Regioselective synthesis of poly-substituted naphthalenes via a Pd-catalyzed cyclization of modified Baylis-Hillman adducts: Selective 6-endo Heck reaction and an aerobic oxidation cascade

Article abstract of DOI:10.1016/j.tetlet.2010.09.127

Poly-substituted naphthalenes were synthesized via a Pd-catalyzed cyclization of modified Baylis-Hillman adducts having an o-bromophenyl acetonitrile moiety at the secondary position, in reasonable yields. The reaction involved a sequential 6-endo Heck re

Full text of DOI:10.1016/j.tetlet.2010.09.127

Tetrahedron Letters 51 (2010) 6305–6309
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Regioselective synthesis of poly-substituted naphthalenes via a Pd-catalyzed
cyclization of modified Baylis–Hillman adducts: selective 6-endo Heck
reaction and an aerobic oxidation cascade
Se Hee Kim a, Sangku Lee b, Hyun Seung Lee a, Jae Nyoung Kim a,
⇑
a Department of Chemistry and Institute of Basic Science, Chonnam National University, Gwangju 500-757, Republic of Korea
b Natural Medicine Research Center, KRIBB, Daejeon 305-806, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Poly-substituted naphthalenes were synthesized via a Pd-catalyzed cyclization of modified Baylis–
Hillman adducts having an o-bromophenyl acetonitrile moiety at the secondary position, in reasonable
yields. The reaction involved a sequential 6-endo Heck reaction and an aerobic oxidation process.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 17 August 2010
Revised 21 September 2010
Accepted 22 September 2010
Available online 1 October 2010
Keywords:
Palladium
Naphthalenes
Baylis–Hillman adducts
6-endo Heck reaction
Chemical transformations of Baylis–Hillman adducts have
received much attention during the last two decades.1–3 Various
cyclic and acyclic compounds have been prepared by various
chemical transformations from Baylis–Hillman adducts.1–3
Although Pd-catalyzed chemical transformations of modified
Baylis–Hillman adducts started very recently, they have provided
many interesting carbo- and heterocyclic compounds.2,3
Recently, we reported a Pd-catalyzed synthesis of tetracyclic
indeno[1,2-a]indanes from modified Baylis–Hillman adducts, as
shown in Scheme 1.3a In the reaction, indeno[1,2-a]indane was
formed as the major product via a Pd-catalyzed 5-exo-trig cycliza-
tion and aryl C–H activation when the EWG is an ester group
(Eq. 1). When the EWG is a nitrile, carbopalladation occurred in a
6-endo mode to provide a naphthalene derivative exclusively
(Eq. 2). The selectivity between 5-exo and 6-endo modes was
explained based on the change of conformations according to the
bulkiness of OTBS moiety and EWG.3a,4 Based on our previous
results we expected that if we replace the bulky OTBS to a small
nitrile group the proportion of 6-endo carbopalladation would
increase irrespective of the size of EWG,3a,4 and we could obtain
poly-substituted naphthalenes5 as shown in Scheme 1 (Eq. 3).
Thus we decided to examine the Pd-catalyzed cyclizations of
modified Baylis–Hillman adducts 3. The starting materials 3a–f
were prepared by the reactions of cinnamyl bromides 1a–e3a,6
and 2-bromoaryl acetonitriles 2 in the presence of K2CO3 via the
corresponding DABCO salts of 1a–e, in good to moderate yields
(Table 2), as reported.7 (Scheme 2).
The reactions of 3a under various conditions were examined,
and we observed the formation of four compounds 4a, 5a, 6a,
and 7a, in variable yields as shown in Table 1.8 When we applied
the conditions of Eq. 1 (Scheme 1),3a the starting material 3a was
decomposed completely at 110 °C. Thus we examined the reaction
at slightly lower temperature (90 °C, entry 1); however, 4a was iso-
lated in low yield (22%) along with a indeno[1,2-a]indane 6a (11%).
