Palladium-mediated direct synthesis of N-substituted 4-methyl- and 4-ethylisoquinolone derivatives

Article abstract of DOI:10.1055/s-2008-1067244

N-Substituted 4-methyl- and 4-ethylisoquinolone derivatives are prepared from different N-allylbenzamide derivatives in a single step through a ligand-free palladium-mediated intramolecular Heck cyclization. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1067244

PAPER
2991
Palladium-Mediated Direct Synthesis of N-Substituted 4-Methyl- and
4-Ethylisoquinolone Derivatives
Synthesis of
N
-Sub
r
stituted
i
Isoqui
s
Department of Chemistry, University of Kalyani, Kalyani 741235, WB, India
Fax +91(33)25828282; E-mail: kcm_ku@yahoo.co.in
Received 14 February 2008; revised 11 June 2008
R
Abstract: N-Substituted 4-methyl- and 4-ethylisoquinolone deriv-
atives are prepared from different N-allylbenzamide derivatives in
a single step through a ligand-free palladium-mediated intramolec-
R
R
I
(ii)
Ar
N
O
(i)
Ar
N
H
ular Heck cyclization.
Ar
N
Key words: isoquinolones, Heck cyclization, intramolecular cy-
O
clization, palladium acetate
R = H
1a Ar =
1e Ar =
R = H
O
N
Substituted isoquinolones are important from both syn-
R = H
Me
1b Ar =
thetic and application points of view. The isoquinolone
moiety is found in several alkaloids and other pharmaco-
Cl
R = Me
1f Ar =
logically important compounds.1–13 Isoquinolones have
R = H
1c Ar =
Cl
been employed as useful intermediates in the synthesis of
indenoisoquinolines, protoberberines, and dibenzoquino-
lizines. These are of much interest in medicinal chemistry.
Due to their biological and pharmacological importance,
R = H
1d Ar =
1g Ar =
R = Me
O
N
O
O
several methods have been reported for the synthesis of
isoquinolone derivatives.14–19 Only few methods have uti-
lized palladium catalyst. Paladium-catalyzed20,21 reac-
tions have been extensively used for carboannulation22–25
and heteroannulation26–35 processes. Several research
groups have reported the synthesis of aromatic heterocy-
cles via palladium-catalyzed annulation of internal
alkynes.36,37 Others have shown that palladium-catalyzed
cyclizations are valuable synthetic tools for the prepara-
tion of a wide variety of heterocycles using vinylic com-
pounds, terminal alkynes, allenes, and other substrates. In
continuation of our work on palladium-catalyzed
cyclization38–40 we report here a straightforward protocol
for the synthesis of hitherto unreported substituted isoqui-
nolone derivatives.
Me
Scheme 1 Reagents and conditions: (i) 2-iodobenzoyl chloride, an-
hyd CH2Cl2, Et3N, DMAP (cat.), r.t.; (ii) Pd(OAc)2, Bu4NBr, KOAc,
anhyd DMF, D.
Table 1 Cyclization of 1a to 2aa
O
I
N
N
O
Entry Catalystb
Basec
Solvent
DMF
DMF
DMF
DMF
MeCN
DMF
Yield (%)
1
2
3
4
5
6
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
PdCl2
KOAc
K2CO3
Cs2CO3
Et3N
95
50
65
The Heck precursors 1a–g were synthesized in one step
by the reaction between N-allyl derivatives of the corre-
sponding amines obtained with 2-iodobenzoyl chloride in
anhydrous dichloromethane in the presence of triethyl-
amine and a catalytic amount of DMAP as outlined in
Scheme 1.
d
–
d
KOAc
KOAc
–
When the intramolecular Heck reaction was carried out
with substrate 1a (Table 1) in the presence of 10 mol% of
Pd(OAc)2 as catalyst, KOAc (2.5 equiv) as base and tetra-
butylammonium bromide as a promoter in DMF at about
80 °C for one hour, we obtained the corresponding N-sub-
stituted 4-methylisoquinolone derivative 2a in 90% yield.
