New Convenient One-Pot Methods of Conversion of Alkynes to Cyclobutenediones or α,β-Unsaturated Carboxylic Acids Using Novel Reactive Iron Carbonyl Reagents

Article abstract of DOI:10.1021/jo971929d

Reactions of NaHFe(CO)₄/RX or [HFe₃(CO)₁₁]^- reagents with alkynes lead to the formation of the corresponding α,β-unsaturated carboxylic acids and/or the cyclobutenediones. The reagent generated in situ using the NaHFe(CO)₄/CH₃I combination in THF, on reaction with alkynes followed by CuCl₂·2H₂O oxidation, gives the corresponding cyclobutenediones (27-42%) and α,β-unsaturated carboxylic acids (10-22%), whereas the reagent generated using CH₂Cl₂ in place of CH₃I leads to α,β-unsaturated carboxylic acids (37-60%) and their derivatives (35-55%) at 25°C. The same reagent system in the presence of acetic acid (4 equiv) yields the corresponding cyclobutenedione (33%). The reaction using Me₃SiCl gives the corresponding α,β-unsaturated carboxylic acids (45-54%) at 25°C and the corresponding cyclobutenediones (51-63%) at 60°C. Interestingly, the reaction of the [HFe₃(CO)₁₁]^- species generated using Fe(CO)₅/NaBH₄/CH₃COOH, with alkynes at 25°C, followed by CuCl₂·2H₂O oxidation gives the corresponding cyclobutenediones (60-73%). The possible intermediates and pathways for the formation of α,β-unsaturated carboxylic acids and cyclobutenediones are discussed.

Full text of DOI:10.1021/jo971929d

4
930
J . Org. Chem. 1998, 63, 4930-4935
New Con ven ien t On e-P ot Meth od s of Con ver sion of Alk yn es to
Cyclobu ten ed ion es or r,â-Un sa tu r a ted Ca r boxylic Acid s Usin g
Novel Rea ctive Ir on Ca r bon yl Rea gen ts
,
†
†
Mariappan Periasamy,* Chellappan Rameshkumar,
†
‡
Ukkiramapandian Radhakrishnan, and J ean-J acques Brunet
School of Chemistry, University of Hyderabad, Central University P.O., Hyderabad 500 046, India, and
Labratoire de Chimie de Coordination du CNRS, Unite No. 8241, 205 Route de Narbonne,
3
1077 Toulouse Cedex, France
Received October 20, 1997
4 3
/RX or [HFe
(CO)11]- reagents with alkynes lead to the formation of the
Reactions of NaHFe(CO)
corresponding R,â-unsaturated carboxylic acids and/or the cyclobutenediones. The reagent gener-
ated in situ using the NaHFe(CO) /CH I combination in THF, on reaction with alkynes followed
by CuCl ‚2H O oxidation, gives the corresponding cyclobutenediones (27-42%) and R,â-unsaturated
carboxylic acids (10-22%), whereas the reagent generated using CH Cl in place of CH I leads to
4
3
2
2
2
2
3
R,â-unsaturated carboxylic acids (37-60%) and their derivatives (35-55%) at 25 °C. The same
reagent system in the presence of acetic acid (4 equiv) yields the corresponding cyclobutenedione
(
5
3
33%). The reaction using Me SiCl gives the corresponding R,â-unsaturated carboxylic acids (45-
4%) at 25 °C and the corresponding cyclobutenediones (51-63%) at 60 °C. Interestingly, the
-
reaction of the [HFe
3
(CO)11] species generated using Fe(CO)
5
/NaBH
4 3
/CH COOH, with alkynes at
2
5 °C, followed by CuCl
2
‚2H
2
O oxidation gives the corresponding cyclobutenediones (60-73%). The
possible intermediates and pathways for the formation of R,â-unsaturated carboxylic acids and
cyclobutenediones are discussed.
In tr od u ction
There has been immense interest in the use of iron
followed by CuCl
2
2
‚2H O oxidation gives the correspond-
ing cyclobutenediones (27-42%) and the R,â-unsaturated
carboxylic acids (10-22%) (eq 1).5
1
carbonyl reagents in recent years. The readily accessible
-
HFe(CO)
transformations. It has been reported that the reaction
of [Et N]HFe(CO) with CH I in CH CN leads to the
formation of Fe(CO) (CH CN) and CH
.2 It appeared that
this method of generation of “Fe(CO) ” in situ would serve
4
is a versatile reagent used in many organic
1
a
4
4
3
3
4
3
4
4
as a simple alternate method for synthetic applications
3
of these species. In continuation of our efforts on the
4
synthesis and utilization of reactive iron carbonyls, we
became interested in examining the reactivity pattern
of “Fe(CO) ” species generated using the NaHFe(CO) /
4 4
RX system with alkynes.
The transformation has been found to be general.
Several substituted alkynes, propargyl alcohol deriva-
tives, and enynes were converted to the corresponding
cyclobutenediones and R,â-unsaturated carboxylic acids.
