One-step synthesis of alpha-pyrones from acyl chlorides by the Stille reaction.

Article abstract of DOI:10.1021/jo025518v

Palladium-catalyzed stereoselective annulation of a functional vinylstannane by acyl chlorides gives the corresponding alpha-pyran-2-ones in good yields. This annulation most probably proceeds through a Stille reaction/cyclization sequence.

Full text of DOI:10.1021/jo025518v

J . Org. Chem. 2002, 67, 3941-3944
3941
Sch em e 1
On e-Step Syn th esis of r-P yr on es fr om Acyl
Ch lor id es by th e Stille Rea ction
J e´roˆme Thibonnet,†,‡ Mohamed Abarbri,‡
J ean-Luc Parrain,*,† and Alain Ducheˆne*,‡
Laboratoire de Synthe`se Organique, UMR-CNRS 6009,
Boite D12, Faculte´ des Sciences de St J e´roˆme, 13397
Marseille Cedex 20, France, and Laboratoire de
Physicochimie des Interfaces et des Milieux Re´actionnels,
EA 2098-LRC-MO2, Faculte´ des Sciences de Tours,
Parc de Grandmont, 37200 Tours, France
onstrated its efficiency in transferring but-3-enoic-d4 acid
synthons onto miscellaneous substrates.5 To broaden the
use of 2 in synthesis, we planned to prepare R-pyrones
from acyl chlorides using tandem Stille and lactonization
reactions (Scheme 1).
jl.parrain@univ.u-3mrs.fr
Received J anuary 11, 2002
We report the stereoselective synthesis of R-pyrones
under palladium complex catalysis from the functional
vinyltin 2.
The required organotin precursor 2 is easily obtained
by radical hydrostannation6 of but-3-ynoic acid 1 (pre-
pared via carboxylation of the corresponding allenylmag-
nesium bromide7) with 83% yield as a thermodynamic
mixture (E/Z ) 85/15). It should be noted that radical
hydrostannation conducted at a lower temperature (e.g.
in benzene) led to a 50/50 mixture of 2 and its internal
isomer. Our investigation began with the coupling of 2
Abstr a ct: Palladium-catalyzed stereoselective annulation
of a functional vinylstannane by acyl chlorides gives the
corresponding R-pyran-2-ones in good yields. This annulation
most probably proceeds through a Stille reaction/cyclization
sequence.
The R-pyrones constitute an important class of biologi-
cally active compounds, and their synthesis has been a
focus of considerable attention in synthetic organic
chemistry1 as well as in medicinal chemistry.2 In the past
decade, numerous methods reported for the synthesis of
these structures utilize halolactonization or transition
metals (Ag, Hg, Rh, Pd) to promote intramolecular
addition of carboxylic acid to alkynes.3 In general, these
reactions of 4-alkynoic acids occur with poor regioselec-
tivity and in many cases mixtures of γ-alkylidenebuteno-
lides and R-pyrones are obtained. The problem of regio-
selectivity was recently solved by Larock et al., who
demonstrated that substituted isocoumarins or R-pyrones
could be prepared by treating â-halogeno R,â-unsaturated
esters with internal alkynes in the presence of a pal-
ladium catalyst.4 Nevertheless, although these methods
are efficient, they use â-halogeno acid or ester precursors
which are not commercially available. In addition, we
have previously described the synthesis of 2 and dem-
Sch em e 2
with benzoyl chloride acid under standard Stille condi-
tions. To obtain good yields of 3a , we examined the
reaction under various conditions (solvent, catalyst). The
influence of the solvent on conversion rates was examined
in the first step. The cross-coupling reaction failed in the
presence of a palladium(II) complex, and numerous tin
byproducts were obtained in addition to butenoic acid.
