Indium-mediated 1,2,4,5-hexatetraen-3-ylation of 4-acetoxy-2-azetidinones and their applications to the Diels-Alder reactions for the synthesis of 2-azetidinone derivatives

Article abstract of DOI:10.1021/jo800594y

(Chemical Equation Presented) 4-Acetoxy-2-azetidinones reacted with organoindium reagent generated in situ from indium and 1,6-dibromo-2,4-hexadiyne in the presence of LiCl in DMF to selectively produce 2-azetidinones possessing 1,2,4,5-hexatetraen-3-yl group on the C4-position. The Diels-Alder reactions of 4-(1,2,4,5-hexatetraen-3-yl)-2-azetidinones with a variety of dienophiles and subsequent aromatizations afforded valuable functional group-substituted 2-azetidinones in good yields.

Full text of DOI:10.1021/jo800594y

butadien-2-yl8 groups, is mostly attractive and fundamental
problem in the synthesis of ꢀ-lactam antibiotics due to further
functionalization of these groups.9 In general, it has been
accomplished by the ability of 4-acetoxy-2-azetidinone to take
part in to nucleophilic substitution reactions very easily on the
C4-position, these taking place via acyliminium intermediates.10
Therefore, lots of efforts have been devoted to the selective
introduction of these groups via the reaction of 4-acetoxy-2-
azetidinones with a variety of organometallic compounds.1b In
the context of our ongoing research interest in synthesis of
functionalized ꢀ-lactam compounds using a variety of generated
in situ organoindium reagents,11 we reported selective indium-
mediated propargylation, allenylation, and 1,3-butadien-2-ylation
reactions and their applications to cyclization reactions.12
However, introduction of 1,2,4,5-hexatetraen-3-yl group on
2-azetidinone ring have been remained a formidable challenge
despite the enormous further functionalization through the
Diels-Alder reactions as well as aromatizations of adducts and
transition metal-catalyzed cyclizations of 1,2,4,5-hexatetraen-
3-yl group.13 Described herein is the selective introduction of
1,2,4,5-hexatetraen-3-yl group on C4-position of 2-azetidinones
with organoindium reagent generated in situ from indium and
1,6-dibromo-2,4-hexadiyne and subsequent the Diels-Alder
reactions and aromatizations for the synthesis of 2-azetidinone
derivatives (Scheme 1).
Indium-Mediated 1,2,4,5-Hexatetraen-3-ylation of
4-Acetoxy-2-azetidinones and Their Applications
to the Diels-Alder Reactions for the Synthesis of
2-Azetidinone Derivatives
Heashim Yu and Phil Ho Lee*
National Research Laboratory for Catalytic Organic
Reaction, Department of Chemistry and Institute for
Molecular Science & Fusion Technology, Kangwon National
UniVersity, Chunchon 200-701, Republic of Korea
phlee@kangwon.ac.kr
ReceiVed March 14, 2008
At the outset, optimum conditions for indium-mediated
1,2,4,5-hexatetraen-3-ylation on C-4 position of 2-azetidinones
(3) (a) Kobayashi, T.; Ishida, N.; Hiraoka, T. Chem. Commun. 1980, 736.
(b) Hua, D. H.; Verma, A. Tetrahedron Lett. 1985, 26, 547. (c) Aratani, M.;
Hirai, H.; Sawada, K.; Hashimoto, M. Heterocycles 1985, 23, 1889. (d) Fliri,
H.; Mak, C.-P. J. Org. Chem. 1985, 50, 3438. (e) Fujimoto, K.; Iwano, Y.; Hirai,
K. Bull. Chem. Soc. Jpn. 1986, 59, 1363. (f) Blaszczak, L. C.; Armour, H. K.;
Hallign, N. G. Tetrahedron Lett. 1990, 31, 5693. (g) Tarling, C. A.; Holmes,
A. B.; Markwell, R. E.; Pearson, N. D. J. Chem. Soc., Perkin Trans. 1990, 1,
1695. (h) Kang, S.-K.; Baik, T.-G.; Jiao, X.-H.; Lee, K.-J.; Lee, C. H. Synlett
1999, 447.
4-Acetoxy-2-azetidinones reacted with organoindium reagent
generated in situ from indium and 1,6-dibromo-2,4-hexadiyne
in the presence of LiCl in DMF to selectively produce
2-azetidinones possessing 1,2,4,5-hexatetraen-3-yl group on
the C4-position. The Diels-Alder reactions of 4-(1,2,4,5-
hexatetraen-3-yl)-2-azetidinones with a variety of dienophiles
and subsequent aromatizations afforded valuable functional
group-substituted 2-azetidinones in good yields.