We have investigated these transformations further to
standardize conditions to obtain the cyclobutenediones
or R,â-unsaturated carboxylic acids from alkynes in
acceptable yields. The results are described here.
4 3
Preliminary experiments using the NaHFe(CO) /CH I
reagent combination revealed that the reaction of the
species generated in this way with alkynes at 60 °C
†
University of Hyderabad.
Laboratoire de Chimie de Coordination du CNRS.
‡
(1) (a) Brunet, J . J . Chem. Rev. 1990, 90, 1041. (b) Khumtaveeporn,
K.; Alper, H. Acc. Chem. Res. 1995, 28, 414. (c) Liebeskind, L. S.;
Baysdon, S. L.; South, M. S.; Iyer, S.; Leeds, J . P. Tetrahedron 1985,
4
9
1, 5839. (d) Fatiadi, A. J . J . Res. Natl. Inst. Stand. Technol. 1991,
6, 1.
Resu lts a n d Discu ssion
(2) Whitmire, K. H.; Lee, T. R.; Lewis, E. S. Organometallics 1986,
R ea ct ion of Na H F e(CO)
4 2 2
/CH Cl Syst em w it h
5
, 987.
Alk yn es. It has been reported by Whitmire et. al. that
(3) (a) Poliakoff, M.; Turner, J . J . J . Chem. Soc., Dalton Trans. 1974,
-
-
2
8
4
1
276. (b) Black, J . D.; Braterman, P. S, J . Organomet. Chem. 1975,
5, C7. (c) Kane, V. V.; Light, J . R. C.; Whiting, M. C. Polyhedron 1985,
, 533. (d) Pearson, A. J .; Dubbert, R. A. Organometallics 1994, 13,
656. (e) Pearson, A. J .; Perosa, A. Organometallics 1995, 14, 5178. (f)
HFe(CO)
4 3 2 2
slowly decomposes to [HFe (CO)11] in CH Cl
” intermediate (eq 2).6
through the “Fe(CO)
4
We have carried out experiments using CH
2 2
Cl in place
Elzinga, J .; Hogeveen, H. J . Chem. Soc., Chem. Commun. 1997, 705.
of CH I to examine the difference in reactivity, if any. It
was observed that the species generated in situ by
3
(
g) Narasaka, K.; Shibata, T. Chem. Lett. 1994, 315.
4) (a) Devasagayaraj, A.; Periasamy, M. Trans. Met. Chem. 1991,
6, 503. (b) Periasamy, M.; Devasagayaraj, A.; Radhakrishnan, U.
(
1
Organometallics 1993, 12, 1424. (c) Periasamy, M.; Reddy, M. R.;
Radhakrishnan, U.; Devasagayaraj, A. J . Org. Chem. 1993, 58, 4997.
(5) Periasamy, M.; Radhakrishnan, U.; Brunet, J . J .; Chauvin, R.;
El-Zaizi, A. W. J . Chem. Soc., Chem. Commun. 1996, 1499.
(6) Whitmire, K. H.; Lee, T. R. J . Organomet. Chem. 1985, 282, 95.
(d) Radhakrishnan, U.; Periasamy, M. Organometallics 1997, 16, 1800.
S0022-3263(97)01929-4 CCC: $15.00 © 1998 American Chemical Society
Published on Web 06/26/1998

Conversion of Alkynes to Cyclobutenediones
J . Org. Chem., Vol. 63, No. 15, 1998 4931
Ta ble 1. Rea ction of Na HF e(CO)4/CH2Cl2 w ith RCtCR′
in THF
4 2 2
treating NaHFe(CO) (1 equiv) with CH Cl (13 equiv)
in THF on reaction with terminal and internal alkynes
gave the hydrocarboxylated products in a regio- and
stereocontrolled fashion after CuCl
2
‚2H
2
O oxidation (eq
7
3
). The reaction proceeds satisfactorily under mild
conditions at 25 °C. The results obtained using repre-
sentative terminal and internal alkynes are summarized
in Table 1.
In the case of diphenylacetylene (entry 1, Table 1), the
cyclobutenedione 1a was isolated as a side product (21%).
However, with other alkynes (entries 2-4, Table 1), the
reaction proceeds well at 25 °C to give â-(E)-alkenoic
acids, and only a trace of cylobutenedione (<2%) was
isolated. 1-Decyne undergoes R-carbonylation (i.e., at the
terminal position), but the reaction with 1-heptyne leads
to â-carbonylation (entries 4 and 5, Table 1). The
regioselective carbonylation is interesting since only one
of the isomers is formed out of the four regio- and
stereoisomers possible for the transformation. It is also
of interest to note the difference in the regioselectivities
in the case of 1-heptyne and 1-decyne. Previously, it has
been reported by Alper et al. that regio- and stereose-
lectivity of certain Pd-catalyzed hydrocarboxylations is
a
The regio- and stereoselectivity of the product 1b were
confirmed by analysis of spectral data and comparison with the
reported data. The regio- and stereoselectivity of the products
2b and 3b were confirmed by comparison of the spectral data
obtained for the corresponding methyl ester, which is prepared
following a reported procedure.1 The regio- and stereochemistry
of products 4b and 5b were confirmed by the analysis of spectral
data and comparisons with the reported data.8 b Yields are of
products isolated by column chromatography and based on the
amount of alkynes used.
