A domino reaction of α,β-acetylenic λ-hydroxy nitriles with arenecarboxylic acids: An unexpected facile shortcut to 4-cyano-3(2 H)-furanones

Article abstract of DOI:10.1021/ol1011532

(Figure Presented) An unexpected facile domino reaction of α,β-acetylenic λ-hydroxy nitriles with arenecarboxylic acids (Et₃N, MeCN, 20-25 °C, 48 h) affords 4-cyano-3(2H)-furanones in 67-86% yield. The reaction is triggered by the addition of a

Full text of DOI:10.1021/ol1011532

ORGANIC
LETTERS
2010
Vol. 12, No. 14
3200-3203
A Domino Reaction of r,ꢀ-Acetylenic
γ-Hydroxy Nitriles with Arenecarboxylic
Acids: An Unexpected Facile Shortcut
to 4-Cyano-3(2H)-furanones
Boris A. Trofimov,*,† Olesya A. Shemyakina,† Anastasiya G. Mal’kina,†
Igor’ A. Ushakov,† Olga N. Kazheva,‡ Grigorii G. Alexandrov,§ and
Oleg A. Dyachenko‡
A. E. FaVorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy
of Sciences, 1 FaVorsky Str., 664033 Irkutsk, Russia, Institute of Problems of Chemical
Physics, Russian Academy of Sciences, 1 Academician N. N. SemenoV Str.,
142432 ChernogoloVka, Russia, and N. S. KurnakoV Institute of General and Inorganic
Chemistry, Russian Academy of Sciences, 31 Leninskii Prosp.,
119991 Moscow, Russia
boris_trofimoV@irioch.irk.ru
Received May 19, 2010
ABSTRACT
An unexpected facile domino reaction of r,ꢀ-acetylenic γ-hydroxy nitriles with arenecarboxylic acids (Et3N, MeCN, 20-25 °C, 48 h) affords
4-cyano-3(2H)-furanones in 67-86% yield. The reaction is triggered by the addition of an arenecarboxylic acid to a triple bond, followed by
the domino reaction sequence: intramolecular transesterification-enol formation and Claisen condensation of the ketoacetonitrile tautomer
with ester functional group.
The 3(2H)-furanone is a key structural unit in many
naturally occurring compounds such as bullatenon,1
geiparvarin,1b,d,2 eremantholide A,3 jatrophone,4 and pseuro-
tin A.5 In addition, the 3(2H)-furanone derivatives are
considered to be promising pharmaceutical candidates which
(2) (a) Jerris, P. J.; Smith, A. B., III. J. Org. Chem. 1981, 46, 577. (b)
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† A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the
Russian Academy of Sciences.
‡ Institute of Problems of Chemical Physics, Russian Academy of
Sciences.
§ N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian
Academy of Sciences.
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10.1021/ol1011532  2010 American Chemical Society
Published on Web 06/10/2010

exhibit antitumor,1b,d,2g,i,3e,6 antiulcer,1c antiallergic,7 selec-
tive COX-2 inhibition,2g,8 selective MAO-B inhibition
activities,2f,g,i,9 and ligands for nuclear hormone receptors.10
These features have spurred growing efforts to develop more
efficient syntheses of 3(2H)-furanones. Traditional routes to
substituted 3(2H)-furanones utilize a cyclization/dehydration
reaction of 1-hydroxy-2,4-diketones under the action of
acids2a,4b,11 or K2CO3.5a Among the alternative methods are
the hydrogenolyses and subsequent acidic hydrolyses of
isoxazoles,2c,6b,12 the aldol reaction of 3-silyloxyfuranes,13
the base-catalyzed cyclizations of 1-halo-2,4-diketones,14 and
the Knoevenagel-type condensation of R-acyloxycarbonyl
compounds.1d,15 Recently, Au(III)-, Ag(I)-, Cu(I)-, Hg(II)-,
Pd(II)-, or Pt(II)-catalyzed cyclizations of propargylic
ketols,2g,16 R-hydroxy ynones,17 and 2-oxo-3-butynoic esters
or disubstituted 1,2-diones18 to 3(2H)-furanones have at-
tracted attention. More recently, the combination of (p-
CF3C6H4)3PAuCl and AgOTf has been shown to actively
catalyze the cyclizations of γ-hydroxyalkynones to 3(2H)-
furanones.2i Still, the further development of more efficient
and atom-economical routes to functionalized 3(2H)-fura-
nones remains a focus of modern organic synthesis.
free conditions at 20-25 °C in the presence of Et3N in
MeCN (Table 1).
Table 1. Synthesis of 4-Cyano-3(2H)-furanonesa
Herein, we report the hitherto unknown and extremely
facile domino reaction between R,ꢀ-acetylenic γ-hydroxy
nitriles 1-3 and arenecarboxylic acids 4-11 to deliver a
novel family of functionalized 3(2H)-furanones, namely
5-aryl-4-cyano-2,2-dialkyl-3(2H)-furanones 12-21 in 67-86%
yield. The reaction proceeds smoothly under transition-metal-
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a Reaction conditions: acetylenes 1-3 (1 mmol), arenecarboxylic acids
4-11 (1 mmol), Et3N (1 mmol), MeCN (6 mL), 20-25 °C, 48 h. b Isolated
yield after recrystallization or preparative TLC.
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The 3(2H)-furanones 12-21 are crystalline compounds
with sharp melting points and good solubility in most organic
solvents (examples: acetone, acetonitrile, benzene, chloro-
form, diethyl ether, dimethyl sulfoxide, ethanol, methanol)
and poor solubility in water. In addition, the structure of
Org. Lett., Vol. 12, No. 14, 2010
3201