45
a Bu4NBr (TBAB) was used as the promoter. All the reactions were
performed at 80 °C for 1–1.3 h.
b Amount of catalyst used: 10 mol%.
c Amount of base used: 2.50 equiv.
d No reaction.
SYNTHESIS 2008, No. 18, pp 2991–2995
x
x.
x
x
.
2
0
0
8
Advanced online publication: 22.08.2008
DOI: 10.1055/s-2008-1067244; Art ID: Z04508SS
© Georg Thieme Verlag Stuttgart · New York

2992
K. C. Majumdar et al.
PAPER
We have examined the influence of factors such as the na- also examined the influence of the base like Cs2CO3,
ture of the base, solvent, catalyst, and the temperature on K2CO3, and triethylamine. KOAc proved to be the most
the formation of the cyclized product 2a. With increase of effective base for the cyclization. Changing the solvent
temperature the yield of the product decreases due to ex- neither reduced the reaction time nor improved the yield
tensive decomposition of the starting material. We have of the reaction. Use of a low-boiling solvent such as
Table 2 Compounds 2 Prepared
Entry
Precursor
Time (h)
Product
Yield (%)
95
I
1
1
N
N
O
O
2a
1a
I
N
N
2
1.1
85
O
O
Cl
Cl
2b
1b
I
3
4
1.1
1.2
90
80
N
N
O
O
2c
1c
I
N
N
O
O
O
O
O
O
2d
1d
I
N
N
5
1.3
85
O
O
O
N
Me
O
N
Me
2e
1e
I
N
N
6
1
75
O
O
Cl
Cl
1f
2f
I
N
N
7
1.2
70
O
O
O
N
O
N
Me
Me
2g
1g
Synthesis 2008, No. 18, 2991–2995 © Thieme Stuttgart · New York

PAPER
Synthesis of N-Substituted Isoquinolones
2993
was used for TLC. Petroleum ether (PE) refers to the fraction boil-
ing at 60–80 °C.
MeCN did not give any cyclized product. We have also
examined the influence of PdCl2 as a catalyst, and in this
case the reaction is found to be very slow. However, we
obtained the same product 2a in low yield. Results are
summarized in Table 1.
Substituted N-Allylbenzamide Derivatives 1; N-Allyl-2-iodo-N-
phenylbenzamide (1a); Typical Procedure
A solution of 2-iodobenzoyl chloride (300 mg, 1.12 mmol) in anhyd
CH2Cl2 (10 mL)was added dropwise to a stirred solution of N-allyl-
aniline (150 mg, 1.12 mmol) in anhyd CH2Cl2 (10 mL) in the pres-
ence of DMAP (5 mg) and Et3N (2 mL), and the mixture was stirred
for 2 h. After completion of the reaction, the mixture was washed
with H2O (3 × 15 mL) and dried (Na2SO4). The solvent was re-
moved and the residual mass was purified by column chromatogra-
phy over silica gel using PE–EtOAc (20:1) as eluent to afford the
desired compound 1a; pale yellow liquid; yield: 387 mg (95%).
Substrates 1b–e were treated similarly with Pd(OAc)2 and
KOAc in DMF for 1–1.3 hours to afford different N-sub-
stituted 4-methylisoquinolone derivatives (Table 2).
The substrates 1f,g gave the corresponding N-substituted
4-ethylisoquinolone derivatives. However, when the reac-
tion was carried out with monosubstituted N-allyl-2-iodo-
benzamide (3a) no cyclized product was obtained, instead
it afforded the deiodinated product 3b (Scheme 2).
IR (film): 1651, 1595 cm–1.
1H NMR (400 MHz, CDCl3): d = 4.52 (d, J = 5.96 Hz, 2 H), 5.16–
5.24 (m, 2 H), 5.97–6.00 (m, 1 H), 6.79–6.84 (m, 1 H), 6.98 (dd,
J = 7.6, 1.5 Hz, 1 H), 7.05–7.10 (m, 2 H), 7.14–7.16 (m, 4 H), 7.65
(d, J = 7.96 Hz, 1 H).
H
N
H
N
O
O
I
MS: m/z = 363 (M+).