11
1
2a
2b
8
dependent on the steric bulk of substitutents. The
â-silyl-(E)-R,â-unsaturated carboxylic acids of the type 2b
and 3b are potential intermediates in many reactions as
they contain silyl and carbonyl moieties in the adjacent
carbon atoms. Many efforts have been directed previ-
ously toward the synthesis of such compounds.9
The presence of CH Cl as coreactant is required for
2 2
this transformation. It was observed that the reaction
leads to a low yield of carboxylic acid (<10%) without
ester 1c in addition to the corresponding cyclobutenedi-
one 1a . The corresponding amide 1d was obtained when
diethylamine was used instead of CH OH. A similar
3
transformation was also observed with 1-heptyne (Table
2).
CH
2 2
Cl . As mentioned earlier, it has been observed by
2
Whitmire et al. that the reaction of [Et
CH Cl affords [HFe (CO)11] . Presumably, the reactive
4
4
N]HFe(CO) with
-
R ea ct ion of Na H F e(CO)
Alk yn es. We have also examined the reactivity of the
species generated using the NaHFe(CO) /Me SiCl com-
4 3
/Me SiCl Syst em w it h
2 2 3
species responsible for the formation of both cyclobutene-
diones and carboxylic acids may be derived from these
species.
4
3
bination to compare the results obtained using the alkyl
halides. It was observed that the intermediate complex,
]-
It is well-known that acylferrate anion [RCOFe(CO)
4
generated in situ by treating NaHFe(CO)
4
(3 equiv ) with
reacts with I
CH OH and R
2
in the presence of nucleophiles such as
2
NH to give the corresponding carboxylic
Me SiCl (3 equiv), reacts with terminal and internal
3
3
1
0
alkynes (1 equiv) at 25 °C to yield R,â-unsaturated
carboxylic acids with excellent regio- and stereoselectivi-
ties (eq 5).
acid derivatives. A similar type of reactivity may be
anticipated for the intermediate formed here. Regio- and
stereoselective synthesis of R,â-unsaturated carboxylic
acid derivatives could be achieved if such generalizations
could be made. Indeed, this has been observed (eq 4).
The intermediate generated in situ (eq 4) upon I
treatment in the presence of methanol gives the methyl
2
(
7) Periasamy, M.; Radhakrishnan, U.; Rameshkumar, C.; Brunet,
J . J . Tetrahedron Lett. 1997, 38, 1623.
8) (a) Amer, I.; Alper, H. J . Organomet. Chem. 1990, 383, 573. (b)
Zargarian, D.; Alper, H. Organometallics 1993, 12, 712.
9) Takeuchi, R.; Sugiura, M.; Ishii, N.; Sato, N. J . Chem. Soc.,
Chem. Commun. 1992, 1358 and references therein.
10) Collman, J . P, Acc. Chem. Res. 1975, 8, 342.
(
The reaction was found to be general, and various
alkynes were converted to (E)-alkenoic acids (Table 3).
This reactivity pattern is similar to that realized using
(
(
4 2 2
NaHFe(CO) /CH Cl reagent system. In all these cases,

4
932 J . Org. Chem., Vol. 63, No. 15, 1998
Periasamy et al.
Ta ble 2. Rea ction of Na HF e(CO)4/CH2Cl2/RCtCR′ w ith
was observed. The yields (45-54%) of the R,â-unsatur-
ated carboxylic acids realized using NaHFe(CO)
/Me SiCl
4 3
I2/ROH or R2NH
(
Table 3) are slightly better in some cases than the yields
obtained with the NaHFe(CO) /CH Cl system (Table 1).
However, the latter system has the advantage that it
requires the use of the inexpensive CH Cl
4
2
2
2
2
.
We have observed an interesting temperature effect
for this reaction. It was found that the reagent, prepared
using NaHFe(CO)
diphenylacetylene followed by CuCl
produced cyclobutenedione 1a (63%) as the only product
eq 6).
4
/Me
3
SiCl at 60 °C, on reaction with
2
‚2H O oxidation
2
(
The reaction was found to be general. The correspond-
ing cyclobutenediones were obtained in relatively good
yields using representative terminal, internal, and sub-
stituted alkynes (Table 4). It may be of interest to note
a
1
Products were identified by analysis of spectral data (IR, H
1
3
NMR, C NMR, and MS). The amide 2d was identified by
comparing the spectral data with that of the reported data.
Yields are of products isolated by column chromatography and
based on the amount of alkynes used.
that Graham et al. reported that the R
heating gives an Fe(CO) species that readily undergoes
trimerization to Fe
Rea ction of th e [HF e
Usin g F e(CO) /Na BH /CH
further examine the possibility of whether an
3 4
Si(H)Fe(CO) on
1
1
b
4
1
3-15
3
(CO)12
(CO)11]- Rea gen t P r ep a r ed
COOH w ith Alk yn es. To
.