(4) Mori, S.; Iwakura, H.; Takechi, S. Tetrahedron Lett. 1988, 29, 5391.
(5) (a) Shibasaki, M.; Nishida, A.; Ikegami, S. Chem. Commun. 1982, 1324.
(b) Haruta, J.-I.; Nishi, K.; Kikuchi, K.; Matsuda, S.; Tamura, Y.; Kita, Y. Chem.
Pharm. Bull. 1989, 37, 2338. (c) Alcaide, B.; Almendros, P.; Alonso, J. M. J.
Org. Chem. 2004, 69, 993.
(6) (a) Prasad, J. S.; Liebeskind, L. S. Tetrahedron Lett. 1988, 29, 4253. (b)
Prasad, J. S.; Liebeskind, L. S. Tetrahedron Lett. 1988, 29, 4257. (c) Alcaide,
B.; Almendros, P.; Aragoncillo, C. Chem.-Eur. J. 2002, 8, 1719.
(7) (a) Sharma, A. K.; Mazumdar, S. N.; Mahajan, M. P. J. Org. Chem.
1996, 61, 5506. (b) Alcaide, B.; Almendros, P. Tetrahedron Lett. 1999, 40, 1015.
(c) Alcaide, B.; Almendros, P.; Salgado, N. R. J. Org. Chem. 2000, 65, 3310.
(d) Alcaide, B.; Almendros, P.; Salgado, N. R.; Martinez-Alcazar, M. P.;
Hernandez-Cano, F. Eur. J. Org. Chem. 2001, 2001. (e) Alcaide, B.; Almendros,
P.; Aragoncillo, C. M.; Redondo, C. Eur. J. Org. Chem. 2005, 98.
(8) Sendo, Y.; Kii, M.; Sakanoue, M.; Motokawa, K.; Kimura, Y. Chem.
Pharm. Bull. 1992, 40, 2410.
Because the 2-azetidinone nucleus is the central building
blocks of ꢀ-lactam antibiotics, functionalization of the 2-aze-
tidinone framework is essential for the development of new
ꢀ-lactam antibiotics.1 Therefore, introduction and transformation
of functional groups on the ring of 2-azetidinones is one of the
most important motifs in ꢀ-lactam chemistry.2 Although intro-
duction of various heteroatoms such as oxygen, halide, and
nitrogen on the C4-position of 2-azetidinone have been reported,
the selective introduction of carbon nucleophiles, such as vinyl,3
ethynyl,4 allyl,3 propargyl,5 allenyl,6 1,3-butadien-1-yl,7 and 1,3-
(9) (a) Kobayashi, T.; Ishida, N.; Hiraoka, T. Chem. Commun. 1980, 736.
(b) Hua, D. H.; Verma, A. Tetrahedron Lett. 1985, 26, 547.
(10) Georg, G. I. The Organic Chemistry of ꢀ-Lactams; VCH: New York,
1992; pp 64-70.
(11) (a) Li, C.-J. Chem. ReV. 1993, 93, 2023. (b) Cintas, P. Synlett 1995,
1087. (c) Li, C.-J. Tetrahedron 1996, 52, 5643. (d) Li, C.-J.; Chan, T.-H. Organic
Reactions in Aqueous Media; Wiley: New York, 1997. (e) Li, C.-J.; Chan, T.-
H. Tetrahedron 1999, 55, 11149. (f) Babu, G. P.; Perumal, T. Aldrichim. Acta
2000, 33, 16. (g) Lee, P. H.; Lee, K.; Kang, Y. J. Am. Chem. Soc. 2006, 128,
1139. (h) Lee, P. H. Bull. Korean Chem. Soc. 2007, 28, 17.
