4-halogeno-1,1,1-trifluorobut-3-yn-2-one [4+2] cycloadducts and their cross-coupling with organozinc compounds

Article abstract of DOI:10.1007/s11172-009-0317-7

The reactions of 4-chloro-1,1,1-trifluorobut-3-yn-2-one and 4-bromo-1,1,1-trifluorobut-3-yn-2-one with conjugated dienes afford [4+2] cycloadducts in high yields. The halogen atom in the products is readily replaced by a (het)aryl residue in the cross-coupling with organozinc compounds.

Full text of DOI:10.1007/s11172-009-0317-7

Russian Chemical Bulletin, International Edition, Vol. 58, No. 11, pp. 2271—2275, November, 2009
2271
4ꢀHalogenoꢀ1,1,1ꢀtrifluorobutꢀ3ꢀynꢀ2ꢀone [4+2] cycloadducts
and their crossꢀcoupling with organozinc compounds
A. B. Koldobskii, N. P. Tsvetkov, O. S. Shilova, E. V. Solodova, and V. N. Kalinin
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 65 49. Eꢀmail: andikineos@rambler.ru
The reactions of 4ꢀchloroꢀ1,1,1ꢀtrifluorobutꢀ3ꢀynꢀ2ꢀone and 4ꢀbromoꢀ1,1,1ꢀtrifluorobutꢀ
3ꢀynꢀ2ꢀone with conjugated dienes afford [4+2] cycloadducts in high yields. The halogen atom
in the products is readily replaced by a (het)aryl residue in the crossꢀcoupling with organozinc
compounds.
Key words: halogenotrifluoroacetylacetylenes, diene, dienophile, [4+2] cycloaddition reꢀ
action, the Negishi reaction, organofluorine compounds.
Acetylenic dienophiles and enophiles that have two
activating substituents, one of which is halogen, are of
significant interest as polyfunctional substrates in the synꢀ
thesis of biologically active compounds.1 [4+2] Cycloꢀ
addition reactions of halogenoacetylenes activated by
alkoxycarbonyl,2 acyl,3 and sulfonyl1 groups, and further
transformations of the obtained cycloadducts have been
studied.2 Recently,4 we have synthesized halogenoaceꢀ
tylenes that contain an ethoxalyl substituent and demonꢀ
strated that these compounds are active dienophiles; they
react with many dienes even at 20 °C. Though trifluoroꢀ
acetyl group is related to the most powerful electronꢀ
withdrawing groups, still only few examples of the Diels—
Alder reactions with acetylenes activated by this substituꢀ
ent are known.5—7 At present, halogenꢀactivated trufluoroꢀ
acetylacetylenes are intensively investigated in our laboꢀ
ratory; it turned out that these compounds with high elecꢀ
trophilicity undergo [2+2] cycloaddition with alkyl vinyl
ethers8 and even with nonꢀactivated alkenes9 in the
absence of a catalyst and radiation.
Earlier, in a short communication10 we have described
the reaction of bromide 1b with the simplest dienes. It
seemed promising to investigate acetylenes 1a,b as dienoꢀ
philies in the reaction with different dienes, including
heterocyclic dienes. Cycloadduct that formed should conꢀ
tain βꢀhalogenovinyl trifluoromethyl ketone fragments,
which are of great interest for biochemistry and organic
synthesis.11
Scheme 1
X = Cl (a), Br (b)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2202—2206, November, 2009.
1066ꢀ5285/09/5811ꢀ2271 © 2009 Springer Science+Business Media, Inc.

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Koldobskii et al.
Scheme 3
We have established that dienophiles 1a,b react with
cyclopentadienes even at –20 °C giving the corresponding
cycloadducts 2a,b in virtually quantitative yields (Scheme 1).
Less reactive cyclohexaꢀ1,3ꢀdiene and 2,3ꢀdimethylbutaꢀ
diene exothermically add compounds 1a,b at room temꢀ
perature. The least reactive diene of the studied dienes,
anthracene, reacts with acetylenes 1a,b when refluxed in
benzene to afford cycloadducts 5а,b in high yields as well.
Starting to investigate the reaction of acetylenes 1a,b
with styrene, we thought that as in the reaction with
alkenes,9 [2+2] cycloaddition would be observed, but, in
reality, 1ꢀtrifluoroacetylꢀ2ꢀhalogenonaphthalenes 6a,b
were isolated in 36—39% yields. Apparently, [4+2]
cycloaddition takes place in the first step of this transforꢀ
mation, and then the intermediate dihydronaphthalene
is oxidized by the second dienophile molecule, which
explains low yield of the final products (Scheme 2).