Chloroform, DMF, and toluene were found to be ineffec-
tive while dioxane afforded low yields of phenylpyrone
3a . Switching PdII to phosphine-liganded Pd0 and using
chloroform as solvent also yielded very small quantities
of phenylpyrone 3a and a mixture of Z and E isomers as
major products of the enone resulting from the Stille
reaction. Fortunately, vinyltin reagent 2 yielded the
desired heterocycle 3a in 1,4-dioxane and in the presence
of 5% of tetrakis(triphenylphosphine)palladium. At-
tempts conducted at lower temperature (ca 40-50 °C)
led to lower yields. Nevertheless, we found that the use
of a strongly degassed medium gave better yield in 3a
even at 50 °C. It should be noted that tributyltin
carboxylate was found to be inert toward acyl chloride
function.
† Faculte´ des Sciences de St J e´roˆme.
‡ Faculte´ des Sciences de Tours.
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76, 625. (b) Rao, Y. S. Chem. Rev. 1964, 64, 353. (c) Knight, D. W.
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Y.; Maruno, M.; Wakamatsu, T. Synlett 1995, 871.
Other acyl chlorides were engaged under similar
conditions to determine the scope of the reaction. Reac-
tion of vinyl stannane 2 with a range of acyl chlorides
proceeded to give fair to good yields of R-pyrones 3a -o
(Table 1). A plausible explanation for the heteroannula-
(5) Thibonnet, J .; Abarbri, M.; Parrain, J .-L.; Ducheˆne, A. Tetrahe-
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10.1021/jo025518v CCC: $22.00 © 2002 American Chemical Society
Published on Web 05/03/2002

3942 J . Org. Chem., Vol. 67, No. 11, 2002
Ta ble 1. Syn th esis of r-P yr on es 3
Notes
nation. Cyclization would then occur via a lactonization
reaction on the dienol derived from A and with the
concomitant formation of bis(tributyltin) oxide. At this
stage, the determining role of 1,4-dioxane is difficult to
rationalize.
Finally, the synthesis of sibirinone 3f isolated from a
culture of Hypomyces semitranslucens G. Arnold,9 (E)-6-
pent-1-enyl-pyran-2-one 3i extracted from Solenopsis
invicta,10 6-pentylpyranone 3d found in a number of
plants and as a pheromone of ant11,12 and Paracotoin 3m ,
an intermediate in the biosynthesis of shikimic acid,13
was realized by this procedure.
In conclusion, a method was developed for the rapid
synthesis of R-pyrones using a functional vinyltin reagent
and acyl chloride. This was then applied to the synthesis
of natural pyrones isolated from different sources. Stille
cross-coupling followed by cyclization of the dienol form
resulted in the formation of fair to good yields of the
desired product in one step.
Exp er im en ta l Section
Gen er a l Meth od s. 1H NMR spectra were recorded at 200
MHz or at 300 MHz using CDCl3 as the solvent. Data, reported
using the residual proton resonance of CDCl3 (δH ) 7.25 ppm)
as the internal reference, are as follows in the order chemical
shift (δ in ppm relative to Me4Si), multiplicity (s, d, t, m, b for
singlet, doublet, triplet, quartet, broad), coupling constants
(J in Hz). 13C NMR was recorded at 50.5 or 75 MHz using CDCl3
solvent peak at δC ) 77.0 ppm as the reference. Electron impact
mass spectra were measured at 70 eV by GC-MS. Melting points
are uncorrected. Standard column chromatography was per-
formed on Merck silica gel (60 Å, 230-400 mesh silica gel) by
use of flash column chromatography techniques. Analytical thin-
layer chromatography (TLC) was conducted on Merck precoated
silica gel 60 F254 plates. All reactions were performed in oven-
dried glassware under positive argon pressure, unless otherwise
noted. Reaction mixtures were stirred magnetically. Toluene and
1,4-dioxane were distilled from sodium and benzophenone prior
to use. All reagents were purchased from Aldrich and used
without further purification.