The use of K2CO3 (entry 2) and tetrabutylammonium bromide (en-
try 3) increased the yield of 4a. Although the yield of 4a was mod-
erate (44–66%) we found that 6-endo carbopalladation is
a
preferred pathway as expected. When the reaction was performed
in toluene (entry 4) the yield of 4a was reasonable (64%) although a
somewhat longer reaction time (5 h) was required. Finally, the
optimum condition was found to be the one using TBAB in toluene
(entry 5) in respects of both the yield of 4a and the selectivity of
products (4a/5a + 6a + 7a). It is interesting to note that the use of
Et3N as a base produced 7a as the major product (entry 6). Under
the influence of such a weak base (Et3N), further oxidation of 7a
(or 5a) at the benzylic position to ketone9 was not observed as in
our previous report.3b
The mechanism for the formation of 4a–7a could be postulated,
as shown in Scheme 3. The 6-endo carbopalladation of the arylpal-
ladium intermediate (I) to (II) and a following b-H elimination
produced the dihydronaphthalene derivative 5a. Aerobic oxidation
of 5a afforded naphthalene 4a.3b The 5-exo carbopalladation of (I)
⇑
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 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.127

6306
S. H. Kim et al. / Tetrahedron Letters 51 (2010) 6305–6309
TBSO
H
Br
Br
Pd(OAc)2, PPh3
TBSO
Ph
TBSO
Cs2CO3, DMF, 110 o
C
+
(1)
Ref. 3a
COOMe
COOMe
89%
Ph
3%
Pd(OAc)2, PPh3
TBSO
Cs2CO3, DMF, 110 o
C
OH
EWG
(2)
(3)
CN
Ph
Ref. 3a
Ph
Ph
CN
88%
B-H adduct
Br
Pd(OAc)2, TBAB
O
K2CO3, toluene, reflux
NC
Ph
H
NC
+
this work
EWG
Ph
EWG
EWG
4 (major)
5 (trace)
3 (syn/anti mixture)
EWG = COOMe, COOEt, CN
Scheme 1.
1. DABCO (1.1 equiv)
CH3CN, rt, 30 min.
HBr (for 1a-c
and 1e)
NC
R
Ar
OH
EWG
Br
R
EWG
EWG
R
2. 2a or 2b (1.2 equiv)
K2CO3 (1.1 equiv), rt, 12 h
PBr3 (for 1d)
1a-e (71-93%)
3a-f
Table 2 for the structure of 3a-f
1a: R = Ph, EWG = COOMe (Z)
1b: R = Ph, EWG = COOEt (Z)
1c: R = p-tolyl, EWG = COOMe (Z)
1d: R = Me, EWG = COOMe (Z)
1e: R = Ph, EWG = CN (E)
2a: 2-bromophenylacetonitrile
2b: 6-bromo-1,3-benzodioxole-5-acetonitrile
Scheme 2.
Table 1
Optimization of reaction conditions of 3aa
O
NC
Ph
NC
NC
H
conditions
+
3a
+
+
Ph
Ph
COOMe
6a
COOMe
COOMe
4a
5a
7a
Entry
Conditions
4a (%)b
5a (%)bc
6a (%)b
7a (%)b,c
1
2
3
4
PPh3 (10 mol %), Cs2CO3 (2.0 equiv), DMF, 90 °C, 30 min
PPh3 (10 mol %), K2CO3 (2.0 equiv), DMF, 90 °C, 30 min
TBAB (1.0 mol %), K2CO3 (2.0 equiv), DMF, 90 °C, 30 min
PPh3 (10 mol %), K2CO3 (2.0 equiv), toluene, reflux, 5 h
22
66
44
64
0
0
0
2
11
6
5
0
0
0
0
5
5
6
TBAB (1.0 mol %), K2CO3 (2.0 equiv), toluene, reflux, 3 h
0
3
0
0
PPh3 (10 mol %), Et3N (1.2 equiv), DMF, 110 °C, 1 h
20
19
a
b
c
Conditions: Pd(OAc)2 (10 mol %) is common.
Isolated yields.
