Palladium-catalyzed oxidative heterocyclodehydration-alkoxycarbonylation of 3-yne-1,2-diols: a novel and expedient approach to furan-3-carboxylic esters

Article abstract of DOI:10.1016/j.tetlet.2010.01.054

A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-catalyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1. The process, corresponding to a sequential combination between a 5-endo-dig heterocyclodehydration step and an oxidative alkoxycarbonylation stage, is catalyzed by PdI₂ in conjunction with an excess of KI under relatively mild conditions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air).

Full text of DOI:10.1016/j.tetlet.2010.01.054

Tetrahedron Letters 51 (2010) 1663–1665
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Palladium-catalyzed oxidative heterocyclodehydration-alkoxycarbonylation
of 3-yne-1,2-diols: a novel and expedient approach to furan-3-carboxylic esters
b
b
a
b
Bartolo Gabriele a, , Lucia Veltri , Raffaella Mancuso , Pierluigi Plastina , Giuseppe Salerno
*
Mirco Costa c
a Dipartimento di Scienze Farmaceutiche, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy
b Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy
c Dipartimento di Chimica Organica e Industriale, Università di Parma, 43100 Parma, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-cata-
lyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1. The process, corresponding
to a sequential combination between a 5-endo-dig heterocyclodehydration step and an oxidative alkoxy-
carbonylation stage, is catalyzed by PdI2 in conjunction with an excess of KI under relatively mild condi-
tions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air).
Received 8 January 2010
Accepted 18 January 2010
Available online 25 January 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Furans are a very important class of heterocyclic derivatives.
The furan motif is present in many important naturally occurring
and biologically active compounds,1 and furan derivatives find
extensive application in many applicative fields.2 The possibility
to construct functionalized furans in a regioselective way by het-
erocyclization of suitable acyclic precursors has accordingly at-
tracted an increasing attention,3 and several methods have been
developed to date for the synthesis of substituted furans by annu-
lation processes, mainly based on metal catalysis.4 However, to the
best of our knowledge, no direct synthesis of furan-3-carboxylic
esters 2 by carbonylation of acyclic precursors has been reported
so far.5 In this Letter, we report a novel, convenient and atom-eco-
nomical6 method for the preparation of this important class of het-
erocyclic derivatives,7 based on direct oxidative carbonylation of
readily available 3-yne-1,2-diols 18 (Eq. (1)).
Our first experiments were carried out using 2-methyloct-3-
yne-1,2-diol 1a (R1 = Me, R2 = Bu), which was let to react at 80 °C
in MeOH (1a concentration = 0.25 mmol per mL of MeOH) under
20 atm of a 4:1 mixture of CO-air, in the presence of PdI2
(1 mol %) and KI (10 mol %). After 2 h, the GC–MS analysis of the
reaction crude showed a substrate conversion of ca. 70% and the
formation of two products, whose MS spectra were compatible
with the furan-3-carboxilic ester derivatives 2a and 3a, respec-
tively (Table 1, entry 1).
Product 2a (28% GLC yield) was easily isolated by column
chromatography, and its structure fully confirmed by spectro-
scopic techniques, while every attempt to isolate pure 3a (13%
GLC yield) failed. However, an indirect proof of the validity of
the proposed structure was given by the results obtained from
the reaction carried out at 100 °C rather than 80 °C: in fact, prod-
uct 3a partly converted into the methyl ester 2a (Table 1, entry
2), which is in agreement with methanolysis of 3a with forma-
tion of 2a and 1a. Clearly, a higher selectivity toward 2a was
to be expected working at lower substrate concentration. The re-
sult shown in entry 3 (Table 1) confirmed that this was indeed
the case: with an 1a concentration of 0.05 mmol per mL of
MeOH, the GLC yield of 2a and 3a turned out to be 60% and
2%, respectively. A still higher 2a/3a ratio was obtained with a
lower 1a concentration, but the total yield obtained was less sat-
isfactory (Table 1, entry 4). On the other hand, the use of a lower
amount of KI (5 mol per mol of PdI2, Table 1, entry 5) led to bet-
ter results with respect to the initial reaction, carried out with a
KI/PdI2 molar ratio of 10 (Table 1, entry 1). A further decrease of
the KI/PdI2 ratio was, however, detrimental (Table 1, entry 6). Fi-
nally, an increase of the total pressure to 40 atm caused a signif-
icant increase of the total yield (81%, entry 7).