Heck conditions
Anal. Calcd for C16H14INO: C, 52.91; H, 3.89; N, 3.86. Found: C,
53.02; H, 3.96; N, 3.90.
3b
3a
N-Allyl-N-(3-chlorophenyl)-2-iodobenzamide (1b)
Scheme 2
Pale yellow liquid; yield: 85%.
IR (film): 1651, 1590 cm–1.
Usually a ligand such as PPh3 is necessary41 for carrying
out this type of palladium-mediated Heck cyclization.
However, no ligand is needed for achieving this type of
reaction reported here. Mechanistically, these reactions
appear to proceed as depicted in Scheme 3.
1H NMR (400 MHz, CDCl3): d = 4.50 (d, J = 4.9 Hz, 2 H), 5.12–
5.25 (m, 2 H), 5.95–6.03 (m, 1 H), 6.85–6.89 (m, 1 H), 6.93–7.20
(m, 6 H), 7.66 (d, J = 7.84 Hz, 1 H).
MS: m/z = 397 (M+).
Anal. Calcd for C16H13ClINO: C, 48.33; H, 3.30; N, 3.52. Found: C,
48.42; H, 3.37; N, 3.48.
Ar
Ar
N
Ar
N
O
N
O
O
N-Allyl-2-iodo-N-(naphthalen-2-yl)benzamide (1c)
Yellow liquid; yield: 85%.
I
PdI
PdI
cat. Pd
IR (film): 1650, 1628 cm–1.
4a
4c
4b
1H NMR (400 MHz, CDCl3): d = 4.60 (d, J = 5.76 Hz, 2 H), 5.11–
5.25 (m, 2 H), 6.01–6.11 (m, 1 H), 6.73–6.77 (m, 1 H), 6.98–7.00
(m, 2 H), 7.28 (d, J = 1.6 Hz, 1 H), 7.41–7.48 (m, 2 H), 7.57–7.85
(m, 5 H).
– HI
Ar
N
MS: m/z = 413 (M+).
Ar
Ar
N
O
O
N
O
Anal. Calcd for C20H16INO: C, 58.13; H, 3.90; N, 3.39. Found: C,
58.26; H, 3.95; N, 3.43.
PdI
HPdI
HPdI
+
N-Allyl-2-iodo-N-(2-oxo-2H-chromen-6-yl)benzamide (1d)
Yellow liquid; yield: 80%.
4f
4e
4d
IR (film): 1731, 1651 cm–1.
Scheme 3
1H NMR (400 MHz, CDCl3): d = 4.51 (d, J = 5.04 Hz, 2 H), 5.09–
5.22 (m, 2 H), 5.96–6.00 (m, 1 H), 6.36 (d, J = 9.6 Hz, 1 H), 6.83
(t, J = 7.24 Hz, 1 H), 7.04–7.13 (m, 3 H), 7.28–7.36 (m, 2 H), 7.53
(d, J = 9.6 Hz, 1 H), 7.63 (d, J = 7.9 Hz, 1 H).
In conclusion, we have achieved an expedious synthesis
of hitherto unreported N-substituted 4-methyl- and 4-eth-
ylisoquinolone derivatives through a ligand-free palladi-
um-mediated intramolecular Heck cyclization.
MS: m/z = 431 (M+).
Anal. Calcd for C19H14INO3: C, 52.97; H, 3.24; N, 3.29. Found: C,
53.10; H, 3.29; N, 3.34.
Melting points were determined in open capillaries and are uncor-
rected. IR spectra were recorded on a PerkinElmer L 120-000A
spectrometer. H NMR (400 MHz) spectra were recorded on a
Bruker DPX-400 spectrometer in CDCl3 with TMS as internal stan-
dard. Silica gel [(60–120, 230–400 mesh), Spectrochem, India] was
used for chromatographic separation. Silica gel G [E-Merck (India)]
N-Allyl-2-iodo-N-(1-methyl-2-oxo-1,2-dihydroquinolin-6-
yl)benzamide (1e)
Yellow liquid; yield: 90%.
IR (film): 1651, 1646 cm–1.
