Polymer-mediated pinacol rearrangements

Article abstract of DOI:10.1055/s-0030-1261148

Both poly(3,4-ethylenedioxythiophene) and poly(pyrrole) mediate a pinacol rearrangement of 1,2-diols. The yields of ketone or aldehyde products are comparable to those observed for treatment with mineral acids or Lewis acids. The advantage of this protocol is a two-phase reaction medium in hydrocarbon solvents that allows facile recovery of the products by simple filtration of the polymer and removal of solvents. Both the polymer and the hydrocarbon solvent may be recovered and used in subsequent reactions. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0030-1261148

LETTER
2191
Polymer-Mediated Pinacol Rearrangements
P
olymer-Mediate
h
dPinacol Re
r
arrangem
i
e
nts stopher Pavlik, Martha D. Morton, Michael B. Smith*
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
Received 16 May 2011
egorized as acidic polymers. Poly(3,4-ethylenedioxy-
thiophene), known as PEDOT (see 1), is the fundamental
structural unit of an important commercial polymer
known as PEDOT-PSS,7 and polypyrrole (PPY, 2) is a
Abstract: Both poly(3,4-ethylenedioxythiophene) and poly(pyr-
role) mediate a pinacol rearrangement of 1,2-diols. The yields of ke-
tone or aldehyde products are comparable to those observed for
treatment with mineral acids or Lewis acids. The advantage of this
protocol is a two-phase reaction medium in hydrocarbon solvents readily available and important polymer.8,9 The hexamer-
that allows facile recovery of the products by simple filtration of the
polymer and removal of solvents. Both the polymer and the hydro-
ic unit 1 and the tetrameric unit 2 are taken as one equiv-
alent of the polymer and were used to determine the
carbon solvent may be recovered and used in subsequent reactions.
stoichiometry of polymer/diol. As shown in Scheme 1,
Key words: pinacol, diol, PEDOT, poly(pyrrole), rearrangement
oxidative polymerization of the monomer, 3,4-ethylene-
dioxythiophene (EDOT) with FeCl3 gives poly(3,4-ethyl-
enedioxythiophene) PEDOT+ (1).10,7c Similar oxidative
The pinacol rearrangement is a cationic rearrangement polymerization of pyrrole leads to poly(pyrrole) 2.8,9
reaction1 of 1,2-diols (vic-diols) that rearrange to give al-
In previous work, we reported that 1 mediated ether-form-
dehydes or ketones when they are treated with acids.2 It
ing reactions11 and also Friedel–Crafts alkylation reac-
has been shown that the acid used to initiate the reaction,
tions of alcohols.12 While these transformations are
and the concentration at which the reaction is done,3 are
consistent with an acid-catalyzed process, no acid was
important factors.2 When Lewis acids are used rather than
added to the reaction. Our previous work provides evi-
protonic acids, differences in the reaction pathway are of-
dence that the polymer is responsible for the various trans-
ten observed.4 When asymmetrical diols are treated with
formations and not endogenous acid associated with the
acid, mixtures of carbonyl compund products may be pro-
polymer. The reactivity we observed prompted a study of
duced, and which group preferentially migrates may de-
other acid-catalyzed reactions using the polymer rather
pend on the reaction conditions as well as on the nature of
than a classical acid. We found that glucitol was converted
the substrate.
into 1,6-anhydroglucitol in 82% yield, and that this cyclo-
We are currently studying the potential for using polymers dehydration reaction plays an important role in the con-
to mediate synthetically useful organic reactions, initiated ductivity of PEDOT-PSS films.13,14
by the polymer itself without the need to attach a reactive
This study has now been extended to include the pinacol
functional group. For the most part, polymers that are
rearrangement. Both PEDOT+ (1)11–14 and PPY (2)8 medi-
ate the conversion of 1,2-diols to aldehydes or ketones in
an experimentally simple procedure that gives good yields
known to induce reactions in other molecules are those
with acidic properties such as Nafion,5 and there are many
reactions catalyzed by ion-exchange resins.6 Our work
of the product. The diol substrates are grouped into three
uses two well-known industrial polymers that are not cat-
O
O
O
O
–
O
O
FeCl4
O
O
+S
FeCl3
S
S
CHCl3
S
S
S
n
+
Cl–
S
O
O
O
O
O
O
EDOT
1
FeCl3
CHCl3
H
N
H
N
N
N
N
m
H
H+
FeCl4
H
–
2
Scheme 1 Poly(3,4-ethylenedioxythiophene) (1) and poly(pyrrole) (2)
SYNLETT 2011, No. 15, pp 2191–2194
x
x
.x
x
.2
0
1
1
Advanced online publication: 31.08.2011
DOI: 10.1055/s-0030-1261148; Art ID: S04511ST
© Georg Thieme Verlag Stuttgart · New York

