,3 employment of ionic liquids as reaction medium,4 and microwave irradiation technology.5
Research into effective transmetallating agents is a field of attention. With these agents, the transition
metal-catalyzed reactions can be carried out efficiently under mild conditions and the reactions become
applicable to unstable compounds with labile functional groups.
Progress in chemistry of main group elements6 contributes much to the development of efficient
transmetallating agents because main group compounds exhibit suitable properties for the metal catalyzed
reaction. Particularly, heavier element compounds below the third row show soft nucleophilic
characteristics, and are considered to be reasonable partners for soft electrophiles such as α,β-unsaturated
carbonyl compounds.

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HETEROCYCLES, Vol. 77, No. 2, 2009
For 1,4-conjugate addition, one of the most conventional and prevailing methods is the use of soft copper
reagents such as organocuprates.7 However, because these reagents have to be prepared from moisture
sensitive organolithiums,8 Grignard reagents,9 and organozinc reagents,10 the reactions must be carried
out in strict anhydrous conditions under an inert atmosphere.
Another method for 1,4-conjugate addition was pioneered by Miyaura and co-workers by use of boronic
acid in the presence of rhodium catalysts.11 Inspired by this work, a number of main group compounds
were investigated for the transition metal catalyzed 1,4-conjugate addition including organo-aluminum,12
-boron,13 -tin,14 -silicon,15 -bismuth,16 -indium,17 -plumbum,18 -zirconium,19 and -zinc20 compounds.
Unlike copper reagents, these compounds exhibit a tolerance for hard electrophiles such as water and the
reactions can be carried out in aqueous medium.
Over the past few years, we have investigated the chemistry of organoantimony compounds and revealed
that 1,5-azastibocines (1) with N-Sb intramolecular interaction are excellent transmetallating agents in
Pd-catalyzed cross-coupling reactions.21 These results prompted us to investigate metal-catalyzed
1,4-conjugate addition using 1,5-azastibocines (1), and we now disclose that the reaction of
α,β-unsaturated carbonyl compounds with 1 in the presence of rhodium catalyst resulted in
1,4-conjugated addition in aqueous media. It should be noted that the mode of the reaction is largely
dependent on the nature of the transition metal catalyst employed, and the reaction by use of rhodium
catalyst gave 1,4-conjugate adduct exclusively, while that of palladium catalyst afforded Heck-type
adduct. Details are described here along with preliminary results.22
RESULTS AND DISCUSSION
1. Investigation of Metal Catalyst and Solvent
According to Pauling’s electronegativity, antimony atom is more electronically positive than carbon atom
(Sb, 1.9; C, 2.5).23 Thus, phenyl carbon atom in 1,5-azastibocine is slightly negatively charged and is
considered to exhibit a nucleophilic character. However, it was not reactive enough toward 1,4-conjugate
addition without a metal catalyst. None of the reactions of 1,5-azastibocine occurred with methyl vinyl
ketone even after prolonged heating at 100 ˚C for 24 h in 1,4-dioxane : H2O (10 : 1).
So, we first investigated suitable metal catalysts (Table 1, entries 1-10). Nickel catalysts are reported to be
effective for indium-mediated 1,4-conjugate addition,17 however, neither NiCl2(PPh3)2 nor Ni(cod)2
promoted the reaction of 1,5-azastibocine (1a) with methyl vinyl ketone (2a) and all the starting stibocine
(1a) was recovered unchanged (entries 1 and 2). In the presence of 5 mol% palladium catalyst, the
reaction of 1,5-azastibocine (1a) and methyl vinyl ketone (2a) afforded Heck-type adduct (4aa) solely
and no 1,4-conjugate adduct (3aa) was obtained (entries 3-5). Palladium-catalyzed reactions of
organoantimony compounds to alkenes have already been reported, such as phenylantimony chlorides and

HETEROCYCLES, Vol. 77, No. 2, 2009
1271
triarylantimony diacetates, to give Heck-type adduct.24 Furthermore, palladium-catalyzed reactions of
organoboron and silicon compounds with alkenes also gave the Heck-type adduct.25 It is characteristic of
palladium catalyst to undergo β-elimination with ease to give Heck-type adduct. Thus, it is reasonable for
Sb-aryl-1,5-azastibocine to give Heck-type adduct efficiently in the presence of Pd(OAc)2.
Under the rhodium catalysts, the reaction proceeded efficiently to afford the expected 1,4-adduct as the
major product (entries 6-10). Especially, rhodium catalyst with diene ligand (cod: cyclooctadiene) worked
effectively to suppress the competitive Heck reaction completely. In terms of yield and selectivity of the
product, [RhCl(cod)]2 was found to be a suitable catalyst (entry 10).