1
Synthesis 2008, No. 18, 2991–2995 © Thieme Stuttgart · New York

2994
K. C. Majumdar et al.
PAPER
1H NMR (400 MHz, CDCl3): d = 3.60 (s, 3 H), 4.53 (d, J = 5.36 Hz,
2 H), 5.17–5.22 (m, 2 H), 5.97–6.07 (m, 1 H), 6.65 (d, J = 9.4 Hz, 1
H), 6.80–6.84 (m, 1 H), 7.04–7.15 (m, 3 H), 7.35–7.38 (m, 2 H),
7.49 (d, J = 9.4 Hz, 1 H), 7.62 (d, J = 8.0 Hz, 1 H).
HRMS: m/z calcd for C16H12ClNO [M + H]+: 270.0680; found:
270.0703.
Anal. Calcd for C16H12ClNO: C, 71.25; H, 4.48; N, 5.19. Found: C,
71.35; H, 4.58; N, 5.24.
MS: m/z = 444 (M+).
4-Methyl-2-(naphthalen-2-yl)isoquinolin-1(2H)-one (2c)
Colorless solid; yield: 90%; mp 110–112 °C.
IR (KBr): 1660, 1625 cm–1.
Anal. Calcd for C20H17IN2O2: C, 54.07; H, 3.86; N, 6.31. Found: C,
54.16; H, 3.94; N, 6.35.
N-(But-2-enyl)-N-(3-chlorophenyl)-2-iodobenzamide (1f)
Pale yellow liquid; yield: 85%.
IR (film): 1651, 1589 cm–1.
1H NMR (400 MHz, CDCl3): d = 2.33 (d, J = 0.6 Hz, 3 H), 7.10 (d,
J = 0.6 Hz, 1 H), 7.47–7.59 (m, 4 H), 7.65 (d, J = 7.9 Hz, 1 H),
7.73–7.82 (m, 1 H), 7.87–7.97 (m, 4 H), 8.53 (d, J = 7.80 Hz, 1 H).
1H NMR (400 MHz, CDCl3): d = 1.54 (s, 3 H), 4.08 (s, 2 H), 5.34
(s, 2 H), 6.83–6.87 (m, 1 H), 7.02–7.24 (m, 6 H), 7.64 (d, J = 7.72
Hz, 1 H).
MS: m/z = 269 (M+).
Anal. Calcd for C20H15NO: C, 84.19; H, 5.30; N, 4.91. Found: C,
84.29; H, 5.37; N, 4.96.
MS: m/z = 411 (M+).
4-Methyl-2-(2-oxo-2H-chromen-6-yl)isoquinolin-1(2H)-one
(2d)
Colorless solid; yield: 80%; mp 186–190 °C.
Anal. Calcd for C17H15ClINO: C, 49.60; H, 3.67; N, 3.40. Found: C,
49.67; H, 3.65; N, 3.43.
N-(But-2-enyl)-2-iodo-N-(1-methyl-2-oxo-1,2-dihydroquinolin-
6-yl)benzamide (1g)
Yellow liquid; yield: 80%.
IR (film): 1651, 1646 cm–1.
IR (KBr): 1731, 1659 cm–1.
H NMR (400 MHz, CDCl3): d = 2.32 (s, 3 H), 6.47 (d, J = 9.52 Hz,
1 H), 7.01 (s, 1 H), 7.44 (d, J = 9.52 Hz, 1 H), 7.48–7.78 (m, 6 H),
8.49 (d, J = 7.80 Hz, 1 H).
1H NMR (400 MHz, CDCl3): d = 1.60 (s, 3 H), 3.62 (s, 3 H), 4.05
(s, 2 H), 5.56 (s, 2 H), 6.63 (d, J = 9.5 Hz, 1 H), 6.79–6.83 (m, 1 H),
7.34–7.33 (m, 5 H), 7.47 (d, J = 9.5 Hz, 1 H), 7.60 (d, J = 7.9 Hz, 1
H).
MS: m/z = 303 (M+).
Anal. Calcd for C19H13NO3: C, 75.24; H, 4.32; N, 4.62. Found: C,
75.36; H, 4.40; N, 4.67.
MS: m/z = 458 (M+).