3
Ta ble 3. Rea ction of Na HF e(CO)4/Me3SiCl w ith RCtCR′
a t 25 °C
5
4
3
-
[
HFe
3
(CO)11
]
related species is responsible for the
formation of cyclobutenedione, we decided to prepare the
-
[
[
HFe
HFe
3
(CO)11] species to examine its reactivities. The
-
3
(CO)11] species has been previously prepared using
/NaBH /CH OH/CH COOH in THF and isolated
as the PPN salt in 73% yield (eq 7).
Fe(CO)
5
4
3
3
1
8
We have observed that the [HFe
prepared in situ using Fe(CO) /NaBH /CH
with alkynes to give the corresponding cyclobutenediones
in good yields (60-73%) after CuCl ‚2H O oxidation (eq
). Several alkynes were converted to the correspond-
3
(CO)11]- species,
COOH, reacts
5
4
3
2
2
1
9
8
ing cyclobutenediones. The results are summarized in
the Table 5.
Evidently, the reagent system can tolerate unmasked
functional groups such as hydroxy group (entries 5a and
6a, Table 5). The formation of cyclobutenedione from an
enyne shows that the reagent reacts with alkynes with-
a
Products were identified by analysis of the spectral data.
b
Yields are of products isolated by column chromatography using
hexane/ethyl acetate (97:3) as eluent and based on the amount of
alkynes used. The compound 1b was identified by comparison
of the spectral data with the reported data.
c
1
1 d
The regio- and
stereoselectivity of the product 2b was confirmed by comparison
with the spectral data obtained for the methyl ester with the data
1
2a
e
(11) Handbook of Proton NMR Spectra and Data; Asahi Research
Center Co., Ltd., Ed.; Academic Press: Tokyo, 1986; Vols. 1-9.
reported.
The regio- and stereoselectivity of the products 4b
and 5b were confirmed by analysis of spectral data and comparison
(
12) (a) Takeuchi, R.; Sugiura, M. J . Chem. Soc., Perkin Trans. 1
8
with the reported data.
1
993, 1031. (b) Ono, N.; Yamada, T.; Saito, T.; Tanaka, K.; Kaji, A.
Bull. Chem. Soc. J pn. 1978, 51, 2401.
the corresponding cyclobutenediones were obtained in
very low yields (<5%). Even in the case of dipheny-
lacetylene, the R,â-unsaturated carboxylic acid 1b was
isolated as the major product (53%) in addition to only
traces (<5%) of the corresponding cyclobutenedione 1a .
The stereochemistry of the (E)-alkenoic acids was
(13) Nasta, M. N.; MacDiarmid, A. G. J . Am. Chem. Soc. 1971, 93,
813.
2
(
(
14) J etz, W.; Graham, W. A. G. J . Am. Chem. Soc. 1969, 91, 3375.
15) J etz, W.; Graham, W. A. G. Inorg. Chem. 1971, 10, 4.
(16) (a) Hoberg, H.; Herrera, A. Angew. Chem., Int. Ed. Engl. 1980,
9, 927. (b) Herrera, A.; Hoberg, H. Synthesis 1981, 831.
1
(
17) (a) Parker, M. S. A.; Rizzo, C. J . Synth. Commun. 1995, 25,
2
781. (b) Ried, W.; Schmidt, A. H. Angew. Chem., Int. Ed. Engl. 1972,
confirmed by comparison of 1 C and H NMR spectral
3
1
11, 997.
(18) Hodali, H. A.; Arcus, C.; Shriver, D. F. Inorg. Synth. 1980, 20,
18.
19) Preliminary communication: Periasamy, M.; Rameshkumar,
C.; Radhakrishnan, U. Tetrahedron Lett. 1997, 38, 7229.
data with that of the reported compounds.8
,11,12
Again,
2
in the case of 1-decyne (entry 4, Table 3), R-carbonylation
i.e., at the terminal position) rather than â-carbonylation
(
(

Conversion of Alkynes to Cyclobutenediones
J . Org. Chem., Vol. 63, No. 15, 1998 4933
Ta ble 4. Rea ction of Na HF e(CO)4/Me3SiCl w ith Alk yn es
Ta ble 5. Rea ction of F e(CO)5/Na BH4/CH3COOH w ith
Alk yn es
a t 60 °C
a
Products were identified by the spectral data. b Yields are of
products isolated by column chromatography and based on the
amount of alkynes used. c The spectral data of products 8a , 9a ,
and 10a are comparable to the spectral data reported for the
a
Products were identified by analyzing the spectral data (IR,
1
13
b
16a d
H NMR, C NMR, and MS). Yields are of products isolated by
product 7a .
analysis of spectral data and comparison with the reported data.
The cyclobutenedione 11a was identified by
1
6b
column chromatography using hexane/ethyl acetate (98:2) as
eluent and based on the amount of alkynes used. c The cy-
clobutenedione 1a was identified by analysis of spectral data and
e
For the cyclobutenedione 6a , HRMS data were also obtained.