2192
C. Pavlik et al.
LETTER
categories: symmetrical acyclic diols, symmetrical cyclic We extended this reaction to 1,2-diphenyl-1,2-ethanediol
diols, and asymmetrical diols. The yields of products are (5). Conversion of 5 into 6 proceeded in 89% yield upon
comparable to those cited in the literature for acid-cata- heating to 104 °C with aqueous acetic acid.16 Heating with
lyzed rearrangements. The primary advantage of our 1 led to an 88% yield of aldehyde 6 in toluene, and an 86%
methodology is the use of a heterogeneous system, in hy- yield of 6 in hexane. Heating with 2 in toluene gave 6 in
drocarbon solvents with a trivial workup procedure, and 86% yield. For the next example in this series, the conver-
the ability to effect the transformation without complicat- sion of 7 into 8 is well known in the literature: 8 was
ing effects sometimes observed when strong acids are formed in 60% yield upon heating with sulfuric acid,17 in
used. Further, the polymer is not reduced during the reac- quantitative yield upon treatment with SbCl5 (followed by
tion, demonstrated by the lack of a color change associat- aqueous NaHCO3),18 and in 90% yield in a solvent-free
ed with the reduced form of the polymer, and this gives us reaction.19 When diol 7 was heated with 1, 8 was formed
the ability to reuse the same polymer to initiate additional in 77% yield in toluene and in 70% yield in hexane. Heat-
pinacol rearrangements.
ing with 2 in hexane gave 8 in 70% yield and in 77% yield
when heated with 2 in toluene. Finally, the literature
shows that bis(cyclopentyl) derivative 9 is converted into
10 in 85% yield with 25% aqueous sulfuric acid,20 and in
90% yield with SnCl4 and CH(OMe)3 in dichloro-
methane.21 When 9 was heated with 1, 10 was isolated in
81% yield in toluene, and in 84% yield in hexane. Ketone
10 was isolated in 80% yield when 9 was heated in toluene
with 2.
We chose four symmetrical diols for the first group: 3, 5,
7, and 9 (Table 1). There is a report that the reaction of 3
in aqueous sulfuric acid gave 4 in 72% yield.15 When 2,3-
dimethyl-2,3-butanediol [pinacol (3)] was heated with 1 at
reflux in heptane for two days, a 71% yield of pinacolone
(4) was isolated. Similar heating in hexane for about 20
hours (overnight; now our standard reaction time) gave a
79% yield of 4, but heating in toluene led to an intractable
mixture of products. Diol 3 was converted into 4 in 75% The next class of diols examined were cyclic diols 11 and
using poly(pyrrole) (2) at reflux in heptane. We recovered 13 (the cis diastereomer). The literature shows a report for
the polymer 1 from the conversion of 3 into 4 by filtration. the quantitative conversion of 11 into 12 when heated
Washing the used 1 with diethyl ether and then water was with sulfuric acid.22 When 11 was heated with 1 in tolu-
followed by drying in vacuo. We repeated the reaction ene, 12 was isolated in 91% yield, and heating in hexane
with 3 using the recycled polymer and obtained 4 in 70% led to 12 in 88% yield. Heating with 2 in toluene gave 12
isolated yield. This experiment is a proof-of-principle in 92% yield. The reaction of cis-1,2-dimethylcyclohex-
demonstration that the polymer can be recycled in the pi- ane-1,2-diol (13) and aqueous sulfuric acid reportedly
nacol rearrangement.
gave a 74% yield of 2,2-dimethylcyclohexanone via a
Wagner–Meerwein rearrangement.23 When heating the
trans-diol with aqueous perchloric acid at 60 °C, the yield
of 14 was 61%,24 heating of 13 to 150–160 °C in sulfuric
acid gave a 79% yield of 14.25 In our hands, heating of 13
with 1 in toluene gave a 68% yield of 14, and heating
in hexane gave a 72% yield. Heating with 2 in toluene
afforded 14 in 70% yield.