4-Methyl-2-(1-methyl-2-oxo-1,2-dihydroquinolin-6-yl)isoquin-
olin-1(2H)-one (2e)
Colorless solid; yield: 85%; mp 198–200 °C.
IR (KBr): 1651, 1649 cm–1.
Anal. Calcd for C21H19IN2O2: C, 55.04; H, 4.18; N, 6.11. Found: C,
55.15; H, 4.24; N, 6.16.
Heck Reaction of Substituted N-Allylbenzamide Derivatives 2;
4-Methyl-2-phenylisoquinolin-1(2H)-one (2a); Typical Proce-
dure
1H NMR (400 MHz, CDCl3): d = 2.33 (s, 3 H), 3.76 (s, 3 H), 6.75
(d, J = 9.4 Hz, 1 H), 7.00 (s, 1 H), 7.45 (d, J = 9.4 Hz, 1 H), 7.54–
7.58 (m, 1 H), 7.64–7.68 (m, 4 H), 7.74–7.77 (m, 1 H), 8.50 (d,
J = 7.8 Hz, 1 H).
13C NMR (125 MHz, CDCl3): d = 162.53, 162.35, 139.69, 138.85,
137.79, 135.98, 133.07, 129.89, 129.60, 128.95, 127.58, 126.89,
126.57, 123.66, 123.00, 121.37, 115.40, 113.02, 30.03, 15.77.
A mixture of N-allyl-2-iodo-N-phenylbenzamide (100 mg, 0.275
mmol), TBAB (220 mg, 0.69 mmol), KOAc (40 mg, 0.4 mmol),
Pd(OAc)2 (2.5 mg, 1.1 × 10–4 mmol), and anhyd DMF (5 mL) was
heated at 80 °C for 1 h. After completion of the reaction, H2O (20
mL) was added and the mixture was extracted with CH2Cl2 (3 × 15
mL). The combined CH2Cl2 extracts were washed with H2O (3 × 15
mL) and dried(Na2SO4). The solvent was removed and the residual
mass was purified by column chromatography over silica gel using
PE–EtOAc (20:1) as eluent to afford the compound 2a; colorless
solid; yield: 58 mg (90%); mp 102–104 °C.
MS: m/z = 316 (M+).
Anal. Calcd for C20H16N2O2: C, 75.93; H, 5.10; N, 8.86. Found: C,
76.08; H, 5.15; N, 8.90.
2-(3-Chlorophenyl)-4-ethylisoquinolin-1(2H)-one (2f)
Colorless solid; yield: 75%; mp 120–122 °C.
IR (KBr): 1662, 1627 cm–1.
1H NMR (400 MHz, CDCl3): d = 2.30 (d, J = 0.6 Hz, 3 H), 7.02 (d,
J = 0.6 Hz, 1 H), 7.30–7.52 (m, 5 H), 7.54–7.59 (m, 1 H), 7.63 (d,
J = 7.9 Hz, 1 H), 7.71–7.75 (m, 1 H), 8.50 (d, J = 7.88 Hz, 1 H).
IR (KBr): 1660, 1625 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.28 (t, J = 7.4 Hz, 3 H), 2.75 (q,
J = 7.4 Hz, 2 H), 6.95 (s, 1 H), 7.30–7.55 (m, 5 H), 7.69–7.75 (m, 2
H), 8.50 (d, J = 8.0 Hz, 1 H).
MS: m/z = 235 (M+).
MS: m/z = 283 (M+).
Anal. Calcd for C16H13NO: C, 81.68; H, 5.57; N, 5.59. Found: C,
81.81; H, 5.62; N, 5.64.
Anal. Calcd for C17H14ClNO: C, 71.96; H, 4.97; N, 4.94. Found: C,
80.08; H, 5.02; N, 5.01.
2-(3-Chlorophenyl)-4-methylisoquinolin-1(2H)-one (2b)
Colorless solid; yield: 85%; mp 118–120 °C.
IR (KBr): 1665, 1630 cm–1.
