Formation of Fluorinated Heterocycles from Aromatic Silyl Enol Ethers

Full text of DOI:10.1021/jo971989j

J . Org. Chem. 1998, 63, 5623-5626
5623
Notes
Sch em e 1
F or m a tion of F lu or in a ted Heter ocycles
fr om Ar om a tic Silyl En ol Eth er s
Yan-Song Liu,† Suzanne T. Purrington,*,† and
Wei-Yuan Huang‡
Department of Chemistry, Box 8204, North Carolina State
University, Raleigh North Carolina 27695-8204, and
Shanghai Institute of Organic Chemistry, Chinese Academy
of Sciences, 354 Fenglin Rd., Shanghai 200032, China
Received October 29, 1997
Because of the interesting characteristics bestowed on
many organic compounds that contain fluorine, there has
been considerable effort to broaden synthetic methods for
the incorporation of fluorine.1 Fluorinated acrylates have
been used as building blocks for formation of heterocyclic
compounds containing polyfluoroalkyl side chains.2 In
an effort to extend this methodology, we have investi-
gated the reaction of 2′-hydroxyphenones with a poly-
fluoroacrylate ester. Although more than one product
was formed in these reactions and low yields were
obtained, the reactions show a rich mechanistic diversity.
It is interesting that two such similar compounds react
by such different pathways.
Sch em e 2
In the presence of triethylamine, reaction of 2′-hy-
droxyacetophenone 1a or 2′-hydroxypropiophenone 1b
with ethyl 2,2-dihydrononafluorohexanoate 23 gave rise
to the aryloxy esters 3 as shown in Scheme 1. The
fluorinated ester first loses HF to form an intermediate
acrylate which adds Michael fashion with loss of fluoride
ion to give the product. Only the Z isomer was formed
7a with the loss of the ethoxy group. The tricyclic system
6a was formed as a mixture of E and Z isomers separable
by column chromatography. Compounds with this ring
system have found use as antiasthma agents;7 to our
knowledge, no fluorine-containing analogues have been
reported. On the other hand the propiophenone deriva-
tive 5b undergoes less extensive dehydrofluorination to
form the 3(2H)-benzofuranone 8b and with the loss of
the ethoxy group, lactone 9b. The steric effect of the
methyl group in 5b alters the pathway for formation of
the lactone. The proposed mechanisms for the formation
of compounds 6a , 7a , 8b, and 9b from 5a and 5b are
illustrated in Scheme 3.
3
as determined from the J (CF) coupling constant of 5.3
Hz.4 In the case of ketone 1b, byproduct 4b was formed
in 9% yield.
The trimethylsilylenol ethers of the ketones 5 were
prepared in good yield from esters 3a /3b and chlorotri-
methylsilane5 as shown in Scheme 1. The silyl com-
pounds, upon treatment with tetrabutylammonium fluo-
ride in acetonitrile, each gave two major products (Scheme
2). One of the resulting compounds suffered extensive
dehydrofluorination while the other lost the ethoxy
moiety. Loss of fluorine from polyfluoroalkyl chains has
been reported previously.6 The acetophenone derivative
5a gives rise to 6a with the loss of fluorine and lactone
Upon treatment with tetrabutylammonium fluoride,
the oxygen-silicon bond of compound 5 is cleaved with
the formation of an enolate ion, which undergoes an
intramolecular Michael addition reaction to the R,â-
unsaturated ester. The result is intermediate I (Scheme
3), which then ring opens with the aryloxy anion as a
leaving group, and the formation of intermediate II,
which can either isomerize to III or enolize to IV. In
intermediate III, the aryloxy anion acts as a nucleophile
to attack the double bond to give rise to V, which
dehydrofluorinates further and gives 8. Starting with
propiophenone derivative 5b, where R′ is a methyl group,
† North Carolina State University.
‡ Shanghai Institute of Organic Chemistry.
(1) (a) Banks, R. E.; Smart, B. E.; Tatlow, J . C. Organofluorine
Chemistry, Principles and Commercial Applications; Plenum Press:
New York, 1994. (b) Hu, C.-M.; Qing, F.- L.; Huang, W.-Y. J . Org.
