An expedient synthesis of β-aralkyl cycloalkanones via the sequential conjugate addition of allyl arylacetates and Pd-catalyzed decarboxylative protonation protocol

Article abstract of DOI:10.1016/j.tetlet.2009.04.006

An expedient protocol for the synthesis of β-aralkyl cycloalkanones was developed via the conjugate addition of allyl arylacetate to cycloalkenones and the following Pd-catalyzed decarboxylative protonation strategy.

Full text of DOI:10.1016/j.tetlet.2009.04.006

Tetrahedron Letters 50 (2009) 3038–3041
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An expedient synthesis of b-aralkyl cycloalkanones via the sequential
conjugate addition of allyl arylacetates and Pd-catalyzed decarboxylative
protonation protocol
*
Se Hee Kim, Hyun Seung Lee, Sung Hwan Kim, Jae Nyoung Kim
Department of Chemistry and Institute of Basic Science, Chonnam National University, Gwangju 500-757, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
An expedient protocol for the synthesis of b-aralkyl cycloalkanones was developed via the conjugate
addition of allyl arylacetate to cycloalkenones and the following Pd-catalyzed decarboxylative proton-
ation strategy.
Received 5 March 2009
Revised 30 March 2009
Accepted 2 April 2009
Available online 7 April 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Palladium
Decarboxylative protonation
b-Aralkyl cycloalkanones
Introduction of carbon nucleophile at the b-position of cyclo-
alkenone in a Michael fashion is an important chemical transforma-
tion in organic synthesis.1,2 Conjugate addition of organometallic
compounds in the presence of copper salt is the most common
and efficient method.1a,b Besides organocopper reagents, organo-
zinc in combination with (AlMeO)n1c and RLi/RMgX in combination
Very recently, we used the Pd-catalyzed decarboxylative pro-
tonation protocol elegantly for the synthesis of 1,5-dicarbonyls
and related compounds from Baylis–Hillman adducts.5 During
the project we imagined that we could introduce p-nitrobenzyl
moiety at the b-position of 2-cyclohexene-1-one (1a) as shown
in Scheme 1. The strategy was the sequential conjugate addition
of allyl p-nitrophenylacetate (2a) to form 3a and the following
Pd-catalyzed decarboxylative protonation of 3a to make 4a.
The conjugate addition of 2a to 1a was carried out in the pres-
ence of TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene)7 in toluene to
produce 3a in high yield (84%) in short time. The Pd-catalyzed
decarboxylative protonation of 3a was carried out under the influ-
ence of Et3N/HCOOH in CH3CN to produce 4a in high yield (90%) in
short time (1 h).8 The reaction of 3a in aqueous CH3CN5 produced
4a in low yield (67%) together with some intractable side products.
The plausible mechanism for the reaction is depicted in Scheme 1:
the sequential (i) oxidative addition of O-allyl bond of 3a to Pd(0)
1d
with BeCl2 have also been used for the reaction. However, the
preparation of functionalized organometallic compounds and their
use in organic synthesis are often faced with some problems like
functional group incompatibility. Especially, the preparation of ni-
tro-containing organometallic compounds is difficult due to the
reactivity of nitro group, although nitroaryl Grignard reagents can
be generated at low temperature and used efficiently in some case-
s.3a In these contexts, conjugate addition of nitrobenzyl group at the
b-position of cycloalkenones is regarded as a tedious matter.2,3
After Tsuji’s brilliant contributions,4a–d Pd-catalyzed decarboxy-
lative protonation and allylation have been used widely in organic
synthesis.4–6 As is often the case the corresponding
p-allylpalla-
to form the
two canonical C-
p
-allylpalladium carboxylate (I), (ii) loss of CO2 to form
-allylpalladium (II) and O- -allylpalladium (III)
dium carboxylate intermediate cannot lose carbon dioxide without
an electron-accommodating group.4–6 Many functional groups
have been reported as the suitable electron-accommodating moie-
ties including ester, nitrile, and acetyl groups.4,5 Recently, Tunge
and co-workers used electron-deficient aryl and heterocyclic moi-
eties as the electron-accommodating group in their Pd-catalyzed
decarboxylative allylation.6
p
p
intermediates, (iii) formation of palladium formate (IV) with liber-
ation of propene, and (iv) liberation of CO2 and Pd(0) to produce
product 4a.
