Polymer-mediated reactions. A Nazarov-like cyclization

Article abstract of DOI:10.1055/s-0030-1261194

The polymer PEDOT⁺ mediates a Nazarov-like cyclization of dienones, in an heterogeneous system and in hydrocarbon solvents. The polymer-mediated reactions show clear differences in product formation when compared to the same reaction with tosic acid, or when compared to reports in the literature. Comparable or improved yields are observed, as well as the ability to give a -Nazarov product in cases where treatment with acid fails to give cyclization, or leads to an undesirable rearrangement. In addition, the ability to recycle the polymer makes this a potentially useful protocol for an important organic chemical reaction. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0030-1261194

LETTER
2195
Polymer-Mediated Reactions. A Nazarov-Like Cyclization
a
a
b
b
a,b
P
C
olymer-Mediate
h
dReactions.
r
ANaza
i
rov-Lik
s
e
Cycliza
t
tion opher Pavlik, Martha D. Morton, Michael A. Invernale, Ian D. Berghorn, Gregory A. Sotzing,
a
Michael B. Smith*
a
Department of Chemistry, University of Connecticut, 55 N. Eagleville Rd., Storrs, CT 06269-3060, USA
Fax +1(860)4862981; E-mail: michael.smith@uconn.edu
University of Connecticut, Polymer Program, 97 N. Eagleville Rd. U-3136, Storrs, CT 06269-3136, USA
b
Received 16 May 2011
by chemical oxidation of EDOT with ferric chloride to
+
Abstract: The polymer PEDOT mediates a Nazarov-like cycliza-
tion of dienones, in an heterogeneous system and in hydrocarbon
solvents. The polymer-mediated reactions show clear differences in
product formation when compared to the same reaction with tosic
give a polymer with a repeating hexameric dication unit 1
–
–
(
a bipolaron) with Cl and FeCl4 counterions. Electro-
chemically induced polymerization of EDOT in an aceto-
+
acid, or when compared to reports in the literature. Comparable or nitrile solution containing lithium triflate gives PEDOT
improved yields are observed, as well as the ability to give a
Nazarov product in cases where treatment with acid fails to give cy-
with a repeating trimeric unit (2). The repeating units
shown in Scheme 1 for 1 and 2 were used to determine the
clization, or leads to an undesirable rearrangement. In addition, the
stoichiometry in reactions with the polymer. There is a po-
ability to recycle the polymer makes this a potentially useful proto-
tential problem with respect to the actual molecular
col for an important organic chemical reaction.
weight of the polymer because 1 and 2 are known to be
Key words: dienones, Nazarov cyclization, PEDOT, polymer,
oligomeric. In previous work, we have shown that 1 or 2
cyclopentenones
14
mediate ether-forming reactions, Friedel–Crafts alkyla-
1
5
tion reactions of alcohols, and a cyclodehydration reac-
tion of alditols and keto-hexoses.1 All of the observed
reactions are consistent with an acid-catalyzed process, al-
though no acid is added to the reaction. This observation
prompted a study of classical acid-catalyzed reactions us-
ing 1 or 2 rather than a classical acid. In this work we
show that a Nazarov cyclization occurs when a dienone is
heated in the presence of PEDOT.
6,17
The Nazarov cyclization is an important reaction in organ-
1
ic chemistry, and it has been the object of considerable
2
interest in recent years. This acid-catalyzed cyclization of
divinyl ketones (dienones) produces cyclopentenone de-
rivatives. The mechanism is thought to involve formation
3
of a complex that generates an oxocarbenium ion, with
subsequent cyclization via reaction with the pendant alk-
ene unit to give an oxo-allyl cation. Elimination of a pro-
ton to give a complex and subsequent protonation gives
We chose a series of dienones (3, 8, 11, 14, 16, 19, 22, 24,
2
6) for this study that have representative structural fea-
4
5
tures. The chosen dienones allowed us to examine key
features of the Nazarov cyclization, including reactivity,
regioselectivity, and the diastereoselectivity for those re-
actions for which it is an issue.
the product. Both Lewis acids and Brønsted–Lowry
6
acids may be used, and it is known that the temperature,
the nature of the acid, and structure of the dienone have
a significant impact on the reaction. The Nazarov cycliza-
7
8
tion sometimes exhibits problems with respect to reactiv- The first set of dienones possessed phenyl substituents
4
ity and selectivity. The Nazarov cyclization is, for the (derivatives 3, 8, and 11), and the results are shown in
5
,6,9,10
most part, an acid-mediated reaction.