(1) (a) Manhas, M. S.; Wagle, D. R.; Chiang, J.; Bose, A. K. Heterocycles
1988, 27, 1755. (b) Georg, G. I. The Organic Chemistry of ꢀ-Lactams; VCH:
New York, 1992. (c) Ojima, I. AdV. Asym. Synth. 1995, 1, 95. (d) Ojima, I.;
Delaloge, F. Chem. Soc. ReV. 1997, 26, 377. (e) Palomo, C.; Aizpurua, J. M.;
Ganboa, I.; Oiarbide, M. Amino Acids 1999, 16, 321. (f) Alcaide, B.; Almendros,
P. Chem. Soc. ReV. 2001, 30, 226. (g) Alcaide, B.; Almendros, P. Org. Prep.
Proced. Int. 2001, 33, 315. (h) Palomo, C.; Aizpurua, J. M.; Ganboa, I.; Oiarbide,
M. Synlett 2001, 1813. (i) Alcaide, B.; Almendros, P. Synlett 2002, 381.
(2) Alcaide, B.; Almendros, P.; Aragoncillo, C. Chem. ReV. 2007, 107, 4437.
(12) (a) Lee, P. H.; Kim, H.; Lee, K.; Lee, M.; Noh, K.; Kim, H.; Seomoon,
D. Angew. Chem., Int. Ed. 2005, 44, 1840. (b) Lee, K.; Lee, P. H. Chem.-Eur.
J. 2007, 13, 8877.
(13) (a) Eaton, B. E.; Rollman, B.; Kaduk, J. A. J. Am. Chem. Soc. 1992,
114, 6245. (b) Sigman, M. S.; Eaton, B. E. J. Am. Chem. Soc. 1996, 118, 11783.
(c) Sigman, M. S.; Eaton, B. E. Organometallics 1996, 15, 2829.
10.1021/jo800594y CCC: $40.75
Published on Web 05/29/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 5183–5186 5183

SCHEME 1. 1,2,4,5-Hexatetraen-3-ylations and
Aromatizations
FIGURE 1. Possible products from the reaction of 3a with indium
and 2.
TABLE 2. Optimization of the Diels-Alder Reactions of 3a with
N-Phenylmaleimidea
entry
solvent
temp (°C)
time (h)
yield (%)b
TABLE 1. Optimization of 1,2,4,5-Hexatetraen-3-ylation
1
Toluene
1,4-Dioxane
1,4-Dioxane
CH3CN
Benzene
CH2Cl2
CH2Cl2
1,4-Dioxane
CH2Cl2
CHCl3
CHCl3
CHCl3
CHCl3
110
25
25
25
25
25
25
25
25
25
25
25
62
5
3
2
3
2
1.5
1.5
3
3
24
5
0
25
0
0
15
20
20
18
2
3c
4
5
6
ln
2
additive
(equiv)
temp time yield
(°C) (h)
(%)a
7d
8e
9e
10f
11g
12h
13h
entry (equiv) (equiv)
solvent
1
2
3
4
5
6
7
8
2.2
2.2
2.2
2.2
2.2
2.2
3.0
3.0
3.0
3.0
3.0
1.1
1.1
1.1
1.1
1.1
1.1
2.5
2.5
2.5
2.5
2.5
LiCl (2.2) DMF
LiBr (2.2) DMF
25
25
25 18
3
36
20
45
53
2.5 46
Lil (2.2)
DMF
0
-
DMF/H2Ob 70
5
5 (28)c
10
4
70
LiCl (2.2) DMF/H2Ob 70 12
0
0
0
38
63
40
37
70 (1:1.6)i
Lil (2.2)
LiCl (3.0) THF
DMF
DMF/H2Ob 70 12
25 24
a Dienophile (4 equiv) was used. b Isolated yield. c InCl3 (5 mol%)
was used. d [bmim]SbF6 (1 equiv) was used. e Diene (2 equiv) and
dienophile (1 equiv) were used. f Diene (1 equiv) and dienophile (1
equiv) were used. g Diene (1 equiv) and dienophile (2 equiv) were used.
h Diene (1.5 equiv) and dienophile (1 equiv) were used. i Isomeric ratio.
-
25
25
25
25
3
3
4
3
9
10
11
LiCl (3.0) DMF
LiBr (3.0) DMF
Lil (3.0)
DMF
a Isolated yield. b DMF/H2O ) 2:1. c 1,3,5-Hexatetraen-3-yl-tethered
2-azetidinone.
were seen at 101.0, 90.0, 80.0, and 79.5 ppm, indicating that
compound 3a was selectively produced.