Encouraged by the successful results, we prepared allyl esters
3a–k by the reaction of four cycloalkenones 1a–d and five allyl ary-
lacetates 2a–e, which have a suitable electron-accommodating
moiety. Most of the starting materials were prepared by the cata-
lytic action of TBD,7 however, the reaction of allyl pyridylacetate
(2d) was not efficient with TBD thus TBAF (n-tetrabutylammonium
fluoride, THF solution)9 was used as the catalyst (entries 4 and 9).
* Corresponding author. Tel.: +82 62 530 3381; fax: +82 62 530 3389.
E-mail address: kimjn@chonnam.ac.kr (J.N. Kim).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.04.006

S. H. Kim et al. / Tetrahedron Letters 50 (2009) 3038–3041
3039
NO2
O
O
O
Pd(OAc)2 (5 mol%)
TBD (0.5 equiv)
toluene, rt, 20 min
NO2
NO2
PPh3 (10 mol%)
+
Et3N/HCOOH
CH3CN, reflux, 1 h
O
O
COOallyl
3a (84%)
1a
2a
4a (90%)
3a
4a
- CO2
- Pd(0)
Pd(0)
O
O
NO2
O
NO2
Pd
O
NO2
O
O
N
- CO2
Et3N/HCOOH
- propene
O
O
Pd
Pd
H
Pd
O
O
(IV)
(III)
(II)
(I)
Scheme 1.
As summarized in Table 1, the yields of starting materials 3a–k
were moderate to good (58–89%). Most of the starting materials
were isolated as a 1:1 syn/anti mixture except 3b (2:1 mixture).
The starting material 3k, prepared from 1d and 2a, has three ste-
reocenters and showed the formation of four stereoisomers. Two
isomers of cis-form were observed in trace amounts (<5%, 1:1 mix-
ture) while the two isomers of trans-form were observed in large
amounts (>95%, 1:1 mixture) in its 1H NMR spectrum, as reported
in a similar case.10 With these substrates 3a–k, we synthesized our
desired products 4a–k in high yields (75–95%) under the condi-
tions of Pd(OAc)2/PPh3/Et3N/HCOOH in refluxing CH3CN in short
time. It is interesting to note that the reaction of 3e in CH3CN
showed almost no reaction presumably due to the weak electron
accommodating capability of –SO2Me group than the nitro group
in other cases. However, we could obtain 4e in 75% yield when
we used DMF as a solvent for long time (6 h), very fortunately.
The results are summarized in Table 1.
63% isolated yield. The reaction was carried out in non-polar sol-
vent such as toluene with relatively larger amounts of PPh3 (Pd/
PPh3 = 0.125) as deeply studied by Tsuji and co-workers.4,11 In
the reaction, decarboxylative protonation product 4a (23%) was
also isolated. Decarboxylative allylation of 3b produced com-
pound 6 in 83% yield similarly under the same conditions to-
gether with 4b (8% yield). When we used small amounts of
PPh3 (Pd/PPh3 = 2.5) in the reaction of 3b, we obtained com-
pound 7 in 53% isolated yield via the Pd-catalyzed decarboxyl-
ation–elimination mechanism.11,12
It is interesting to note that the stereoisomeric ratio was chan-
ged after the reaction in some examples (4b from 3b in entry 2 in
Table 1; 5 from 3a and 6 from 3b in Scheme 2). The results could be
a strong evidence for the involvement of the intermediate (III) in
the reaction mechanism, as exemplified for the conversion of 3b
to 4b in Scheme 3. The configuration of chiral center in (II) could
be epimerized via the canonical structure (III). In this manner 3b
(2:1 mixture) was converted into 4b (1:1 mixture) although we
did not determine their syn/anti stereochemistry.