Scheme 1. Early work by Vorländer and Schroedter
showed that reaction of dibenzylideneacetone (3) with
concentrated sulfuric acid gave a complex that could be
converted to 5.18 This intermediate ‘complex’ has been
trapped with acetic anhydride and then o-toluidine, which
indicated formation of structure 4. Treatment with aque-
ous sodium carbonate, and then aqueous acid gave 5 in
We are currently studying the potential of polymers to
mediate synthetically useful organic reactions. Poly(3,4-
ethylenedioxythiophene), known as PEDOT (see 1 and 2
+
in Scheme 1), is the fundamental structural unit of an im-
19
1
1
portant commercial polymer PEDOT-PSS. Oxidative
polymerization of the monomer 3,4-ethylenedioxy-
thiophene (EDOT) in aqueous media, and in the presence
of the polyanion PSS [poly(styrenesulfonate)], gives
poly(3,4-ethylenedoxythiophene)poly(styrenesulfonate),
otherwise known as PEDOT-PSS. PEDOT-PSS has been
used as an antistatic for photographic films, and it is a
key component of many organic-based electronics.
PEDOT , without the acidic PSS unit, is readily prepared
9
2% yield as the osazone derivative. It has been reported
that heating 3 in supercritical water, in the presence of su-
percritical carbon dioxide, gave rearranged product 6 in
20
3
8% yield, but not 7. A second example is dieneone 8,
1
2
which was reported to give the normal Nazarov product 9
2
1
1
3
as a 5:1 trans/cis mixture when treated with HCl. A re-
+
ductive Nazarov cyclization reaction of 8 or 11 with BF3
and two equivalents of Et SiH, followed by treatment
3
with water or 1 M HCl, gave cyclopentenones 10 or 13 in
9
8% and 63% yield, respectively, as a mixture of diaste-
SYNLETT 2011, No. 15, pp 2195–2199
Advanced online publication: 24.08.2011
DOI: 10.1055/s-0030-1261194; Art ID: S04411ST
x
x
.x
x
.2
0
1
1
reomers (8.1:1 a-Me/b-Me and 5.6:1 a-Me/b-Me, respec-
tively).22
©
Georg Thieme Verlag Stuttgart · New York

2
196
C. Pavlik et al.
LETTER
O
O
O
O
O
O
FeCl4–
O
O
OSO2CF3
S
+
S
+
S
S
S
S
S
+S
S
Cl–
n
n
O
O
O
O
O
O
O
O
O
O
O
1
2
O
O
PEDOT+
Ph
TsOH
with 1 71%
with 2 63%
toluene, reflux
toluene
reflux
Ph
Ph
Ph
Ph
Ph
Ph
6
3
7
45%
O
O
PEDOT+
toluene, reflux
with TsOH 43% 3:1 trans/cis
with
with
1
2
39% 5:1 trans/cis
43% 5:1 trans/cis
Ph
Ph
8
Ph
9
Ph
O
O
PEDOT+
toluene, reflux
with TsOH mixture of products
with 1 72%
11
Ph 12
OAc
O
O
O
+
–
X OSO
HO
Ph
Ph
Ph 13
Ph
Ph
Ph
Ph
10
4
5
X = o-MeC6H4NH3+
Scheme 1 PEDOT 1 and 2; reactions of phenyl-substituted dienones with PEDOT+
It is known that the nature of the acid has a significant in- products with no clear indication that 15 was present.
fluence on the reactivity of the dienone for a Nazarov cy- When 14 was heated with 1 in toluene we isolated 15 in
8
,7
clization. We wanted a Bronsted–Lowry acid mediated 40% yield. In the presence of 2, 15 was isolated in 43%
reaction to serve as a benchmark. We therefore used the yield. The cyclization of dienone 16 posed a different
tosic acid induced reaction in this study for comparison challenge because the major product reported in the liter-
with the polymer-mediated reactions. In many cases we ature was rearranged cyclopentenone 17 after treatment
found clear differences.