R1 CO2R
OH
R1
R2
PdI2 cat
R2
ð1Þ
CO, ROH, O2
O
OH
1
2 (56-72%)
(R1, R2 = H, alkyl, aryl; R = alkyl)
The process, corresponding to a sequential combination be-
tween a 5-endo-dig heterocyclodehydration step and an oxidative
alkoxycarbonylation stage, is catalyzed by a very simple catalytic
system, consisting of PdI2 in conjunction with an excess of KI and
oxygen as the oxidant, and takes place at 100 °C in an alcohol as
the solvent, under 40 atm of a 4:1 mixture of CO-air9.
* Corresponding author. Tel.: +39 0984 492813; fax: +39 0984 492044.
E-mail address: b.gabriele@unical.it (B. Gabriele).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.01.054

1664
B. Gabriele et al. / Tetrahedron Letters 51 (2010) 1663–1665
Table 1
Reactions of 2-methyloct-3-yne-1,2-diol 1a with CO, O2, and MeOH in the presence of the PdI2-KI catalytic systema
Me
OH
Bu
O
OH
OH
Me CO2Me
Me
Me
O
PdI2 cat
2 H2O
Bu
+ CO + MeOH + (1/2) O2
+
Bu
O
Bu
O
1a
3a
2a
Entry
PdI2:KI:1a molar ratio
T (°C)
Concentration of 1ac
Yield of 2ad (%)
Yield of 3ad (%)
Total yieldd (%)
1b
2
3
4
5
1:10:100
1:10:100
1:10:100
1:10:100
1:5:100
80
100
80
80
80
0.25
0.25
0.05
0.02
0.25
0.25
0.25
28
55
60
45
52
37
49
13
9
2
1
15
9
41
64
62
46
67
46
81
6
1:2:100
1:10:100
80
80
7e
32
a
Unless otherwise noted, all reactions were carried out in MeOH for 2 h under 20 atm (at 25 °C) of a 4:1 mixture of CO-air. Unless otherwise noted, substrate conversion
was quantitative in all cases.
b
Substrate conversion was 70%, by GLC.
mmol of 1a per mL of MeOH.
Based on starting 1a, by GLC.
The reaction was carried out under 40 atm (at 25 °C) of a 4:1 mixture of CO-air.
c
d
e
Based on these results, the next experiment was carried out at
100 °C under 40 atm of a 4:1 mixture of CO-air with a substrate
concentration of 0.05 mmol per mL of MeOH, in the presence of
PdI2 + 5 KI. Under these optimized conditions, the reaction selec-
tively led to the methyl furan-3-carboxylate 2a with a GLC yield
of 76% and an isolated yield of 69% (Table 2, entry 1). Other differ-
ently substituted 3-yne-1,2-diols 1b–e behaved similarly, to give
the corresponding furan-3-carboxylates selectively with yields
ranging from 56% to 72% (Table 2, entries 2–5). The reaction also
worked well using EtOH rather than MeOH as the solvent and
nucleophile, as shown by the result obtained in Table 2, entry
6.10,11
On the basis of the existing knowledge on PdI2-catalyzed car-
bonylative annulation reactions,12,13 we can propose the mecha-
nism shown in Scheme 1 for the formation of 2 from 1. Thus, a
5-endo-dig cyclization may occur by intramolecular nucleophilic
attack of the hydroxyl group at C-1 on the triple bond coordinated
to the metal center, followed by alkoxycarbonylation of the result-
ing vinylpalladium intermediate and dehydration or vice versa,
with formation of 2, Pd(0) and HI. The latter is then reoxidized to
PdI2 by the action of iodine, formed in its turn by oxidation of HI
by oxygen.12–14
PdI2
R2
OH
O
OH
O
R1 OH
OH
PdI
R2
CO2R
R2
R1
R1
CO, ROH
[Pd(0)+HI]
HI
H2O
H2O
R1 PdI
R2
I2 + H2O
CO, ROH
[Pd(0)+HI]
2
O
2 HI + (1/2) O2
Pd(0) + I2
PdI2
Scheme 1. Plausible reaction pathways leading to furan-3-carboxylic esters 2.