As shown in Scheme 2, we examined the Pd-mediated
decarboxylative allylation reaction with 3a and obtained 5 in
Table 1
Synthesis of b-aralkyl cycloalkanones 4
SO2Me
O2N
O
NO2
NO2
N
O
O
O
O
O
Me
O
O
O
O
O
O
O
O
1a
1b
1c
1d
2a
2b
2c
2d
2e
Entry
Substrates
Conditions
3a (%)
Conditionsb (h)
4 (%)
1
2
3
4
5
6
7
8
9
1a + 2a
1a + 2b
1a + 2c
1a + 2d
1a + 2e
1b + 2a
1b + 2b
1b + 2c
1b + 2d
1c + 2a
1d + 2a
TBD (0.5 equiv), toluene, rt, 20 min
TBD (0.5 equiv), toluene, rt, 20 min
TBD (0.5 equiv), toluene, rt, 60 min
TBAF (0.5 equiv), THF, rt, 20 min
TBD (0.5 equiv), toluene, rt, 20 min
TBD (0.5 equiv), toluene, rt, 20 min
TBD (0.8 equiv), toluene, rt, 20 min
TBD (0.5 equiv), toluene, rt, 20 min
TBAF (0.5 equiv), THF, rt, 20 min
TBD (0.8 equiv), toluene, rt, 20 min
TBD (0.5 equiv), toluene, rt, 20 min
3a (84, 1:1)
3b (63, 2:1)
3c (65, 1:1)
3d (89, 1:1)
3e (76, 1:1)
3f (83, 1:1)
3g (62, 1:1)
3h (68, 1:1)
3i (82, 1:1)
3j (82, 1:1)
3k (58, 1:1)d
1
1
1
1
6c
1
1
3
1
1
1
4a (90)
4b (86, 1:1)a
4c (86)
4d (90)
4e (75)
4f (92)
4g (84, 1:1)a
4h (92)
4i (95)
10
11
4j (90)
4k (90)e
Isolated yield and the syn/anti ratio was determined by 1H NMR and is arbitrary.
Conditions: Pd(OAc)2 (5 mol %), PPh3 (10 mol %), Et3N (1.3 equiv), HCOOH (1.1 equiv), CH3CN, reflux.
DMF was used as solvent and the reaction was carried out at 80 °C.
Two diastereomers (1:1) of trans form were the major and two diastereomers of cis form were mixed together (1:1), 5%.
a
b
c
d
e
Single compound of trans form.

3040
S. H. Kim et al. / Tetrahedron Letters 50 (2009) 3038–3041
O
O
Pd(OAc)2 (5 mol%)
PPh3 (10 mol%)
Pd(OAc)2 (5 mol%)
PPh3 (40 mol%)
NO2
3a
(1:1)
4a (90%)
4a (23%)
4b (16%)
+
+
Et3N/HCOOH
CH3CN, reflux, 1 h
(entry 1 in Table 1)
toluene, reflux, 2 h
(Pd/PPh3 = 0.125)
5 (63%, 9:1)
O
Pd(OAc)2 (5 mol%)
PPh3 (40 mol%)
Pd(OAc)2 (10 mol%)
PPh3 (4 mol%)
NO2
NO2
3b
(2:1)
4b (8%)
+
toluene, reflux, 2 h
(Pd/PPh3 = 0.125)
CH3CN, reflux, 2 h
(Pd/PPh3 = 2.5)
7 (53%)
6 (83%, 3:1)
Scheme 2.
O
Pd
O
NO2
O
O
N
(IV)
(I)
3b (2:1)
4b (1:1)
*
Pd
(II)
(III)
Scheme 3.
O
O
NO2
O
1a
Grubbs cat (3 mol%)
toluene, 50 oC, 1 h
NO2
NO2
NO2
Pd(OAc)2 (5 mol%)
PPh3 (40 mol%)
TBAF (1.0 equiv)
THF, rt, 30 h
toluene, reflux, 2 h
(Pd/PPh3 = 0.125)
COOallyl
9 (37%, 1:1)
N
Mes
Ph
Mes
N
COOallyl
Cl
Ru
11 (98%)
10 (56%)
+ 5 (6%)
8
Cl
PCy3
Scheme 4.
2. For the synthesis and synthetic applications of 3-benzylcycloalkanones, see: (a)
Yus, M.; Pastor, I. M.; Gomis, J. Tetrahedron 2001, 57, 5799–5805; (b) Pastor, I.
M.; Yus, M. Tetrahedron Lett. 2001, 57, 2371–2378; (c) MacDonald, M.; Velde, D.
V.; Aube, J. J. Org. Chem. 2001, 66, 2636–2642; (d) Petrier, C.; De Souza Barbosa,
J. C.; Dupuy, C.; Luche, J.-L. J. Org. Chem. 1985, 50, 5761–5765; (e) Matzger, A.;
Schade, M. A.; Knochel, P. Org. Lett. 2008, 10, 1107–1110.
3. For the incompatibility of nitro group with organometallic compounds, see: (a)
Sapountzis, I.; Knochel, P. Angew. Chem., Int. Ed. 2002, 41, 1610–1611. and
further references cited therein; (b) Bosco, M.; Dalpozzo, R.; Bartoli, G.;
Palmieri, G.; Petrini, M. J. Chem. Soc., Perkin Trans. 2 1991, 657–663; (c) Dobson,
D. R.; Gilmore, J.; Long, D. A. Synlett 1992, 79–80; (d) Bartoli, G.; Palmieri, G.;
Bosco, M.; Dalpozzo, R. Tetrahedron Lett. 1989, 30, 2129–2132.