with HBr and acetic acid.23 When the cyclization was
done using only HBr, Nazarov product 18 was formed in
We found that 3 reacted with tosic acid to give 6 in 45%
yield (Scheme 1). This result contrasts sharply with the re-
action of 3 in the presence of 1 in toluene at reflux, which
gave a 71% yield of the normal Nazarov product 7. Simi-
larly, heating 3 in toluene at reflux in the presence of 2
gave a 63% yield of 7. When 8 was heated at reflux in tol-
uene with tosic acid, 9 was isolated in 43% yield, as a 3:1
trans/cis mixture of diastereomers. The reaction of 8 in
the presence of 1 gave 9 in 39% yield as a 5:1 trans/cis
1
5% yield, but the major product was 17, in 55% yield.23
When we reacted 16 with tosic acid, we obtained 17 in
1
2% yield, and other products were clearly present as part
of a complex mixture. We did not observe 18. When 16
was heated with 1 in toluene at reflux, however, we isolat-
ed a 31% yield of 18. While this yield is rather low, it con-
stitutes a distinct improvement when compared to the
reaction with tosic acid or with mineral acids.
mixture, and reaction in the presence of 2 gave 9 in 43% For the last example in this series we found no report of
yield as a 5:1 trans/cis mixture. Finally, we found that the the direct conversion of dienone 19 to 21, although a suit-
reaction of 11 with tosic acid gave several products in a ably substituted pyrone was converted to 21 upon treat-
rather complex mixture. This stands in sharp contrast to ment with tosic acid, presumably via formation of 19 in
24
heating 11 in the presence of 1, which gave a 72% yield of situ. There is also the report by West and Geise of a re-
2. In this case we did not examine the reaction with 2. ductive Nazarov cyclization that converted 19 to 20 as a
.2:2.8:1 mixture of three diastereomers (84% yield), us-
ing the BF -silane procedure noted above for the prepara-
1
1
We next examined dienones that possess alkyl rather than
phenyl substituents, specifically 14, 16, and 19. We found
no report of a Nazarov reaction that directly converted 14
to 15 by treatment with an acid. In our hands (Scheme 2),
treatment of 14 with tosic acid gave a complex mixture of
3
22
tion of 10 and 13. When we heated 19 with tosic acid, we
obtained a 35% yield of the Nazarov product 21 as a 5:1
trans/cis mixture, but there were several byproducts. Re-
Synlett 2011, No. 15, 2195–2199 © Thieme Stuttgart · New York

LETTER
Polymer-Mediated Reactions. A Nazarov-Like Cyclization
2197
action of 19 in the presence of 1 in toluene at reflux, how-
ever, gave a 69% isolated yield of 21 as a 10:1 trans/cis
mixture. Similar reaction of 19 in the presence of 2 gave
O
O
PEDOT+
toluene, reflux
2
1 in 70% yield, as a 9:1 trans/cis mixture.
Ph
SiMe3
Ph
2
2
2
3
with TsOH intractable mixture
O
O
with
with
1
2
41%
37%
PEDOT+
O
O
toluene, reflux
PEDOT+
1
5
toluene, reflux
14
with TsOH complex mixture
SiMe3
with
2
45%
24
2
5
O
with TsOH intractable mixture
O
PEDOT+
with
1
59%
O
O
O
toluene, reflux
PEDOT+
TsOH
1
8
toluene, reflux
16
toluene
reflux
SiMe3
27
with 1 82% 5:1 trans/cis
with TsOH 12% of 17
with 31%
1
28
7
5%
26
O
O
Scheme 3 Reactions of trimethylsilyl-dienones with PEDOT+
PEDOT+
toluene, reflux
toluene, however, we obtained 25 in 59% isolated yield.
Once again, this yield is comparable to that reported by
Denmark and co-workers. When 26 was treated with tosic
acid, we obtained a 75% yield of the more substituted
product 28. When 26 was heated with 1, we obtained an
19
with TsOH 35%
with
with
5:1 trans/cis
69% 10:1 trans/cis
70% 9:1 trans/cis
1
2
8
2% yield of 27 as a 5:1 trans/cis mixture. The predomi-
O
O
nance of the trans isomer is presumably the result of
equilibration due to a longer heating time when compared
to the results reported by Denmark.
