Synthesis of cyclobutenediones and anhydrides from alkynes using the Fe(CO)5/Me3NO reagent system

Article abstract of DOI:10.1021/om049429f

Coordinatively unsaturated "Fe(CO)₄" species prepared using inexpensive Me₃NO and Fe(CO)₅ reacts with alkynes under ambient conditions to give cyclobutenediones in moderate to good yields (50-75%) after CuCl₂·2H

Full text of DOI:10.1021/om049429f

Organometallics 2004, 23, 6323-6326
6323
Synthesis of Cyclobutenediones and Anhydrides from
Alkynes Using the Fe(CO)5/Me3NO Reagent System
Mariappan Periasamy,* Amere Mukkanti, and D. Shyam Raj
School of Chemistry, University of Hyderabad, Hyderabad 500046, India
Received July 26, 2004
Table 1. Reaction of Alkynes (2.5 mmol) with
Fe(CO)5 (15 mmol) and Me3NO (12 mmol) Followed
by CuCl2‚2H2O Oxidation
Summary: Coordinatively unsaturated “Fe(CO)4” species
prepared using inexpensive Me3NO and Fe(CO)5 reacts
with alkynes under ambient conditions to give cyclo-
butenediones in moderate to good yields (50-75%) after
CuCl2‚2H2O oxidation. The corresponding cyclic anhy-
drides are obtained in 60-80% yields when an excess of
the amine oxide was used.
Introduction
The requirement of efficient reagents for the prepara-
tion of multifunctional molecules continues to spur
research activity in the development of new synthetic
methods employing organometallic reagents, particu-
larly using metal carbonyls.1-3 Generally, commercially
available metal carbonyls are coordinatively saturated,
18-electron species, and hence one of their CO ligands
should be removed for them to participate in chemical
reactions. Several chemical promoters such as R3NO,
R3PO, KOMe, KH, and NaBH4 were reported to facili-
tate the CO dissociation.4-7 Trimethylamine N-oxide
(Me3NO) is a well-known mild, efficient oxidizing agent,
which removes one of the carbonyl ligands of Fe(CO)5
as CO2 to form the reactive, coordinatively unsaturated
“Fe(CO)4” species.5,7 During the course of our efforts on
the preparation of reactive iron carbonyl species for
applications in organic synthesis,6 we have observed
that the unsaturated “Fe(CO)4” species, prepared using
the inexpensive Fe(CO)5/Me3NO reagent system, reacts
with alkynes to give the corresponding cyclobutenedi-
* To whom correspondence should be addressed. E-mail: mpsc@
uohyd.ernet.in.
(1) (a) Fatiadi, A.J. J. Res. Natl. Inst. Stand. Technol. 1991, 96, 1.
(b) Shore, N. E. Chem. Rev. 1988, 88, 1081. (c) Noyori, R.; Hayakawa,
Y. Tetrahedron 1985, 41, 5879. (d) Bird, C. W. Chem. Rev. 1962, 62,
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(3) (a) Pearson, A. J.; Shively, R. J., Jr.; Dubbert, R. A. Organome-
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metallics 1994, 13, 578. (c) Pearson, A. J.; Perosa, A. Organometallics
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a Products were identified by the spectral data (IR, 1H, 13C
NMR, and MS) and comparison with reported data.8 b Yields
reported are for the isolated products and based on the amount of
alkynes used.
ones or the anhydrides after CuCl2 oxidation. The
results are described here.
Results and Discussion
We have observed that Fe(CO)4, prepared in THF
using Me3NO and Fe(CO)5, reacts with alkynes at room
temperature to give corresponding diones in moderate
to good yields (50-75%) after CuCl2‚2H2O oxidation (eq
1). Several alkynes were converted to cyclobutenediones,
and the results are summarized in Table 1. Evidently,
this reagent system tolerates unmasked functional
groups such as hydroxyl and silyl groups (entries 4-7).