4. For the Pd-catalyzed decarboxylative protonation and allylation, see: (a) Tsuji,
J.; Nisar, M.; Shimizu, I. J. Org. Chem. 1985, 50, 3416–3417; (b) Mandai, T.; Imaji,
M.; Takada, H.; Kawata, M.; Nokami, J.; Tsuji, J. J. Org. Chem. 1989, 54, 5395–
5397; (c) Tsuji, J. Pure Appl. Chem. 1986, 58, 869–878; (d) Tsuji, J. Proc. Jpn. Acad.,
B 2004, 80, 349–358; (e) Marinescu, S. C.; Nishimata, T.; Mohr, J. T.; Stoltz, B. M.
Org. Lett. 2008, 10, 1039–1042; (f) Ragoussis, V.; Giannikopoulos, A. Tetrahedron
Lett. 2006, 47, 683–687.
5. (a) Gowrisankar, S.; Kim, K. H.; Kim, S. H.; Kim, J. N. Tetrahedron Lett. 2008, 49,
6241–6244. and further references cited therein; (b) Kim, J. M.; Kim, S. H.; Lee,
H. S.; Kim, J. N. Tetrahedron Lett. 2009, 50, 1734–1737.
As a next trial, we examined the synthesis of spiro compound
11 via the RCM (ring-closing metathesis) reaction of 10 which
was prepared by the Pd-mediated decarboxylative allylation of 9
(Scheme 4). Required starting material 9 was prepared by the Mi-
chael addition of 8 to 1a in THF under the influence of TBAF (rt,
30 h) although the yield was low. The Pd-catalyzed decarboxyla-
tive allylation was carried out similarly (high loading of PPh3),
and compound 10 was isolated in 56% yield. Next RCM reaction
of 10 was carried out with 3 mol % of second generation Grubbs
catalyst (toluene, 50 °C, 1 h) to afford 11 in 98% yield.
In summary, we disclosed an efficient aralkylation method at
the b-position of cycloalkenones via a sequential conjugate addi-
tion of allyl arylacetate and the following Pd-catalyzed decarboxy-
lative protonation strategy. In addition, we demonstrated some
interesting applications of this protocol including the synthesis of
vinyl compound and spiro compound.
6. For the Pd-catalyzed decarboxylative allylation and related reactions involving
nitro arene or pyridine moiety by Tunge and co-workers, see: (a) Waetzig, S. R.;
Tunge, J. A. J. Am. Chem. Soc. 2007, 129, 14860–14861; (b) Waetzig, S. R.; Tunge,
J. A. J. Am. Chem. Soc. 2007, 129, 4138–4139; (c) Tunge, J. A.; Burger, E. C. Eur. J.
Org. Chem. 2005, 1715–1726. and further references cited therein; (d) Weaver,
J. D.; Tunge, J. A. Org. Lett. 2008, 10, 4657–4660.
7. (a) Ye, W.; Xu, J.; Tan, C.-T.; Tan, C.-H. Tetrahedron Lett. 2005, 46, 6875–6878;
(b) Subba Rao, Y. V.; De Vos, D. E.; Jacobs, P. A. Angew. Chem., Int. Ed. 1997, 36,
2661–2663.
Acknowledgments
This work was supported by the Korea Research Foundation
Grant funded by the Korean Government (MOEHRD, KRF-2008-
313-C00487). Spectroscopic data were obtained from the Korea Ba-
sic Science Institute, Gwangju branch.
8. Typical experimental procedure for the synthesis of 3a and 4a: A mixture of 1a
(96 mg, 1.0 mmol), 2a (287 mg, 1.3 mmol), and TBD (70 mg, 0.5 mmol) in
toluene (3 mL) was stirred at room temperature for 20 min. After the usual
aqueous workup and column chromatographic purification process (hexanes/
EtOAc/CH2Cl2, 3:1:1) compound 3a was obtained as a pale yellow solid, 266 mg
(84% yield) as a syn/anti (1:1) mixture. A mixture of compound 3a (160 mg,
0.5 mmol), Et3N (66 mg, 0.65 mmol), HCOOH (25 mg, 0.55 mmol), Pd(OAc)2
(6 mg, 5 mol %), and PPh3 (13 mg, 10 mol %) in acetonitrile (2 mL) was heated
References and notes
1. For the conjugate addition of organometallic compounds, see: (a) Kanai, M.;
Nakagawa, Y.; Tomioka, K. Tetrahedron 1999, 55, 3843–3854; (b) Van Heerden,
P. S.; Bezuidenhoudt, B. C. B.; Steenkamp, J. A.; Ferreira, D. Tetrahedron Lett.
1992, 33, 2383–2386; (c) Blake, A. J.; Shannon, J.; Stephens, J. C.; Woodward, S.