20
+
Our work clearly shows that PEDOT mediates the con-
17
version of divinyl ketones to cyclopentenones, but the
question of how the polymer mediates this reaction is un-
resolved. There is uncertainty with respect to the stoichi-
Scheme 2 Reactions of alkyl-substituted dienones with PEDOT+
The last set of dienones to be examined (Scheme 3) incor- ometry due to the oligomeric nature of the polymer, and
porated a trimethylsilyl group at the b-position relative to there are difficulties in direct analysis of the polymer. The
the carbonyl (see 22, 24, and 26). Denmark and co-work- conducting nature of the polymer makes direct analysis of
ers discovered that the presence of a trimethylsilyl group the polymer by NMR difficult or impossible by any meth-
on the vinyl moiety led to facile Nazarov cyclization upon od except magic-angle solid-state NMR, for example.
treatment with Lewis acids such as ferric chloride, and the These facts hinder standard mechanistic approaches used
product was the less substituted cyclopentenone.7 In- in organic chemistry. We speculate that the mechanism
deed, Denmark and Jones reported the conversion of silyl involves coordination of the dienone to the polymer and
derivative 22 to 23 in 27% yield, 24 to 25 in 54% yield, involvement of water, which is known to be present in the
,25
7
a
27
and 26 to 27 in 95% yield. Cyclopentenone 27 was iso-
polymer. This assumption is consistent with the clear
7
lated as a 59:41 mixture of cis/trans isomers. It is noted
that both 23 and 25 have been prepared via a Nazarov cy-
clization in which the requisite dienone was generated in
situ by reaction of a conjugated acid chloride and a vinyl- because our previous work with alcohols1
differences in reactivty when compared to a tosic acid cat-
alyzed process. We believe the tosic acid reactions are
reasonable models based on our working mechanism, and
4–17
does not fit
2
6
silane.
a Lewis acid model.
Our results are shown in Scheme 3. We found that phenyl
derivative 22 gave an intractable mixture when heated
with tosic acid, but reaction in the presence of 1 gave a or 2 are insoluble, but water is present from preparation of
All reactions were carried out in a two-phase system in
hydrocarbon solvents such as heptane or toluene, where 1
4
1% isolated yield of 23. Similarly, the reaction of 22 in the polymer, and it cannot be removed by normal drying
the presence of 2 gave a 37% yield of 23. These yields are techniques.2
7b,28
comparable to those reported when the reaction is mediat-
Both water and the dienone are associated with the poly-
mer, and we speculate there may be an association with
the polymer. Complexation or association leads to local-
ized hydronium ion formation and stabilization of the req-
7
a
ed by ferric chloride. When 24 was treated with tosic ac-
id, we obtained a complex mixture, and there was no
indication of formation of 25 or 15, the more substituted
Nazarov product. When 24 was heated with 1 in refluxing
Synlett 2011, No. 15, 2195–2199 © Thieme Stuttgart · New York

2
198
C. Pavlik et al.
LETTER
uisite enol. It is not necessary to generate a free 13C NMR (75.5 MHz, CD
carbocation, as it is possible that as positive charge begins
OD): d = 209.6, 176.6, 131.8, 47.6, 45.4,
3
2
8.3, 27.6, 21.8, 21.4, 13.8, 10.4.
to develop on the distal carbon, participation of the prox- MS (EI): m/z = 194.1, 151, 140, 111, 43, 41.
imal C=C unit leads directly to cyclization. Presumably,
water removes the proton from the cyclized intermediate 194.1731.
in an E1-type reaction to give an enol, and tautomerization
gives the final product. This mechanism does not require
reduction of the polymer, which is consistent with our ob-
servations. Water is essential for the observed reactivity
due to formation of a localized acid. This working hypoth-
esis requires experimental verification, of course, but is
consistent with the data we have collected so far.
+
+
HRMS (ESI ): m/z [M + H ] calcd for C H O: 194.1704; found:
1
3
22
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett. Included are
experimental details for all Nazarov products.
References
(
1) (a) Nazarov, I. N.; Torgov, I. B.; Terekhova, L. N. Izv. Akad.
Nauk. SSSR, Otd. Khim. Nauk 1941, 211. (b) Braude, E. A.;
Forbes, W. F. J. Chem. Soc. 1953, 2208.
In conclusion, we have shown that dienones are converted
to Nazarov cyclization products in the presence of the
polymer PEDOT , in an heterogeneous system and in hy-
+
(
2) (a) Smith, M. B.; March, J. March’s Advanced Organic
drocarbon solvents. We have shown examples in which a
normal Nazarov cyclization product is formed upon expo-
sure to the polymer, where poor reactivity or rearrange-
ment is reported in the literature. We believe that this new
protocol offers some advantages when compared to a typ-
ical Nazarov cyclization in terms of the experimental
technique, in that the dienone is simply heated at reflux in
the hydrocarbon solvent with the polymer, cooled, and fil-
tered to give the product. Improved yields in some cases,
and the ability to give a Nazarov cyclization product in
cases where treatment with acid fails or leads to an unde-
sirable rearrangement, make this protocol a useful addi-
tion to Nazarov cyclization reactions reported in the
literature.