The formation of cyclobutenedione from enyne shows
10.1021/om049429f CCC: $27.50 © 2004 American Chemical Society
Publication on Web 11/23/2004

6324 Organometallics, Vol. 23, No. 26, 2004
Notes
Table 2. Reaction of Alkynes (2.5 mmol) with
that this reagent system reacts with alkynes without
affecting the olefin moiety (entry 8). In the case of
1-heptyne, the corresponding cyclobutenedione is ob-
tained in lower yield besides a mixture of the corre-
sponding 2,5- and 2,6-dialkylbenzoquinones (30%, 60:
40) (entry 3, Table 1).
Fe(CO)5 (10 mmol) and Me3NO (15 mmol)
Although THF was found to be a suitable solvent,
other solvents such as CH3CN and acetone also gave
comparable results. However, the use of solvents such
as CHCl3 and CH2Cl2 gave unidentified mixtures of
carbonyl products. Presumably, the coordinating sol-
vents may form weak complexes with the Fe(CO)4
species that help in this transformation.7a,b
The formation of cyclobutenediones from alkynes can
be explained by considering a tentative mechanism
depicted in Scheme 1. Addition of Fe(CO)5 to a solution
Scheme 1
a Products were identified by the spectral data (IR, 1H, 13C
NMR, and MS) and comparison with reported data (entries 1 and
3).9 b Yields reported are for the isolated products and based on
the amount of alkynes used.
of Me3NO in THF at -20 °C gives a red-colored solution
with immediate evolution of CO2 through the nucleo-
philic attack of amine oxide to coordinated CO.7 These
species would further react with alkynes followed by CO
insertion to give maleoyl complexes of type 1 or ferrole
complexes of type 2. Such complexes could give cy-
clobutenediones after CuCl2‚2H2O oxidation.8c,d
We have also made efforts to identify the intermediate
species involved in the above transformation. It was
observed that the addition of Et3N and CH3COCl to the
iron carbonyl formed in situ in the reaction of Fe(CO)4
and alkyne in THF gives the iron complex 5 in 48% yield
(Figure 1).6,10
after CuCl2‚2H2O oxidation along with traces of cy-
clobutenediones (3-5%), Table 2.
In conclusion, the present method of preparation of
coordinatively unsaturated iron carbonyl species for
synthetic applications has advantages over the erstwhile
known methods since this method avoids the use of Fe3-
(CO)12 or Fe2(CO)9, which are in turn prepared from Fe-
(CO)5.5 Me3NO is a mild, efficient oxidizing agent.5a,b
Since it is transformed into the volatile trimethylamine,
it does not interfere with the isolation of products.
Cyclobutenediones and their derivatives have proven
applications. They have been used as NLO materials,11a,b
growth regulators, potassium channel openers, drug
molecules,11c-j anion recognition systems,12 chiral
(11) (a) Ashwell, G. J.; Jefferies, G.; Hamilton, D. G.; Lynch, D. E.;
Roberts, M. P. S.; Bahra, G. S.; Brown, C. R. Nature 1995, 375, 385.
(b) Law, K. Y.; Bailey, F. C. J. Org. Chem. 1992, 57, 3278. (c) Abou-
Gharbia, M.; et al. J. Med. Chem. 1998, 41, 236. (d) Gilbert, A. M.; et
al. J. Med. Chem. 2000, 43, 1203. (e) Bang-Andersen, B.; Ahmadian,
H.; Lenz, S. M.; Stensbøl, T. B.; Madsen, U.; Bogeso, K. P.; Krogsgaard-
Larsen, P. J. Med. Chem. 2000, 43, 4910. (f) Tietze, L. F.; Arlt, M.;
Beller, M.; Glusenkamp, K. H.; Jahde, E.; Rajewsky, M. F. Chem. Ber.
1991, 124, 1215. (g) Kinney, A. W. Tetrahedron Lett. 1993, 34, 2715.
(h) Gardner, S. H.; Freyschmidt-paul, P.; Hoffman, R.; Sundberg, J.
P.; Happle, R.; Nigel, J.; Tobin, D. J. Eur. J. Dermatol. 2000, 10, 443.
(i) Kazumasa, M.; Motonobu, N.; Miyako, N.; Tatsuo, K.; Yoshiki, M.