Chem. Eur. J. 2007, 13, 2462–2472; (d) Krief, A.; De Vos, M. J.; De Lombart, S.;
Bosret, J.; Couty, F. Tetrahedron Lett. 1997, 38, 6295–6298.

S. H. Kim et al. / Tetrahedron Letters 50 (2009) 3038–3041
3041
to reflux for 1 h. After the usual aqueous workup and column chromatographic
purification process (hexanes/EtOAc, 1:1) compound 4a was obtained as
colorless oil, 105 mg (90% yield). Other compounds were synthesized similarly
and the selected spectroscopic data of 3a, 4a, 4k, 5, 7, and 11 are as follows.
Compound 3a: 84% yield (1:1 syn/anti mixture); pale yellow solid, mp 75–77 °C;
J = 8.4 Hz, 2H), 8.18 (d, J = 8.4 Hz, 2H); 13C NMR (CDCl3, 75 MHz) d 24.9, 28.7,
36.7, 41.2, 43.2, 46.4, 51.2, 117.3, 123.6, 129.3, 135.2, 146.7, 150.2, 210.6;
ESIMS m/z 274 (M++1). Anal. Calcd for C16H19NO3: C, 70.31; H, 7.01; N, 5.12.
Found: C, 70.05; H, 7.34; N, 4.97.
Compound 7: 53% yield; white solid, mp 91–93 °C; IR (KBr) 1712, 1596, 1516,
IR (KBr) 1732, 1713, 1522, 1348, 1155 cmÀ1
;
1H NMR (CDCl3, 300 MHz) d 1.17–
1345 cmÀ1 1H NMR (CDCl3, 300 MHz) d 1.51–1.80 (m, 2H), 1.95–2.13 (m, 2H),
;
*
1.30 (m, 1H), 1.47–2.64 (m, 8H), 3.57 (d, J = 10.2 Hz, 0.5H 2), 4.51–4.67 (m, 2H),
2.28–2.58 (m, 4H), 2.97–3.05 (m, 1H), 5.25 (s, 1H), 5.37 (s, 1H), 7.46 (d,
J = 9.0 Hz, 2H), 8.20 (d, J = 9.0 Hz, 2H); 13C NMR (CDCl3, 75 MHz) d 24.7, 30.3,
41.2, 42.4, 46.7, 115.2, 123.7, 127.5, 147.2, 148.2, 150.2, 210.4; ESIMS m/z 246
(M++1). Anal. Calcd for C14H15NO3: C, 68.56; H, 6.16; N, 5.71. Found: C, 68.82;
H, 6.11; N, 5.57.
*
5.20–5.29 (m, 2H), 5.78–5.92 (m, 1H), 7.50 (d, J = 8.7 Hz, 2H 0.5), 7.54 (d,
*
*
*
J = 8.7 Hz, 2H 0.5), 8.20 (d, J = 8.7 Hz, 2H 0.5), 8.21 (d, J = 8.7 Hz, 2H 0.5); 13C
NMR (CDCl3, 75 MHz) d 24.2, 24.4, 28.4, 29.7, 40.9, 41.0, 41.7, 41.8, 45.0, 46.0,
57.4, 57.5, 65.9, 66.0, 119.0, 119.1, 123.8, 123.9, 129.3, 129.4, 131.2, 131.3,
143.4, 143.9, 147.5, 147.6, 171.0, 171.3, 209.2, 209.4; ESIMS m/z 318 (M++1).
Anal. Calcd for C17H19NO5: C, 64.34; H, 6.03; N, 4.41. Found: C, 64.55; H, 6.34;
N, 4.17.