Chem. 1991, 56, 2801.
(2) (a) Huang, W.-Y.; Liu, Y.-S.; Lu, L. J . Fluorine Chem. 1994, 66,
263. (b) Liu, Y.-S.; Huang, W.-Y. J . Chem. Soc., Perkin Trans I, 1997,
981.
(3) Huang, W.-Y.; Lu, L.; Zhang, Y.-F. Chin. J . Chem. 1990, 281.
(4) Be´gue´, J .-P.; Bonnet-Delpon, D.; Mesureur, D.; Ourevitch, M.
Magn. Reson. Chem. 1991, 29, 675.
(5) Cazeau, P.; Duboudin, F.; Moulines, F.; Babot, O.; Dunogues J .
Tetrahedron 1987, 43, 2075.
(6) (a) Dondy, B.; Portella, C. J . Org. Chem. 1993, 58, 6671. (b) Haas,
A.; Hardt, T. P.; Wallmichrath, T. 15th Int. Symp. on Fluorine Chem.
Vancouver, Canada, August 1997.
(7) Wright, J . B.; J ohnson, H. G. J . Med. Chem. 1973, 16, 861.
S0022-3263(97)01989-0 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/18/1998

5624 J . Org. Chem., Vol. 63, No. 16, 1998
Notes
Sch em e 3
Sch em e 4
Sch em e 5
8b is the final product. With the acetophenone derivative
5a where R′ is H, 8a tautomerizes to VI. In VI, the enol
acts as a nucleophile and adds intramolecularly in a 1,6-
conjugate manner followed by elimination of fluoride to
give 6a as the final product.
From the other intermediate, enolate IV, the products
also depend on the R′ groups. When R′ is H, the oxygen
of the enolate attacks the carbonyl group of the ester to
give compound 7a . This compound is formed from the
s-cis conformer of the enolate. When R′ is a methyl
group, because of the steric hindrance between the
methyl and the heptafluoropropyl groups, the enolate
favors conformer VII, which can form enol ether IX.
Subsequent hydrolysis by water present in the tetrabu-
tylammonium fluoride solution leads to 9b (Scheme 4).
It was found that the reaction product ratio (6a vs 7a ,
8b vs 9b) depends on the reaction conditions. K2CO3 was
used in order to increase the amounts of defluorination
products 6a and 8b. However, to our surprise, 7a (62%)
and 9b (64%) were found to be the major products with
only trace amounts of 6a (5%) and 8b (6%). It is possible
that the presence of base accelerates the rate of conver-
sion from II to enolate IV, leading to the increasing yields
of 7a and 9b.
chemical shifts are reported in parts per million downfield
(positive) of the standard: CFCl3 for 19F and tetramethylsilane
for 1H and 13C NMR spectra. Elemental analyses were per-
formed by Atlantic Microlab, Inc., Norcross, GA, and the HRMS
were performed by the mass spectrometry facility at NCSU.
P r ep a r a tion of 2.3 With magnetic stirring, a mixture of
Na2S2O4 (17.4 g, 100 mmol) and NaHCO3 (8.7 g, 104 mmol) was
added to a solution of C4F9I (34.6 g, 100 mmol), ethyl vinyl ether
(9.36 g, 130 mmol), 130 mL of CH3CN, and 80 mL of H2O at
5-10 °C. After 10 min the solution was diluted with 300 mL of
water. The organic layer was separated, the aqueous layer was
extracted with Et2O (30 mL × 3), and 80 mL of acetone was
added to the combined organic layer. Then
a mixture of
chromium trioxide (20 g, 200 mmol), concentrated sulfuric acid
(20 mL), and H2O (100 mL) was added dropwise to the solution,
maintaining the temperature of the reaction mixture below 10
°C. After stirring at room temperature overnight, the mixture
was extracted with ether (100 mL x 3). After removal of solvent,
EtOH (30 mL), benzene (50 mL), and p-toluenesulfonic acid (1
g) were added to the residue. The mixture was refluxed for 16
h, and the water formed during the reaction was removed using
a Dean-Stark trap. The reaction mixture was diluted with 50
mL of H2O and extracted with ether (60 mL × 3). The combined
organic layer was washed with 5% NaHCO3 (40 mL) and
saturated NaCl solution (50 mL) and dried over MgSO4. Distil-
lation gave 2 (20.13 g, 66%) as a colorless liquid: bp, 146-149
°C. 1H NMR (CDCl3): δ 1.27 (t, 3H, J ) 7.2 Hz), 3.10 (t, 2H, J
) 17.5 Hz), 4.21 (q, 2H, J ) 7.2 Hz). 19F NMR (CDCl3): δ -81.6
(t, 3F, J ) 10.5 Hz), -112.4 (m, 2F), -124.4 (m, 2F), -126.4 (m,
2F).