1
6 d
comparisons with the reported data.
For the cyclobutenedione
a , HRMS data were also obtained. The spectral data of product
(IR, NMR) were identical to the data reported for this
e
2
7
a
1
7a
compound.
The spectral data of product 10a are comparable
to the spectral data reported for the cyclobutenedione 7a .
out affecting the olefin moiety (entry 4a). The yields of
the cyclobutenediones obtained following this method are
somewhat better than that realized using the NaH-
Fe(CO)
the NaHFe(CO)
in turn is prepared from Fe(CO)
preparation of the reactive species from the Fe(CO)
NaBH /CH COOH combination is relatively less compli-
cated. Further, in the latter method the reaction is
carried out at ambient conditions and hence should be
more convenient for synthetic applications.
4
/Me
3
SiCl system (Table 4). Moreover, whereas
preparation requires Na Fe(CO) , which
/Na/naphthalene, the
case, the use of an additional amount of CH
3
COOH in
4
2
4
the reaction using NaHFe(CO) /CH Cl should also give
4
2
2
5
similar results. Indeed, this was observed. The corre-
sponding cyclobutenedione was obtained in 33% yield,
and the R,â-unsaturated carboxylic acid was not formed
under these conditions (eq 9).
5
/
4
3
The UV spectra recorded for the reaction mixture in
all reagent combinations described above exhibit char-
-
acteristic absorptions reported for [HFe
3
(CO)11] in solu-
tion.20 If the reactive species is derived from this reagent,
then the reactivity difference between the species gener-
ated using Fe(CO)
reagent prepared using NaHFe(CO)
difficult to rationalize. The reaction of the former
combination with alkynes leads to cyclobutenediones (eq
5
/NaBH
4
/CH
3
COOH in THF and the
/CH Cl in THF is
Although the nature of the reactive species is not
clearly understood, it may be of interest to compare the
results with previous reports on the reaction of iron
carbonyls with alkynes so as to provide a working
hypothesis to rationalize the transformations. It has
4
2
2
9
), and the latter results in the R,â-unsaturated carboxy-
lic acids (eq 3). Probably, the CH COOH used to destroy
the excess NaBH may play a role in the formation of
the reactive species from [HFe
3
been reported that Fe(CO) reacts with alkynes to give
5
4
the corresponding cyclobutadiene-Fe(CO) complexes or
3
-
3
(CO)11] . If this is the
cyclopentadienone-Fe(CO) complexes under different
3
conditions.21 Whereas di-tert-butylacetylene on reaction
(20) Case, J . R.; Whiting, M. C. J . Chem. Soc. 1960, 4632.
2 9 3 2 2 2 6
with Fe (CO) or Fe (CO)12 gives the (t-Bu C )Fe (CO)

4
934 J . Org. Chem., Vol. 63, No. 15, 1998
Periasamy et al.
Sch em e 1
Sch em e 2
Presumably, heating of the reaction mixture after
addition of Me SiCl (eq 6) and decomposition of the iron
carbonyl species formed using Fe(CO) /NaBH with acetic
acid (eq 8) may give another reactive iron carbonyl
species, which on reaction with alkyne followed by CuCl
O oxidation results in the formation of cyclobutene-
3
2 2 2 2 4
or (t-Bu C ) Fe (CO)
complexes,22 acetylene and mono-
substituted acetylenes have been reported to give the
corresponding tropone derivatives.23 A mixture of 2,5-
and 2,6-disubstituted quinones is obtained in the photo-
5
4
2
‚
2
H
2
diones. However, the mechanistic proposals and inter-
mediates suggested can be only tentative.
chemical reaction of Fe(CO)
alkynes. The quinones have been also obtained in 30%
yield in the reaction of alkynes with Fe(CO) in aqueous
alkali at 80-90 °C.24 However, acetylene gives the dienol
5
with some monosubstituted
5
Con clu sion s
3
complex I at room temperature, which after FeCl oxida-
The reaction of the reagent generated using NaH-
tion in ether yields cyclobutenedione.25 It has been
reported that the yields of the dienol complexes I were
poor for higher alkynes even after a long reaction time
Fe(CO)
carboxylic acids [(E)-isomer] (37-60% yields) in a regio-
and stereoselective manner after CuCl ‚2H O oxidation.