Table 1. Investigation of Catalyst and Solvent
But
metal catalyst
O
O
O
(5 mol%)
N
+
+
Ph
Me
Ph
Me
Me
solvent
Sb
Ph
a
°
4aa
100 C
2a
(3 mmol)
3aa
conjugate adduct
1a
Heck adduct
(1 mmol)
Entry
Catalyst
Solvent
Time (h)
3aa (%)b
4aa (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
NiCl2(PPh3)2
Ni(cod)2
Pd(OAc)2
25
24
24
24
24
24
16
14
16
9
---
---
---
---
---
36
55
78
80
81
70
84
75
---
76
77
83
74
---
---
79
43
14
36
11
---
11
---
---
---
---
---
6
dioxane : H2O (10 : 1)
PdCl2
PdCl2(PPh3)2
Rh(acac)(C2H4)2
Rh(nbd)ClO4
Rh(cod)BF4
[Rh(OH)(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
THF : H2O (10 : 1)
DME : H2O (10 : 1)
C2H5OH
5.5
3.5
1
1.5
1
2.5
1
1
CH3COOH
DMU : H2O (10 : 1)
TMU : H2O (10 : 1)
NMP : H2O (10 : 1)
NMP
---
---
9
a Oil bath temperature.
b Isolated yield.
Next, the most suitable solvent for the reaction was investigated by use of [RhCl(cod)]2 as the catalyst
(Table 1, entries 10-18). When the reaction was attempted in aqueous ethereal solvents, the conjugate

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HETEROCYCLES, Vol. 77, No. 2, 2009
adduct (3aa) was produced in good yield, although the reaction required a prolonged time for completion
(entries 10-12). A neutral protic solvent like ethanol was a good alternative to aqueous ethereal solvents
(entry 13), however, acidic protic solvents such as acetic acid were not suitable because of decomposition
of 1,5-azastibocine (1a) in acidic media (entry 14). Aqueous dipolar solvents were appropriate for the
reaction to give the conjugate adduct (3aa) in good yield in short time (entries 15-17). Among them,
aqueous NMP was found to be the best choice of solvent giving the expected product (3aa) exclusively in
83% yield in 1 h and no Heck type adduct (4aa) was observed (entry 17). Also apparent was that water
plays an important role in the present reaction. When the reaction was conducted in dehydrated NMP,
Heck type adduct (4aa) was formed in 9% yield which was never observed in aqueous NMP (entry 18).
The ratio of water in the reaction medium is one of the important factors in controlling the competing
1,4-conjugate reaction and Mizoroki-Heck reaction in other rhodium catalyzed reaction.26
2. The Reaction of Various Sb-Aryl-1,5-azastibocines with Methyl Vinyl Ketone (Table 2)
Under the optimized condition proved above, various Sb-aryl-1,5-azastibocines (1a-h) were reacted with
methyl vinyl ketone (2a) and the results are summarized in Table 2. Sb-Aryl-1,5-azastibocine derivatives
(1a-d) were prepared by the reported procedure.21 Following this procedure, Sb-(p-fluorophenyl) (1e) and
thienyl-1,5-azastibocine (1f-h) were also prepared. Thus, lithium or Grignard reagent of p-fluorophenyl-
and thienyl- derivatives were reacted with Sb-bromo-1,5-azastibocine to give the Sb-(p-fluorophenyl) (1e)
and thienyl-1,5-azastibocines (1f-h) in stable crystalline form (See experimental section). Regardless of
the electronic nature of aryl groups, all the Sb-aryl-1,5-azastibocines gave the corresponding
1,4-conjugate adducts (3aa-3ha) in good yields in 1 h at 100 ˚C. From these results, Sb-aryl-1,5-aza-
stibocines (1) are proved to be good aryl donors in the present 1,4-conjugate addition.
3. The Reaction of Sb-Phenyl-1,5-azastibocine with Various Enones and Enoates (Table 3)
The reactions of Sb-phenyl-1,5-azastibocine (1a) with various enones and enoates (2b-k) were
investigated and the results are shown in Table 3. The reaction with enone unsubstituted at β-position and
with cyclic enones gave the expected 1,4-adducts in good yield (entries 1-4). However, the yields of the
1,4-adduct were decreased in the reaction of enones with bulky substituent at β-position (entries 5 and 6).
In the reaction of enoates, steric hindrance of ester moiety did not affect the reaction and methyl, butyl,
and t-butyl esters gave the 1,4-adducts in high yield (entries 7-9). However, substituents on double bonds
inhibited the 1,4-addition and the corresponding adducts were formed in moderate yields (entries 10, 11).
In all cases, the 1,4-adducts were obtained exclusively and none of the Heck-type adduct was observed.
Under the [RhCl(cod)]2 catalyst in aqueous NMP, methyl vinyl ketone (2a) also underwent 1,4-conjugate
addition with triphenylstibane (Ph3Sb) which was not activated by intramolecular N-Sb interaction.