J. Dermatol. 2002, 29, 661. (j) Xie, J.; Comeau, A. B.; Seto, C. T. Org.
Lett. 2004, 6, 83.
Figure 1. Diacetylferrole complex.
We have also observed that use of excess amine oxide
gives the corresponding cyclic anhydrides (60-80%)
(8) (a) Liebeskind, L. S.; Baysdon, S. L. Tetrahedron Lett. 1984, 25,
1747. (b) Parker, M. S. A.; Rizzo, C. J. Synth. Commun. 1995, 25, 2781.
(c) Periasamy, M.; Rameshkumar, C.; Radhakrishnan, U.; Brunet, J.
J. J. Org. Chem. 1998, 63, 4930. (d) Rameshkumar, C.; Periasamy, M.
Organometallics 2000, 19, 2400. (e) Allen, A. D.; Lai, W. Y.; Ma, J.;
Tidwell, T. T. J. Am. Chem. Soc. 1994, 116, 2625.
(9) (a) Dean, W. D.; Blum, D. J. Org. Chem. 199, 58, 7916. (b) Florac,
C.; Baudy-Floch, M.; Robert, A. Tetrahedron 1990, 46, 445. (c) Herrera,
A.; Hoberg, H. Synthesis 1981, 10, 831.
(10) Periasamy, M.; Mukkanti, A.; Shyam Raj, D. Organometallics
2004, 23, 619.
(12) (a) Tomas, S.; Rotger, M. C.; Gonzalez, J. F.; Deya, P. M.;
Ballester, P.; Costa, A. Tetrahedron Lett. 1995, 36, 2523. (b) Tomas,
S.; Prohens, R.; Deslongchamps, G.; Ballester, P.; Costa, A. Angew.
Chem., Int. Ed. 1999, 38, 2208. (c) Prohens, R.; Martorell, G.; Ballester,
P.; Costa, A. Chem. Commun. 2001, 1456.

Notes
Organometallics, Vol. 23, No. 26, 2004 6325
ligands,13 and versatile starting materials for the syn-
thesis of multifunctional molecules.14 Hence, easy ac-
cessibility of this useful class of compounds via the
procedure reported here should facilitate research in
these areas.
MHz): δ 208.3, 199.9, 196.6, 184.8, 31.2, 27.1, 25.6, 22.1, 13.7.
MS (EI): m/z 152 [M+, 13%].
3d. Yield: 0.43 g (75%). The sample was crystallized from
hexane-ethyl acetate (97:3). Mp: 101-102 °C (lit.8e mp 102.8-
103.2 °C). IR (neat): 1774, 1766 cm-1. 1H NMR (400 MHz): δ
7.8-7.2 (m, 5H); 0.45 (s, 9H). 13C NMR (100 MHz): δ 202.6,
200.3, 199.3, 197.8, 133.5,129.4,129.3 129.2,-1.8. MS (EI): m/z
230 [M+, 8%].
Experimental Section
3e. Yield: 0.38 g (68%). IR (neat): 1778, 1766 cm-1. 1H NMR
(200 MHz): δ 2.87 (t, J ) 7.3, 2H); 1.17-1.67 (m, 6H); 0.92 (t,
J ) 6.9 Hz, 3H); 0.35 (s, 9H). 13C NMR (50 MHz): δ 211.3,
207.7, 201.5, 200.1, 31.7, 29.1, 26.9, 22.2, 13.7; -2.1. MS (EI):
m/z 224 [M+, 10%].
General Procedures. 1H NMR (400 and 200 MHz) and
13C NMR (100 and 50 MHz) spectra were recorded on a Bruker
spectrometer in CDCl3, and TMS was used as reference (δ )
0 ppm). Melting points are uncorrected. IR spectra were
recorded on a JASCO FT-5300 instrument with polystyrene
as reference. Mass spectral analyses were carried out on a VG
7070H mass spectrometer using the EI technique at 70 eV.