The structures of compounds 7a and 9b were further
confirmed by an etherification reaction. When 7a (or 9b)
was treated with methyl iodide in acetonitrile in the
presence of potassium carbonate, 7c (or 9c) was obtained
in high yield (Scheme 5).
Exp er im en ta l Section
Melting points are uncorrected. Analytical thin-layer chro-
matography (TLC) was performed on Baker-flex silica gel IB2-F
plates. Flash chromatography was performed on Aldrich silica
gel (70-230 mesh). 1H NMR, 19F NMR, and 13C NMR spectra
were recorded at 300, 282, and 75 MHz, respectively. All

Notes
P r ep a r a tion of Ar yloxy Ester s 3. Ethyl 2,2-dihydronon-
J . Org. Chem., Vol. 63, No. 16, 1998 5625
6a 1. Yellow solid, mp 101-103 °C, 0.09 g (25%). IR
afluorohexanoate 2 (0.61 g, 2.0 mmol), 2′-hydroxyacetophenone,
1a (0.27 g, 2.0 mmol) or 2′-hydroxypropiophenone 1b (0.30 g,
2.0 mmol), and 6 mmol of triethylamine in 5 mL of acetonitrile
were stirred under reflux until 19F NMR indicated the complete
consumption of 2 (2-4 h). The solvent was then evaporated,
and the residue was purified by column chromatography using
petroleum ether/ethyl acetate (30:1) as eluant to afford 3a (or
3b) as a light yellow oil.
(CHCl3): 1723, 1643, 1595, 1258, 1237 cm-1 1H NMR (CDCl3):
.
δ 1.33 (t, 3H, J ) 7.1 Hz), 4.26 (q, 2H, J ) 7.1 Hz), 5.97 (s, 1H),
7.37 (m, 1H), 7.49 (m, 2H), 7.69 (d, 1H, J ) 7.6 Hz). 19F NMR
(CDCl3): δ -65.53 (d, 3F, J ) 21.2 Hz), -137.37 (q, 1F, J )
21.2 Hz). 13C NMR (CDCl3): δ 14.43, 60.95, 101.66 (d, J ) 5.5
Hz), 112.70, 118.15, 119.08, 119.51 (q, J ) 266.0 Hz), 123.42,
123.72, 124.64, 128.46, 137.94, 138.68 (d, J ) 14.5 Hz), 148.82
(d, J ) 269.1 Hz), 154.59, 165.17. MS m/z: 342 (M+), 297 (70),
270 (100), 187 (12), 160 (9). UV: λabs(CHCl3) 342.0 nm.
6a 2. Yellow solid, mp 89-91 °C, 0.054 g (16%). IR (CHCl3):
3a . Yield: 0.68 g (85%). IR (neat): 1730, 1682, 1599, 1576,
1237 cm-1 1H NMR (CDCl3): δ 1.00 (t, 3H, J ) 7.1 Hz), 2.64
.
(s, 3H), 3.91 (q, 2H, J ) 7.1 Hz), 6.30 (s, 1H), 6.94 (d, 1H, J )
1718, 1609, 1405, 1243, 1215 cm-1 1H NMR (CDCl3): δ 1.39
.