HETEROCYCLES, Vol. 77, No. 2, 2009
1273
Table 2. Reaction of Various Sb-aryl-1,5-azastibocines (1a-h) with methyl vinyl ketone (2a)
But
O
O
5 mol% [RhCl(cod)]2
NMP : H2O (10 : 1)
N
+
Ar
Me
Me
Sb
Ar
a
1a-h
(1 mmol)
°
2a
3aa-3ha
100 C
1 h
(1.5 mmol)
Entry
Ar
3 (%)
Entry
1
1
Ar
1
3 (%)
5
6
7
F
a :
b :
c :
90
e :
80
Me
94
79
86
f :
g :
h :
2
3
74
87
87
S
Me
OMe
Cl
S
8
Me
d :
4
S
a Oil bath temperature
Table 3. Reaction of Sb-phenyl-1,5-azastibocines (1a) with various enones and enoates (2)
But
5 mol% [RhCl(cod)]2
N
electrophile
1,4-conjugate adduct
+
NMP:H2O (10:1)
Sb
Ph
a
°
100 C , 1 h
3aa-ak
1a
2a-k
(1 mmol)
(1.5 mmol)
Entry Electrophile 2
Adduct 3
Yield (%)b
Entry Electrophile 2
Adduct 3 Yield (%)b
O
O
O
O
1
2
3
a:
b:
c:
80
86
80
7
8
9
g:
h:
i:
84
Ph
OMe
Me
Ph
Me
OMe
OBu
O
O
O
O
94
Et
O
Ph
OBu
Ph
Et
O
O
O
>99
OBut
OMe
OBut
O
Ph
Ph
Ph
O
O
O
O
O
4
d:
92
10 j:
11 k:
66
51
Me
Me
Ph
OMe
Ph
Ph
O
O
Me
5
6
e:
f:
59
57
Me
OMe
OMe
Me
Me
Me
Me
O
Ph
O
Me
a Oil bath temperature.
b Isolated yield
Me Me
Me
Me
Me

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HETEROCYCLES, Vol. 77, No. 2, 2009
However, the reaction required a much longer time (24 h). These results suggest that the intramolecular
N-Sb interaction in 1,5-azastibocine (1) contributed to activation of the aryl group on antimony and
reduction of the reaction time.
A possible mechanism of this reaction has already been proposed in the preliminary report,22 which may
be similar to the mechanism for 1,4-addition of organoboronic acid to enones.27
In summary, Sb-aryl-1,5-azastibocines were shown to be good aryl donors in the rhodium catalyzed
1,4-conjugate addition to α,β-unsaturated carbonyl compounds. In this reaction, high selectivity for the
1,4-conjugate adduct was achieved and the competing Heck-type reaction was completely suppressed
which can be realized by use of a palladium catalyst.
EXPERIMENTAL
General information. Reactions requiring anhydrous conditions were performed in pre-dried glassware
under an argon atomosphere. Elementary combustion analyses were determined with a Yanako CHN
CORDER MT-5 and melting points were taken on a Yanagimoto micro melting point hot-stage apparatus
(MP-S3) and are uncorrected. LRMS (EI) spectra were obtained on a JEOL JMS-SX 102A instrument
1
and IR spectra were recorded on a HORIBA FT-720 instrument. H NMR (TMS: δ 0.00 ppm as an
internal standard) and 13C NMR (CDCl3: δ 77.0 ppm as an internal standard) spectra were recorded on a
JEOL JNM-ECA-400 (400 MHz and 100 MHz) spectrometer in CDCl3. All chromatographic separations
were accomplished with Silica Gel 60N (Kanto Chemical Co., Inc.). TLC was performed with
Macherey-Nagel Pre-coated TLC plates Sil G25 UV254. Dehydrated diethyl ether and THF were
purchased from Kanto Chemical Co., Inc. (Cat. No. 14547-84 and 40993-85) and used without further
distillation. N-t-Butyl-12-bromo-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine, N-t-butyl-12-phenyl-
5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a), N-t-butyl-12-(4-tolyl)-5,6,7,12-tetrahydrodibenz-
[c,f][1,5]azastibocine
(1b),
N-t-butyl-12-(4-methoxyphenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]-
azastibocine (1c), N-t-butyl-12-(4-chlorophenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1d)
were prepared from the reported procedure.21
Preparation of N-t-butyl-12-(4-fluorophenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1e)
n-Butyllithium (1.57 M, 3.82 mL, 6.00 mmol) was added dropwise to a solution of p-bromofluoro-
benzene (1.05 g, 6.00 mmol) in Et2O (20 mL) at 0 ˚C and the mixture was stirred at this temperature for 1
h. A THF solution (30 mL) of N-t-butyl-12-bromo-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1.81 g,
4.00 mmol) was added slowly and the mixture was stirred at 0 ˚C for 2 h. The reaction mixture was
diluted with an excess amount of Et2O and quenched with water. The organic layer was washed with
brine and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo and the residue

HETEROCYCLES, Vol. 77, No. 2, 2009
1275
was recrystallized from CHCl3-EtOH.