X = Cl (a), Br (b)
the expected unstable bicyclic compound 8а together with
the unusual product of electorophilic alkynylation 8b. It
is worth noting that bromide 1b, contrary to 1а, exotherꢀ
mically react with Nꢀmethoxycarbonylpyrrole giving only
compound 8b without any admixture of the correspondꢀ
ing [4+2] cycloadduct (Scheme 4).
Scheme 4
Scheme 2
or
1a: products 8a (62%) and 8b (19%); 1b: product 8b (78%)
Thus, the Diels—Alder reactions involving acetylenes
1a,b represent a simple method for the synthesis of comꢀ
pounds with a βꢀhalogenovinyl trifluoromethyl ketone
fragment that can be used in different functionalization
and heterocyclization processes.11 However, till now only
the simplest (mainly, acyclic) representatives of this class
of compounds have been known, for which the synthetic
potential is mainly undisclosed. We made an attempt to
elaborate a convenient method for their βꢀfunctionalizaꢀ
tion by substituting the halogen atom with different aryl
substituents in the Negishi reaction. At the same time, we
were concerned that organozinc compounds, in addition
to halogen substitution, would also add to the reactive
carbonyl center, which would result in a mixture of prodꢀ
ucts. Fortunately, it turned out that the reaction of broꢀ
mide 2b with (het)arylzinc chlorides in the presence
of tetrakis(triphenylphosphine)palladium leads exclusively
to the crossꢀcoupling products 9a—c in high yields
(Scheme 5).
X = Cl (a), Br (6b)
Reaction of styrene with dienophiles 1a,b can result in
two regioisomers. The position of the substituents in comꢀ
pound 6b was determined by the chemical method:
hydrodebromination of this compound with Bu3SnH gives
the known 1ꢀtrifluoroacetylnaphthalene (see Scheme 2).
One of the very promising directions of the Diels—
Alder reactions is the involvement of heterocyclic dienes,
among which furans and Nꢀacylpyrroles are the most ofꢀ
ten used. However, it is known1,2 that even reactive
dienophiles of the acetylene series react with these dienes
only on heating to 90—100 °C for 20—30 h. We found
that acetylenes 1a,b exothermically react with furan even
at 20 °C giving bicyclic cycloadducts 7a,b in good yields
(Scheme 3).
Similarly to the known processes with halogenoꢀ
acetylenes1,2 activated by electronꢀwithdrawing substituꢀ
ents, it can be supposed that the reaction of Nꢀmethoxyꢀ
carbonylpyrrole with acetylenes 1a,b would also follow
the [4+2] cycloaddition pattern. In fact, chloride 1а gives
Thus, halogenated trifluroacetylacetylenes are reacꢀ
tive dienophiles in the Diels—Alder reaction, they smoothly
react with different dienes under mild conditions. The

[4+2] Cycloaddition of haloacetylenes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 11, November, 2009 2273
Scheme 5
20 °C for 5 h. The mixture was concentrated in vacuo, the residue
was distilled.
1ꢀ(3ꢀChlorobicyclo[2.2.2]octaꢀ2,5ꢀdienꢀ2ꢀyl)ꢀ2,2,2ꢀtrifluoroꢀ
ethanone (3а) was obtained from chloroacetylene 1а and
cyclohexaꢀ1,3ꢀdiene. Yield 2.10 g (89%), b.p. 53—54 °C (1 Torr).
Found (%): C, 50.56; H, 3.30; F, 24.40. C10H8ClF3O. Calculꢀ
ated (%): C, 50.76; H, 3.41; F, 24.40. IR, ν/cm–1: 1608, 1665
(C=C); 1706 (C=O). 1H NMR, δ: 1.44—1.68 (m, 4 H, CH2CHCH2);
4.08 (m, 1 H, HC(1)); 4.27 (m, 1 H, HC(4)); 6.35 (m, 1 H,
CH=C); 6.48 (m, 1 H, CH=C). 13C NMR, δ: 24.9, 25.2
(CH2CH2); 38.4, 49.9 (C(1), C(4)); 114.5 (q, CF3, J = 290 Hz);
133.8, 135.2 (CH=CH); 137.0, 146.4 (C=C); 176.1 (q, C=O,
J = 36 Hz).