Anionic iodide ligands are omitted for clarity.
In conclusion, we have reported the first example of a direct
synthesis of an important class of heterocyclic derivatives, such
as furan-3-carboxylic esters, by a one-step carbonylative hetero-
cyclization approach. The method is based on the use of readily
available substrates (3-yne-1,2-diols, CO, and O2) and a very simple
catalytic system (PdI2-KI), and is characterized by good product
yields and high atom economy.
References and notes
Table 2
1. For very recent examples, see: (a) Wang, W. L.; Chai, S. C.; Ye, Q.-Z. Bioorg. Med.
Chem. Lett. 2009, 19, 1080–1083; (b) Jeon, T. W.; Kim, C. H.; Lee, S. K.; Shin, S.;
Choi, J. H.; Kang, W.; Kim, S. H.; Kang, M. J.; Lee, E. S.; Jeong, T. C. Biomol. Ther.
2009, 17, 318–324; (c) Dong, Y. Z.; Shi, Q.; Liu, Y. N.; Wang, X.; Bastow, K. F.;
Lee, K.-H. J. Med. Chem. 2009, 52, 3586–3590; (d) Evidente, A.; Cristinzio, G.;
Punzo, B.; Andolfi, A.; Testa, A.; Melck, D. Chem. Biodivers. 2009, 6, 328–334; (e)
Fuji, H.; Urano, E.; Futahashi, Y.; Hamatake, M.; Tatsumi, J.; Hoshino, T.;
Morikawa, Y.; Yamamoto, N.; Komano, J. J. Med. Chem. 2009, 52, 1380–1387; (f)
Chandrappa, S.; Kavitha, C. V.; Shahabuddin, M. S.; Vinaya, K.; Kumar, C. S. A.;
Ranganatha, S. R.; Raghavan, S. C.; Rangappa, K. S. Bioorg. Med. Chem. 2009, 17,
2576–2584; (g) Amaro, M. I.; Monasterios, M.; Avendano, M.; Charris, J. J. Appl.
Toxicol. 2009, 29, 36–41.
Synthesis of furan-3-carboxylic esters 2 by PdI2-catalyzed oxidative carbonylative
heterocyclization of 3-yne-1,2-diols 1a
R1 CO2R
OH
R1
R2
PdI2 cat
R2
+ CO + ROH + (1/2) O2
2 H2O
O
OH
1
2
Entry
1
R1
R2
R
2
Yield of 2b (%)
1
2
3
4
5
6
1a
1b
1c
1d
1e
1a
Me
Me
Ph
Ph
H
Bu
Ph
Bu
Ph
Bu
Bu
Me
Me
Me
Me
Me
Et
2a
2b
2c
2d
2e
2a0
69c
60
61
56
72
66
2. For recent examples, see: (a) Umeyama, T.; Takamatsu, T.; Tezuka, N.; Matano,
Y.; Araki, Y.; Wada, T.; Yoshikawa, O.; Sagawa, T.; Yoshikawa, S.; Imahori, H. J.
Phys. Chem.
C 2009, 113, 10798–10806; (b) Peart, P. A.; Tovar, J. D.
Macromolecules 2009, 42, 4449–4455; (c) Gandini, A.; Silvestre, A. J. D.;
Pascoal Neto, C.; Souza, A. F.; Gomes, M. J. Polym. Sci. Pol. Chem. 2009, 47, 295–
298; (d) Zhang, Y.; Broekhuis, A. A.; Picchioni, F. Macromolecules 2009, 42,
1906–1912; (e) Nagano, T.; Mikami, Y.; Kim, S.; Chiba, K. Electrochemistry 2008,
76, 874–879; (f) Baldwin, L. C.; Chafin, A. P.; Deschampes, J. R.; Hawkins, S. A.;
Wright, M. E.; Witker, D. L.; Prokopuk, N. J. Mater. Sci. 2008, 43, 4182–4191.