N-t-Butyl-12-(4-fluorophenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1e): 1.21 g (65%),
colorless prisms, mp 146-147 ˚C. Anal. Calcd for C24H25FNSb: C, 61.56; H, 5.38; N, 2.99. Found: C,
1
61.61; H, 5.35; N, 2.81. LRMS (EI) m/z: 467 (M+, 35%), 372 (100%), 316 (41%).225 (12%). H NMR
(CDCl3) δ: 1.23 (9H, s), 3.86 (2H, d, J = 15.1 Hz), 4.17 (2H, d, J = 15.1 Hz), 7.02-7.17 (10H, m),
2
7.60-7.63 (2H, m). 13C NMR (CDCl3) δ: 26.9 (q), 54.8 (t), 57.6 (s), 115.5 (d, JF = 19.1 Hz), 126.2 (d),
3
1
127.1 (d), 128.0 (d), 136.0 (d), 136.4 (s), 140.5 (d, JF = 6.75 Hz), 141.4 (s), 146.7 (s), 163.4 (d, JF =
262.5 Hz).
Preparation of N-t-butyl-12-(2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1f)
General procedure: To a suspension of magnesium (0.74 g, 30.7 mmol) in dry Et2O (80 mL),
2-bromothiophene (5 g, 30.7 mmol) was added slowly at rt in the presence of a catalytic amount of iodine.
After almost all magnesium metal was dissolved, a THF solution (80 mL) of N-t-butyl-12-bromo-
5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (13.9 g, 30.7 mmol) was added dropwise and the mixture
was stirred at rt for 3 h. The mixture was diluted with Et2O and quenched with water. The organic layer
was washed with brine and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo
and the crude residue was purified on a silica gel column chromatography (hexane : Et2O = 10 : 1).
N-t-Butyl-12-(2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1f): 10.8 g (77%), colorless
prisms, mp 138-139 ˚C (from hexane-benzene). LRMS (EI) m/z: 455 (M+, 17%), 398 (12%), 372 (93%),
316 (100%), 225 (16%), 165 (13%). Anal. Calcd for C22H24NSSb: C, 57.91; H, 5.30; N, 3.07. Found: C,
57.85; H, 5.35; N, 3.00. 1H NMR (CDCl3) δ: 1.24 (9H, s), 3.87 (2H, d, J = 15.3 Hz), 4.18 (2H, d, J = 15.3
Hz), 7.03-7.12 (4H, m), 7.15-7.21 (2H, m), 7.30 (1H, t, J = 3.43 Hz), 7.37 (2H, d, J = 7.33 Hz), 7.43 (1H,
13
d, J = 3.21 Hz), 7.74 (1H, d, J = 5.04 Hz). C NMR (CDCl3) δ: 26.9 (q), 54.8 (t), 57.9 (s), 126.0 (d),
127.2 (d), 128.2 (d), 131.8 (d), 136.2 (s), 136.2 (d), 138.0 (d), 142.8 (s), 146.1 (s).
N-t-Butyl-12-(3-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1g)
N-t-Butyl-12-(3-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1g) was prepared
from magnesium (432 mg, 18.0 mmol), 2-bromo-3-methylthiophene (3.19 g, 18.0 mmol) and N-t-butyl-
12-bromo-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (6.78 g, 15 mmol) by the procedure described
above.
N-t-Butyl-12-(3-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1g): 5.91 g (84%),
colorless prisms, mp 145-146 ˚C (from hexane-benzene). LRMS (EI) m/z: 469 (M+, 8%), 412 (8%), 372
(68%), 316 (100%), 225 (14%). Anal. Calcd for C23H26NSSb: C, 58.74; H, 5.57; N, 2.98. Found: C,
58.89; H, 5.46; N, 2.86. 1H NMR (CDCl3) δ: 1.23 (9H, s), 1.26 (3H, br. s), 3.88 (2H, d, J = 15.3 Hz), 4.17

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HETEROCYCLES, Vol. 77, No. 2, 2009
(2H, d, J = 15.3 Hz), 7.04-7.12 (5H, m), 7.14-7.19 (2H, m), 7.34 (2H, d, J = 7.80 Hz), 7.63 (2H, d, J =
5.04 Hz). 13C NMR (CDCl3) δ: 18.0 (q), 26.9 (q), 54.9 (t), 57.8 (s), 126.0 (d), 127.1 (d), 128.1 (d), 130.3
(s), 131.1 (d), 135.4 (s), 136.2 (d), 136.7 (s), 146.2 (s).
N-t-Butyl-12-(5-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1h)
N-t-Butyl-12-(5-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1h) was prepared
from magnesium (432 mg, 18.0 mmol), 2-bromo-5-methylthiophene (3.19 g, 18.0 mmol) and
N-t-butyl-12-bromo-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (6.78 g, 15 mmol) by the procedure
described above.