Mixture of cis/trans.
provided an alkylpalladium intermediate (III). Aromatic C–H acti-
vation3a of (III) to form (V) via the palladacycle (IV) and the follow-
ing base-mediated aerobic oxidation of (V) produced an
indeno[1,2-a]indane 6a. Similar air oxidation of benzylic cyanides
was reported under basic conditions.9 Competitive d-carbon elim-
ination and concomitant decarboxylation of (III) generated methy-
leneindane 7a, as observed many times in similar cases.3a,3b,10
Thus we chose the conditions in entry 5 (Table 1) as the best
ones and carried out the synthesis of poly-substituted naphtha-
lenes 4a–f, and the results are summarized in Table 2. The reac-
tions of 3b–d showed very similar results with that of 3a.
Naphthalenes 4b–d were obtained in moderate yields (65–79%)
along with small amounts of indeno[1,2-a]indane derivatives
6b–c (3–5%). The reaction of 3e produced a somewhat lower yield
of 4e (47%) than other entries. However, the yield of 4e increased
to 61% when the reaction was performed under the conditions of
TBAB/K2CO3/DMF (entry 3 in Table 1). The reaction of 3f afforded
4f (57%) along with a small amount of 4f0 (18%). This compound
must be formed via a base-mediated elimination of HCN from
the corresponding dihydronaphthalene.

S. H. Kim et al. / Tetrahedron Letters 51 (2010) 6305–6309
6307
Table 2
Synthesis of naphtahlenes 4a–f
Entry
Substrate (%)a
Products (%)b
Br
O
O
H
H
NC
Ph
NC
1
COOMe
COOMe
6a (3)
Ph
COOMe
4a (74)
3a (86, 3:2)
Br
Br
Br
NC
Ph
NC
Ph
2
COOEt
COOEt
COOEt
4b (77)
3b (95, 2:1)
6b (3)
O
H
NC
Ar
NC
Ar
3c
COOMe
COOMe
6c (5)
Me
COOMe
4c (79)
3c (94, 3:2)
O
O
O
NC
Ph
O
NC
Ph
4
5
6d (—)
COOMe
3d (85, 3:1)
COOMe
4d (65)
Br
NC
NC
Me
6e (—)
COOMe
Me
COOMe
4e (47)e
3e (41, 1:1)d
Br
NC
Ph
NC
Ph
6f (—)
6
CN
Ph
CN
CN
4f' (18)
4f (57)
3f (94, 3:2)
a
Formed as a syn/anti mixture and used without separation.
Isolated yield.
Ar is p-tolyl.
The yield of 3e was low (41%) due to the competitive formation of a primary adduct (24%).
Compound 4e was obtained in 61% under the conditions of entry 3 in Table 1.
b
c
d
e
aerobic
oxidation
NC
Ph
6-endo
- HPdBr
5a
4a
BrPd
NC
BrPd COOMe
(II)
Pd0
NC
H
NC
H
C(sp2)-H
activation
3a
aerobic
- Pd0
COOMe
oxidation
Ph
6a
NC
(I)
H
COOMe
(V)
COOMe
(IV)
Pd
5-exo
δ-carbon elimination
/decarboxylation
COOMe
PdBr
(III)
H
7a
Scheme 3.
The structure of 4a was unequivocally confirmed by NOE exper-
base-mediated ring-opening to dihydronaphthalene (VII), and the
following aerobic oxidation process.3b
In summary, we disclosed the synthesis of poly-substituted
naphthalenes from the modified Baylis–Hillman adducts having
an o-bromophenyl acetonitrile moiety at the secondary position
iments, as shown in Scheme 4. From the NOE data of 4a we could
rule out the possibility for the formation of another plausible naph-
thalene 8, which could be formed from the intermediate (III) via a
C(sp3)–H activation to form the cyclopropane intermediate (VI),

6308
S. H. Kim et al. / Tetrahedron Letters 51 (2010) 6305–6309
δ = 8.04 (d)
NC
Ph
CN
CN
H
H
CN
Ph
Ph
C(sp3)-H activation
nOe
H
(III)
δ = 8.61 (s)
O
O
Me
δ = 3.65 (s)
nOe
COOMe
(VI)
COOMe
(VII)
COOMe
8
4a
Scheme 4.