1ꢀ(3ꢀBromobicyclo[2.2.2]octaꢀ2,5ꢀdienꢀ2ꢀyl)ꢀ2,2,2ꢀtrifluoroꢀ
ethanone (3b) was obtained from bromoacetylene 1b and cycloꢀ
hexaꢀ1,3ꢀdiene. Yield 2.39 g (85%), b.p. 68—69 °C (1 Torr).
Found (%): C, 42.47; H, 2.86; Br, 28.09; F, 20.00. C10H8BrF3O.
Calculated (%): C, 42.73; H, 2.87; Br, 28.43; F, 20.28. IR,
ν/cm–1: 1603, 1660 (C=C); 1700 (C=O). 1H NMR, δ: 1.40—1.66
(m, 4 H, CH2CH2); 4.05 (m, 1 H, HC(1)); 4.24 (m, 1 H, HC(4));
6.32 (m, 1 H, CH=C); 6.46 (m, 1 H, CH=C). 13C NMR, δ:
24.1, 24.6 (CH2CH2); 39.7, 51.6 (C(1), C(4)); 115.6 (q, CF3,
J = 290 Hz); 132.0, 133.5 (CH=CH); 135.8, 144.3 (C=C);
176.6 (q, C=O, J = 36 Hz).
R = 2ꢀthienyl (9a), 2ꢀfuryl (9b), 4ꢀFC6H4 (9c)
synthetic potential of the obtained adducts, undoubtedly,
requires further investigations.
Experimental
1,1,1ꢀTrifluooroꢀ4ꢀchlorobutꢀ3ꢀynꢀ2ꢀone (1а) and 4ꢀbromoꢀ
1,1,1ꢀtrifluorobutꢀ3ꢀynꢀ2ꢀone (1b) were synthesized by haloꢀ
genation of 4ꢀtrimethylstannylꢀ1,1,1ꢀtrifluorobutꢀ3ꢀynꢀ2ꢀone as
described.9,10 Dienes were distilled directly before the reaction,
anthracene was used without purification. 1H and 13C NMR
spectra were recorded on a Bruker AMX 400 instrument (working
frequencies 400 and 100 MHz, respectively) in СDCl3. IR spectra
were obtained on a Вruker IFS 25 spectrometer in thin layer
or Nujol.
1ꢀ(3ꢀChlorobicyclo[2.2.1]heptaꢀ2,5ꢀdienꢀ2ꢀyl)ꢀ2,2,2ꢀtriꢀ
fluoroethanone (2а). Freshly distilled cyclopentadiene (0.79 g,
0.012 mol) in dichloromethane (5.0 mL) was added dropwise
with stirring to a solution of acetylene 1а (1.56 g, 0.010 mol) in
anhydrous dichloromethane (5.0 mL) at –20 °C. The cooling
bath was kept, the reaction mixture was allowed to warm to
20 °С, after 15 min the mixture was concentrated in vacuo, and
the residue was distilled. Yield 2.05 g (92%), b.p. 40—41 °C
(1 Torr). Found (%): C, 48.40; H, 2.62; F, 25.80. C9H6ClF3O.
Calculated (%): C, 48.56; H, 2.72; F, 25.60. IR, ν/cm–1: 1706
(C=O); 1602 (C=C). 1H NMR, δ: 2.22 (d, 1 H, CH2, J = 7.2 Hz);
2.36 (d, 1 H, CH2, J = 7.2 Hz); 3.64 (s, 1 H, HC(1)); 4.14 (s,
1 H, HC(4)); 6.84 (d, 1 H, CH=CH, J = 4.9 Hz); 6.89 (d, 1 H,
CH=CН, J = 4.9 Hz). 13C NMR, δ: 51.0 (C(7)); 60.7, 70.7 (C(1),
C(4)); 115.9 (q, CF3, J = 290 Hz); 139.5, 140.1 (CH=CH);
143.3, 170.5 (C(2), C(3)); 175.8 (q, C=O, J = 37 Hz).
1ꢀ(3ꢀBromobicyclo[2.2.1]heptaꢀ2,5ꢀdienꢀ2ꢀyl)ꢀ2,2,2ꢀtriꢀ
fluoroethanone (2b) was obtained as described for compound
2а starting from acetylene 1b (0.010 mol) and cyclopentaꢀ
diene (0.012 mol). Yield 2.51 g (94%), b.p. 55—56 °C (1 Torr).