8.2 Hz), 7.17 (m, 1H), 7.43 (m, 1H), 7.86 (d, 1H, J ) 7.2 Hz). 19
F
(t, 3H, J ) 7.1 Hz), 4.33 (q, 2H, J ) 7.1 Hz), 5.80 (s, 1H), 7.38
(m, 1H), 7.51 (m, 1H), 7.64 (d, 1H, J ) 8.4 Hz), 7.74 (d, 1H, J )
7.8 Hz). 19F NMR (CDCl3): δ -65.72 (d, 3F, J ) 20.8 Hz),
-147.43 (q, 1F, J ) 20.8 Hz). 13C NMR (CDCl3): δ 14.36, 60.59,
99.76 (d, J ) 6.0 Hz), 112.94, 117.12, 118.99, 124.27, 124.57,
128.78, 137.05 (d, J ) 8.9 Hz), 139.75, 149.06 (d, J ) 259.7 Hz),
154.48, 165.23. MS m/z: 342 (M+), 297 (66), 270 (100), 257 (1),
241 (7), 148 (8), 123 (6). UV: λabs(CHCl3) 341.0 nm. HRMS:
calcd for C16H10F4O4, 342.0515; found, 342.0508.
NMR (CDCl3): δ -80.72 (t, 3F, J ) 10.6 Hz), -117.34 (m, 2F),
-126.08 (s, 2F). 13C NMR (CDCl3): δ 13.7, 31.4, 61.6, 107.8,
111.3, 112.5 (t, J ) 5.3 Hz), 113.9, 115.7 (m), 119.5 (m), 124.0,
128.6, 130.9, 133.5, 148.8 (t, J ) 26.5 Hz), 155.7, 161.6, 197.9.
MS m/z: 402 (M+), 359 (5), 315 (80), 267 (10), 187 (60), 137 (80),
121 (100). Anal. calcd for C16H13F7O4: C, 47.77; H, 3.26.
Found: C, 48.00; H, 3.40.
3b. Yield: 0.57 g (69%). IR (neat): 1729, 1686, 1600, 1210
cm-1
.
1H NMR (CDCl3): δ 0.99 (t, 3H, J ) 7.1 Hz), 1.18 (t, 3H,
7a . Yellow solid, mp 174-176 °C, 0.078 g (22%). IR
J ) 7.2 Hz), 3.00 (q, 2H, J ) 7.2 Hz), 3.90 (q, 2H, J ) 7.1 Hz),
6.29 (s, 1H), 6.94 (d, 1H, J ) 8.2 Hz), 7.16 (m, 1H), 7.41 (m,
1H), 7.82 (d, 1H, J ) 7.7 Hz). 19F NMR (CDCl3) δ: -80.77 (t,
3F, J ) 10.3 Hz), -117.33 (m, 2F), -126.15 (s, 2F). MS m/z:
416 (M+), 387 (1), 343 (7), 315 (100), 247 (6), 196 (24), 167 (11),
(CHCl3): 3338 (br), 1723, 1600, 1536, 1349, 1237, 1215 cm-1
.
1H NMR (CDCl3): δ 6.48 (s, 1H), 6.81 (br, 1H), 6.95 (m, 2H),
7.16 (s, 1H), 7.31 (t, 1H, J ) 7.7 Hz), 7.77 (d, 1H, J ) 7.9 Hz).
1H NMR (CDCl3-D2O): δ 6.52 (s, 1H), 6.94 (d, 1H, J ) 8.2 Hz),
7.04 (t, 1H, J ) 7.7 Hz), 7.13 (s, 1H), 7.37 (m, 1H), 7.80 (m, 1H).
19F NMR (CDCl3): δ -80.32 (t, 3F, J ) 10.3 Hz), -116.57 (m,
2F), -126.48 (s, 2F). 13C NMR (CDCl3): δ 100.81, 112.93 (t, J
) 7.3 Hz), 116.91, 117.74, 121.43, 128.50, 133.14, 145.11, 154.69,
159.71, 160.61. MS m/z: 356 (M+), 328 (100), 299 (21), 209 (33),
121 (21). Anal. calcd for
Found: C, 49.25; H, 3.56.
C17H15F7O4: C, 49.05; H, 3.63.
4b. Colorless oil eluted off the column after 3b, 0.075 g (9%).
IR (neat): 2985, 1745, 1675, 1584, 1232, 1125, 1029 cm-1 1H
.