Chemistry, 6th ed.; John Wiley and Sons: Hoboken, 2007,
1095. (b) The Merck Index, 14th ed.; Merck: Whitehouse
Station NJ, 2006, ONR-64. (c) Mundy, B. P.; Ellerd, M. G.;
Favaloro, F. G. Jr. Name Reactions and Reagents in Organic
Synthesis, 2nd ed.; Wiley-Interscience: Hoboken, 2005,
448–449. For recent reviews, see: (d) Denmark, S. E. In
Comprehensive Organic Synthesis, Vol. 5; Paquette, L. A.,
Ed.; Pergamon Press: Oxford, 1991, 751–784.
(
1
e) Habermas, K. L.; Denmark, S. E. Org. React. 1994, 45,
. (f) Pellissier, H. Tetrahedron 2005, 61, 6479. (g) Tius,
M. Eur. J. Org. Chem. 2005, 2193. (h) Frontier, A. J.;
Collison, C. Tetrahedron 2005, 61, 7577.
(
3) Hayashi, S.; Motoyoshiya, J.; Yazaki, T. J. Org. Chem.
1
989, 56, 735.
4) (a) Frontier, A. J.; Collison, C. Tetrahedron 2005, 61, 7577.
b) Habermas, K. L.; Denmark, S. E.; Jones, T. K. Org.
(
(
React. 1994, 45, 1. (c) Santelli-Rouvier, C.; Santelli, M.
Synthesis 1983, 429. For a reagent-free Nazarov cyclization
that proceeds without added Lewis acids, see: (d) Douelle,
F.; Tal, L.; Greaney, M. F. Chem. Commun. 2005, 660.
5) (a) Akiyama, T. Chem. Rev. 2007, 107, 5744. (b) Basak, A.
K.; Shimada, N.; Bow, W. F.; Vicic, D. A.; Tius, M. A.
J. Am. Chem. Soc. 2010, 132, 8266. (c) Bolaño, T.;
Typical Experimental Procedure
3
,4-Diphenylcyclopent-2-enone (12)
(
A 100 mL round-bottomed flask was charged with toluene (60 mL)
and a magnetic stirbar. (1E,4E)-1,5-Diphenylpenta-1,4-dien-3-one
2
9
(
3, 0.234 g, 1 mmol) was added, followed by 1 (0.57 g, 1 mmol).
Castarlanas, R.; Esteruelas, M. A.; Oñate, E. J. Am. Chem.
Soc. 2009, 131, 2064. (d) Zhang, J.; Vaidya, T.; Brennessel,
W. W.; Frontier, A. J.; Eisenberg, R. Organomet. 2010, 29,
A reflux condenser fitted with a septum was attached and a nitrogen
inlet inserted in the septum. The system was heated at reflux over-
night. After cooling, the polymer was removed by filtration and
3341. (e) Vaidya, T.; Atesin, A. C.; Herrick, I. R.; Frontier,
washed with Et O (10 mL). The filtrate was concentrated in vacuo
2
A. J.; Eisenberg, R. Angew. Chem. Int. Ed. 2010, 49, 3363.
(f) Janka M., He W., Haedicke I. E., Fronczek F. R., Frontier
A. J., Flaschenriem C., Eisenberg R.; J. Am. Chem. Soc.;
to give a brown oil. Purification by flash chromatography (EtOAc–
hexane) gave 3,4-diphenylcyclopent-2-enone (7) as a clear oil
3
0
(
0.166 g, 0.071 mmol, 71%).
2
006, 128: 5312 . For a Nazarov cyclization catalyzed by a
1
H NMR (300 MHz, CD OD): d = 7.55–7.49 (m, 2 H), 7.30–7.12
3
supramolecular host, see: (g) Hastings, C. J.; Pluth, M. D.;
(
m, 8 H), 6.74 (d, J = 1.6 Hz. 1 H), 4.61 (ddd, J = 1.7, 2.4, 7.5 Hz,
Bergman, R. G.; Raymond, K. N. J. Am. Chem. Soc. 2010,
1
H), 3.11 (dd, J = 7.3, 18.8 Hz, 1 H), 2.45 (dd, J = 2.1, 18.5 Hz, 1
132, 6938.