Table 1 Polymer-Induced Pinacol Rearrangements
O
OH
R1
R4
R3
polymer
OH
R4
R1
R2
solvent, reflux
overnight
R2
R3
Diol R1
R2
R3
R4 Product 1a
1b 1c
2
The last group of diols to be examined were asymmetrical
diols, which in the absence of cation-stabilizing effects
are prone to give mixtures. Diol 15 is a simple example of
an unsymmetrical diol, and it was known in the literature
that heating of 15 with aqueous perchloric acid gave 16.26
When 15 was heated with 1 in toluene, there was exten-
sive decomposition, but heating in hexane gave a 69%
yield of 16, along with 10% of 2,2-dimethylethanal [piv-
aldehyde (17)]. Similar heating in heptane led to a 65%
yield of 16 and 14% of 17. Heating of 15 with 2 in toluene
gave 16 in 60% yield and 17 in 12% yield.
(yield)
3
5
7
9
Me Me
Ph
Me
H
Me
Ph
Ph
4
6
–
71 79 75c
H
88 86
77 70
81 84
91 88
68 72
86a
77a
80a
92a
70a
Me Ph
–(CH2)4–
Me
8
–(CH2)4–
10
11 Ph –(CH2)2–
Ph 12
Me 14
13 Me (cis-) –(CH2)4–
15 Me Me
Me
H
16d
19e
8
65 69 60c
57 51 59c
We were unable to find an example in the literature in
which diol 18 was converted into an aldehyde or a ketone
via a pinacol cyclization. However, heating of 18 with 1
in heptane gave a 57% yield of 19, along with 26% of
5-methylhexan-2-one (20). Similar heating in hexane
gave a 57% yield of 19 and 20% of 20. Heating with 1 in
toluene led to extensive decomposition and formation of
several products in an intractable mixure. Heating with 2
in heptane, however, gave a mixture of 19 in 59% yield
and 20 in 29% yield.
18 CH2CHMe2 Me
H
H
21 Me Me
22 –(CH2)4–
Ph
Ph
Ph
81 83
93 84
79a
92a
Ph 23
a In toluene at reflux.
b In hexane at reflux.
c In heptane at reflux.
d +17 (–, 10%, 14%, 12%).
e +20 (–, 20%, 26%, 29%).
Synlett 2011, No. 15, 2191–2194 © Thieme Stuttgart · New York

LETTER
Polymer-Mediated Pinacol Rearrangements
2193
brown oil. Purification using flash chromatography (20% EtOAc–
hexane,) gave 2,2-diphenylacetaldehyde (6)39 as a clear oil (0.0169
g, 0.86 mmol, 86%) 1H NMR (300 MHz, CD3OD): d = 9.79 (s, 1 H)
7.31–6.98 (m, 10 H), 4.92 (s, 1 H). 13C NMR (75.5 MHz, CD3OD):
d = 198.6, 136.6, 129.3, 129.1, 127.8, 63.9.
The reaction of 21 has been reported in the literature: heat-
ing of 21 with sulfuric acid gave a 73% yield of 8,27
whereas heating with acetic anhydride gave an 85% yield
of 8.28 Heating of diol 21 with 1 in toluene gave ketone 8
in 81% yield, and heating in hexane afforded 8 in 83%
yield. Heating with 2 in toluene gave 8 in 79% yield. In
the final example, there was a literature report that heating
of 22 with acetic acid gave an 85% yield of 23.29 Like-
wise, heating of 22 with sulfuric acid afforded 23 in 99%
yield.27 When 22 was heated with 1 in toluene, we ob-
tained a 93% yield of 23, and heating in hexane gave an
84% yield of 23. Heating with 2 in toluene afforded 23 in
92% yield.
Preparation of 3,3-Dimethyl-2-butanone (4)
Under standard conditions, 3 (0.118 g, 1.0 mmol) was heated with
1 (0.57 g, 1.0 mmol) in heptane to give a brown oil. Purification by
flash column chromatography (20% EtOAc–hexane) gave 415 as an
1
oil (0.07 g, 0.71 mmol, 71%). H NMR (300 MHz, CD3OD): d =
2.11 (s, 3 H), 1.15 (s, 9 H). 13C NMR (75.5 MHz, CD3OD): d =
211.7, 46.8, 25.6.