Basavaiah, D.; Reddy, K. R.; Kumaragurubaran, N. Nat. Protoc. 2007, 2, 2665–
2676; (c) Das, B.; Banerjee, J.; Ravindranath, N. Tetrahedron 2004, 60, 8357–
8361.
via a Pd-catalyzed cascade reaction in reasonable yields. Further
studies on the reaction progress and mechanistic details are
underway.11
7. For the introduction of nucleophiles at the secondary position of Baylis–
Hillman adducts using DABCO salt concept, see: (a) Chung, Y. M.; Gong, J. H.;
Kim, T. H.; Kim, J. N. Tetrahedron Lett. 2001, 42, 9023–9026; (b) Lee, K. Y.;
Gowrisankar, S.; Lee, Y. J.; Kim, J. N. Tetrahedron 2006, 62, 8798–8804. and
further references cited therein.
Acknowledgment
8. Typical procedure for the synthesis of 4a: A stirred mixture of 3a (185 mg,
0.5 mmol), Pd(OAc)2 (12 mg, 10 mol%), TBAB (162 mg, 0.5 mmol), and K2CO3
(139 mg, 1.0 mmol) in toluene (1.0 mL) was heated to reflux for 3 h. After the
usual aqueous workup and column chromatographic purification process
(hexanes/EtOAc, 20:1), compounds 4a (106 mg, 74%) and 6a3a (4 mg, 3%) were
obtained. Other compounds were prepared similarly, and the selected
spectroscopic data of 4a, 4b, 4d, 4f, 6c, and 7a are as follows.
This research was supported by the Basic Science Research Pro-
gram through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
(2010-0015675). Spectroscopic data were obtained from the Korea
Basic Science Institute, Gwangju branch.
Compound 4a: 74% yield; white solid, mp 167–169 °C; IR (KBr) 2223, 1731,
1299, 1212 cmꢀ1 1H NMR (CDCl3, 300 MHz) d 3.65 (s, 3H), 7.39–7.56 (m, 5H),
;
References and notes
7.70 (t, J = 8.1 Hz, 1H), 7.82 (t, J = 8.4 Hz, 1H), 8.04 (d, J = 8.1 Hz, 1H), 8.34 (d,
J = 8.4 Hz, 1H), 8.61 (s, 1H); 13C NMR (CDCl3, 75 MHz) d 52.41, 111.77, 116.38,
125.60, 128.24 (2C), 128.66, 128.73, 129.39, 129.45, 130.87, 131.16, 133.64,
135.14, 137.76, 145.25, 167.07; ESIMS m/z 288 (M++1). Anal. Calcd for
1. For the leading reviews on Baylis–Hillman reaction, see: (a) Basavaiah, D.; Rao,
A. J.; Satyanarayana, T. Chem. Rev. 2003, 103, 811–891; (b) Gowrisankar, S.; Lee,
H. S.; Kim, S. H.; Lee, K. Y.; Kim, J. N. Tetrahedron 2009, 65, 8769–8780; (c) Kim,
J. N.; Lee, K. Y. Curr. Org. Chem. 2002, 6, 627–645; (d) Lee, K. Y.; Gowrisankar, S.;
Kim, J. N. Bull. Korean Chem. Soc. 2005, 26, 1481–1490; (e) Radha Krishna, P.;
Sachwani, R.; Reddy, P. S. Synlett 2008, 2897–2912; (f) Declerck, V.; Martinez, J.;
Lamaty, F. Chem. Rev. 2009, 109, 1–48; (g) Singh, V.; Batra, S. Tetrahedron 2008,
64, 4511–4574.
C
19H13NO2: C, 79.43; H, 4.56; N, 4.88. Found: C, 79.66; H, 4.78; N, 4.65.