H).
(
6) (a) Dalpozzo, R.; Bartoli, G.; Sambri, L.; Melchiorre, P.
Chem. Rev. 2010, 110, 3501. (b) Rueping, M.; Ieawsuwan,
W.; Antonchick, A. P.; Nachtsheim, B. J. Angew. Chem. Int.
Ed. 2007, 46, 2097.
1
3
C NMR (75.5 MHz, CD OD): d = 206.0, 154.0, 141.0, 140.0,
3
1
31.0, 129.4, 128.7, 128.0, 127.8, 127.3, 126.4, 49.7, 39.3.
MS (EI): m/z = 234, 205, 191, 179, 157, 128, 102, 91, 77, 63.
(7) (a) Denmark, S. E.; Jones, T. K. J. Am. Chem. Soc. 1982,
1
04, 2642. (b) Denmark, S. E.; Habermas, K. L.; Hiite, G. A.
3
,4-Diisopropyl-2,5-dimethylcyclopent-2-enone (21)
Helv. Chim. Acta 1988, 71, 168. (c) Basak, A. K.; Shimada,
N.; Bow, W. F.; Vicic, D. A.; Tius, M. A. J. Am. Chem. Soc.
The reaction of (3E,6E)-2,4,6,8-tetramethylnona-3,6-dien-5-one
2
2
(
19, 0.194 g, 1 mmol) and 1 (0.57 g, 1 mmol) under the standard
condtions gave 3,4-diisopropyl-2,5-dimethylcyclopent-2-enone
21)24 as a waxy solid (0.133 g, 0.69 mmol, 69%, 10:1 trans/cis by
2
010, 132, 8266. (d) Malona, J. M.; Cariou, K.; Frontier, A.
J. J. Am. Chem. Soc. 2009, 131, 7560. (e) Spencer, W. T.;
Levin, M. D.; Frontier, A. J. Org. Lett. 2011, 13, 414.
(
NMR analysis). Spectral data are reported for the trans compound.
(
f) Tius, M. A. Acc Chem. Res. 2003, 36, 284.
1
H NMR (300 MHz, CD OD): d = 2.87–2.61 (m, 2 H), 2.54 (m, 1
(8) (a) He, W.; Herrick, I. R.; Atesin, T. A.; Caruana, P. A.;
Lellenberger, C. A.; Frontier, A. J. J. Am. Chem. Soc. 2008,
130, 1003. (b) Liang, G.; Gradl, S. N.; Trauner, D. Org. Lett.
3
H), 2.23 (q, J = 7.3 Hz, 1 H), 1.93 (m, 3 H), 1.31 (d, J = 3.5 Hz, 3
H), 1.15 (d, J = 4.3 Hz, 6 H), 0.97 (d, J = 4.5, 6 H).
Synlett 2011, No. 15, 2195–2199 © Thieme Stuttgart · New York

LETTER
Polymer-Mediated Reactions. A Nazarov-Like Cyclization
2199
2
003, 5, 4931. (c) Huang, J.; Frontier, A. J. J. Am. Chem.
(17) Onorato, A.; Pavlik, C.; Invernale, M. A.; Berghorn, I. D.;
Sotzing, G. A.; Smith, M. B. Carbohydr. Res. 2011, 346, in
press; DOI: 10.1016/j.carres.2011.04.017.
(18) (a) Allen, C. F. H.; VanAllan, J. A.; Tinker, J. F. J. Org.
Chem. 1955, 20, 1387. (b) Vorländer, D.; Schroedter, M.
Ber. Dtsch. Chem. Ges. 1903, 36, 1490.
Soc. 2007, 129, 8060. (d) Malona, J. A.; Colbourne, J. M.;
Frontier, A. J. Org. Lett. 2006, 8, 5661. (e) Polo, V.;
Andrés, J. J. Chem. Theory Comput. 2007, 3, 816.
9) Shindo, M.; Yaji, K.; Kita, T.; Shishido, K. Synlett 2007,
(
1
096.
10) (a) Suzuki, T.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc.
997, 119, 6774. For an enamine-iminium ion Nazarov
(
(19) Shoppee, C. W.; Cooke, B. J. A. J. Chem. Soc., Perkin
Trans. 1 1972, 2271.