Elemental analyses were carried out using a Thermo Finnigan/
Flash EA1112 CHN analyzer. Fe(CO)5 and Me3NO were
supplied by Fluka and Aldrich, respectively. The alkynes used
in the reactions (except heptyne) were prepared by following
the reported procedure.15 THF was distilled over sodium
benzophenone ketyl. Chromatographic purification was con-
ducted by column chromatography using 100/200 mesh silica
gel obtained from Acme Synthetic Chemicals, India. All
reactions and manipulations were carried out under nitrogen
atmosphere. All the yields reported are isolated yields of
materials, judged homogeneous by TLC analyses.
Preparation of Cyclobutenediones 3a-3h. To a solution
of anhydrous Me3NO (0.9 g, 12 mmol) in THF (30 mL) was
dropwise added Fe(CO)5 (1.9 mL, 15 mmol) in THF (40 mL)
over a period of 30 min at -20 °C under dry nitrogen. The
reaction starts with immediate evolution of CO2, and the color
changes from yellow to dark brown. The reaction mixture was
stirred for another 1 h and slowly brought to room tempera-
ture. Diphenylacetylene (0.44 g, 2.5 mmol) was added, and the
contents were further stirred for 10 h at room temperature.
The metal carbonyl complexes were oxidized using CuCl2‚2H2O
(4.2 g, 25 mmol) in acetone (15 mL). A saturated NaCl solution
was added, and the contents were extracted with ether (2 ×
75 mL). The combined organic extract was dried over anhy-
drous Na2SO4 and concentrated under reduced pressure. The
residue was subjected to column chromatography (silica gel,
hexane-EtOAc). Ethyl acetate (1%) in hexane eluted the 3,4-
diphenyl-3-cyclobutene-1,2-dione 3a.
3f. Yield: 0.49 g (70%). IR (neat): 3479, 1789, 1770 cm-1
.
1H NMR (400 MHz): δ 8.2-7.2 (m, 10H); 2.9 (s, 1H); 2.1 (s,
3H). 13C NMR (50 MHz): δ 197.8, 196.5, 195.8, 189.2, 142.6,
133.6, 131.2, 128.9, 128.8, 128.4, 127.6, 124.9, 74.9, 28.2. MS
(EI): m/z 278 [M+, 15%].
3g. Yield: 0.55 g (65%). IR (neat): 3483, 1784, 1768 cm-1
.
1H NMR (400 MHz): δ 8.4-7.3 (m, 15H); 3.2 (s, 1H). 13C NMR
(50 MHz): δ 198.4, 197.5, 195.2, 189.8, 141.4, 133.5, 131, 128.9,
128.8, 128.7, 128.4, 80.5. MS (EI): m/z 340 [M+, 8%]. Anal.
Calcd. for C23H16O3: C, 81.16; H, 4.74. Found: C, 81.22; H,
4.73.
3h. Yield: 0.33 g (57%). IR (neat): 3033, 1776, 1768 cm-1
.
1H NMR (400 MHz): δ 7.3-7.1 (m, 1H); 6.4 (dd, J ) 10.7, 1.5
Hz, 2H); 2.6 (t, J ) 7.5 Hz, 2H); 1.9 (dd, J ) 5.5, 1.5 Hz, 2H);
1.6 (m, 2H); 1.2 (m, 10H); 0.8 (t, J ) 7.0 Hz, 3 H). 13C NMR
(100 MHz): δ 198.2, 197.8, 195.6, 190.4, 146.5, 119.4, 31.7,
29.6, 29.1, 29, 26.5, 26.2, 22.5, 20, 14. MS (EI): m/z 234 [M+,
12%]. Anal. Calcd for C15H22O2: C, 76.88; H, 9.46; Found: C,
77.06; H, 9.47.
Preparation of Cyclic Anhydrides 4a-d. To a solution
of anhydrous Me3NO (1.1 g, 15 mmol) in THF (30 mL) was
dropwise added Fe(CO)5 (1.3 mL, 10 mmol) in THF (40 mL)
over a period of 30 min at -20 °C under dry nitrogen.
Diphenylacetylene (0.44 g, 2.5 mmol) was added and slowly
allowed to reach room temperature. Stirring was furthur
continued for 10 h at room temperature. The metal carbonyl
complexes were oxidized using CuCl2‚2H2O (4.2 g, 25 mmol)
in acetone (15 mL). After usual wokup the residue was
subjected to column chromatography (silica gel, hexane-
EtOAc). Ethyl acetate (1%) in hexane eluted the cyclic anhy-
dride 4a.