Among the additives examined, LiCl provided the best results
under the optimum conditions (entries 9-11). The use of indium
in less than 3 equiv and 1,6-dibromo-2,4-hexadiyne (2) in less
than 2.5 equiv resulted in sluggish reaction and gave lower
yields, indicating that the stoichiometry of indium and 2 is
critically important for successful reactions. The present method
indicates that 1,6-dibromo-2,4-hexadiyne acts selectively as
synthon of 3-anion of 1,2,4,5-hexadiyne. These results contrast
that 1,6-dibromo-2,4-hexadiyne acts selectively as synthon of
3,6-dianion of 1,2-hexadien-4-yne in the reaction of aldehydes
and ketones with organoindium generated in situ from indium
and 1,6-dibromo-2,4-hexadiyne.15
were examined by the reaction of 2-azetidinone (1) with
organoindium reagents generated in situ from indium and 1,6-
dibromo-2,4-hexadiyne (2) (Table 1). Reactions of 1 with indium
(2.2 equiv) and 2 (1.1 equiv) in the presence of LiCl and LiBr
(2.2 equiv) in DMF selectively produced the desired product
3a in 36 and 46% yields, respectively, (entries 1 and 2), whereas
LiI gave messy results (entry 3). DMF-H2O (2:1) as a solvent
afforded 1,3,5-hexatetraen-3-yl-tethered 2-azetidinone in 28%
yield without additive (entry 4). However, cosolvent of DMF
and H2O gave rise to the messy results in the presence of LiCl
and LiI (entries 5 and 6) because bis(allene) 3a was apt to
decompose under these reaction conditions. DMF was the best
solvent among several reaction media (DMF, THF, and DMF-
H2O) that were screened. Among several reaction conditions
that were examined, the best results were obtained with the
organoindium reagent generated in situ from the reaction of
indium (3 equiv) with 2 (2.5 equiv) in the presence of LiCl (3
equiv), producing selectively 3a in 63% yield (entry 9).
Surprisingly, there are no diyne compounds (3b) through 2,4-
hexadiyn-1-ylation, allenynes (3c and 3d) through 4,5-hexadien-
2-yn-1-ylation and 1,2-hexadien-4-yn-3-ylation, and 1,6-
Encouraged by these results, we examined the reaction of
4-acetoxy-2-azetidinone (4) with organoindium reagent, afford-
ing 4-(1,2,4,5-hexatetraen-3-yl)-2-azetidinone (5) in 45% yield
(eq 1).
eliminated compound of 2 (Figure 1).14 The H and 13C NMR
1
Diels-Alder reactions of 3a with N-phenylmaleimide (6a)
were studied to show the synthetic applicability of 4-(1,2,4,5-
hexatetraen-3-yl)-2-azetidinones (Table 2). Treatment of 3a with
6a (4 equiv) gave the desired adduct 7d in 25% yield in 1,4-
spectra of 3a are consistent with 2-azetidinone possessing 1,2-
bis(allenyl) group. The two sp resonances (400 MHz) of 1,2,4,5-
hexatetraen-3-yl group appeared at 209.1 and 208.2 ppm. The
four sp2 resonances (400 MHz) of 1,2,4,5-hexatetraen-3-yl group
(15) (a) Kim, S.; Lee, K.; Seomoon, D.; Lee, P. H. AdV. Synth. Catal. 2007,
349, 2449. (b) Lu, W.; Ma, J.; Yang, Y.; Chan, T. H. Org. Lett. 2000, 2, 3469.
(c) Miao, W.; Lu, W.; Chan, T. H. J. Am. Chem. Soc. 2003, 125, 2412.
(14) Werner, C.; Hopf, H.; Dix, I.; Bubenitschek, P.; Jones, P. G. Chem.-
Eur. J. 2007, 13, 9462.
5184 J. Org. Chem. Vol. 73, No. 13, 2008

TABLE 3. Diels-Alder Reactions of 1,2,4,5-Hexatetraen-3-yl-tethered 2-Azetidinones with Dienophiles
a Isolated yield. b Diene (1.5 equiv) and dienophiles (1 equiv) were used. c Isomeric ratio. d Diene (1 equiv) and dienophiles (2 equiv) were used.
e Diene (1 equiv) and dimethyl fumarate (5 equiv) were used.
dioxane at 25 °C for 3 h (entry 2). Use of InCl3 (5 mol%) did
not produce the desired product (entry 3). Adduct 7d was only
obtained in 20% yield with ionic liquid (1 equiv) as an additive
(entry 7). Although a variety of solvents, such as toluene, 1,4-
dioxane, acetonitrile, benzene, and dichloromethane, were
examined, 7d was not obtained in good yields (entries 1-7).