1
cyclization, see: (b) Bow, W. F.; Basak, A. K.; Jolit, A.;
Vicic, D. A.; Tius, M. A. Org. Lett. 2010, 12, 440. For
enzyme-like catalysts, see: (c) Hastings, C. J.; Pluth, M. D.;
Bergman, R. G.; Raymond, K. N. J. Am. Chem. Soc. 2010,
(20) Leikoski, T.; Kaunisto, J.; Alkio, M.; Aaltonen, O.; Yli-
Kauhaluoma, J. Org. Process Res. Dev. 2005, 9, 629.
(21) Duelle, F.; Tal, L.; Greaney, M. F. Chem. Commun. 2005,
660.
(22) Giese, S.; West, F. G. Tetrahedron 2000, 56, 10221.
(23) (a) Hirano, S.; Takagi, S.; Hiyama, T.; Nozaki, H. Bull.
Chem. Soc. Jpn. 1980, 53, 169. (b) Hirano, S.; Hiyama, T.;
Nozaki, H. Tetrahedron Lett. 1974, 1429.
(24) Quindt, V.; Saurenz, D.; Schmitt, O.; Schär, M.; Dezember,
T.; Wolmershäuser, G.; Sitzmann, H. J. Organomet. Chem.
1999, 579, 376.
(25) Jones, T. K.; Denmark, S. E. Helv. Chim. Acta 1983, 66,
2377.
(26) Kjeldsen, G.; Knudsen, J. S.; Ravn-Petersen, L. S.; Torssell,
K. B. G. Tetrahedron 1983, 39, 2237.
(27) (a) Huang, J.; Miller, P. F.; Wilson, J. S.; de Mello, A. J.;
de Mello, J. C.; Bradley, D. D. C. Adv. Funct. Mater. 2005,
15, 290. (b) Okuzakia, H.; Suzukia, H.; Ito, T. Synth. Met.
2009, 159, 2233.
1
32, 6938.
11) (a) Kirchmer, S.; Reuter, K. J. Mater. Chem. 2005, 15,
077. (b) Greczynski, G.; Kugler, T.; Keil, M.; Osikowicz,
(
(
2
W.; Fahlman, M.; Salaneck, W. J. Electron Spectrosc. Relat.
Phenom. 2001, 121, 1. (c) Groenendaal, L.; Jonas, F.;
Freitag, D.; Pielartzik, H.; Reynolds, J. Adv. Mater. 2000,
1
2, 481.
12) (a) Bayer AG, EP 440 957, 1991 (b) Agfa Gevaert, EP 564
11, 1993 (c) Jonas, F.; Krafft, W.; Muys, B. Macromol.
Symp. 1995, 100, 169. (d) Bayer AG, EP 553 671, 1993
e) Bayer AG, EP 686 662, 1995 (f) Bayer AG, US 5 792
58, 1996
9
(
5
(
13) Groenendaal, L.; Jonas, F.; Freitag, D.; Pielartzik, H.;
Reynolds, J. R. Adv. Mater. 2000, 12, 481.
(
14) D’Angelo, J. G.; Sawyer, R.; Kumar, A.; Onorato, A.;
McCluskey, C.; Delude, C.; Vollenweider, L.; Reyes, N.;
French, R.; Warner, S.; Chou, J.; Stenzel, J.; Sotzing, G. A.;
Smith, M. B. J. Polym. Sci., Part A: Polym. Chem. 2007, 45,
(28) Bendikov, T. A.; Harmon, T. C. Anal. Chim. Acta 2005, 551,
30.
(29) (a) Larock, R. C.; Hershberger, S. S. J. Org. Chem. 1980, 45,
3840. (b) Khalaf, A. A.; Aly, K. I.; Mohammed, I. A.
J. Macromol. Sci., Part A: Pure Appl. Chem. 2002, A39, 333.
(30) (a) Corey, E. J.; Uda, H. J. Am. Chem. Soc. 1963, 85, 1788.
(b) Polo, E.; Barbieri, A.; Traverso, O. Eur. J. Inorg. Chem.
2003, 324.
2328.
(
15) D’Angelo, J. G.; Kumar, A.; Onorato, A.; Delude, C. J.;
Sotzing, G. A.; Smith, M. B. Polymer 2007, 48, 4328.
16) Onorato, A.; Invernale, M. A.; Berghorn, I. D.; Pavlik, C.;
Sotzing, G. A.; Smith, M. B. Synth. Met. 2010, 160, 2284.
(
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