N-t-Butyl-12-(5-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1h): 6.90 g (98%),
colorless prisms, mp 166-167 ˚C (from hexane-benzene). LRMS (EI) m/z: 469 (M+, 8%), 412 (7%), 372
(52%), 316 (100%), 225 (14%). Anal. Calcd for C23H26NSSb: C, 58.74; H, 5.57; N, 2.98. Found: C,
1
58.85; H, 5.40; N, 2.83. H NMR (CDCl3) δ: 1.23 (9H, s), 2.62 (3H, s), 3.85 (2H, d, J = 15.6 Hz), 4.17
(2H, d, J = 15.6 Hz), 6.92-7.24 (8H, m), 7.45 (2H, d, J = 6.90 Hz). 13C NMR (CDCl3) δ: 15.4 (q), 26.9 (q),
54.8 (t), 57.8 (s), 125.9 (d), 126.8 (d), 127.2 (d), 128.1 (d), 136.2 (d), 136.3 (s), 138.4 (d), 140.7 (s), 146.1
(s), 146.7 (s).
Palladium-catalyzed reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine
(1a) with 3-butene-2-one (2a)
A mixture of 1,5-azastibocine (1a) (449 mg, 1.00 mmol), 3-butene-2-one (2a) (105 mg, 1.50 mmol) and
Pd(OAc)2 (23 mg, 0.1 mmol) in 1,4-dioxane : H2O (10 : 1) was stirred at 100 ˚C for 1 h under argon
atomosphere. The mixture was diluted with Et2O and washed with brine. The organic layer was separated
and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo and the crude residue
was purified on silica gel column chromatography (hexane : EtOAc = 9 : 1 as eluent). 4-Phenyl-3-
butene-2-one (4aa): 114 mg (79%), colorless oil. LRMS (EI) m/z: 146 (M+, 75%), 131 (100%), 103
-1
-1 1
(70%), 77 (26%). IR (KBr) ν: 1668 (C=O) cm , 1610 (C=C) cm . H NMR (CDCl3) δ: 2.37 (3H, s),
6.72 (1H, d, J = 16.5 Hz), 7.37-7.40 (3H, m), 7.50 (1H, d, J = 16.5 Hz), 7.52-7.55 Hz (2H, m). 13C NMR
(CDCl3) δ: 27.5 (t), 127.1 (d), 128.2 (d), 129.0 (d), 130.5 (d), 134.4 (s), 143.4 (d), 198.4 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with 3-butene-
2-one (2a)
General procedure: A mixture of 1,5-azastibocine (1a) (449 mg, 1.00 mmol), 3-butene-2-one (2a) (105
mg, 1.50 mmol) and [RhCl(cod)]2 (25 mg, 0.05 mmol) in NMP : H2O (10 : 1) was stirred at 100 ˚C for 1
h under argon atomosphere. The mixture was diluted with Et2O and washed with brine. The organic layer

HETEROCYCLES, Vol. 77, No. 2, 2009
1277
was separated and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo and the
crude residue was purified using silica gel column chromatography (hexane : EtOAc = 9 : 1 as eluent).
4-Phenyl-2-butanone (3aa): 118 mg (80%), colorless oil. LRMS (EI) m/z: 148 (M+, 100%), 133 (16%),
-1
1
105 (61%), 91 (43%), 77 (12%). IR (KBr) ν: 1712 (C=O) cm . H NMR (CDCl3) δ: 2.10 (3H, s), 2.74
(2H, t, J = 7.79 Hz), 2.88 (2H, t, J = 7.79 Hz), 7.15 – 7.20 (3H, m), 7.25-7.28 (2H, m). 13C NMR (CDCl3)
δ: 29.7 (t), 30.0 (q), 45.1 (t), 126.0 (d), 128.2 (d), 128.4 (d), 207.8 (s).
Reaction of N-t-butyl-12-(4-tolyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1b) with 3-
butene-2-one (2a)
4-(4-Tolyl)-2-butanone (3ba): 120 mg (74%), colorless oil. LRMS (EI) m/z: 162 (M+, 100%), 147 (29%),
119 (45%), 105 (72%), 91 (16%), 77 (8%). IR (KBr) ν: 1716 (C=O) cm -1. 1H NMR (CDCl3) δ: 2.12 (3H,
s), 2.31 (3H, s), 2.73 (2H, t, J = 7.78 Hz), 2.85 (2H, t, J = 7.78 Hz), 7.00 (2H, d, J = 7.50 Hz), 7.20 (2H, d,
13
J = 7.50 Hz). C NMR (CDCl3) δ: 20.9 (q), 29.3 (t), 30.0 (q), 45.6 (t), 128.1 (d), 129.1 (d), 135.5 (s),
137.8 (s).
Reaction of N-t-butyl-12-(4-methoxyphenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1c)
with 3-butene-2-one (2a)
4-(4-Methoxyphenyl)-12-butanone (3ca): 154 mg (87%), colorless oil. LRMS (EI) m/z: 178 (M+, 85%),
163 (8%), 135 (12%), 121 (100%), 108 (8%), 91 (11%). IR (KBr) ν: 1712 (C=O) cm -1. 1H NMR (CDCl3)
δ: 2.13 (3H, s), 2.74 (2H, t, J = 7.33 Hz), 3.77 (3H, s), 6.82 (2H, d, J = 8.70 Hz), 7.09 (2H, d, J = 8.70
13
Hz). C NMR (CDCl3) δ: 28.8 (t), 30.1(q), 45.4 (t), 55.2 (q), 113.8 (d), 129.2 (d), 132.9 (s), 157.9 (s),
208.1 (s).