Because bis(allene) 3a as well as triene 7d were easily apt to
decompose under the reaction conditions, more than 1 equiv of
3a was used in some cases. Among several reaction conditions
that were examined, the best results were obtained with the
reaction of 3a (1.5 equiv) with 6a (1 equiv) in CHCl3 at 62 °C
for 4 h, producing 7d in 70% (dr ) 1:1.6) yield (entry 13).
Next, we turned our attention to the Diels-Alder reaction of
3a and 5 with various dienophiles and the results are sum-
marized in Table 3. Reactions of 5 with dienophiles 6a and 6b
afforded adducts 7a and 7b in 70% (dr ) 1:1) and 75% yields,
respectively, under the optimum conditions (entries 1 and 2).
As shown in entry 3 and 13, the Diels-Alder reactions followed
by aromatizations proceeded by treating 5 and 3a with 1,4-
naphthoquinone, producing 7c and 7m in 65 and 85% yields.
Compound 3a reacted with maleimide (6d) and N-methylma-
leimide (6e) to give 7e and 7f in 65% (dr ) 1:2.3) and 72% (dr
) 1:2.2) yields, respectively (entries 5 and 6). Subjecting 3a (1
equiv) to 6b (2 equiv) provided adduct 7g in 83% yield in CHCl3
at 62 °C for 2 h (entry 7). Exposure of 3a to 6f and 6j produced
the desired products 7h (isomeric ratio)3.3:2:1) and 7i (isomeric
ratio ) 2:1.8:1) in 80% and 65% yields, respectively (entries 8
and 9). Dimethyl fumarate (6g) and dimethyl maleate (6h)
reacted with 3a to give rise to adducts 7j (75%, dr ) 1:1.7)
and 7k (49%, dr ) 1:3.7), respectively (entries 10 and 11).
Treatment of 3a with 6i furnished the adduct 7l in 70% yield
(dr ) 1:1.8, entry 12).
Because three isomers were produced from the reaction of
3a with methyl vinyl ketone (6f), NMR spectrum of 7h was
complicated. Therefore, we tried to aromatize the Diels-Alder
adducts 7h to simplify NMR spectrum. In addition, the fact that
there is not easy to introduce aromatic moieties on C4-position
of 2-azetidinones led us to aromatization of adducts. Among
several reaction conditions that were scrutinized, the best results
were obtained with the reaction of 7h with DBU (1 equiv) in
toluene at 110 °C for 1 h, affording 8b and 8c (isomeric ratio
) 1:4.6) in 94% yield (Table 4, entry 2). TsOH (0.8 equiv)
gave the aromatic compound in 33% yield, whereas pyridine,
PPTS, LDA, and DDQ did not produce the desired product.
On the basis of these results, adduct 7d was treated with DBU
(1 equiv) in toluene at 110 °C, affording 2-azetidinone deriva-
tives 8a in 95% yield (Table 4, entry 1). Adducts 7j and 7k
J. Org. Chem. Vol. 73, No. 13, 2008 5185

TABLE 4. Aromatizationa
(172.2 mg, 1.5 mmol) and lithium chloride (63.6 mg, 1.5 mmol)
in DMF (1.5 mL) was added 1,6-dibromo-2,4-hexadiyne (2) (294.9
mg, 1.25 mmol) under a nitrogen atmosphere at room temperature.
After being stirred for 40 min, 4-acetoxy-2-azetidinone (1) (143.7
mg, 0.5 mmol) in DMF (0.5 mL) was added. After reaction mixture
was stirred at room temperature for 3 h, the reaction mixture was
poured into saturated aqueous ammonium chloride solution (10 mL),
extracted with CH2Cl2 (3 × 20 mL), and washed with brine (20
mL). The organic layers were dried over anhydrous MgSO4 and
evaporated under reduced pressure. The crude product was purified
by silica gel column chromatography (EtOAc/hexane ) 1/5) to
afford 3a (96.0 mg, 63%). mp ) 80 °C; Rf ) 0.3 (EtOAc/Hexane
1
) 1/5); H NMR (400 MHz, CDCl3) δ 6.15 (s, 1H), 5.75 (t, J )
5.5 Hz, 1H), 5.07-5.04 (m, 4H), 4.30 (d, J ) 2.1 Hz, 1H),
4.25-4.19 (m, 1H), 3.16 (dd, J ) 2.1, 3.87 Hz, 1H) 1.18 (d, J )
6.4 Hz, 3H), 0.88 (s, 9H), 0.06 (s, 3H), 0.05 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 209.1, 208.2, 169.3, 101.0, 89.8, 79.6, 79.5,
65.2, 64.6, 49.2, 26.1, 22.9, 18.3, -3.9, -4.7; IR (film) 3232, 2954,
2929, 2886, 2857, 1951, 1759, 1254, 836, 777 cm-1; HRMS (FAB)
calcd for C17H27NO2Si M+ 305.1811, found M+ + H 306.1895.