Found (%): C, 40.61; H, 2.42; Br, 29.61; F, 21.09. C9H6BrF3O.
Calculated (%): C, 40.48; H, 2.26; Br, 29.92; F, 21.34. IR,
ν/cm–1: 1702 (C=O); 1600 (C=C). 1H NMR, δ: 2.23 (d, 1 H,
CH2, J = 8.4 Hz); 2.39 (d, 1 H, CH2, J = 8.4 Hz); 3.69 (s, 1 H,
HC(1)); 4.10 (s, 1 H, HC(4)); 6.85 (d, 1 H, CH=CН, J = 5.0 Hz);
6.90 (d, 1 H, CH=CН, J = 5.0 Hz). 13C NMR, δ: 51.7 (C(7));
62.6, 71.1 (C(1), C(4)); 115.8 (q, CF3, J = 289 Hz); 140.2, 142.7
(CH=CH); 143.0, 160.4 (C(2), C(3)); 175.4 (q, C=O, J = 36 Hz).
Cycloadducts 3a,b and 4a,b (general method). Cyclohexaꢀ
1,3ꢀdiene (1.00 g, 0.013 mol) or 2,3ꢀdimethylbutaꢀ1,3ꢀdiene
(1.03 g, 0.013 mol) was added with stirring to a solution of
acetylene 1а or 1b (0.010 mol) in dichloromethane (5.0 mL)
at 0 °C. The cooling bath was removed and after completion
of the exothermic reaction the reaction mixture was stirred at
1ꢀ(2ꢀChloroꢀ4,5ꢀdimethylꢀ1,4ꢀcyclohexadienꢀ1ꢀyl)ꢀ2,2,2ꢀ
trifluoroethanone (4а) was obtained from chloroacetylene
1а and 2,3ꢀdimethylbutaꢀ1,3ꢀdiene. Yield 1.32 g (79%),
b.p. 50—51 °C (1 Torr). Found (%): C, 50.44; H, 4.19; F, 24.02.
C10H10ClF3O. Calculated (%): C, 50.33; H, 4.23; F, 23.88.
IR, ν/cm–1: 1598, 1652 (C=C); 1703 (C=O). 1H NMR, δ: 1.65
(d, 3 H, Me, J = 0.7 Hz); 1.69 (d, 3 H, Me, J = 0.7 Hz); 2.90 (m,
2 H, CH2); 3.28 (m, 2 H, CH2). 13C NMR, δ: 18.1, 19.5 (2 Me);
35.8, 42.9 (2 CH2); 116.8 (q, CF3, J = 290 Hz); 120.9, 123.9
(CH=CH); 132.2, 144.2 (C=C); 175.2 (q, C=O, J = 36 Hz).
1ꢀ(2ꢀBromoꢀ4,5ꢀdimethylꢀ1,4ꢀcyclohexadienꢀ1ꢀyl)ꢀ2,2,2ꢀ
trifluoroethanone (4b) was obtained from bromoacetylene
1b and 2,3ꢀdimethylbutaꢀ1,3ꢀdiene. Yield 2.38 g (84%),
b.p. 65—66 °C (1 Torr). Found (%): C, 42.63; H, 3.77; Br,
28.63; F, 20.33. C10H10BrF3O. Calculated (%): C, 42.43;
H, 3.56; Br, 28.23; F, 20.13. IR, ν/cm–1: 1600, 1650 (C=C);
1
1700 (C=O). H NMR, δ: 1.63 (d, 3 H, Me, J = 0.5 Hz); 1.65
(d, 3 H, Me, J = 0.5 Hz); 2.91 (m, 2 H, CH2); 3.24 (m, 2 H,
CH2). 13C NMR, δ: 18.6, 19.9 (2 Me); 37.0, 42.6 (2 CH2); 118.2
(q, CF3, J = 290 Hz); 121.5, 124.5 (CH=CH); 134.8, 145.6
(C=C); 177.6 (q, C=O, J = 38 Hz).