The recovered 1 was washed with Et2O (2 × 30 mL) and H2O
(2 × 30 mL) and dried overnight in vacuo. Under standard condi-
In conclusion, we have demonstrated that two readily tions, 3 (0.110 g, 0.93 mmol) was heated with the recovered 1 (0.53
g, 0.8 mmol) in heptane. Workup gave 4 as an oil (0.07 g, 0.70
available polymers mediate the pinacol rearrangement of
1,2-diols in good yield. Putative advantages over known
methodology include a mild procedure that avoids strong
mineral acids or strong Lewis acids, the use of hydrocar-
bon solvents in a heterogeneous system, the ability to re-
use or recycle the polymer, and a trivial workup
procedure. We believe that this protocol is a mild and use-
ful addition to known procedures used for the pinacol cy-
clization. In addition, this protocol demonstrates a
transformation that is compatible with several green
chemistry principles, and may be applicable to process
chemistry.
mmol, 70%).
Preparation of 2,4-Dimethylpentanal (19) and 5-Methyl-2-hex-
anone (20)
The reaction of 5-methylhexane-2,3-diol (18)40 (0.132 g, 1.0 mmol)
and 1 (0.57 g, 1.0 mmol), under the standard conditons in heptane,
gave 2,4-dimethylpentanal (19)41 as a colorless oil (0.065 g, 0.57
mmol, 57%). 1H NMR (300 MHz, CD3OD): d = 9.61 (s, 1 H), 2.43
(ddq, J = 4.2, 4.2, 4.3 Hz, 1 H), 1.63 (m, 1 H), 1.59 (m, 1 H), 1.20
(m, 1 H), 1.08 (d, J = 6.9 Hz, 3 H), 0.94 (d, J = 6.8 Hz, 6 H). 13C
NMR (75.5 MHz, CD3OD): d = 205.4, 45.1, 39.8, 25.7, 22.8, 22.5,
20.9, 13.9; and also 5-methyl-2-hexanone (20)42 as a pale yellow oil
1
(0.0395 g, 0.261 mmol, 26%). H NMR (300 MHz, CD3OD): d =
2.42 (t, J = 4.5 Hz, 2 H), 2.14 (s, 3 H), 1.65–1.33 (m, 3 H), 0.89 (d,
J = 8.1 Hz, 6 H). 13C NMR (75.5 MHz, CD3OD): d = 209.4, 41.8,
32.7, 29.8, 27.7, 27.4.
All chemicals were used as received. All glassware was oven-dried
under vacuum, and all reactions were performed under a nitrogen
atmosphere, unless otherwise noted. All solvents were dried accord-
ing to standard procedures. Thin-layer chromatography was done
on aluminum-packed TLC plates with fluorescent indicator and 0.2
mm silica gel layer thickness, and p-anisaldehyde in EtOH was used
as a developing agent. Column chromatography was done using 60
Å porosity, 32–63 mm silica gel. A GC-MS with an HP-1 column
gas chromatography/mass spectrometer was used to obtain GC-MS
References
(1) (a) Fittig, R. Annalen 1860, 114, 54. (b) Collins, C. J.
Quart. Rev. Chem. Soc. 1960, 14, 357. (c) Mundy, B. P.;
Otzenberger, R. D. J. Chem. Educ. 1971, 48, 431. (d) The
Merck Index, 14th ed.; Merck: Whitehouse Station (NJ),
2006, ONR-74. (e) Mundy, B. P.; Ellerd, M. G.; Favaloro, F.
G. Jr. Name Reactions and Reagents in Organic Synthesis,
2nd ed.; Wiley-Interscience: New Jersey, 2005, 514–516.
(2) For a reaction initiated by iminium salts, see: (a) Lopez, L.;
Mele, G.; Mazzeo, C. J. Chem. Soc., Perkin Trans. 1 1994,
779. For reactions initiated by radical cations, see: (b) de
Sanabia, J. A.; Carrión, A. E. Tetrahedron Lett. 1993, 34,
7837. SbCl5 has been used, see: (c) Harada, T.; Mukaiyama,
T. Chem. Lett. 1992, 81.
(3) De Lezaeta, M.; Sattar, W.; Svoronos, P.; Karimi, S.;
Subramaniam, G. Tetrahedron Lett. 2002, 43, 9307.
(4) Corey, E. J.; Danheiser, R. L.; Chandrasekaran, S. J. Org.
Chem. 1976, 41, 260.
(5) (a) Yang, Z.-Y.; Wang, L.; Drysdale, N.; Doyle, M.; Sun, Q.;
Choi, S. K. Angew. Chem. Int. Ed. 2003, 42, 5462.
(b) Harmer, M. A.; Sun, Q. Appl. Catal. A 2001, 221, 45.
(c) Souzy, R.; Ameduri, B.; Boutevin, B.; Capron, P.;
Marsacq, D.; Gebel, G. Fuel Cells 2005, 3, 383.