Reaction of N-t-butyl-12-(4-chlorophenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1d) with
3-butene-2-one (2a)
4-(4-Chlorophenyl)-2-butanone (3da): 158 mg (87%), colorless oil. LRMS (EI) m/z: 182 (M+, 100%),
-1
1
167 (23%), 147 (23%), 139 (32%), 125 (69%), 103 (27%). IR (KBr) ν: 1716 (C=O) cm . H NMR
(CDCl3) δ: 2.13 (3H, s), 2.74 (2H, t, J = 7.33 Hz), 2.86 (2H, t, J = 7.33 Hz), 7.11 (2H, d, J = 8.24 Hz),
7.24 (2H, d, J = 8.24 Hz). 13C NMR (CDCl3) δ: 28.9 (t), 30.1 (q), 44.8 (t), 128.5 (d), 129.7 (d), 131.8 (s),
139.4 (s).
Reaction of N-t-butyl-12-(4-fluorophenyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1e) with
3-butene-2-one (2a)
4-(4-Fluorophenyl)-2-butanone (3ea): 150 mg (90%), colorless oil. LRMS (EI) m/z: 166 (M+, 100%),

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HETEROCYCLES, Vol. 77, No. 2, 2009
151(21%), 123 (27%), 109 (73%). IR (KBr) ν: 1718 (C=O) cm -1. 1H NMR (CDCl3) δ: 2.13 (3H, s), 2.73
(2H, t, J = 7.56 Hz), 2.86 (2H, t, J = 7.56 Hz), 6.95 (2H, dd, J2,3 = J3,F = 8.47 Hz), 7.13 (2H, dd, J2,3
=
8.47 Hz, J2,F = 5.50 Hz). 13C NMR (CDCl3) δ: 28.8 (t), 30.1 (q), 45.1 (t), 115.2 (d, 2JF = 21.1 Hz), 129.7
(d, 3JF = 7.67 Hz), 136.6 (s), 161.3 (d, 1JF = 243.5 Hz), 207. 6 (s).
Reaction of N-t-butyl-12-(2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1f) with 3-
butene-2-one (2a)
A mixture of 12-(2-thienyl)-1,5-azastibocine (1f) (455 mg, 1.00 mmol), 3-butene-2-one (2) (105 mg, 1.50
mmol) and [RhCl(cod)]2 (25 mg, 0.05 mmol) in NMP : H2O (10 : 1) was stirred at 100 ˚C for 1 h under
argon atomosphere. The mixture was diluted with Et2O and washed with brine. The organic layer was
separated and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo and the crude
residue was purified on silica gel column chromatography (hexane : EtOAc = 9 : 1 as eluent).
4-(2-Thienyl)-2-butanone (3fa): 145 mg (94%), colorless oil. LRMS (EI) m/z: 154 (M+, 100%), 97 (87%),
84 (7%). IR (KBr) ν: 1716 (C=O) cm -1. 1H NMR (CDCl3) δ: 2.16 (3H, s), 2.18 (2H, t, J = 7.33 Hz), 3.11
(2H, t, J = 7.33 Hz), 6.79 (1H, dd, J = 3.66 Hz, J = 1.37 Hz), 6.90 (1H, dd, J = 5.04 Hz, J = 3.66 Hz),
7.11 (1H, dd, J = 5.04 Hz, J = 1.37 Hz). 13C NMR (CDCl3) δ: 23.8 (q), 30.0 (q), 45.2 (t), 123.3 (d), 124.5
(d), 126.8 (d), 143.6 (s), 207.2 (s).
Reaction of N-t-butyl-12-(3-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1g)
with 3-butene-2-one (2a)
4-(3-Methyl-2-thienyl)-2-butanone (3ga): 133 mg (79%), colorless oil. LRMS (EI) m/z: 168 (M+, 35%),
125 (20%), 111 (100%), 97 (8%). IR (KBr) ν: 1716 (C=O) cm -1. 1H NMR (CDCl3) δ: 2.15 (3H, s), 2.16
(3H, s), 2.76 (2H, d, J = 7.56 Hz), 3.00 (2H, d, J = 7.56 Hz), 6.76 (1H, d, J = 5.04 Hz), 7.01 (1H, d, J =
13
5.04 Hz). C NMR (CDCl3) δ: 13.5 (q), 21.7 (t), 30.0 (q), 44.7 (t), 121.2 (d), 130.0 (d), 133.0 (s), 136.5
(s), 207.3 (s).