[[3R(1′R,4S)]-3-[1′-(tert-Butyldimethylsilyloxy)ethyl]-2-oxo-aze-
tidin-4-yl]-1,4-dimethylanthraquinone (7m). The reaction mixture
of 3a (305.4 mg, 1.0 mmol) and 1,4-naphthoquinone (79.1 mg,
0.5 mmol) in chloroform (1.0 mL) was refluxed at 62 °C. After
being stirred for 15 h, solvent was removed under reduced pressure
and the crude product was purified by silica gel column chroma-
tography (EtOAc/hexane ) 1/5) to afford 7m (196.2 mg, 85%).
mp) 233.1 °C; Rf ) 0.3 (EtOAc/Hexane ) 1/5);1H NMR (400
MHz, CDCl3) δ 8.12 (m, 2H), 7.72 (m, 2H), 7.67 (s, 1H), 6.39 (s,
1H), 5.23 (d, J ) 2.2 Hz, 1H), 4.35 (qd, J ) 6.3, 3.1 Hz, 1H), 3.03
(dd, J ) 2.2, 3.1 Hz, 1H), 2.72 (s, 3H), 2.64 (s, 3H), 1.22 (d, J )
6.3 Hz, 3H), 0.93 (s, 9H), 0.13 (s, 3H), 0.12 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 187.1, 185.9, 169.5, 145.6, 140.3, 137.3,
135.0, 134.8, 134.6, 134.2, 134.0, 133.9, 132.5, 126.9, 126.7, 69.4,
65.2, 49.2, 26.2, 24.3, 23.5, 18.4, 17.9, -3.9, -4.4; IR (film) 3180,
2953, 2928, 2857, 1755, 1321, 1255, 835, 720 cm-1; HRMS (FAB)
calcd for C27H33NO4Si M+ 463.2179, found M+ + H 464.2254.
a Reactions were carried out using DBU (1 equiv.) in toluene (0.1 M)
at 110 °C for 1 h. b Isolated yield. c Ratio of 8b to 8c. d Ratio of 8e to
8f.
were aromatized to give 2-azetidinones 8d in 93% and 95%
yields, respectively (entries 3 and 4). In the case of adducts 7i,
ꢀ-lactam compounds (8e and 8f) having ethyl benzoate group
were produced in 91% (dr ) 1:5.5) yield.
In summary, we have shown that reaction of 4-acetoxy-2-
azetidinones with organoindium reagent generated in situ from
indium and 1,6-dibromo-2,4-hexadiyne in the presence of LiCl
in DMF produced selectively 2-azetidinones possessing 1,2,4,5-
hexatetraen-3-yl group on the C4-position. The present method
indicates that 1,6-dibromo-2,4-hexadiyne acts selec-tively as
synthon of 3-anion of 1,2,4,5-hexatetraene. The Diels-Alder
reactions of 4-(1,2,4,5-hexatetraen-3-yl)-2-azetidinones with a
variety of dienophiles and subsequent aromatizations afforded
valuable functional group-substituted 2-azetidinones in good
yields; in this way, it serves as a new synthetic methodology
of ꢀ-lactam compounds.
Acknowledgment. This work was supported by the Korea
Science and Engineering Foundation (KOSEF, R01-2006-000-
11283-0) and by KOSEF through the National Research
Laboratory. Program funded by the Ministry of Science and
Technology (No. M10600000203-06J0000-20310). The NMR
data were obtained from the central instrumental facility in
KNU. Dr. Sung Hong Kim at the KBSI (Daegu) is thanked for
obtaining the MS data.
Supporting Information Available: Spectral data of all of
the new compounds. This material is available free of charge
via the Internet at http://pubs.acs.org.
Experimental Section
[3R(1′R,4S)]-3-[1′-(tert-Butyldimethylsilyloxy)ethyl]-4-(1,2,4,5-
hexatetraen-3-yl)-2-azetidinone (3a). To a suspension of indium
JO800594Y
5186 J. Org. Chem. Vol. 73, No. 13, 2008