3. For some recent reviews, see: (a) Van Otterlo, W. A. L.; de Koning, C. B. Chem.
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Moreira, D. N.; Zanatta, N.; Bonacorso, H. G. Chem. Rev. 2008, 108, 2015–2050;
Me
a
All reactions were carried out in ROH (substrate concentration = 0.05 mmol per
mol of ROH, 1–2 mmol scale based on 1) at 100 °C for 2 h under 40 atm (at 25 °C) of
a 4:1 mixture of CO-air, in the presence of PdI2 (1 mol %) in conjunction with KI (KI/
PdI2 molar ratio = 5). Substrate conversion was quantitative in all cases.
b
Isolated yield based on starting 1.
The GLC yield was 76%.
c

B. Gabriele et al. / Tetrahedron Letters 51 (2010) 1663–1665
1665
(d) Patil, N. T.; Yamamoto, Y. Chem. Rev. 2008, 108, 3395–3442; (e) Cadierno, V.;
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A. M.; Shestopalov, A. A.; Rodonovskaya, L. A. Synthesis 2008, 1–25; (i) Hashmi,
A. S. K. Chem. Rev. 2007, 107, 3180–3211; (j) Balme, G.; Bouyssi, D.; Monteiro, N.
Heterocycles 2007, 73, 87–124; (k) Kirsch, S. F. Org. Biomol. Chem. 2006, 4, 2076–
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4. For very recent examples, see: (a) Egi, M.; Azechi, K.; Akai, S. Org. Lett. 2009, 11,
5002–5005; (b) Yoshida, M.; Al-Amin, M.; Shishido, K. Synthesis 2009, 2454–
2466; (c) Briel, D.; Askar, G. B.; Ortwein, J.; Unverferth, K. Pharmazie 2009, 64,
477–478; (d) Hu, L. X.; Boykin, D. W. Synthesis 2009, 2143–2145; (e) Saquib,
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or Et, 28 mL). The autoclave was sealed and, while the mixture was stirred, the
autoclave was pressurized with CO (32 atm) and air (up to 40 atm). After being
stirred at 100 °C for 2 h, the autoclave was cooled, degassed, and opened. The
solvent was evaporated, and the products were purified by column
chromatography on silica gel (eluent: 9:1 hexane–acetone for 2a and 2b;
95:5 hexane–AcOEt for 2c and 2d; 6:4 hexane–acetone for 2e; 98:2 hexane–
AcOEt for 2a0) to give pure furans 2, which were fully characterized by
spectroscopic techniques and elemental analysis.11
11. Characterization data for products: For 2a: Yellow oil. IR (film):
m = 1739, 1442,
1256, 763 cmꢁ1 1H NMR (300 MHz, CDCl3): d = 7.04 (s, br, 1H), 3.82 (s, 3H),
;
2.98–2.90 (m, 2H), 2.13 (s, br, 3H), 1.69–1.57 (m, 2H), 1.42–1.28 (m, 2H), 0.92
(t, J = 7.3, 3H) ppm; 13C NMR (75 MHz, CDCl3): d = 165.2, 164.3, 137.9, 121.2,