4-cyano-2,2-dimethyl-5-phenyl-3(2H)-furanone 12 was con-
firmed by single-crystal X-ray analysis (Figure 1).
the Table 1 reaction conditions), the expected 3(2H)-furanone
12 was detected (1H NMR) in the reaction mixture (30%
conversion after 3 h).
In addition, the keto ester 26 (R1 ) R2 ) Me, R3 ) 2-Me)
was obtained as a mixture with 3(2H)-furanone 27 in a ratio
of 3:1, respectively (Scheme 2).
Scheme 2. Reaction of Acetylene 1 with
2-Methylbenzenecarboxylic Acid
Figure 1. X-ray crystal structures of A and B molecules of 12.
The reaction conditions and resulting products in Table 1
indicate a domino sequence that is triggered by the nucleo-
philic addition of arenecarboxylic acids 4-11 across the
triple bonds of acetylenes 1-3 to afford the enol esters 22
(Scheme 1). The enol esters are transformed via intramo-
Scheme 1
.
Plausible Scheme of Domino Sequence Leading to
3(2H)-Furanones 12-21
Keto esters similar to 26 were formed as adducts between
3- and 4-aminobenzenecarboxylic acids and R,ꢀ-acetylenic
γ-hydroxy nitriles 1-3.19
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lecular transesterification to the enols 23, subsequently
tautomerizing to the keto esters 24. The latter undergo a ring
closure via intramolecular Claisen condensation with par-
ticipation of the active CH2 group of the ꢀ-ketonitrile and
the carbonyl function of the ester residue to give hemiketals
25. After dehydration to form a Csp2-Csp2 bond, the 3(2H)-
furanones 12-21 are produced.
The reaction can be stopped at the stage of the intermediate
keto esters 24. For example, the keto ester 24 (R1 ) R2 )
Me, R3 ) H) was isolated from the reaction mixture in 31%
yield, after acetylene 1 and benzenecarboxylic acid 4 were
allowed to react in the presence of 10 mol % of K2CO3 at
20-25 °C for 48 h (the water was not specially added to
the reaction mixture). When ketone 24 had been kept in
acetonitrile in the presence of Et3N at 20-25 °C (i.e., under
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Org. Lett., Vol. 12, No. 14, 2010

It is noteworthy that an equimolar amount of aqueous
K2CO3 did not catalyze the addition of benzenecarboxylic
acid 4 to acetylene 1 to afford 3(2H)-furanone 12 (water-
MeCN, 1:2; 20-25 °C, 48 h). Instead, hydration of acetylene
1 to 5-amino-2,2-dimethyl-3(2H)-furanone 28 in a yield of
76% occurred (Scheme 3).19,20
Scheme 4. Synthesis of R,ꢀAcetylenic γ-Hydroxy Nitriles 1-3
introduced into the cyclopentanone moiety. Evidently, the
reaction should be of general character and be valid for
various carboxylic acids and R,ꢀ-acetylenic γ-hydroxy
nitriles with tertiary alcohol moieties. Certainly, the scope
and limitation of the reaction is still to be further scrutinized.
R,ꢀ-Acetylenic γ-hydroxy nitriles with primary and second-
ary alcohol moieties are poorly understood (among them only
4-hydroxy-2-butynenitrile is known27). Amino analogues of
hydroxyacetylenes 1-3 are almost inaccessible: just 4-amino-
2-butynenitrile has been so far described as hydrochloride.27b
In the case of aliphatic carboxylic acids, under the conditions
studied, a mixture of products containing the expected 3(2H)-
furanones and intermediate keto esters (in ratio 1-2:1) is
formed; hence, the reaction promises to be successfully
optimized.
Scheme 3. Synthesis of 5-Amino-2,2-dimethyl-3(2H)-furanone 28
Commonly, carboxylic acids are known to add to various
acetylenes21 (terminal alkynes,21a,c,d,f,g,i-k propargyl alcohols
and their derivatives,21a,b,f,h,i dimethyl acetylenedicar-
boxylate21e) under heating (60-110 °C) for 4-96 h21
exclusively in the presence of ruthenium catalysts, mostly
complexes of complicated structure. Of industrial importance
remains the classic vinylation of carboxylic acids with
acetylenes by the action of HgSO4, Zn(OAc)2/C, H3PO4/C,
Zn/Cd, and Zn/Cd/Hg catalytic systems.22 Also known are
attempts to vinylate carboxylic acids with acetylenes over
palladium.23
Thus, the first stage of the Scheme 1 domino reaction
represents a unique example of transition-metal-free additions
of carboxylic acids to carbon-carbon triple bonds. Taking
into account that the starting acetylenic hydroxy nitriles 1-3
are readily available from acetylenic alcohols and copper
cyanide through the intermediary acetylenic bromides (Scheme
4),24 the domino assembly presented here may be considered
as one of the most concise and expedient approaches so far
known to functionalized 3(2H)-furanones.
In summary, a new synthetic concept for the design of
functionalized 3(2H)-furanones in a one-step, extremely
facile domino reaction of available R,ꢀ-acetylenic γ-hydroxy
nitriles and arenecarboxylic acids has been put forward and
experimentally proved. The concept may find a widespread
application and propagation in the synthesis of pharmaceuti-
cally important functionalized 3(2H)-furanones.
Acknowledgment. This work was supported by the
Russian Foundation for Basic Research (Grant No. 08-03-
00156), Presidium of RAS (Program 24), Presidium of
Department of Chemical Sciences and Materials RAS (Grant
No. 5.1.3), and Integration Projects No. 93 and 5.9.
Of special synthetic significance of this synthesis is that
it allows the cyano group (which may be easily converted
to amino,25 amido,26 or carboxylic26a-c functions) to be
Supporting Information Available: Experimental pro-
cedures and full spectroscopic data for all new compounds.
This material is available free of charge via the Internet at
http://pubs.acs.org.
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