12ꢀChloroꢀ11ꢀtrifluoroacetylꢀ9,10ꢀdihydroꢀ9,10ꢀethenoꢀ
anthracene (5а). A solution of acetylene 1а (1.56 g, 0.010 mol)
and anthracene (1.78 g, 0.010 mol) in anhydrous benzene
(10 mL) was refluxed for 6 h. The reaction mixture was cooled
to 50 °C, the precipitate that formed was filtered off, the filtrate
was concentrated in vacuo, the residue was chromatographed
(silica gel, ethyl acetate—hexane (1 : 20)). Yield 2.40 g (72%),
m.p. 102—103 °C. Found (%): C, 64.81; H, 2.95; Cl, 10.68;
F, 17.24. C18H10ClF3O. Calculated (%): C, 64.58; H, 3.02;
Cl, 10.59; F, 17.03. IR, ν/cm–1: 1610 (C=C); 1700 (C=O).
1H NMR, δ: 5.52 (s, 1 H, HC(9)); 5.80 (s, 1 H, HC(10));
7.06—7.19 (m, 4 H, НAr); 7.40—7.59 (m, 4 H, НAr). 13C NMR,
δ: 63.5, 64.9 (C(9), C(10)); 117.5 (q, CF3, J = 288 Hz); 124.4,
124.9, 126.9, 128.0 (Ar); 180.6 (q, C=O, J = 38 Hz).
11ꢀBromoꢀ12ꢀtrifluoroacetylꢀ9,10ꢀdihydroꢀ9,10ꢀethenoꢀ
antracene (5b) was obtained as described for compound 5а.

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Koldobskii et al.
Yield 2.85 g (75%), m.p. 81—83 °C. Found (%): C, 56.85;
H, 2.87; F, 15.34. C18H10BrF3O. Calculated (%): C, 57.02;
H, 2.66; F, 15.03. 1H NMR, δ: 5.45 (s, 1 H, HC(9)); 5.76 (s,
1 H, HC(10)); 7.04—7.20 (m, 4 H, НAr); 7.38—7.55 (m, 4 H,
НAr). 13C NMR, δ: 63.8, 65.2 (C(9), C(10)); 116.8 (q, CF3,
J = 288 Hz); 122.6, 125.7, 127.4, 128.7 (Ar); 178.4 (q, C=O,
J = 40 Hz).
2ꢀChloroꢀ1ꢀtrifluoroacetylnaphthalene (6а). Acetylene 1а
(1.56 g, 0.010 mol) and freshly distilled styrene (1.04 g, 0.010 mol)
were mixed. After completion of the exothermic reaction,
the reaction mixture was kept at 20 °C for 12 h and distilled
in vacuo. The fraction with b.p. 102—108 °C (1 Torr) was
collected and chromatographed (silica gel, ethyl acetate—hexane
(1 : 20)). Compound 6а was obtained as an yellowish oil (0.95 g,
37%). Found (%): C, 55.96; H, 2.40; Cl, 13.39; F, 21.83.
C12H6ClF3O. Calculated (%): C, 55.73; H, 2.34; Cl, 13.71;
F, 22.04. IR, ν/cm–1: 1703 (C=O). 1H NMR, δ: 7.48—7.67 (m,
3 H, НAr); 7.82—8.05 (m, 3 H, НAr). 13C NMR, δ: 119.4 (q,
CF3, J = 288 Hz); 126.9, 128.4, 129.9, 131.0, 132.8, 134.5,
139.4, 148.2, 148.8, 150.3, 176.9 (q, C=O, J = 40 Hz).
2ꢀBromoꢀ1ꢀtrifluoroacetylnaphthalene (6b) was obtained
as described for compound 6а, fraction with b.p. 111—115 °C
(1 Torr) was collected. Yield 1.03 g (34%). Found (%): C, 47.40;
H, 2.25; F, 18.65. C12H6BrF3O. Calculated (%): C, 47.56;
H, 2.00; F, 18.81. IR, ν/cm–1: 1701 (C=O). 1H NMR, δ:
7.50—7.70 (m, 3 H, НAr); 7.81—8.00 (m, 3 H, НAr). 13C NMR,
δ: 118.6 (q, CF3, J = 288 Hz); 127.2, 128.9, 129.5, 132.1, 133.0,
134.9, 139.9, 146.2, 148.5, 152.2, 174.9 (q, C=O, J = 40 Hz).