4-Ethyl-2-(1-methyl-2-oxo-1,2-dihydroquinolin-6-yl)isoquino-
lin-1(2H)-one (2g)
1H NMR (400 MHz, CDCl3): d = 2.30 (s, 3 H), 6.98 (s, 1 H), 7.33–
7.46 (m, 4 H), 7.53–7.56 (m, 1 H), 7.62 (d, J = 7.9 Hz, 1 H), 7.72–
7.76 (m, 1 H), 8.49 (d, J = 7.9 Hz, 1 H).
13C NMR (125 MHz, CDCl3): d = 162.01, 142.77, 137.77, 135.13,
133.06, 130.57, 129.61, 129.06, 128.58, 127.74, 127.58, 126.66,
125.64, 123.64, 112.95, 15.76.
Colorless solid; yield: 70%; mp 205–207 °C.
IR (KBr): 1651, 1649 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.30 (t, J = 7.5 Hz, 3 H), 2.74 (q,
J = 7.5 Hz, 2 H), 3.76 (s, 3 H), 6.75 (d, J = 9.5 Hz, 1 H), 7.01 (s, 1
H), 7.46 (d, J = 9.6 Hz, 1 H), 7.48–7.67 (m, 5 H), 7.71–7.77 (m, 1
H), 8.51 (d, J = 8.1 Hz, 1 H).
Synthesis 2008, No. 18, 2991–2995 © Thieme Stuttgart · New York

PAPER
Synthesis of N-Substituted Isoquinolones
2995
MS: m/z = 330 (M+).
(19) Clark, R. D.; Jahangir; Souchet, M.; Kern, J. R. J. Chem.
Soc., Chem. Commun. 1989, 930.
(20) Heck, R. F. Palladium Reagents in Organic Synthesis;
Academic Press: London, 1985.
Anal. Calcd for C21H18N2O2: C, 76.34; H, 5.49; N, 8.48. Found: C,
76.44; H, 5.55; N, 8.53.
(21) (a) Heck, R. F. Org. React. 1982, 27, 345. (b)Heck,R.F. In
Comprehensive Organic Synthesis; Trost, B. M.; Fleming,
I., Eds.; Pergamon: Oxford, 1991, 833.
(22) Zhang, Y.; Negishi, E. J. Am. Chem. Soc. 1989, 111, 3454.
(23) Trost, B. M.; Shih, S. J. Am. Chem. Soc. 1993, 115, 12491.
(24) (a) Ithle, N. C.; Heathcock, C. H. J. Org. Chem. 1993, 58,
560. (b) Larock, R. C.; Doty, M. J.; Cacchi, S. J. Org. Chem.
1993, 58, 5479.
(25) Trost, B. M.; Tanoury, G. J.; Lautens, M.; Chan, C.;
McPherson, D. T. J. Am. Chem. Soc. 1994, 116, 4255.
(26) Hegedus, L. S. Angew. Chem. Int. Ed. 1998, 27, 1113.
(27) Sakamoto, T.; Kondo, Y.; Yamanaka, H. Heterocycles 1998,
27, 2225.
(28) Arcadi, A.; Cacchi, S.; Marinelli, F. Tetrahedron Lett. 1989,
30, 2581.
(29) Tidwell, J. H.; Senn, D. R.; Buchwald, S. L. J. Am. Chem.
Soc. 1991, 113, 4685.
(30) Larock, R. C.; Berrios-Pena, N. G.; Fried, C. A.; Yum, E. K.;
Leogn, C. W. J. Org. Chem. 1993, 58, 4509.
(31) Liao, H.-Y.; Cheng, C. H. J. Org. Chem. 1995, 60, 3711.
(32) Trost, B. M.; McIntosh, M. C. J. Am. Chem. Soc. 1995, 117,
7255.
(33) Arcadi, A.; Cacchi, S.; Fabrizi, G.; Marinelli, F.; Pacc, P.
Synlett 1996, 568.
(34) Negishi, E.-I.; Coperet, C.; Ma, S.; Lion, S.-Y.; Lire, F.
Chem. Rev. 1996, 96, 365.