NMR (CDCl3): δ 1.20 (t, 3H, J ) 7.2 Hz), 1.81 (d, 3H, J ) 7.0
Hz), 3.05 (m, 2H), 4.10 (m, 2H), 5.59 (q, 1H, J ) 7.0 Hz), 7.06
(m, 2H), 7.22 (t, 1H, J ) 7.7 Hz), 7.42 (d, 1H, J ) 7.7 Hz). 19F
NMR (CDCl3): δ -81.11 (m, 3F), -121.71 (m, 2F), -124.55 (m,
2F). 13C NMR (CDCl3): δ 9.67, 13.90, 37.75, 61.14, 98.44 (t, J
) 27.6 Hz), 102.92, 116.93, 117.48, 122.45, 122.87, 129.48,
140.63, 146.83, 166.15. MS m/z: 416 (M+), 387 (1), 369 (5), 329
(18), 315 (11), 247 (12), 205 (11), 159 (13), 131 (100). HRMS:
calcd for C16H13F7O4, 416.0859, found, 416.0842.
187 (50), 121 (92), 92 (44). HRMS: calcd for C14H7F7O3,
356.0283; found, 356.0271. UV: λabs(CHCl3) 366.0 nm.
8b. Yellow oil, 0.103 g (28%). IR (neat): 1729, 1611, 1381,
1344, 1296, 1173, cm-1
.
1H NMR (CDCl3): δ 1.27 (t, 3H, J )
7.1 Hz), 1.72 (s, 3H), 4.21 (q, 2H, J ) 7.1 Hz), 6.59 (s, 1H), 7.15
(m, 2H), 7.68 (m, 2H). 19F NMR (CDCl3): δ -68.64 (dd, 3F, J )
21.7, 11.6 Hz), -132.96 (dq, 1F, J ) 141.0, 11.6 Hz), -165.13
(dq, 1F, J ) 141.0, 21.7 Hz). 13C NMR (CDCl3): δ 14.01, 23.00,
61.82, 87.81, 113.71, 119.08, 123.21, 125.53, 128.10, 138.05 (d,
J ) 18.8 Hz), 139.11, 163.12, 170.94, 197.92. MS m/z: 376 (M+),
348 (4), 331 (9), 303 (8), 275 (32), 256 (37), 228 (100), 121 (69).
HRMS: calcd for C17H13F5O4, 376.0734, found, 376.0738. UV:
P r ep a r a tion of Silyl En ol Eth er s 5. Under N2, 2 mmol of
compound 3a (0.80 g) or 3b (0.83 g), 3 mmol (0.33 g) of freshly
distilled chlorotrimethylsilane, 5 mmol (0.30 g) of anhydrous
triethylamine, 0.01 g of anhydrous NaI, and 5 mL of anhydrous
acetonitrile were placed in a three-necked flask.5 The reaction
mixture was stirred at room temperature for 1 h, then was
heated to reflux for about 3 h. After the complete consumption
of 3, the reaction mixture was cooled to room temperature and
poured onto crushed ice, extracted with Et2O (30 mL × 3),
washed with saturated NaCl solution (20 mL × 2), and dried
over anhydrous MgSO4. After removal of solvent, the residue
was purified by column chromatography, using petroleum ether/
ethyl acetate (50:1) as eluant to give impure 5 as yellow oil.
5a . Yield: 0.80 g (84%). 1H NMR (CDCl3): δ 0.23 (s, 9H),
0.97 (t, 3H, J ) 7.2 Hz), 3.87 (q, 2H, J ) 7.1 Hz), 4.70 (s, 1H),
4.96 (s, 1H), 6.19 (s, 1H), 6.87-7.60 (m, 4H). 19F NMR (CDCl3):
δ -80.8 (t, 3F, J ) 10.3 Hz), -117.1 (m, 2F), -126.1 (m, 2F).