Compound 4b: 77% yield; white solid, mp 79–81 °C; IR (KBr) 2222, 1720, 1239,
1209 cmꢀ1 1H NMR (CDCl3, 300 MHz)
0.97 (t, J = 7.2 Hz, 3H), 4.10 (q,
;
d
J = 7.2 Hz, 2H), 7.40–7.51 (m, 5H), 7.71 (t, J = 8.1 Hz, 1H), 7.82 (t, J = 8.4 Hz, 1H),
8.04 (d, J = 8.1 Hz, 1H), 8.33 (d, J = 8.4 Hz, 1H), 8.60 (s, 1H); 13C NMR (CDCl3,
75 MHz) d 13.57, 61.53, 111.66, 116.45, 125.60, 128.20, 128.23, 128.60, 128.84,
129.39, 130.03, 130.78, 131.21, 133.59, 135.04, 138.00, 145.15, 166.93; ESIMS
m/z 302 (M++1). Anal. Calcd for C20H15NO2: C, 79.72; H, 5.02; N, 4.65. Found: C,
79.81; H, 5.31; N, 4.56.
2. For the recent Pd-catalyzed reactions of modified Baylis–Hillman adducts, see:
(a) Vasudevan, A.; Tseng, P.-S.; Djuric, S. W. Tetrahedron Lett. 2006, 47, 8591–
8593; (b) Coelho, F.; Veronese, D.; Pavam, C. H.; de Paula, V. I.; Buffon, R.
Tetrahedron 2006, 62, 4563–4572; (c) Kohn, L. K.; Pavam, C. H.; Veronese, D.;
Coelho, F.; De Carvalho, J. E.; Almeida, W. P. Eur. J. Med. Chem. 2006, 41, 738–
744; (d) Liu, H.; Yu, J.; Wang, L.; Tong, X. Tetrahedron Lett. 2008, 49, 6924–6928;
(e) Szlosek-Pinaud, M.; Diaz, P.; Martinez, J.; Lamaty, F. Tetrahedron 2007, 63,
3340–3349; (f) Declerck, V.; Ribiere, P.; Nedellec, Y.; Allouchi, H.; Martinez, J.;
Lamaty, F. Eur. J. Org. Chem. 2007, 201–208; (g) Ribiere, P.; Declerck, V.;
Nedellec, Y.; Yadav-Bhatnagar, N.; Martinez, J.; Lamaty, F. Tetrahedron 2006, 62,
10456–10466; (h) Sauvagnat, B.; Lamaty, F.; Lazaro, R.; Martinez, J. Tetrahedron
2001, 57, 9711–9718; (i) Jellerichs, B. G.; Kong, J.-R.; Krische, M. J. J. Am. Chem.
Soc. 2003, 125, 7758–7759. Further references were compiled in Ref. 1b.
3. For our recent contributions on Pd-catalyzed reactions of modified Baylis-
Hillman adducts, see: (a) Kim, K. H.; Lee, H. S.; Kim, S. H.; Kim, S. H.; Kim, J. N.
Chem. Eur. J. 2010, 16, 2375–2380; (b) Kim, S. H.; Lee, H. S.; Kim, K. H.; Kim, J. N.
Tetrahedron Lett. 2010, 51, 4267–4271; (c) Kim, J. M.; Kim, S. H.; Lee, H. S.; Kim,
J. N. Tetrahedron Lett. 2009, 50, 1734–1737; (d) Kim, K. H.; Kim, E. S.; Kim, J. N.
Tetrahedron Lett. 2009, 50, 5322–5325; (e) Kim, J. M.; Kim, K. H.; Kim, T. H.;
Kim, J. N. Tetrahedron Lett. 2008, 49, 3248–3251; (f) Lee, H. S.; Kim, S. H.;
Gowrisankar, S.; Kim, J. N. Tetrahedron 2008, 64, 7183–7190; (g) Gowrisankar,
S.; Kim, K. H.; Kim, S. H.; Kim, J. N. Tetrahedron Lett. 2008, 49, 6241–6244; (h)
Gowrisankar, S.; Lee, H. S.; Kim, J. M.; Kim, J. N. Tetrahedron Lett. 2008, 49,
1670–1673.