(35) (a) Cavicchioli, M.; Decortiat, S.; Bouyssis, D.; Gore, J.;
Bahme, G. Tetrahedron 1996, 52, 11463. (b) Bouyssi, D.;
Cavicchioli, M.; Balme, G. Synlett 1997, 944.
(36) Larock, R. C.; Yum, E. K.; Doty, M. J.; Sham, K. K. C.
J. Org. Chem. 1995, 60, 3270.
(37) Jeschke, T.; Wensbo, D.; Annby, U.; Gronoaitz, S.; Cohen,
L. A. Tetrahedron Lett. 1993, 34, 6471.
(38) Majumdar, K. C.; Chattopadhaya, B.; Taher, A. Synthesis
2007, 3647.
Acknowledgment
We thank the DST (New Delhi) and the CSIR (New Delhi) for fi-
nancial assistance. Two of us (S.C. and K.R.) are thankful to the
CSIR (New Delhi) for fellowships.
References
(1) Kametani, T. The Chemistry of the Isoquinoline Alkaloids;
Hirokawa & Elsevier: Tokyo & Amsterdam, 1968.
(2) Martin, S. F. The Alkaloids, Vol. 31; Brossi, A. R., Ed.;
Academic: New York, 1987, 252.
(3) Clark, R. D.; Souchet, M. Tetrahedron Lett. 1990, 31, 193.
(4) Mondon, A. Erythria Alkaloids, In Chemistry of the
Alkaloids; Pelletier, S. W., Ed.; Van Nostrand R.: New
York, 1970, 137.
(5) (a) Tsuda, Y.; Isobe, K. J. Chem. Soc. 1971, 1555.
(b) Stevens, R. V.; Dupree, L. E. Jr.; Loewenstein, P. L.
J. Org. Chem. 1972, 37, 977.
(6) Whitlock, W. H. Jr.; Smith, G. L. J. Am. Chem. Soc. 1967,
87, 3600.
(7) Kametani, T.; Rukumoto, K. Heterocycles 1975, 3, 931.
(8) Kametani, T.; Kajiwara, M.; Takahashi, T.; Fukumoto, K.
Heterocycles 1975, 3, 179.
(9) Kametani, T.; Hirai, Y.; Kajiwara, M.; Takahashi, T.;
Fukumoto, K. Chem. Pharm. Bull. 1975, 23, 2634.
(10) Irie, H.; Akagi, K.; Tani, S.; Yabusaki, K.; Yamane, H.
Chem. Pharm. Bull. 1973, 21, 855.
(11) Irie, H.; Fukudome, J.; Ohmori, T.; Tanaka, J. J. Chem. Soc.,
Chem. Commun. 1975, 63.
(12) Stork, G.; Guthikonda, R. N. J. Am. Chem. Soc. 1972, 74,
5109.
(13) Pettit, G. R.; Gaddamidi, V.; Herald, D. L.; Cragg, G. M.;
Singh, S. B.; Schmidt, J. M. J. Nat. Prod. 1986, 49, 995.
(14) Beugelmans, R.; Choussy, M. B. Synthesis 1981, 729.
(15) Couture, A.; Garandclaudon, P. Synthesis 1986, 576.
(16) Fisher, L. E.; Caroon, J. M.; Jahangir; Stabler, S. R.;
Lundberg, S.; Muchowski, J. M. J. Org. Chem. 1993, 58,
3643.
(17) Cuevas, J. C.; Snieckus, V. Tetrahedron Lett. 1989, 30,
5837.
(18) Kiselyov, A. S. Tetrahedron Lett. 1995, 36, 493.
(39) Majumdar, K. C.; Chattopadhaya, B.; Nath, S. Tetrahedron
Lett., in press.
(40) Majumdar K. C., Debnath P., Taher A., Pal A. K.; Can. J.
Chem., in press.
(41) (a) Christoph, G.; Buchwald, S. L. Chem. Eur. J. 1999, 5,
3107. (b) Bumagin, N. A.; Bykov, V. V.; Sukhomlinova, L.
I.; Tolstaya, T. P.; Beletskaya, I. P. J. Organomet. Chem.
1995, 486, 25.
Synthesis 2008, No. 18, 2991–2995 © Thieme Stuttgart · New York