1ꢀ(3ꢀChloroꢀ7ꢀoxabicyclo[2.2.1]heptaꢀ2,5ꢀdienꢀ2ꢀyl)ꢀ2,2,2ꢀ
trifluoroethanone (7а). Furan (0.075 g, 0.011 mol) was added
with stirring to a solution of acetylene 1а (1.56 g, 0.010 mol) in
absolute dioxane (5.0 mL) in an argon atmosphere. After
completion of the exothermic reaction, the reaction mixture
was kept at 20 °C for 12 h. The reaction mixture was concentrated
in vacuo, the residue was distilled. Compound 7а was obtained
(1.68 g, 75%), b.p. 42—43 °C (1 Torr). Found (%): C, 42.62;
H, 2.02; F, 25.40. C8H4ClF3O. Calculated (%): C, 42.79;
H, 1.80; F, 25.38. IR, ν/cm–1: 1690 (C=C); 1710 (C=O). 1H NMR,
δ: 5.31 (d, 1 H, HC(4), J = 0.6 Hz); 5.88 (d, 1 H, HC(1),
J = 0.6 Hz); 7.18 (dd, 1 H, HC=C, J = 4.9 Hz, J = 0.6 Hz); 7.26
(dd, 1 H, HC=C, J = 4.9 Hz, J = 0.6 Hz). 13C NMR, δ: 84.3,
88.7 (C(1), C(4)); 115.6 (q, CF3, J = 290 Hz); 140.3, 140.4
(CH=CH); 144.7, 169.0 (C=C); 174.3 (q, C=O, J = 38 Hz).
1ꢀ(3ꢀBromoꢀ7ꢀoxabicyclo[2.2.1]heptaꢀ2,5ꢀdienꢀ2ꢀyl)ꢀ2,2,2ꢀ
trifluoroethanone (7b) was obtained as described for compound
2а starting from acetylene 1b (0.010 mol) and furan (0.011 mol).
Yield 1.88 g (70%), b.p. 48—49 °C (1 Torr). Found (%): C, 36.09;
H, 1.64; F, 20.85. C8H4BrF3O. Calculated (%): C, 35.70; H, 1.50;
F, 21.18. IR, ν/cm–1: 1694 (C=C); 1707 (C=O). 1H NMR, δ:
5.46 (d, 1 H, HC(4), J = 0.5 Hz); 5.90 (d, 1 H, HC(1), J = 0.5
Hz); 7.21 (dd, 1 H, HC=C, J = 4.9 Hz, J = 0.5 Hz); 7.30 (dd, 1
H, HC=C, J = 4.9 Hz, J = 0.5 Hz). 13C NMR, δ: 84.4, 90.2
(C(1), C(4)); 115.5 (q, CF3, J = 288 Hz); 140.8, 143.9 (CH=CH);
144.2, 159.2 (C=C); 174.5 (q, C=O, J = 38 Hz).
solution was kept at 0 °C for 12 h. The precipitate that formed
was filtered off, the filtrate was concentrated and chromatoꢀ
graphed (silica gel, ethyl acetate—hexane (1 : 10)). Compound
8а was obtained as a yellowish oil (1.74 g, 62%), which was
storageꢀunstable (the attempt to perform elemental analysis was
unsuccessful). IR, ν/cm–1: 1608 (C=C); 1702 (C=O). 1H NMR,
δ: 3.94 (s, 3 H, MeО); 5.54 (s, 1 H, HC(1)); 5.79 (s, 1 H,
HC(4)); 7.38 (m, 2 H, CH=CН). 13C NMR, δ: 54.9, 56.4, 58.2
(C(1), C(4), MeО); 114.9 (q, CF3, J = 288 Hz); 142.8, 145.4
(CH=CH); 148.7, 152.2 (C=C); 154.2 (NC=O); 172.9 (q, C=O,
J = 40 Hz).
2ꢀ(4,4,4ꢀTrifluoroꢀ3ꢀoxobutꢀ1ꢀynyl)ꢀ1ꢀmethoxycarbonylꢀ
1Нꢀpyrrole (8b). NꢀMethoxycarbonylpyrrole (1.38 g, 0.011 mol)
was added with stirring to a solution of acetylene 1b (2.01 g,
0.010 mol) in absolute dioxane (3.0 mL) in an argon atmosphere.
After completion of the exothermic reaction, the reaction
mixture was kept at 20 °C for 4 h and concentrated in vacuo. The
residue was recrystallized from ethyl acetate—hexane (1 : 5).