3a. Yield: 0.43 g (73%). The sample was crystallized from
4a. Yield: 0.31 g (72%). The sample was crystallized from
hexane-ethyl acetate (97:3). Mp: 95-96 °C (lit.8a-d mp 97 °C).
hexane-ethyl acetate (95:5). Mp: 119-120 °C (lit.9a mp 120-
IR (KBr): 1780 cm-1 1H NMR (200 MHz): δ 8.14 (m, 4H);
.
121 °C). IR (neat): 3117, 1839, 1765 cm-1 1H NMR (200
.
7.45-7.68 (m, 6H). 13C NMR (50 MHz): δ 196.1, 187.4, 134.6,
MHz): δ 7.3-7.9 (m, 5H); 7.0 (s, 1H). 13C NMR (50 MHz): δ
164.5, 163.6, 146.6, 146.5, 133.7, 129.3, 129, 126.4. MS (EI):
m/z 174 [M+, 10%].
131.2, 129.7, 128.7. MS (EI): m/z 235 [M+, 12%].
3b. Yield: 0.24 g (62%). The sample was crystallized from
hexane-ethyl acetate (97:3). Mp: 152-153 °C (lit.8a-d mp 152-
1
4b. Yield: 0.29 g (68%). IR (neat): 3111, 1842, 1772 cm-1
.
153 °C). IR (KBr): 1768 cm-1. H NMR (200 MHz): δ 9.5 (s,
1H NMR (200 MHz): δ 6.5 (s, 1H); 2.5 (t, J ) 7.1 Hz, 2H);
0.8-1.9 (m, 9H). 13C NMR (50 MHz): δ 165.8, 164.0, 153.8,
128.4, 31.1, 26.5, 25.8, 22.1, 13.7. MS (EI): m/z 168 [M+, 12%].
Anal. Calcd for C9H12O3: C, 64.27; H, 7.19. Found: C, 64.25;
H, 7.20.
1H); 7.3-8.0 (m, 5H). 13C NMR (50 MHz): δ 197.7, 196.0,
195.5, 178.3, 134.6, 129.5, 129.4, 128.6.
3c. Yield: 0.19 g (50%). IR (neat): 1778 cm-1. 1H NMR (200
MHz): δ 9.20 (s, 1H); 2.81 (t, J ) 7.3 Hz, 2H); 1.70-1.83 (m,
2H); 1.27-1.40 (m, 4H); 0.82 (t, J ) 7.3 Hz, 3H). 13C NMR (50
4c. Yield: 0.5 g (80%). The sample was crystallized from
hexane-ethyl acetate (95:5). Mp: 156-158 °C (lit.9b mp 156
°C). IR (neat): 1822, 1757, 1637 cm-1. 1H NMR (200 MHz): δ
8.1-7.2 (m, 10H). 13C NMR (50 MHz): δ 164.8, 138.2, 131.1,
129.7, 128.9, 127.2.
(13) Zhang, J.; Zhou, H.-B.; Lu, S.-M.; Luo, M.-M.; Xie, R. G.; Choi,
M. C. K.; Zhou, Z.-Y.; Chan, S. C.; Yang, T.-K. Tetrahedron Asymmetry
2001, 12, 1907.
(14) (a) Liebeskind, L. S.; Baysdon, S. L.; South, M. S. J. Am. Chem.
Soc. 1980, 102, 7397. (b) Liebeskind, L. S.; Mitchell, D.; Foster, B. S.
J. Am. Chem. Soc. 1987, 109, 7908. (c) Foland, L. D.; Karlsson, J. O.;
Perri, S. T.; Schwabe, R.; Xu, S. L.; Patil, S.; Moore, H. W. J. Am. Chem.
Soc. 1989, 111, 975. (d) Liebeskind, L. S. Tetrahedron 1989, 45, 3053.