4 2 2
and CH Cl with alkynes gave R,â-unsaturated
2
2
(
3 days). More recent studies reveal that the complex I
This reagent system was also demonstrated to be useful
in the synthesis of certain R,â-unsaturated carboxylic
esters and amides, albeit in moderate yields. The reac-
2
6
is formed as one among more than 10 products. We
have observed that the use of FeCl in the place of CuCl
O (eq 8) leads a complex mixture of products. How-
3
2
‚
2
H
2
tion of NaHFe(CO)
4
/Me
3
SiCl and alkynes at 25 °C,
ever, the possibility of the intermediates of the type I or
II cannot be ruled out for the transformation reported
here.
followed by CuCl ‚2H
2
2
O oxidation, gave the correspond-
ing R,â-unsaturated carboxylic acids (45-54% yields)
with good regio- and stereoselectivity. The yields are
slightly better than that obtained using the NaHFe(CO)
CH Cl system in some cases. However, the latter
method requires the use of the inexpensive CH Cl and
4
/
2
2
2
2
hence is advantageous for synthetic applications. It was
also observed that addition of alkynes to the species
4 3
generated in the reaction of NaHFe(CO) /Me SiCl at 60
°
C followed by CuCl O oxidation led to the corre-
2
‚2H
2
sponding cyclobutenediones. The cyclobutenediones have
been also obtained in 60-73% yields in the reaction of
A tentative mechanistic pathway for the formation of
cyclobutenediones can be visualized as shown in Scheme
5 4 3
alkynes with the Fe(CO) /NaBH /CH COOH system. The
method is more convenient for application than the
method using NaHFe(CO) /Me SiCl system, and the
1
. The species of the type II could result from coordina-
4
3
tion of the alkyne moiety to the iron carbonyl species
followed by carbon monoxide insertion.
yields are also better in some cases.
It is well-known that cyclobutenediones and their
adducts are highly versatile starting materials for the
synthesis of substituted naphthalenes, phenols, catechols,
The formation of R,â-unsaturated carboxylic acids may
take place through hydrometalation of the alkynes by
-
[HFe
3
(CO)11
]
produced under the reaction conditions
27
heterocycles, and polycyclic aromatics. It has been also
(Scheme 2).
reported that cyclobutenediones might show some bio-
logical activity.28 For instance, it was suggested that
cyclobutenedione derivatives might show interesting
antitumor properties.29 Accordingly, the methods de-
scribed here for the synthesis of cyclobutenediones should
be useful for further synthetic applications.
(
21) (a) Hubel, W.; Braye, E. H. J . Inorg. Nucl. Chem. 1959, 10, 250.
b) Weiss, E.; Hubel, W. Chem. Ber. 1962, 95, 1179. (c) Braye, E. H.;
Hubel, W. J . Organomet. Chem. 1965, 3, 25.
22) (a) Cotton, F. A.; J amerson, J . D.; Stults, B. R. J . Am. Chem.
(
(
Soc. 1976, 98, 1774. (b) Nicholas, K.; Bray, L. S.; Davis, R. E.; Pettit,
R. J . Chem. Soc., Chem. Commun. 1971, 608.
(
23) (a) Braye, E. H.; Hubel, W. J . Organomet. Chem. 1965, 3, 25.
b) Smith, D. L.; Dahl, L. F. J . Am. Chem. Soc. 1962, 84, 1743. (c)
Wiss, E.; Merenyi, R. G.; Hubel, W. Chem. Ind. (London) 1960, 407.
24) (a) Reppe, W.; Vetter, H. J ustus Liebigs Ann. Chem. 1953, 582,
(
(27) (a) Lee, K.; Turnbull, P.; Moore, H. W. J . Org. Chem. 1995, 60,
461. (b) Sun, L.; Liebeskind, L. S. J . Org. Chem. 1995, 60, 8194. (b)
Sun, L.; Liebeskind, L. S. Tetrahedron Lett. 1997, 38, 3663. (c)
Paquette, L. A..; Tae, J . Tetrahedron Lett. 1997, 38, 3151. (d) Pacquette,
L. A.; Doyon, J . J . Org. Chem. 1997, 62, 1723. (e) Zhang, D.; Llorente,
I.; Liebeskind, L. S. J . Org. Chem. 1997, 62, 4330.
(
1
4
33. (b) Victor, R.; Shoshan, R. B.; Sarel, S, Tetrahedron. Lett. 1973,
211.
(
25) Whiting, M. C. Chem. Weekblad. 1963, 59, 119.
(
26) (a) Sternberg, H. W.; Friedel, R. A.; Markby, R.; Wender, I. J .
(28) (a) Kraus, J . L. Tetrahedron Lett. 1987, 28, 1765. (b) Cole, R.
J .; Kirksey, J . W.; Cutler, H. G.; Doupnik, B. L.; Peckham, J . C. Science
1973, 179, 1324.
Am. Chem. Soc. 1956, 78, 3621. (b) Aime, S.; Milone, L.; Sappa, E.;
Tiripicchio, A.; Lanfredi, A. M. M. J . Chem. Soc., Dalton Trans. 1979,
1
664.
(29) Kraus, J . L. Tetrhedron Lett. 1985, 26, 1867.