Yield 1.91 g (78%), m.p. 93 °C. Found (%): C, 49.04; H, 2.51;
N, 5.71. C10H6F3NO3. Calculated (%): C, 48.99; H, 2.47;
N, 5.71. IR, ν/cm–1: 1700, 1748 (C=O). 1H NMR, δ: 4.06 (s,
3 H, MeО); 6.40 (d, 1 H, НAr, J = 3.7 Hz); 7.09 (dd, 1 H, НAr,
J = 3.7 Hz, J = 1.1 Hz); 7.62 (m, 1 H, НAr). 13C NMR, δ: 54.7
(MeO); 89.8, 93.6 (C≡C); 110.7, 113.1 (Ar); 115.0 (q, CF3,
J = 288 Hz); 127.8, 129.7 (Ar); 149.5 (N–C=O); 166.6 (q,
C=O, J = 42 Hz).
Compounds 9а—с (general method). А. 2ꢀThienyl, 2ꢀfurylꢀ
and 4ꢀfluorophenylzinc chlorides. A solution of nꢀbutyllithium
in hexane (6.2 mL, 0.010 mol, 1.6 mol L–1) was added dropwise
at 0 °C in argon flow to a solution of thiophene (0.012 mol) or
furan (0.012 mol) in absolute THF (10.0 mL). The reaction
mixture was stirred at 0 °C for 0.5 h (2ꢀthienyllithium and
2ꢀfuryllithium are formed in quantitative yields under these
conditions12). 4ꢀFluorophenyllithium was obtained by addition
of a solution of nꢀbutyllithium in hexane (6.2 mL, 0.010 mol,
1.6 mol L–1) to a stirred solution of 4ꢀbromofluorobenzene
(0.011 mol) in THF (10.0 mL) at –70 °C followed by holding
the reaction mixture at –70 °C for 1 h. A solution of anhydrous
ZnCl2 (1.57 g, 0.012 mol) in THF (15.0 mL) was added dropwise
with stirring to a solution or suspension of the obtained organoꢀ
lithium compounds cooled to –70 °C, the reaction mixture was
allowed to warm to 20 °C. The solutions of organozinc comꢀ
pounds thus obtained were further used in crossꢀcoupling
reactions.
B. Crossꢀcoupling reactions of compound 2b with organozinc
compounds. Compound 2b (2.670 g, 0.010 mol) and Pd(PPh3)4
(0.005 g, 0.001 mol) were added in one portion to a stirred
solution of the organozinc compound at 20 °C. After completion
of the exothermic stage of the reaction, the reaction mixture was
stirred at 20 °C for 18 h, then a saturated solution of ammonium
chloride (30 mL) was added. The organic layer was separated,
the aqueous layer was extracted with ether (4×20.0 mL).
Combined organic fractions were washed with a saturated
solution of ammonium chloride (20 mL), dried with sodium
sulfate, and concentrated in vacuo. Hexane (30 mL) was added
to the residue, catalyst decomposition products were filtered off
and the filtrate was concentrated in vacuo. The solution of the
residue in hexane–ethyl acetate (2 : 1) was passed through a
thin layer of silica gel; the solution was concentrated. Adduct 9а
was purified by recrystallization form hexane, adducts 9b,c were
distilled in vacuo.
2ꢀChloroꢀ3ꢀtrifluoroacetylꢀ7ꢀmethoxycarbonylꢀ7ꢀazabicycloꢀ
[2.2.1]heptaꢀ2,5ꢀdiene (8а). NꢀMethoxycarbonylpyrrole
(1.38 g, 0.011 mol) was added with stirring to a solution of
acetylene 1а (1.56 g, 0.01 mol) in absolute dioxane (5.0 mL) in
an argon atmosphere. The reaction mixture was kept at 20 °C
for 6 h and concentrated in vacuo. The residue was dissolved in a
mixture of ethyl acetate (2.0 mL) and hexane (8.0 mL), the

[4+2] Cycloaddition of haloacetylenes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 11, November, 2009 2275
2ꢀTrifluoroacetylꢀ3ꢀ(2ꢀthienyl)bicyclo[2.2.1]heptaꢀ2,5ꢀdiene
(9а). Yield 2.16 g (80%), m.p. 62 °C. Found (%): C, 58.1;
H, 3.32; F, 20.95; S, 11.65. C13H9F3OS. Calculated (%):
C, 57.77; H, 3.36; F, 21.09; S, 11.86. IR, ν/cm–1: 1665 (C=C);
1700 (C=O). 1Н NMR, δ: 2.20 (d, 1 H, CH2, J = 7.4 Hz); 2.32
(d, 1 H, CH2, J = 7.4 Hz); 4.24 (d, 1 H, HC(4), J = 1.7 Hz);
4.36 (d, 1 H, HC(1), J = 1.7 Hz); 6.88 (dd, 1 H, HC(5), J = 1.7 Hz,
J = 5.2 Hz); 7.01 (dd, 1 H, HC(6), J = 1.7 Hz, J = 5.2 Hz);
7.33 (dd, 1 H, HAr, J = 3.4 Hz, J = 5.0 Hz); 7.70 (d, 1 H, HAr,
J = 3.4 Hz); 8.16 (d, 1 H, HAr, J = 5.0 Hz). 13С NMR, δ:
51.2, 58.2, 67.8 (C(1), C(4), C(7)); 117.2 (q, CF3, J = 288 Hz);
128.3, 133.3 (C(5), C(6)); 133.7, 134.7, 137.8, 138.8 (С arom.);
144.4; 169.8 (C(2), C(3)); 175.5 (q, C=O, J = 40 Hz).