Tr ibu tylsta n n yl-4-(tr ibu tylsta n n yl)bu t-3-en oa te (2). Un-
der N2 atmosphere, a toluene solution (20 mL) of but-3-ynoic
acid (1 g, 0.012 mol), tributyltin hydride (8.6 g, 0.029 mol), and
azobis(isobutyronitrile) (10 mg) was stirred at 100 °C. After 3
(8) (a) Stille, J . K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508. (b)
Stille, J . K.; Groh, B. L. J . Am. Chem. Soc. 1987, 109, 813. (c) Mitchell,
T. N. Synthesis 1992, 803. (d) Farina, V. In Comprehensive Organo-
metallic Chemistry II; Abel, E. W., Stone, F. G., Wilkinson, G., Eds.;
Elsevier: Oxford, U.K., 1995; Vol. 12, Chapter 3.4, pp 161-241. (e)
Farina, V. Roth, G. P. In Advances in Metal-Organic Chemistry;
Liebeskind, L. S., Ed.; J AI Press: New York, 1996; Vol. 5, pp 1-53.
(f) Farina, V. Krishnamurthy, V.; Scott, W. J . Organic Reactions;
Paquette, L. A., Ed.; J ohn Wiley & Sons: New York, 1997; Vol. 50,
Chapter 1, pp 1-652. (g) Farina, V.; Krishnamurthy, V. The Stille
Reaction; Wiley: New York, 1999.
(9) (a) Crombie, L. J . Chem. Soc. 1955, 999. (b) Crombie, L.;
Manzoor-Khuda, M. J . Chem. Soc. 1957, 2767. (c) Dunstan, W. R.;
Garnett, H. J . Chem. Soc. 1895, 67, 94. (d) Crombie, L. Chem. Ind.
(London) 1952, 2997. (e) J acobson, M. J . Am. Chem. Soc. 1953, 75,
2584. (f) Nokami, J .; Nishiuchi, K.; Wakabayashi, S.; Okawara, R.
Tetrahedron Lett. 1980, 21, 4455. (g) Ono, N.; Miyake, H.; Tanabe, Y.,
Tanaka, K.; Kaji, A. Chem. Lett. 1980, 1365. (h) Mandai, T.; Gotoh, J .;
Otera, J .; Kawada, M. Chem. Lett. 1980, 313. (i) Sato, T., Kawashima,
M.; Fujisawa, T. Tetrahedron Lett. 1981, 22, 2375.
Sch em e 3
(10) Gbewonyo, W. S. K.; Candy, D. J .; Anderson, M. Pestic. Sci.
1993, 37, 57.
(11) Sevenants, M. R.; J ennings, W. G. J . Food Sci. 1971, 36, 536.
Collins, R. P.; Halim, A. F. J . Agr. Food Chem. 1972, 20, 437. Cutler,
H. G.; Cox, R. H.; Crumley, F. G.; Cole, P. D. Agr. Biol. Chem. 1986,
50, 2943.
(12) J anssen, E.; Ho¨lldobler, B.; Kern, F.; Bestmann, H. J .; Tsuji,
K. J . Chem. Ecol. 1997, 23, 1025.
(13) (a) Ominaga, Yoshinori; Ushirogochi, Atsuyuki; Matsuda,
Yoshiro J . Heterocycl. Chem. 1987, 24, 1557. (b) Dae Gong, Y.; Tanaka,
H.; Iwasawa, N.; Narasaka, K. Bull. Chem. Soc. J pn. 1998, 71, 2181.
tion reaction would be the following mechanism. The first
step, according to the Stille mechanism,8 would yield the
tributylstannyl 5-substituted 5-oxopent-3-enoate A by
oxidative addition, transmetalation, and reductive elimi-

Notes
J . Org. Chem., Vol. 67, No. 11, 2002 3943
1
h, toluene was eliminated under vacuum and then carbon
tetrachloride (15 mL) was added to react with the excess
tributyltin hydride. After the solution was stirring for 1 h,
potassium fluoride solution (0.5 M, 15 mL) and acetone (15 mL)
were added. The solution was extracted with diethyl ether after
filtration and then dried over magnesium sulfate. After elimina-
tion of the solvents, tributylstannyl-4-(tributylstannyl)but-3-
enoate (6.56 g) (2) was obtained as a 85/15 mixture of Z and E
(83% yield): IR (neat) 2957, 2924, 2872, 2854, 1655, 1580-1550,
1634, 1559, 1082, 723, 654 cm-1; H NMR (CDCl3, 300 MHz) δ
2.12-2.14 (m, 2H), 2.66 (t, J ) 7.2 Hz, 2H), 3.56 (t, J ) 7.2 Hz,
2H), 6.03 (d, J ) 6.6 Hz, 1H), 6.16 (d, J ) 9.3 Hz, 1H), 7.26 (dd,
J ) 9.3, 6.6 Hz, 1H); 13C NMR (CDCl3, 75 MHz) δ 29.8, 31.3,
44.0, 103.8, 114.0, 144.0, 162.9, 164.9; MS (70 eV, EI) m/z 174
(M+, 10), 172 (31), 144 (34), 95 (100), 82 (12), 81 (33), 39 (19).