Reaction of N-t-butyl-12-(5-methyl-2-thienyl)-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1h)
with 3-butene-2-one (2a)
4-(5-Methyl-2-thienyl)-2-butanone (3ha): 144 mg (86%), colorless oil. LRMS (EI) m/z: 168 (M+, 100%),
-1
1
125 (32%), 111 (66%), 97 (5%). IR (KBr) ν: 1716 (C=O) cm . H NMR (CDCl3) δ: 2.16 (3H, s), 2.42
(3H,s), 2.78 (2H, t, J = 7.33 Hz), 3.02 (2H, t, J = 7.33 Hz), 6.53 (1H, d, J = 2.75 Hz), 6.55 (1H, d, J =
13
2.75 Hz), C NMR (CDCl3) δ: 15.2 (q), 24.0 (t), 30.0 (q), 45.2 (t), 124.2 (d), 124.6 (d), 137.7 (s),
141.2(s), 207.4 (s).

HETEROCYCLES, Vol. 77, No. 2, 2009
1279
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with 1-
pentene-3-one (2b) (Table 3, entry 2)
1-Phenyl-3-pentanone (3ab): 139 mg (86%), colorless oil. LRMS (EI) m/z: 162 (M+, 100%), 133 (48%),
105 (95%), 91 (86%), 77 (20%). IR (KBr) ν: 1716 (C=O) cm -1. 1H NMR (CDCl3) δ: 1.04 (3H, t, J = 7.33
Hz), 2.40 (2H, q, J = 7.33 Hz), 2.72 (2H, t, J = 7.79 Hz), 2.90 (2H, t, J = 7.79 Hz), 7.14-7.20 (3H, m),
7.23-7.30 (2H, m). 13C NMR (CDCl3) δ: 7.7 (t), 29.8 (t), 36.1 (t), 43.8 (t), 126.0 (d), 128.2 (d), 128.4 (d),
141.1 (s), 210.6 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with 2-cyclo-
hexene-1-one (2c) (Table 3, entry 3)
3-Phenylcyclohexanone (3ac): 139 mg (80%), colorless oil. LRMS (EI) m/z: 174 (M+, 100%), 131 (52%),
117 (62%), 104 (56%), 91 (23%). IR (KBr) ν: 1712 (C=O) cm -1. 1H NMR (CDCl3) δ: 1.70-1.82 (2H, m),
13
2.05-2.20 (2H, m), 2.35-2.65 (4H, m), 2.95-3.05 (1H, m), 7.20-7.27 (3H, m), 7.31-7.37 (2H, m). C
NMR (CDCl3) δ: 25.5 (t), 32.7 (t), 41.1 (t), 44.7 (d), 48.9 (t), 126.5 (d), 126.6 (d), 129.5 (d), 144.3 (s),
211.1 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with 2-cyclo-
pentene-1-one (2d) (Table 3, entry 4)
3-Phenylcyclopentanone (3ad): 147 mg (92%), colorless oil. LRMS (EI) m/z: 160 (M+, 100%), 131
-1
1
(26%), 117(44%), 104 (94%), 91 (19%), 77 (10%). IR (KBr) ν: 1739 (C=O) cm . H NMR (CDCl3) δ:
1.91-2.05 (1H, m), 2.25-2.50 (4H, m), 2.61-2.72 (1H, m), 3.35-3.47 (1H, m), 7.23-7.27 (3H, m),
7.31-7.36 (2H, m). 13C NMR (CDCl3) δ: 31.1 (t), 38.8 (t), 42.1 (d), 45.7 (t), 126.5 (d), 126.6 (d), 128.6 (d),
143.0 (s), 218.3 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with 3-
pentene-2-one (2e) (Table 3, entry 5)
4-Phenyl-2-pentanone (3ae): 95 mg (59%), colorless oil. LRMS (EI) m/z: 162 (M+, 79%), 147 (92%), 105
-1
1
(100%), 91 (40%), 77 (21%). IR (KBr) ν: 1716 (C=O) cm . H NMR (CDCl3) δ: 1.26 (3H, d, J = 6.87
13
Hz), 2.05 (3H, s), 2.61-2.78 (2H, m), 3.29 (1H, m), 7.15-7.23 (3H, m), 7.26-7.33 (2H, m). C NMR
(CDCl3) δ: 22.0 (q), 30.5 (q), 35.4 (d), 52.0 (t), 126.3 (d), 126.8 (d), 128.5 (d), 146.1 (s), 207.8 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with 5-methyl-
3-hexene-2-one (2f) (Table 3, entry 6)
5-Methyl-4-phenyl-2-hexanone (3af): 101 mg (57%), colorless oil. LRMS (EI) m/z: 191 (M++1, 12%),

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HETEROCYCLES, Vol. 77, No. 2, 2009
190 (M+, 6%), 147 (20%), 132 (100%), 105 (20%), 91 (25%), 77 (10%). IR (KBr) ν: 1716 (C=O) cm -1.