2ꢀTrifluoroacetylꢀ3ꢀ(2ꢀfuryl)bicyclo[2.2.1]heptaꢀ2,5ꢀdiene
(9b). Yield 1.96 g (77%), b.p. 83—84 °C (1 Torr), m.p. 34 °C.
Found (%): C, 61.68; H, 3.60; F, 22.19. C13H9F3O2. Calculꢀ
ated (%): C, 61.42; H, 3.54; F, 22.42. IR, ν/cm–1: 1659 (C=C);
1703 (C=O). 1Н NMR, δ: 2.29 (d, 1 H, CH2, J = 7.1 Hz); 2.36
(d, 1 H, CH2, J = 7.1 Hz); 4.11 (d, 1 H, HC(4), J = 2.5 Hz);
4.28 (d, 1 H, HC(1), J = 2.5 Hz); 6.93 (dd, 1 H, НAr, J = 1.8 Hz,
J = 3.8 Hz); 6.98 (dd, 1 H, HC(5), J = 2.5 Hz, J = 5.2 Hz); 7.10
(dd, 1 H, HC(6), J = 2.5 Hz, J = 5.2 Hz); 7.69 (m, 1 H, НAr);
7.91 (d, 1 H, НAr, J = 3.8 Hz). 13С NMR, δ: 49.4, 56.7, 67.1
(C(1), C(4), C(7)); 116.1 (q, CF3, J = 288 Hz); 126.6, 131.5,
136.2, 140.2, 144.9, 146.4, 149.8, 156.4 (C(5), C(6), C(2), C(3),
Ar); 173.6 (q, C=O, J = 40 Hz).
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2ꢀTrifluoroacetylꢀ3ꢀ(4ꢀfluorophenyl)bicyclo[2.2.1]heptaꢀ
2,5ꢀdiene (9с). Yield 2.09 g (74%), b.p. 104—105 °C (1 Torr).
Found (%): C, 64.11; H, 3.62; F, 26.70. C15H10F4O. Calculꢀ
ated (%): C, 63.83; H, 3.58; F, 26.93. IR, ν/cm–1: 1660 (C=C);
1700 (C=O). 1Н NMR, δ: 2.21 (d, 1 H, CH2, J = 7.1 Hz); 2.30
(d, 1 H, CH2, J = 7.1 Hz); 3.98 (d, 1 H, HC(4), J = 3.0 Hz); 4.25
(d, 1 H, HC(1), J = 3.0 Hz); 6.98 (dd, 1 H, HC(5), J = 3.0 Hz,
J = 5.1 Hz); 7.14 (dd, 1 H, HC(6), J = 3.0 Hz, J = 5.1 Hz); 7.19
(dd, 2 H, НAr, J = 8.4 Hz, J = 8.9 Hz); 8.15 (dd, 2 H, НAr,
J = 5.5 Hz, J = 8.9 Hz). 13С NMR, δ: 52.0, 59.4, 70.4 (C(1),
C(4), C(7)); 115.9 (d, Ar, J = 22.0 Hz); 116.9 (q, CF3, J = 292 Hz);
129.8 (Ar); 132.5 (d, Ar, J = 9.0 Hz); 140.0, 140.8, 145.0 (C(5),
C(6), C(3)); 166.8 (d, Ar, J = 30.0 Hz); 171.2 (C(2)); 177.2 (q,
C=O, J = 38.0 Hz).
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metallic Chemistry, SpringerꢀVerlag, New York, 1988, 1.
Received May 20, 2009;
in revised form August 17, 2009