Anal. Calcd for C8H9ClO2: C, 55.67; H, 5.26. Found: C, 55.60;
H, 5.23.
6-P r op -1-en ylp yr a n -2-on e (3f): isolated in 61% yield as
white solid; mp 49.5-50.5 °C; IR (KBr) 3100, 2961, 2938, 2915,
1739, 1653, 1536, 1092 cm-1; 1H NMR (CDCl3, 300 MHz) δ 1.87
(dd, J ) 7.2 Hz, 1.8 Hz, 3H), 5.95 (d, J ) 6.6 Hz, 1H), 5.99 (dq,
J ) 15.6 Hz, 1.8 Hz, 1H), 6.12 (d, J ) 9.4 Hz, 1H), 6.65 (dq, J )
15.6, 7.2 Hz, 1H), 7.26 (dd, J ) 9.4, 6.6 Hz, 1H); 13C NMR (CDCl3,
75 MHz) δ 18.7, 103.2, 114.0, 123.3, 134.8, 144.3, 160.0, 162.3;
MS (70 eV, EI) m/z 136 (M+, 19), 108 (86), 107 (16), 95 (40), 79
(39), 69 (15), 44 (42), 39 (31). Anal. Calcd for C8H8O2: C, 70.57;
H, 5.92. Found: C, 70.62; H, 5.90.
1
1461, 1377, 1074 cm-1; H NMR (CDCl3, 200 MHz) δ E isomer
0.8-1.65 (m, 54H), 3.18 (d, J ) 5.0 Hz, J Sn-H ) 12 Hz, 2H), 6.05
(d, J ) 18.9 Hz, J Sn-H ) 70-73 Hz, 1H), 6.15 (dt, J ) 18.9 Hz,
5.0 Hz, J Sn-H ) 61-64 Hz, 1H), Z isomer 3.08 (dd, J ) 7.1 Hz,
1.3 Hz, 2H), 6.00 (dt, J ) 12.6 Hz, 1.3 Hz, 1H), 6.69 (dt, J )
12.6 Hz, 7.1 Hz, 1H); 13C NMR (CDCl3, 50.5 MHz) δ E isomer
9.3 (J Sn-C ) 340-346 Hz, 3C), 13.5 (6C), 16.6 (J Sn-C ) 345-355
Hz, 3C), 26.9 (J Sn-C ) 64 Hz, 3C), 27.1 (J Sn-C ) 53.5 Hz, 3C),
27.8 (J Sn-C ) 21 Hz, 3C), 28.8 (J Sn-C ) 20 Hz, 3C), 44 (J Sn-C
)
65 Hz, 1C), 130.7 (J Sn-C ) 369-386 Hz, 1C), 141.7 (J Sn-C ) 21
Hz, 1C), 176.7 (1C), Z isomer 42.3 (1C), 130.9 (1C), 141.9 (1C);
MS (70 eV, EI) m/z 609 (M+, 55), 507 (29), 319 (21), 291 (100),
269 (36), 267 (45), 235 (60), 57 (51), 56 (48), 49 (29), 43 (34), 42
(46), 41 (90).