1H NMR (CDCl3) δ: 0.74 (3H, d, J = 6.64 Hz), 0.92 (3H, d, J = 6.64 Hz), 2.00 (3H, s), 2.76-2.81 (2H, m),
13
2.91 (1H, m), 7.11-7.20 (3H, m), 7.24-7.29 (2H, m). C NMR (CDCl3) δ: 20.3 (q), 20.7 (q), 30.5 (q),
33.3 (d), 47.6 (t), 48.0 (d), 126.2 (d), 128.1 (d), 128.2 (d), 143.2 (s), 208.3 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with methyl
acrylate (2g) (Table 3, entry 7)
Methyl 3-phenylpropanoate (3ag): 139 mg (82%), colorless oil. LRMS (EI) m/z: 164 (M+, 64%), 131
-1
1
(58%), 91 (100%), 77 (28%). IR (KBr) ν: 1735 (C=O) cm . H NMR (CDCl3) δ: 2.55 (2H, t, J = 7.76
Hz), 2.87 (2H, t, J = 7.76 Hz), 3.58 (3H, s), 7.08-7.16 (3H, m), 7.18-7.24 (2 H, m). 13C NMR (CDCl3) δ:
30.9 (t), 35.6 (t), 51.5 (q), 126.2 (d), 128.4 (d), 140.4 (s), 173.3 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with n-butyl
acrylate (2h) (Table 3, entry 8)
n-Butyl 3-phenylpropanoate (3ah): 195 mg (94%), colorless oil. LRMS (EI) m/z: 206 (M+, 95%), 150
(35%), 133 (30%), 104 (100%), 91 (60%). IR (KBr) ν: 1735 (C=O) cm -1. 1H NMR (CDCl3) δ: 0.91 (3H, t,
J = 7.33 Hz), 1.33 (2H, sextet, J = 7.33 Hz), 1.57 (2H, quintet, J = 7.33 Hz), 2.62 (2H, t, J = 8.01 Hz),
13
2.95 (2H, t, J = 8.01 Hz), 7.15-7.22 (3H, m), 7.25-7.31 (2H, m). C NMR (CDCl3) δ: 13.7 (q), 19.1 (t),
30.6 (t), 31.0 (t), 35.9 (t), 64.3 (t), 126.2 (d), 128.2 (d), 128.4 (d), 140.5 (s), 172.9 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with t-butyl
acrylate (2i) (Table 3, entry 9)
t-Butyl 3-phenylpropanoate (3ai): 204 mg (99%), colorless oil. LRMS (EI) m/z: 207 (M++1, 36%), 206
-1
1
(M+, 23%), 150 (100%), 133 (45%), 104 (45%), 91 (40%). IR (KBr) ν: 1710 (C=O) cm . H NMR
(CDCl3) δ: 1.41 (9H, s), 2.53 (2H, d, J = 7.79 Hz), 2.90 (2H, d, J = 7.79 Hz), 7.14-7.21 (3H, m),
7.24-7.30 (2H, m). 13C NMR (CDCl3) δ: 28.0 (q), 28.1 (s), 31.1 (t), 37.0 (t), 126.0 (t), 128.2 (d), 128.3 (d),
140.7 (s), 172.1 (s).
Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with methyl
crotonate (2j) (Table 3, entry 10)
Methyl 3-phenylbutanoate (3aj): 118 mg (66%), colorless oil. LRMS (EI) m/z: 179 (M+, 36%). IR (KBr)
ν: 1739 (C=O) cm -1. 1H NMR (CDCl3) δ: 1.29 (3H, d, J = 7.33 Hz), 2.57 (2H, m), 3.27 (1H, m), 3.61 (3H,
s), 7.17-7.23 (3H, m), 7.27-7.32 (2H, m). 13C NMR (CDCl3) δ: 21.7 (q), 36.4 (d), 42.7 (t), 51.4 (q), 126.7
(d), 128.5 (d), 145.7 (s), 172.8 (s).

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Reaction of N-t-butyl-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine (1a) with methyl
methacrylate (2k) (Table 3, entry 11)
Methyl 2-methyl-3-phenylpropanoate (3ak): 91 mg (51%), colorless oil. LRMS (EI) m/z: 178 (M+, 52%),
118 (100%). IR (KBr) ν: 1735 (C=O) cm -1. 1H NMR (CDCl3) δ: 1.15 (3H, d, J = 6.87 Hz), 2.68 (2H, m),
3.02 (1H, m), 7.13-7.22 (3H, m), 7.24-7.30 (2H, m). 13C NMR (CDCl3) δ: 16.7 (q), 39.7 (t), 41.4 (d), 51.5
(q), 126.3 (d), 128.3 (d), 128.9 (d), 139.3 (s), 176.5 (s).
ACKNOWLEDGEMENTS
This work was supported in part by a Grant-in-Aid for Scientific Research (C) from Japan Society for the
Promotion of Science (JSPS) (to J. K and N. K); the “Academic Frontier” Project for Private University
from the Ministry of Education, Culture, Sports, Sciences and Technology of Japan (to S. Y). Financial
support was also provided by The Specific Research Fund of Hokuriku University. All of which is
gratefully acknowledged.
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