Compound 4d: 65% yield; white solid, mp 191–193 °C; IR (KBr) 2220, 1709,
1465, 1246 cmꢀ1 1H NMR (CDCl3, 300 MHz) d 3.63 (s, 3H), 6.18 (s, 2H), 7.26 (s,
;
1H), 7.35–7.51 (m, 5H), 7.61 (s, 1H), 8.41 (s, 1H); 13C NMR (CDCl3, 75 MHz) d
52.28, 102.19, 102.29, 104.91, 110.76, 116.80, 127.52, 128.15, 128.47, 128.69,
128.77, 132.46, 133.74, 138.02, 143.68, 149.41, 152.05, 167.12; ESIMS m/z 332
(M++1). Anal. Calcd for C20H13NO4: C, 72.50; H, 3.95; N, 4.23. Found: C, 72.86;
H, 4.09; N, 4.18.
Compound 4f: 57% yield; white solid, mp 208–210 °C; IR (KBr) 2228,
1492 cmꢀ1 1H NMR (CDCl3, 300 MHz) d 7.56–7.65 (m, 5H), 7.77 (t, J = 8.1 Hz,
;
1H), 7.91 (t, J = 8.4 Hz, 1H), 8.04 (d, J = 8.4 Hz, 1H), 8.38 (d, J = 8.4 Hz, 1H), 8.54
(s, 1H); 13C NMR (CDCl3, 75 MHz) d 111.08, 111.63, 115.67, 116.96, 125.94,
128.92, 128.99, 129.04, 129.52, 130.14, 130.96, 132.10, 133.91, 134.87, 139.30,
146.10; ESIMS m/z 255 (M++1). Anal. Calcd for C18H10N2: C, 85.02; H, 3.96; N,
11.02. Found: C, 84.87; H, 4.13; N, 10.89.
Compound 6c: 5% yield; colorless oil; IR (film) 1732, 1719, 1235 cmꢀ1 1H NMR
;
(CDCl3, 300 MHz) d 2.27 (s, 3H), 3.45 (d, J = 17.4 Hz, 1H), 3.71 (s, 3H), 3.99 (d,
J = 17.4 Hz, 1H), 4.59 (s, 1H), 6.95 (s, 1H), 7.03 (d, J = 7.8 Hz, 1H), 7.40–7.46 (m,
2H), 7.61–7.72 (m, 3H); 13C NMR (CDCl3, 75 MHz) d 21.23, 42.56, 52.93, 59.63,
62.71, 124.40, 124.42, 125.40, 125.48, 128.30, 129.15, 134.84, 135.09, 135.45,
138.26, 140.63, 155.24, 173.84, 203.38; ESIMS m/z 293 (M++1). Anal. Calcd for
C
19H16O3: C, 78.06; H, 5.52. Found: C, 78.19; H, 5.76.
Compound 7a: Major isomer (36% yield): pale yellow oil; IR (film) 2239,
1454 cmꢀ1 1H NMR (CDCl3, 300 MHz) d 4.19 (d, J = 7.5 Hz, 1H), 4.40 (dt, J = 7.5
4. For the examples on the control of the carbopalladation regiochemistry, see: (a)
Bombrun, A.; Sageot, O. Tetrahedron Lett. 1997, 38, 1057–1060; (b) Kim, G.;
Kim, J. H.; Kim, W. j.; Kim, Y. A. Tetrahedron Lett. 2003, 44, 8207–8209; (c)
Roesch, K. R.; Larock, R. C. J. Org. Chem. 2001, 66, 412–420; (d) Dankwardt, J. W.;
Flippin, L. A. J. Org. Chem. 1995, 60, 2312–2313; (e) Rigby, J. H.; Hughes, R. C.;
Heeg, M. J. J. Am. Chem. Soc. 1995, 117, 7834–7835; (f) Ferraccioli, R.; Carenzi,
D.; Catellani, M. Synlett 2002, 1860–1864.