6-Isop r op en ylp yr a n -2-on e (3g): isolated in 51% yield; IR
(KBr) 1718, 1605, 1505, 1489, 1236, 1030 cm-1; 1H NMR (CDCl3,
200 MHz) δ 1.97 (s, 3H), 5.32 (bs, 1H), 5.96 (bs, 1H), 6.20 (d,
J ) 6.8 Hz, 1H), 6.22 (q, J ) 9.3 Hz, 1H), 7.34 (dd, J ) 9.3 Hz,
J ) 6.8 Hz, 1H); 13C NMR (CDCl3, 50.5 MHz) δ 18.5, 101.7,
114.8, 118.8, 134.0, 143.3, 160.6, 161.7; MS (70 eV, EI) m/z 136
(M+, 88), 108 (100), 95 (73), 79 (18), 39 (34). Anal. Calcd for
C8H8O2: C, 70.57; H, 5.92. Found: C, 70.68; H, 5.85.
Typ ica l P r oced u r e. In
a Schlenk tube, to a degassed
solution of 2.11 g (15 mmol) of benzoyl chloride in 50 mL of
distilled dioxane was added dropwise 6.64 g (10 mmol) of
tributylstannyl-4-(tributylstannyl)but-3-enoate (E/Z ) 91/9), and
then 570 mg (5% mol) of tetrakis(triphenylphosphine)pallad-
ium(0) was added. After being stirred 6 h at room temperature,
the mixture was hydrolyzed with a saturated solution of am-
monium chloride and extracted with diethyl ether (3 × 50 mL).
The organic phase was washed with a saturated solution of
sodium chloride and dried with magnesium sulfate. A 1.24 g
(7.20 mmol) yield of 6-phenylpyran-2-one was obtained after
purification by column chromatography on silica gel (95/5
hexane/diethyl ether).
6-(2-Met h ylp r op en yl)p yr a n -2-on e (3h ): isolated in 43%
yield; IR (KBr) 3100, 1730, 1650, 1540, 1450, 1370, 1180 cm-1
;
1H NMR (CDCl3, 200 MHz) δ 1.88 (s, 3H), 2.09 (s, 3H), 5.77 (bs,
1H), 5.94 (d, J ) 6.9 Hz, 1H), 6.05 (d, J ) 9.3 Hz, 1H), 7.27 (dd,
J ) 9.3 Hz, 6.9 Hz, 1H); 13C NMR (CDCl3, 50.5 MHz) δ 20.6,
28.0, 104.2, 111.9, 117.1, 143.9, 146.2, 161.2, 162.1; MS (70 eV,
EI) m/z 150 (M+, 100), 122 (58), 107 (42), 95 (17), 93 (10), 79
(32), 55 (10), 39 (18). Anal. Calcd for C9H10O2: C, 71.98; H, 6.71.
Found: C, 71.91; H, 6.74.
(E)-6-P en t-1-en ylp yr a n -2-on e (3i): isolated in 52% yield
6-P h en ylp yr a n -2-on e (3a ): isolated in 72% yield as a yellow
solid; mp 62-63 °C; IR (KBr) 3070, 1722, 1689, 1603, 1580, 1329,
as a colorless liquid; IR (neat) 1734, 1630, 1555, 1243, 1080 cm-1
;
1H NMR (CDCl3, 300 MHz) δ 0.90 (t, J ) 7.5 Hz, 3H), 1.46 (bm,
J = 7.5 Hz, 2H), 2.17 (tdd, J ) 7.5 Hz, 7.2 Hz, 1.5 Hz, 2H), 5.94
(d, J ) 6.6 Hz, 1H), 5.97 (dt, J ) 15.6 Hz, J ) 1.5 Hz, 1H), 6.13
(d, J ) 9.3 Hz, 1H), 6.66 (dt, J ) 15.6 Hz, J ) 7.2 Hz, 1H), 7.26
(dd, J ) 9.3 Hz, J ) 6.6 Hz, 1H); 13C NMR (CDCl3, 75 MHz) δ
14.0, 22.2, 35.2, 103.4, 114.0, 122.1, 139.9, 144.3, 160.1, 162.4;
MS (70 eV, EI) m/z 164 (M++1, 100), 136 (18), 123 (21), 122 (68),
121 (10), 110 (37), 107 (96), 95 (83), 94 (95), 79 (41), 77 (38), 55
(17), 39 (86). Anal. Calcd for C10H12O2: C, 73.15; H, 7.37.