1
spectra. H NMR and 13C NMR spectra were collected at 300.13
MHz and 75.48 MHz, respectively. Chemical shifts are reported in
ppm (d) downfield from TMS. Diol 3 is commerically available.
The other diols were prepared using literature procedures, without
modification of the reported protocols: 5 from a Grignard reaction
of methylcyclohexanone followed by OsO4 dihydroxylation,30 7 via
reaction of acetophenone with TMS/Zn followed by treatment with
TBAF,31 9 via TiCl4 coupling of cyclopentanone,32 11 via TiCl3 cy-
clization of the requisite diketone,33 13 via OsO4 dihydroxylation of
diphenylethene,34 15 via the 2-methylbut-2-ene reaction with hy-
drogen peroxide in formic acid to yield 2-methylbutane-2,3-diol,35
18 via Wittig reaction of isovaleraldehyde followed by OsO4 dihy-
droxylation,36 21 via TiCl4 coupling of benzophenone and ace-
tone,37 and 23 via Grignard reaction with ethyl 1-
hydroxycyclopentanecarboxylate.38
Representative Procedure for the Polymer-Induced Pinacol Re-
arrangement
(6) Gelbard, G. Ind. Eng. Chem. Res. 2005, 44, 8468.
(7) (a) Kirchmer, S.; Reuter, K. J. Mater. Chem. 2005, 15,
2077. (b) Greczynski, G.; Kugler, T.; Keil, M.; Osikowicz,
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,
12, 481.
Preparation of 2,2-Diphenylacetaldehyde (6)
A 100 mL round-bottomed flask was charged with hexane (60 mL)
and a magnetic stirbar. 1,2-Diphenylethane-1,2-diol (5,16a 0.214 g,
1.0 mmol) was added followed by 1 (0.57 g, 1.0 mmol). A reflux
condenser fitted with a septum and a nitrogen inlet was attached.
The system was heated at reflux overnight. After cooling, the poly-
mer was removed by vacuum filtration and washed with Et2O (10
mL). The filtrate was concentrated in vacuo, without heat, to give a
Synlett 2011, No. 15, 2191–2194 © Thieme Stuttgart · New York

2194
C. Pavlik et al.
LETTER
(8) (a) Brezoi, D.-V. J. Sci. Arts 2010, 53. (b) Wolken, J. J.
Light Detectors, Photoreceptors, and Imaging Systems in
Nature; Oxford University Press: New York, 1995.
(c) Tourillon, G. In Handbook of Conducting Polymers, Vol.
1; Skotheim, T. A., Ed.; Marcel Dekker: New York, 1986,
293–350.
(9) (a) Vernitskaya, T. V.; Efimov, O. N. Russ. Chem. Rev.
1997, 66, 443. (b) Grande, H.; Otero, T. F.; Rodriguez, J. In
Electrical and Optical Polymer Systems: Fundamentals,
Methods, and Applications; Wise, D. L., Ed.; Marcel
Dekker: New York, 1998, 17–46.
(10) (a) Corradi, R.; Armes, S. P. Synth. Met. 1997, 84, 453.
(b) Reuter, K.; Kirchmeyer, S. JP 2003261573, 2003.
(c) Reuter, K.; Kirchmeyer, S. US 2003139505, 2003.
(d) Jonas, F.; Wolf, G.-D. EP 0553671, 1993. (e) Jonas, F.;
Karbach, A.; Muys, B.; van Thillo, E.; Wehrmann, R.;
Elschner, A.; Dujardin, R. EP 0686662, 1995. (f) Jonas, F.;
Guntermann, U.; Lerch, K.; Boehnke, A.; Basten, H.;
Thometzek, P. US 5792558, 1996.
(21) Kita, Y.; Yosida, Y.; Mihara, S.; Furukawa, A.; Higuchi, K.;
Fang, D.-F.; Fujioka, H. Tetrahedron 1998, 54, 14689.
(22) Griffin, C. E.; Hager, R. B. J. Org. Chem. 1963, 26, 599.
(23) Bartlett, P. D.; Pöckel, I. J. Am. Chem. Soc. 1937, 59, 820.
(24) Buton, C. A.; Carr, C. D. J. Chem. Soc. 1963, 5854.
(25) (a) Nametkin, S.; Delektrosky, N. Ber. Dtsch. Chem. Ges.
1924, 57, 583. (b) Meerwein, H. Justus Liebigs Ann. Chem.
1939, 542, 123.
(26) Smith, W. B.; Bowman, R. E.; Kmet, T. J. J. Am. Chem. Soc.