Conversion of Alkynes to Cyclobutenediones
J . Org. Chem., Vol. 63, No. 15, 1998 4935
Exp er im en ta l Section
The regio- and stereochemistry of the product 2d were
confirmed by the analysis of spectral data and comparison with
Gen er a l Meth od s. 1H (200 MHz) and 13C NMR (50 MHz)
11
the reported data.
spectra were taken in CDCl
as reference (δ ) 0 ppm). The chemical shifts are reported in
ppm on the δ scale relative to CDCl (77.0 ppm), and coupling
3
unless otherwise stated with TMS
Reaction of NaHFe(CO)
en e a t 25 °C. The NaHFe(CO)
acidification of Na Fe(CO) (7.5 mmol) with CH
mmol, 0.39 g) in THF (30 mL)] was treated with Me
4
/Me
3
SiCl with Diph en ylacetyl-
(7.5 mmol) [generated by
COOH (6
SiCl (7.5
4
3
2
4
3
constants are reported in hertz. Melting points are uncor-
rected. Chromatographic purification was conducted by col-
umn chromatography using 100-200 mesh silica gel obtained
from Acme Synthetic Chemicals, India. The alkynes used in
the reactions (except 1-heptyne) were prepared by following a
3
mmol, 0.81 g) under nitrogen atmosphere. After 1 h, diphe-
nylacetylene (2.5 mmol, 0.45 g) was added, and the contents
were stirred for 8 h at 25 °C. The metal carbonyl complex
was decomposed using CuCl
15 mL). Saturated aqueous NaCl was added, and the result-
ing solution was extracted with ether, washed with brine, dried
over anhydrous MgSO , and concentrated. The residue was
2
‚2H
2
O (20 mmol, 3.4 g) in acetone
3
0
reported procedure. THF supplied by E-Merck, India, was
distilled over sodium-benzophenone ketyl before use. Iron
pentacarbonyl samples supplied by Fluka and Aldrich were
used. Naphthalene supplied by LOBA-Chemie, India, was
sublimed before use. All reactions and manipulations were
conducted under a dry nitrogen atmosphere. All yields
reported are isolated yields of materials judged homogeneous
by TLC, IR, and NMR spectroscopy.
(
4
subjected to column chromatography. A trace (<5%) of the
corresponding cyclobutenedione 1a was isolated using ethyl
acetate (1%) in hexane. The R,â-unsaturated carboxylic acid
1
b (54%, 0.3 g) was isolated using ethyl acetate (2%) in hexane.
The above procedure was followed for the conversion of other
alkynes to the corresponding R,â-unsaturated carboxylic acids,
and the results are summarized in Table 3. The spectral data
were identical to those obtained for the samples previously
Rea ction of Na HF e(CO)
th e P r esen ce of CH Cl . The NaHFe(CO)
30 mL) [generated by acidification of Na Fe(CO)
COOH (6 mmol, 0.39 g)] was treated with 5 mL of
4
w ith Dip h en yla cetylen e in
(6 mmol) in THF
(6 mmol)
2
2
4
(
2
4
with CH
3
isolated using the NaHFe(CO)
Reaction of NaHFe(CO) /Me
en e a t 60 °C. The NaHFe(CO)
generated by acidification of Na
CH COOH (6 mmol, 0.39 g)] was treated with Me
4 2 2
/CH Cl reagent system.
2 2
CH Cl under nitrogen atmosphere. After 1 h, diphenylacety-
lene (2.5 mmol, 0.45 g) was added, and the contents were
heated to 50 °C and stirred for 8 h. The metal carbonyl
4
3
SiCl with Diph en ylacetyl-
4
(7.5 mmol) in THF (30 mL)
[
2
Fe(CO)
4
(7.5 mmol) with
SiCl (7.5
complex was decomposed using CuCl
in acetone (15 mL). Saturated aqueous NaCl was added, and
the resulting solution was extracted with ether, washed with
2
2
‚2H O (20 mmol, 3.4 g)
3
3
mmol, 0.81 g) under nitrogen atmosphere. The reaction
mixture was stirred for 1 h at 50 °C; after the reaction mixture
was cooled, diphenylacetylene (2.5 mmol, 0.45 g) was added,
and the contents were stirred for 8 h at 60 °C. The metal
4
brine, dried over anhydrous MgSO , and concentrated. The
residue was subjected to column chromatography. Ethyl
acetate (1%) in hexane eluted the cyclobutenedione 1a (21%,
carbonyl complex was decomposed using CuCl
mmol, 3.4 g) in acetone (15 mL). Saturated aqueous NaCl was
added, and the resulting solution was extracted with ether. It
2
2
‚2H O (20
0
.25 g), and R,â-unsaturated carboxylic acid 1b (60%, 0.387)
11
was isolated using ethyl acetate (2%) in hexane.
1
6a
1
a : mp 95-96 °C (lit. mp 97 °C); IR (KBr) 1780 cm-1; 1H
4
was washed with brine, dried over anhydrous MgSO , and
concentrated. The residue was subjected to column chroma-
tography. The cyclobutenedione 1a (63%, 0.383 g) was isolated
13
NMR δ 7.45-7.68 (m, 6H), 8.14 (m, 4H); C NMR δ 128.7,
1
29.7, 131.2, 134.6, 187.4, 196.1; MS(EI) m/z 235 (M + 1), 179
(B).
using ethyl acetate (1%) in hexane.