Found: C, 73.26; H, 7.33.
1
1292 cm-1; H NMR (CDCl3, 300 MHz) δ 6.29 (dd, J ) 9.3 Hz,
0.9 Hz, 1H), 6.67 (dd, J ) 6.9 Hz, 0.9 Hz, 1H), 7.41-7.48 (m,
5H), 7.83 (dd, J ) 9.3 Hz, 6.9 Hz, 1H); 13C NMR (CDCl3, 75 MHz)
δ 101.4, 114.4, 126.0, 129.3, 131.3, 131.7, 144.1, 161.5, 162.4;
MS (70 eV, EI) m/z 172 (M+, 56), 145 (11), 144 (100), 115 (40),
95 (15), 77 (26), 51 (12). Anal. Calcd for C11H8O2: C, 76.73; H,
4.68. Found: C, 76.79; H, 4.75.
6-Isop r op ylp yr a n -2-on e (3b): isolated in 66% yield as a
colorless liquid; IR (neat) 3096, 2983, 2897, 1738, 1641, 1570,
1098 cm-1 1H NMR (CDCl3, 200 MHz) δ 1.18 (d, J ) 7.1 Hz,
;
6-Ben zylp yr a n -2-on e (3j): isolated in 53% yield as a color-
less liquid; IR (KBr) 3063, 3030, 1732, 1634, 1603, 1556, 1496,
1455, 1089, 699; 1H NMR (CDCl3, 300 MHz) δ 3.78 (s, 2H), 5.88
(dd, J ) 6.6 Hz, 0.9 Hz, 1H), 6.13 (d, J ) 9.3 Hz, 1H), 7.19-7.36
(m, 6H); 13C NMR (CDCl3, 75 MHz) δ 28.6, 103.8, 113.8, 127.7,
129.2, 129.6, 135.5, 144.1, 162.8, 165.5; MS (70 eV, EI) m/z 186
(M+, 30), 95 (100), 65 (10), 39 (10); HRMS (EI) calcd for C12H10O2
186.0681, found 186.0674. Anal. Calcd for C12H10O2: C, 77.40;
H, 5.41. Found: C, 77.47; H, 5.46.
6H), 2.68 (m, J ) 7.1 Hz, 1H), 5.96 (d, J ) 6.0 Hz, 1H), 6.10 (d,
J ) 9.3 Hz, 1H), 7.26 (dd, J ) 9.3 Hz, 6.6 Hz, 1H); 13C NMR
(CDCl3, 50.5 MHz) δ 18.4 (2C), 33.6, 100.6, 112.8, 144.3, 163.1,
170.9; MS (70 eV, EI) 138 (M+, 12), 83 (13), 75 (100), 73 (26), 59
(79), 49 (69), 47 (25), 45 (17), 31 (35), 29 (25), 27 (10). Anal. Calcd
for C8H10O2: C, 69.54; H, 7.30. Found: C, 69.59; H, 7.28.
6-Isobu tylp yr a n -2-on e (3c): isolated in 62% yield as a
colorless liquid; IR (neat) 3100, 2980, 2895, 1740, 1640, 1570,
1
1095, 805 cm-1; H NMR (CDCl3, 200 MHz) δ 0.83 (d, J ) 8.0
6-(4-Meth oxyp h en yl)p yr a n -2-on e (3k ): isolated in 70%
yield as white solid; mp 96-98 °C; IR (KBr) 3075, 2936,
1720, 1625, 1544, 1511, 1252, 1186; 1H NMR (CDCl3, 300
MHz) δ 3.87 (s, 3H), 6.22 (dd, J ) 9.3 Hz, 0.9 Hz, 1H), 6.56 (d,
J ) 6.9 Hz, 0.9 Hz, 1H), 6.97 (d, J ) 9.0 Hz, 2H), 7.40 (dd,
Hz, 6H), 1.96 (m, 1H), 2.23 (d, J ) 7.2 Hz, 2H), 5.90 (d, J ) 6.5
Hz, 1H), 6.04 (d, J ) 9.4 Hz, 1H), 7.20 (dd, J ) 9.4, 6.5 Hz, 1H);
13C NMR (CDCl3, 50.5 MHz) δ 21.8, 22, 26.5, 42.5, 103.5, 112.6,
143.6, 162.7, 165.4; MS (70 eV, EI) m/z 152 (M+,19), 124 (12),
110 (58), 95 (65), 82 (33), 81 (40), 68 (12), 53 (14), 43 (28), 39
(100), 38 (11). Anal. Calcd for C9H12O2: C, 71.03; H, 7.95.