1959, 81, 997.
(27) Zaugg, H. E.; Freifelder, M.; Horrom, B. W. J. Org. Chem.
1950, 15, 1191.
(28) Lyle, R. E.; Lyle, G. G. J. Org. Chem. 1953, 18, 1058.
(29) Burger, A.; Bennet, W. B. J. Am. Chem. Soc. 1950, 72, 5414.
(30) Chandrasekhar, S.; Narsihmulu, Ch.; Shameem, S. S.;
Reddy, N. Chem. Commun. 2003, 14, 1716.
(31) Boudjouk, P.; Park, M.; So, J. J. Org. Chem. 1988, 53, 5871.
(32) Fürstner, A.; Csuk, R.; Rohrer, C.; Weidmann, H. J. Chem.
Soc., Perkin Trans. 1 1988, 1729.
(11) 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,
2328.
(12) D’Angelo, J. G.; Kumar, A.; Onorato, A.; Delude, C. J.;
Sotzing, G. A.; Smith, M. B. Polymer 2007, 48, 4328.
(13) Onorato, A.; Invernale, M. A.; Berghorn, I. D.; Pavlik, C.;
Sotzing, G. A.; Smith, M. B. Synth. Met. 2010, 160, 2284.
(14) Onorato, A.; Pavlik, C.; Invernale, M. A.; Berghorn, I. D.;
Sotzing, G. A.; Morton, M. D.; Smith, M. B. Carbohydr.
Res. 2011, 346, 1662.
(33) (a) Periasamy, M.; Ramani, G.; Muthukumaragopal, G. P.
Synthesis 2009, 1739. (b) Clerici, A.; Pastori, N.; Porta, O.
Eur. J. Org. Chem. 2002, 3326.
(34) (a) Waser, J.; Carreira, E. M. Angew. Chem. Int. Ed. 2004,
43, 4099. (b) Meerwin, H. Justus Liebigs Ann. Chem. 1939,
542, 123.
(35) Hine, J.; McMahon, R.; Roberts, J. J. Am. Chem. Soc. 1950,
72, 4237.
(36) Kim, S.; Osakada, K.; Takeuchi, D. J. Am. Chem. Soc. 2002,
124, 762.
(37) Hu, Y.; Wang, J.; Xi, Y.; Gu, S. Synth. Commun. 1998, 28,
3299.
(15) Hill, G. A.; Flosdorg, E. W. Org. Synth., Coll. Vol. I 1941,
(38) (a) Roussis, V.; Gloer, K.; Wiemer, D. J. Org. Chem. 1988,
53, 2011. (b) Meerwein, H.; Muhlendyk, W. Justus Liebigs
Ann. Chem. 1914, 405, 129; see p. 174.
(39) Cavdar, H.; Saracoglu, N. Tetrahedron 2009, 65, 985.
(40) (a) Corey, E. J.; Clark, D. A.; Goto, G.; Marfat, A.;
Mioskowski, C.; Samuelsson, B.; Hammarstroem, S. J. Am.
Chem. Soc. 1980, 102, 1436. (b) Wong, J. C. Y.; Lacombe,
P.; Sturino, C. F. Tetrahedron Lett. 1999, 40, 8751.
(41) Guerlavais, V.; Carroll, P. J.; Joullie, M. M. Tetrahedron:
Asymmetry 2002, 13, 675.
462.
(16) (a) Zimmerman, H.; Schuster, D. I. J. Am. Chem. Soc. 1962,
84, 4527. (b) Amedio, J. C. Jr.; Bernard, P. J.; Fountain, M.;
Van Wagenen, G. Jr. Synth. Commun. 1998, 28, 3895.
(17) Stevens, C.; Holland, W. J. Org. Chem. 1958, 23, 781.
(18) Ciminale, F.; Lopez, L.; Nacci, A.; D’Accolti, L.; Vitale, F.
Eur. J. Org. Chem. 2005, 1597.
(19) Bian, Y.; Jia, Z. Youji Huaxue 2009, 29, 975.
(20) Sands, R. D. J. Org. Chem. 1994, 59, 468.
(42) Yoon, J.; Cram, D. J. J. Am. Chem. Soc. 1997, 119, 11796.
Synlett 2011, No. 15, 2191–2194 © Thieme Stuttgart · New York

Copyright of Synlett is the property of Georg Thieme Verlag Stuttgart and its content may not be copied or
emailed to multiple sites or posted to a listserv without the copyright holder's express written permission.
However, users may print, download, or email articles for individual use.