113.2, 50.8, 30.2, 27.9, 22.4, 13.7, 9.9 ppm; GC–MS (EI, 70 eV): m/z = 196 (M+,
25), 154 (32), 153 (100), 139 (32), 135 (44), 123 (47); Anal. Calcd for C11H16O3
(196.24): C, 67.32; H, 8.22. Found: C, 67.23; H, 8.24. For 2b: Yellow oil. IR
(film):
m ;
= 1728, 1448, 1225, 758 cmꢁ1 1H NMR (300 MHz, CDCl3): d = 7.79–
7.74 (m, 1 H), 7.45–7.36 (m, 4 H), 7.24 (q, J = 0.9, 1H), 3.80 (s, 3H), 2.20 (d,
J = 0.9, 3H) ppm; 13C NMR (75 MHz, CDCl3): d = 164.9, 158.0, 139.2, 129.4,
129.1, 128.4, 128.1, 128.0, 122.6, 51.2, 10.0 ppm; GC–MS (EI, 70 eV): m/z = 216
(M+, 82), 185 (100), 128 (53), 127 (33); Anal. Calcd for C13H12O3 (216.23): C,
72.21; H, 5.59. Found: C, 72.30; H, 5.60. For 2c: Colorless oil. IR (film):
m = 1718,
1438, 1391, 1292, 1121, 758 cmꢁ1 1H NMR (300 MHz, CDCl3): d = 7.38–7.29
;
5. Several synthetic approaches to furan-3-carboxylic esters have been
developed; none of these methods, however, involve the direct carbonylation
of acyclic precursors. For recent leading examples, see: (a) Goodman, K. B.;
Bury, M. J.; Cheung, M.; Cichy-Knight, M. A.; Dowdell, S. E.; Dunn, A. K.; Lee, D.;
Lieby, J. A.; Moore, M. L.; Scherzer, D. A.; Sha, D.; Suarez, D. P.; Murphy, D. J.;
Harpel, M. R.; Manas, E. S.; McNulty, D. E.; Annan, R. S.; Matico, R. E.; Schwartz,
B. K.; Trill, J. J.; Sweitzer, T. D.; Wang, D.-y.; Keller, P. M.; Krawiec, J. A.; Jaye, M.
C. Bioorg. Med. Chem. Lett. 2009, 19, 27–30; (b) Barluenga, J.; Riesgo, L.; Vicente,
R.; López, L. A.; Tomás, M. J. Am. Chem. Soc. 2008, 130, 13528–13529; (c)
Tarwade, V.; Dmitrenko, O.; Bach, R. D.; Fox, J. M. J. Org. Chem. 2008, 73, 8189–
8197; (d) Blayo, A.-L.; Gree, D.; Gree, R.; Le Meur, S. Adv. Synth. Catal. 2008, 350,
417–476; (e) Alizadeh, A.; Oskueyan, Q.; Rostamnia, S.; Ghanbari-Niaki, A.;
Mohebbi, A. R. Synthesis 2008, 2929–2932; (f) Terzidis, M. A.; Tsoleridis, C. A.;
Stephanidou-Stephanatou, J.; Terzis, A.; Raptopoulou, C. P.; Psycharis, V.
Tetrahedron 2008, 64, 11611–11617; (g) Taguchi, Y.; Oishi, A.; Iida, H. Chem.
Lett. 2008, 37, 50–51; (h) Yoneda, Y.; Krainz, K.; Liebner, F.; Potthast, A.;
Rosenau, T.; Karakawa, M.; Nakatsubo, F. Eur. J. Org. Chem. 2008, 475–484; (i)
Ranu, B. C.; Laksmikanta, A.; Banerjee, S. Tetrahedron Lett. 2008, 49, 4613–4617.
6. For a recent review on the importance of the development of new atom-
economical processes, see: Trost, B. M. Acc. Chem. Res. 2002, 35, 695–705.