Found: C, 71.10; H, 7.90.
J
) 9.3 Hz, 6.9 Hz, 1H), 7.78 (d, J ) 9.0 Hz, 2H); 13C
NMR (CDCl3, 75 MHz) δ 55.8, 100.0, 113.0, 114.7 (2C), 124.3,
127.7 (2C), 144.4, 161.7, 162.2, 162.6, 162.6; MS (70 eV, EI) m/z
202 (M+, 82), 175 (11), 174 (100), 159 (53), 131 (20), 77 (18), 39
(14); HRMS (EI) calcd for C12H10O3 202.0630, found 202.0620.
Anal. Calcd for C12H10O3: C, 71.28; H, 4.98. Found: C, 71.17;
H, 4.92.
6-P en tylp yr a n -2-on e (3d ): isolated in 55% yield as
a
colorless liquid; IR (neat) 3087, 2957, 2932, 2862, 1732, 1635,
1
1558, 1466, 1084 cm-1; H NMR (CDCl3, 300 MHz) δ 0.83 (t, J
) 7.2 Hz, 3H), 1.22-1.29 (m, 4H), 1.55-1.61 (m, 2H), 2.40 (t, J
) 7.2 Hz, 2H), 5.93 (dd, J ) 6.6 Hz, J ) 0.6 Hz, 1H), 6.06 (bd,
J ) 9.3 Hz, 1H), 7.21 (dd, J ) 9.3 Hz, J ) 6.6 Hz, 1H); 13C NMR
(CDCl3, 75 MHz) δ 14.2, 22.6, 26.9, 31.4, 34.1, 103.0, 113.3, 144.2,
163.2, 167.1; MS (70 eV, EI) m/z 166 (M+, 30), 110 (34), 95 (100),
82 (36), 81 (41), 68 (18), 53 (11), 41 (11), 39 (56); HRMS (EI)
calcd for C10H14O2, 166.0994, found 166.0988. Anal. Calcd for
C10H14O2: C, 72.26; H, 8.49. Found: C, 72.31; H, 8.41.
6-(2-Br om op h en yl)p yr a n -2-on e (3l): isolated in 56% yield
as white solid; mp 57-58 °C; IR (KBr) 3064, 1734, 1628, 1550,
1
1471, 1079; H NMR (CDCl3, 300 MHz) δ 6.35 (dd, J ) 9.3 Hz,
0.9 Hz, 1H), 6.63 (dd, J ) 6.9 Hz, 0.9 Hz, 1H), 7.29-7.33 (m,
1H), 7.38-7.46 (m, 2H), 7.59 (d, J ) 7.8 Hz, 1H), 7.67 (d, J )
7.8 Hz, 1H); 13C NMR (CDCl3, 75 MHz) δ 106.9, 115.4, 121.8,
128.0, 131.2, 131.2, 131.8, 133.6, 134.4, 143.6, 160.6, 162.3; MS
(70 eV, EI) m/z 252 (M+, 51), 250 (52), 224 (98), 222 (100), 195
6-(3-Ch lor op r op yl)p yr a n -2-on e (3e): isolated in 48% yield
as a colorless liquid; IR (neat) 3086, 2957, 2930, 2861, 1730,

3944 J . Org. Chem., Vol. 67, No. 11, 2002
Notes
(10), 185 (10), 155 (13), 115 (59), 95 (32), 75 (14); HRMS (EI)
calcd for C11H7O2Br: 249.9629, found 249.9624. Anal. Calcd for
(E)-6-(2-Ben zo[1,3]d ioxol-5-vin yl)p yr a n -2-on e (3o): iso-
lated in 68% yield as a yellow solid; mp 173-174 °C; IR (KBr)
1728, 1714, 1629, 1531, 1262, 1037; 1H NMR (CDCl3, 200 MHz)