(e) Zhang, S.; Liebeskind, L. S. J. Org. Chem. 1999, 64, 4042. (f) Mingo,
P.; Zhang, S.; Liebeskind, L. S. J. Org. Chem. 1999, 64, 2145. (g) Wipf,
P.; Hopkins, C. R. J. Org. Chem. 1999, 64, 6881. (h) Tiedemann, R.;
Turnbull, P.; Moore, H. W. J. Org. Chem. 1999, 64, 4030. (i) Kondo,
T.; Nakamura, A.; Okada, T.; Suzuki, N.; Wada, K.; Mitsudo, T. J.
Am. Chem. Soc. 2000, 122, 6319.
4d. Yield: 0.37 g (60%). IR (neat): 1840, 1769 cm-1. 1H NMR
(200 MHz): δ 5.8 (m, 1H); 5.2 (dd, J ) 7.5, 1.5 Hz, 2H); 3.1 (d,
J ) 6.3 Hz, 2H); 2.4 (t, J ) 7.0 Hz, 2H); 1.4 (m, 2H); 1.1 (m,
10H); 0.7 (t, J ) 6.2 Hz, 3H). 13C NMR (50 MHz): δ 165.6,
165.4, 145.2, 141.3, 131.1, 118.2, 31.6, 29.4, 29.1, 28.9, 28.2,
27.6, 24.2, 22.5, 13.8. MS (EI): m/z 250 [M+, 8%].
4e. Yield: 0.46 g (75%). The sample was crystallized from
hexane-ethyl acetate (95:5). Mp: 99-101 °C IR (neat): 1832,
1770 cm-1. 1H NMR (400 MHz): δ 7.59-7.45 (m, 5H); 0.25 (s,
9H). 13C NMR (100 MHz): δ 168.3, 166.6, 156.8, 145.4, 132,
(15) (a) Dehmlow, E. V.; Lissel, M. Tetrahedron 1981, 37, 1653. (b)
Brandsma, L.; Verkruijsse, H. D. Synthesis of Acytylenes, Allenes and
Cumulenes; Elsevier: New York, 1974.

6326 Organometallics, Vol. 23, No. 26, 2004
Notes
130.5, 129.8, 129.3, -0.1. MS (EI): m/z 246 [M+, 10%]. Anal.
Calcd for C13H14O3Si: C, 63.39; H, 5.73; Si 11.4. Found: C,
63.43; H 5.79.
periods or exposure to air leads to decomposition. It was
crystallized from methanol. Mp: 152-155 °C (dec) (lit.10 mp
152-155 °C (dec)). IR (KBr): 2083, 2042, 2005, 1956, 1749
cm-1. 1H NMR (200 MHz): δ 1.9 (s, 6H); 7.18-7.25 (m, 10H).
13C NMR (50 MHz): δ 211.8, 207.7, 205.3, 185.5, 168.4, 130.7,
130.5, 128.5, 127.9, 125.6, 20.6.
Preparation of Acyloxyferrole Complex 5. To a solution
of anhydrous Me3NO (0.9 g, 12 mmol) in THF (30 mL) was
dropwise added Fe(CO)5 (1.9 mL, 15 mmol) in THF (40 mL)
over a period of 30 min at -20 °C under dry nitrogen.
Diphenylacetylene (0.44 g, 2.5 mmol) was added and stirred
for 2 h at room temperature. Then Et3N (1.4 mL, 10 mmol)
and CH3COCl (1 mL, 15 mmol) were added, and the contents
were further stirred for 12 h. Ether (100 mL) was added, and
the reaction mixture was washed successively with H2O (40
mL) and brine (2 × 50 mL), dried over Na2SO4, and concen-
trated under reduced pressure. The residue was subjected to
column chromatography (silica gel, hexane-EtOAc). Ethyl
acetate (1%) in hexane eluted the ferroyl complex 5 (yield 0.72
g, 48%). This complex is relatively stable, but standing for long
Acknowledgment. We are thankful to the CSIR
(New Delhi) for financial support. Support of the UGC
under “University of Potential for Excellence” program
is gratefully acknowledged.
Supporting Information Available: 13C NMR spectra of
compounds 3a-3h, 4a-4e, and 5. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM049429F