7. Several molecules incorporating the furan-3-carboxylic ester core have shown
(m, 5H), 7.27 (s, 1H), 3.70 (s, 3H), 3.04–2.96 (m, 2H), 1.76–1.64 (m, 2H), 1.47–
1.33 (m, 2H), 0.95 (t, J = 7.3, 3H) ppm; 13C NMR (75 MHz, CDCl3): d = 164.6,
164.2, 138.4, 132.2, 129.2, 127.9, 127.3, 112.3, 51.0, 30.2, 27.9, 22.4, 13.8 ppm;
GC–MS (EI, 70 eV): m/z = 258 (M+, 41), 215 (39), 197 (100), 183 (54), 128 (34),
127 (49); Anal. Calcd for C16H18O3 (258.31): C, 74.39; H, 7.02. Found: C, 74.19;
H, 7.03. For 2d: Yellow solid, mp = 27–28 °C. IR (KBr):
m
= 1717, 1540, 1482,
1385, 1266, 1152, 924, 768 cmꢁ1
;
1H NMR (300 MHz, CDCl3): d = 7.83–7.77 (m,
2H), 7.50 (s, 1H), 7.47–7.30 (m, 8H), 3.68 (s, 3H) ppm; 13C NMR (75 MHz,
CDCl3): d = 165.1, 156.6, 139.2, 131.7, 130.1, 129.2, 128.6, 128.33, 128.26,
127.7, 127.6, 113.7, 51.6 ppm; GC–MS (EI, 70 eV): m/z = 278 (M+, 100), 247
(92), 191 (42), 189 (55), 105 (42); Anal. Calcd for C18H14O3 (278.30): C, 77.68;
H, 5.07. Found: C, 77.60; H, 5.07. For 2e: Colorless oil. IR (film):
m = 1720, 1605,
1442, 1307, 1201, 1039, 736 cmꢁ1 1H NMR (300 MHz, CDCl3): d = 7.24 (d,
;
J = 2.0, 1H), 6.63 (d, J = 2.0, 1H), 3.82 (s, 3H), 3.00 (t, J = 7.7, 2H), 1.72–1.59 (m, 2
H), 1.42–1.29 (m, 2H), 0.93 (t, J = 7.3, 3H) ppm; 13C NMR (75 MHz, CDCl3):
d = 164.5, 163.5, 140.4, 113.0, 110.7, 51.2, 30.1, 27.3, 22.3, 13.7 ppm; GC–MS
(EI, 70 eV): m/z = 182 (M+, 56), 153 (42), 140 (96), 139 (87), 125 (47), 121 (74),
109 (100); Anal. Calcd for C10H14O3 (182.22): C, 65.91; H, 7.74. Found: C, 65.79;
H, 7.72. For 2a0: Colorless oil. IR (film):
m ;
= 1722, 1267, 1073 cmꢁ1 1H NMR
(300 MHz, CDCl3): d = 7.04 (q, J = 1.3, 1H), 4.29 (q, J = 7.2, 2H), 2.98–2.91 (m,
2H), 2.14 (d, J = 1.3, 3H), 1.69–1.58 (m, 2H), 1.42–1.26 (m, 2H), 1.35 (t, J = 7.2,
3H), 0.92 (t, J = 7.5, 3H) ppm; 13C NMR (75 MHz, CDCl3): d = 164.8, 164.1, 137.8,
121.2, 113.2, 59.8, 30.3, 28.0, 22.4, 14.4, 13.8, 10.0 ppm; GC–MS (EI, 70 eV):
m/z = 210 (M+, 29), 139 (100); Anal. Calcd for C12H18O3 (210.27): C, 68.54; H,
8.63. Found: C, 68.53; H, 8.64.
interesting
pharmacological
activities,
including
antihypertensive,
antimicrobial, and anticancer activity. For recent leading examples, see: (a)
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17, 6905–6909; (e) Dominguez, C.; Smith, L.; Huang, Q.; Yuan, C.; Ouyang, X.;
Cai, L.; Chen, P.; Kim, J.; Harvey, T.; Syed, R.; Kim, T.-S.; Tasker, A.; Wang, L.;
Zhang, M.; Coxon, A.; Bready, J.; Starnes, C.; Chen, D.; Gan, Y.; Neervannan, S.;
Kumar, G.; Polverino, A.; Kendall, R. Bioorg. Med. Chem. Lett. 2007, 17, 6003–
6008; (f) de Oliveira, R. B.; de Souza-Fagundes, E. M.; Siqueira, H. A. J.; Leite, R.
S.; Donnici, C. L.; Zani, C. L. Eur. J. Med. Chem. 2006, 41, 756–760; (g) Funk, O. F.;
Kettmann, V.; Drimal, J.; Langer, T. J. Med. Chem. 2004, 47, 2750–2760.
12. For reviews on PdI2-catalyzed oxidative carbonylation reactions, see: (a)
Gabriele, B.; Salerno, G. Cyclocarbonylation. In Handbook of Organopalladium
Chemistry for Organic Synthesis; Negishi, E., Ed.; Wiley-Interscience: New York,
2002; Vol. II, pp 2623–2641; (b) Gabriele, B.; Salerno, G.; Costa, M.; Chiusoli, G.