Compound 11: 98% yield; colorless oil; IR (film) 1710, 1517, 1346 cmÀ1 1H
;
NMR (CDCl3, 300 MHz) d 1.18–1.72 (m, 3H), 1.91–2.36 (m, 6H), 2.81 (s, 4H),
5.72 (s, 2H), 7.38 (d, J = 9.0 Hz, 2H), 8.17 (d, J = 9.0 Hz, 2H); 13C NMR (CDCl3,
75 MHz) d 25.0, 26.7, 41.0, 41.7, 42.2, 44.0, 49.4, 53.8, 123.2, 128.4, 129.1,
146.1, 155.9, 211.3; ESIMS m/z 286 (M++1). Anal. Calcd for C17H19NO3: C, 71.56;
H, 6.71; N, 4.91. Found: C, 71.45; H, 6.89; N, 4.73.
Compound 4a: 90% yield; colorless oil; IR (film) 1712, 1604, 1517, 1346 cmÀ1
;
1H NMR (CDCl3, 300 MHz) d 1.35–1.48 (m, 1H), 1.57–1.72 (m, 1H), 1.84–1.90
(m, 1H), 2.01–2.42 (m, 6H), 2.71 (dd, J = 13.5 Hz and 6.6 Hz, 1H), 2.78 (dd,
J = 13.2 Hz and 6.6 Hz, 1H), 7.30 (d, J = 8.7 Hz, 2H), 8.16 (d, J = 8.7 Hz, 2H); 13C
NMR (CDCl3, 75 MHz) d 24.8, 30.8, 40.4, 41.2, 42.6, 47.5, 123.6, 129.8, 146.6,
147.2, 210.6; ESIMS m/z 234 (M++1). Anal. Calcd for C13H15NO3: C, 66.94; H,
6.48; N, 6.00. Found: C, 67.08; H, 6.54; N, 6.31.
9. Park, D. Y.; Gowrisankar, S.; Kim, J. N. Tetrahedron Lett. 2006, 47, 6641–6645.
and further references cited therein.
10. Donnoli, M. I.; Scafato, P.; Nardiello, M.; Casarini, D.; Giorgio, E.; Rosini, C.
Tetrahedron 2004, 60, 4975–4981.
Compound 4k: 90% yield; pale yellow solid, mp 52–54 °C; IR (KBr) 1740, 1517,
11. For the Pd-catalyzed decarboxylation–elimination, see: (a) Shimizu, I.; Tsuji, J.
J. Am. Chem. Soc. 1982, 104, 5844–5846; (b) Kataoka, H.; Yamada, T.; Goto, K.;
Tsuji, J. Tetrahedron 1987, 43, 4107–4112.
12. For the synthesis of elimination product like 7, an efficient rhodium-catalyzed
synthetic method of similar compounds was developed recently by the 1,4-
1347 cmÀ1 1H NMR (CDCl3, 300 MHz) d 1.10 (d, J = 7.2 Hz, 3H), 1.40–2.50 (m,
;
6H), 2.70 (dd, J = 13.5 Hz and 8.7 Hz, 1H), 3.14 (dd, J = 13.5 Hz and 4.5 Hz, 1H),
7.37 (d, J = 8.7 Hz, 2H), 8.18 (d, J = 8.7 Hz, 2H); 13C NMR (CDCl3, 75 MHz) d 12.6,
26.9, 37.0, 40.4, 46.1, 49.9, 123.7, 129.7, 146.6, 147.6, 219.5; ESIMS m/z 234
(M++1). Anal. Calcd for C13H15NO3: C, 66.94; H, 6.48; N, 6.00. Found: C, 66.77; H,
6.65; N, 5.81.
addition reaction of alkenylsilane to
a,b-unsaturated carbonyl acceptors, see:
(a) Nakao, Y.; Chen, J.; Imanaka, H.; Hiyama, T.; Ichikawa, Y.; Duan, W.-L.;
Shintani, R.; Hayashi, T. J. Am. Chem. Soc. 2007, 129, 9137–9143; (b) Imai, M.;
Tanaka, M.; Suemune, H. Tetrahedron 2001, 57, 1205–1211; (c) Katritzky, A. R.;
Toader, D. J. Am. Chem. Soc. 1997, 119, 9321–9322.
Compound 5: 63% yield (major isomer in 9:1 mixture); pale yellow oil; IR (film)
1712, 1518, 1346 cmÀ1 1H NMR (CDCl3, 300 MHz) d 1.13–1.69 (m, 3H), 1.83–
;
2.46 (m, 6H), 2.54–2.80 (m, 3H), 4.89–4.98 (m, 2H), 5.43–5.57 (m, 1H) 7.28 (d,