δ 6.03 (s, 1H), 6.14 (d, J ) 6.7 Hz, 1H), 6.23 (d, J ) 9.1 Hz, 1H),
6.48 (d, J ) 15.9 Hz, 1H), 6.84 (d, J ) 6.7 Hz, 1H), 7.01 (d, J )
7.6 Hz, 1H), 7.05 (s, 1H), 7.37 (dd, J ) 9.1 Hz, J ) 6.7 Hz, 1H),
7.43 (d, J ) 15.9 Hz, 1H); 13C NMR (CDCl3, 50.5 MHz) δ 102.1,
105.1, 106.4, 109.3, 114.4, 117.5, 124.3, 130.4, 135.6, 144.4, 148.9,
149.5, 160.5, 162.5; MS (70 eV, EI) m/z 242 (M+, 29), 214 (15),
186 (25), 128 (31), 95 (11), 89 (24), 78 (10), 63 (36), 51 (20), 39
(100). Anal. Calcd for C14H10O4: C, 69.42; H, 4.16. Found: C,
69.55; H, 4.19.
C
11H7BrO2: C, 52.62; H, 2.81. Found: C, 52.65; H, 2.85.
6-Ben zo[1,3]d ioxol-5-ylp yr a n -2-on e (3m ): isolated in 83%
yield as a yellow solid; mp 146-148 °C; IR (KBr) 1718, 1605,
1505, 1489, 1264, 1110; 1H NMR (CDCl3, 200 MHz) δ 6.00 (s,
2H), 6.19 (d, J ) 9.3 Hz, 1H), 6.48 (d, J ) 6.9 Hz, 1H), 6.83 (d,
J ) 8.2 Hz, 1H), 7.23 (s, 1H), 7.32-7.41 (m, 2H); 13C NMR
(CDCl3, 50.5 MHz) δ 100.6, 102.4, 106.3, 109.2, 113.6, 121.2,
126.1, 144.4, 149.0, 150.6, 161.5, 162.5; MS (70 eV, EI) m/z 216
(M+, 26), 188 (48), 102 (30), 91 (10), 65 (24), 63 (34), 51 (17), 50
(12), 39 (100). Anal. Calcd for C12H8O2: C, 66.67; H, 3.73.
Found: C, 66.75; H, 3.76.
Ack n ow led gm en t. We thank the CNRS and MEN-
RT for providing financial support and the “Service
d’analyze chimique du vivant de Tours” for recording
NMR and mass spectra.
(E)-6-Styr ylp yr a n -2-on e (3n ): isolated in 85% yield as a
yellow solid; mp 115-116 °C; IR (KBr) 3047, 1733, 1686, 1637,
1528, 1359, 1094; 1H NMR (CDCl3, 200 MHz) δ 6.10 (d, J ) 6.7
Hz, 1H), 6.16 (d, J ) 9.3 Hz, 1H), 6.57 (d, J ) 16.0 Hz, 1H),
7.23-7.35 (m, 4H), 7.38-7.47 (m, 3H); 13C NMR (CDCl3, 50
MHz) δ 104.9, 114.1, 118.6, 127.3 (2C), 128.8 (2C), 135.1, 135.2,
143.6, 159.5, 161.7; MS (70 eV, EI) m/z 198 (M+, 29), 170 (23),
142 (23), 141 (36), 115 (17), 95 (10), 77 (30), 51 (34), 39 (100).
Anal. Calcd for C13H10O2: C, 78.77; H, 5.09. Found: C, 78.82;
H, 5.06.
Su p p or tin g In for m a tion Ava ila ble: An 1H NMR spec-
trum of 2. This material is available free of charge via the
Internet at http://pubs.acs.org.
J O025518V