P. J. Organomet. Chem. 2003, 687, 219–228; (c) Gabriele, B.; Salerno, G.; Costa,
M.; Chiusoli, G. P. Curr. Org. Chem. 2004, 8, 919–946; (d) Gabriele, B.; Salerno,
G.; Costa, M. Synlett 2004, 2468–2483; (e) Gabriele, B.; Salerno, G. PdI2. In E-
EROS (Electronic Encyclopedia of Reagents for Organic Synthesis); Crich, D., Ed.;
John Wiley & Sons: Chichester, 2006; (f) Gabriele, B.; Salerno, G.; Costa, M. Top.
Organomet. Chem. 2006, 18, 239–272.
13. For recent examples on PdI2-catalyzed oxidative carbonylation reactions, see:
(a) Gabriele, B.; Mancuso, R.; Salerno, G.; Ruffolo, G.; Costa, M.; Dibenedetto, A.
Tetrahedron Lett. 2009, 50, 7330–7332; (b) Della Cà, N.; Campanini, F.; Gabriele,
B.; Salerno, G.; Massera, C.; Costa, M. Adv. Synth. Catal. 2009, 351, 2423–2432;
(c) Gabriele, B.; Mancuso, R.; Salerno, G.; Lupinacci, E.; Ruffolo, G.; Costa, M. J.
Org. Chem. 2008, 73, 4971–4977; (d) Gabriele, B.; Plastina, P.; Salerno, G.;
Mancuso, R.; Costa, M. Org. Lett. 2007, 9, 3319–3322; (e) Plastina, P.; Gabriele,
B.; Salerno, G. Synthesis 2007, 3083–3087; (f) Gabriele, B.; Plastina, P.; Salerno,
G.; Mancuso, R. Synthesis 2006, 4247–4251; (g) Gabriele, B.; Salerno, G.; Fazio,
A.; Veltri, L. Adv. Synth. Catal. 2006, 348, 2212–2222; (h) Gabriele, B.; Salerno,
G.; Veltri, L.; Mancuso, R.; Li, Z.; Crispini, A.; Bellusci, A. J. Org. Chem. 2006, 71,
7895–7898; (i) Bacchi, A.; Costa, M.; Della Cà, N.; Gabriele, B.; Salerno, G.;
Cassoni, S. J. Org. Chem. 2005, 70, 4971–4979; (j) Gabriele, B.; Plastina, P.;
Salerno, G.; Costa, M. Synlett 2005, 935–938.
8. Substrates
-hydroxy aldehyde or
R3C„CMgBr.
1
were easily prepared by alkynylation of the appropriate
a
a
-hydroxy ketone using an excess of R3C„CLi or
9. These conditions (32 atm of CO together with 9 total atm of air, considering
that the autoclave was loaded under 1 atm of air) corresponded to 78.0% of CO
in air and were outside the explosion limits for CO in air (ca. 16–70% at 18–20
°C and atmospheric pressure, 14.8–71.4% at 100 °C and atmospheric pressure.
At higher total pressure, the range of flammability decreases: for example, at
20 atm and 20 °C the limits are ca. 19% and 60%. See: Bartish, C. M.; Drissel, G.
M. In: Kirk-Othmer Encyclopedia of Chemical Technology; Grayson, M., Eckroth,
D., Bushey, G. J., L. Campbell, L., Klingsberg, A., van Nes, L., Eds., 3rd ed.; Wiley-
Interscience: New York, 1978; Vol. 4, p 775.
10. Typical procedure for the oxidative carbonylative annulation of 3-yne-1,2-diols
1
to furan-3-carboxylic esters 2:
A
250 mL stainless steel autoclave was
14. Gabriele, B.; Costa, M.; Salerno, G.; Chiusoli, G. P. J. Chem. Soc., Perkin Trans. 1
1994, 84–87.
charged in the presence of air with PdI2 (5.0 mg, 1.39 ꢀ 10ꢁ2 mmol), KI
(11.5 mg, 6.93 ꢀ 10ꢁ2 mmol), and a solution of 1 (1.39 mmol) in ROH (R = Me