1
b: mp 171.5 °C (lit.31 mp 172-173 °C); IR (KBr) 1678 cm-1;
-
Rea ction of [HF e
3
(CO)11
]
w ith Alk yn es. The Fe(CO)
5
1
13
H NMR δ 7.1-7.4 (m, 10H), 7.9 (s, 1H); C NMR δ 128.1,
(
2.9 g, 15 mmol) in THF (15 mL) was added dropwise for 1 h
to NaBH (0.567 g, 15 mmol) in THF (50 mL) and stirred for
h at 25 °C under nitrogen atmosphere. Acetic acid (2.7 g,
1
1
C
28.3, 128.7, 129.5, 129.8, 130.9, 131.7, 134.4, 135.4, 142.6,
4
73.5; MS(EI) m/z 224 (M), 179 (B). Anal. Calcd for
: C, 80.30; H, 5.35. Found: C, 80.04; H, 5.80.
The above procedure was followed for the conversion of other
8
4
1
15
H
12
O
2
5 mmol) was added and the mixture stirred for 30 min.
-Heptyne (0.24 g, 2.5 mmol) was added, and the contents were
alkynes to the corresponding R,â-unsaturated carboxylic acids.
The regio- and stereochemistry of the products 2b and 3b were
confirmed by comparing the spectral data obtained for the
further stirred for 12 h. The metal carbonyl complex was
decomposed using CuCl ‚2H O (6.8 g, 40 mmol) in acetone (25
2
2
mL). Saturated aqueous NaCl was added, and the contents
were extracted with ether. The combined organic extract was
washed with brine, dried, and concentrated. The residue was
subjected to column chromatography (silica gel, hexane/ethyl
1
2
methyl ester of 2b with the reported data. The stereo- and
regiochemistry of the products 4b and 5b were confirmed by
the analysis of spectral data and comparison with the reported
8
data.
acetate). Ethyl acetate (1%) in hexane eluted cyclobutenedione
Rea ction of Na HF e(CO)
en e a n d I /MeOH. The NaHFe(CO)
mL) [generated by acidification of Na Fe(CO)
CH COOH (6 mmol, 0.39 g)] was treated with 5 mL of CH
4
/CH
2
Cl
2
w ith Dip h en yla cetyl-
(6 mmol) in THF (30
(6 mmol)] with
Cl
16a
7
a (73%, 0.275 g).
2
4
a : yield 56% (0.21%); IR (neat): 1778 cm- ; H NMR δ
1
1
7
2
4
0
2
2
8
.82 (t, J ) 7.3, 3H), 1.27-1.40 (m, 4H), 1.70-1.83 (m, 2H),
.81 (t, J ) 7.3 Hz, 2H), 9.20 (s, 1H); 13C NMR δ 13.7, 22.1,
5.6, 27.1, 31.2, 184.8, 196.6, 199.9, 208.3; MS(EI) m/z 152 (M),
1 (B).
3
2
2
under nitrogen atmosphere. After 1 h, diphenylacetylene (2.5
mmol, 0.45 g) was added, and the contents were heated to 50
°
C and stirred for 8 h. The contents were cooled to room
temperature (25 °C) and then treated with MeOH (5 mL) and
(5 mmol, 1.27 g) in THF. The metal carbonyl complex was
decomposed using CuCl O (20 mmol, 3.4 g) in acetone (15
Ack n ow led gm en t. We thank the UGC and CSIR
I
2
‚2H
2
(New Delhi) for financial support for the work in
Hyderabad. This work is also supported by the Special
Assistance Program of the UGC (New Delhi). The work
on the use of the NaHFe(CO)4 reagent for the prepara-
tion of reactive iron carbonyls was initiated during a
short visit of M. P. to Toulouse, France. We are grateful
to the CNRS, France, for support.
2
mL). Saturated aqueous NaCl was added, and the resulting
solution was extracted with ether, washed with brine, dried
4
over anhydrous MgSO , and concentrated. The residue was
subjected to column chromatography. The R,â-unsaturated
carboxylic ester 1c (55%, 0.325 g) and cyclobutenedione 1a
(
20%, 0.117 g) were isolated.
-
1
1
1
3
c: IR (neat) 1714 cm ; H NMR δ 3.84 (s, 3H, -OCH ),
1
3
6
1
.93-7.98 (m, 11H); C NMR δ 52.4, 127.9, 128.2, 128.7, 129.1.
Su p p or tin g In for m a tion Ava ila ble: 13C NMR spectra (50
29.8, 130.6, 131.5, 142.5, 168.3; MS (EI) m/z 238 (M), 178
(
B).
3
MHz, CDCl ) of all compounds and spectral data for all
compounds (25 pages). This material is contained in libraries
on microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
(30) (a) Dehmlow, E. V.; Lissel, M. Tetrahedron 1981, 37, 1653. (b)
Brandsma, L.; Verkruijsse, H. D. Synthesis of Acetylenes, Allenes and
Cumulenes; Elsevier: New York, 1981.
(31) Weast, R. C., Ed. CRC Hand Book of Chemistry and Physics;
CRC Press: Boca Raton, 1974.
J O971929D