;
and 2.4 Hz, 1H), 4.85 (d, J = 2.4 Hz, 1H), 5.66 (d, J = 2.4 Hz, 1H), 7.28–7.60 (m,
9H); 13C NMR (CDCl3, 75 MHz) d 42.65, 55.98, 107.36, 120.10, 121.32, 124.77,
127.81, 128.37, 128.97, 129.27, 129.86, 137.38, 139.71, 140.09, 149.65; ESIMS
m/z 232 (M++1). Minor isomer (10% yield): pale yellow oil; IR (film) 2242,
1454 cmꢀ1 1H NMR (CDCl3, 300 MHz) d 4.47 (dt, J = 9.0 and 1.8 Hz, 1H), 4.62 (d,
;
5. For the synthesis of poly-substituted naphthalenes, see: (a) Asao, N.; Takahashi,
K.; Lee, S.; Kasahara, T.; Yamamoto, Y. J. Am. Chem. Soc. 2002, 124, 12650–
12651; (b) Asao, N.; Nogami, T.; Lee, S.; Yamamoto, Y. J. Am. Chem. Soc. 2003,
125, 10921–10925; (c) Barluenga, J.; Vazquez-Villa, H.; Ballesteros, A.;
Gonzalez, J. M. Org. Lett. 2003, 5, 4121–4123; (d) Barluenga, J.; Vazquez-Villa,
H.; Merino, I.; Ballesteros, A.; Gonzalez, J. M. Chem. Eur. J. 2006, 12, 5790–5805;
(e) Shi, M.; Lu, J.-M. J. Org. Chem. 2006, 71, 1920–1923; (f) Balamurugan, R.;
Gudla, V. Org. Lett. 2009, 11, 3116–3119; (g) Kim, S. H.; Kim, Y. M.; Lee, H. S.;
Kim, J. N. Tetrahedron Lett. 2010, 51, 1592–1595; (h) Gowrisankar, S.; Lee, H. S.;
Kim, J. N. Tetrahedron Lett. 2007, 48, 3105–3108. Further references were cited
in Ref. 3b.
J = 9.0 Hz, 1H), 5.04 (d, J = 1.8 Hz, 1H), 5.71 (d, J = 1.8 Hz, 1H), 7.21–7.63 (m,
9H); ESIMS m/z 232 (M++1).
During the evaluation process one of the reviewers suggested that we carry out
the reaction of 3a under the PEG-catalyzed conditions. The reaction of 3a in
DMF (90 °C, 30 min) under the influence of Pd(OAc)2/PEG-3400/K2CO3 showed
a similar result in entry 2 in Table 1 (65% of 4a and 5% of 6a).
9. For the similar oxidative decyanation of secondary nitriles to ketones, see: (a)
Kulp, S. S.; McGee, M. J. J. Org. Chem. 1983, 48, 4097–4098; (b) Freerksen, R. W.;
Selikson, S. J.; Wroble, R. R. J. Org. Chem. 1983, 48, 4087–4096.
10. For the similar examples on d-carbon elimination, see: (a) Kim, H. S.; Lee, H. S.;
Kim, S. H.; Kim, J. N. Tetrahedron Lett. 2009, 50, 3154–3157; (b) Kim, H. S.;
Gowrisankar, S.; Kim, E. S.; Kim, J. N. Tetrahedron Lett. 2008, 49, 6569–6572; (c)
Kim, H. S.; Gowrisankar, S.; Kim, S. H.; Kim, J. N. Tetrahedron Lett. 2008, 49,
3858–3861.
6. For the synthesis of cinnamyl bromides in a stereoselective manner from
Baylis–Hillman adducts, see: (a) Gowrisankar, S.; Kim, S. H.; Kim, J. N. Bull.
Korean Chem. Soc. 2009, 30, 726–728. and further references cited therein; (b)

S. H. Kim et al. / Tetrahedron Letters 51 (2010) 6305–6309
6309
11. In order to get some insights, we ran the reactions with major-3a and minor-3a
separately. The products distributions were somewhat different with each
other, although syn and anti derivatives showed the same reactivity in our
previous synthesis of naphthalenes from OTBS derivatives (Eq. 2 in Scheme
1).3a Thus confirmation of the stereochemistry of starting materials 3 and the
studies on the difference of reactivity are currently underway.