5b. Yield: 0.69 g (71%). 1H NMR (CDCl3): δ 0.07 (s, 9H),
0.98 (t, 3H, J ) 7.1 Hz), 1.73 (d, 3H, J ) 6.9 Hz), 3.88 (q, 2H, J
) 7.1 Hz), 5.36 (q, 1H, J ) 6.9 Hz), 6.16 (s, 1H), 6.87 (d, 1H, J
) 8.0 Hz), 7.09 (m, 2H), 7.48 (d, 1H, J ) 7.5 Hz). 19F NMR
(CDCl3): δ -80.9 (t, 3F, J ) 9.9 Hz), -117.3 (m, 2F), -126.4
(m, 2F).
P r ep a r a tion of Com p ou n d s 6-9 w ith ou t K2CO3. To a
solution of 1 mmol of 5a (0.47 g) or 5b (0.49 g) in 5 mL of
anhydrous acetonitrile under N2 was added 1 mL of tetrabutyl-
ammonium fluoride (1 M solution in THF). The reaction mixture
was heated to reflux for about 2 h. The reaction was monitored
by TLC (petroleum ether/CHCl3 3:1) until the complete con-
sumption of 5. Then, the reaction mixture was cooled to room
temperature and 10 mL of water was added. The resulting
solution was extracted with Et2O (30 mL × 3), washed with
saturated NaCl solution (20 mL × 2), and dried over MgSO4.
After removal of solvent, the crude product was subject to column
chromatography, using petroleum ether/ethyl acetate (50:1) as
eluant to give 6a (or 8b). Afterward, the eluant was changed
to petroleum ether/ethyl acetate (3:1) to give 7a (or 9b).
λ
abs(CHCl3) 252.0, 329.0 nm.
9b. Yellow solid, mp 143-145 °C, 0.167 g (43%). IR (neat):
3092 (br), 1745, 1691, 1617, 1467, 1211 cm-1
.
1H NMR
(CDCl3): δ 1.45 (s, 3H), 2.75 (m, 2H), 3.75 (m, 1H), 7.15 (m, 2H),
7.70 (m, 2H). 19F NMR (CDCl3): δ -80.92 (t, 3F, J ) 12.1 Hz),
-110.05 (m, 2F), -124.85 (dd, 2F, J ) 43.2, 9.9 Hz). 13C NMR
(CDCl3): δ 22.06, 29.80, 43.58 (t, J ) 20.6 Hz), 87.47, 113.90,
119.71, 122.86, 125.29, 138.99, 171.32, 175.96, 201.38. MS
m/z: 388 (M+), 371 (1), 329 (1), 267 (7), 201 (8), 173 (18), 148
(50), 121 (100). HRMS: calcd for C15H11F7O4, 388.0546, found,
388.0538. UV: λabs(CHCl3) 250.0, 327.0 nm.
P r ep a r a tion of Com p ou n d s 6-9 u sin g K2CO3. In the
presence of 4 mmol (0.55 g) of K2CO3, the reaction was carried
out in a similar manner with 1 mmol of 5a (0.47 g) or 5b (0.49
g) and gave 6a (0.02 g, 5%), 7a (0.22 g, 62%) or 8b (0.024 g,
6%), and 9b (0.25 g, 64%).
P r ep a r a tion of Meth yl Eth er s 7c, a n d 9c. Compound 7a
(0.018 g, 0.5 mmol) or compound 9b (0.019 g) was dissolved in
2 mL of THF, and methyl iodide (21 mg, 1.5 mmol) and K2CO3
(14 mg, 1 mmol) were added. The solution was heated to reflux
for about 5 h until consumption of 7a (or 9b) was complete. After
the solution was cooled to room temperature, 2 mL of water was
added, and the mixture was extracted with Et2O (10 mL × 3),
washed with saturated NaCl solution, and dried over MgSO4.
After removal of solvent, the residue was subjected to column
chromatography, using petroleum ether/ethyl acetate as eluant
to give 7c (or 9c).
7c. Yellow solid, mp 73-75 °C, 0.018 g (83%). IR (neat):
1745, 1632, 1542, 1594, 1349, 1258 cm-1 1H NMR (CDCl3): δ
.
3.86 (s, 3H), 6.42 (s, 1H), 6.97 (m, 2H), 7.17 (s, 1H), 7.38 (m,
1H), 7.87 (dd, 1H, J ) 7.9, 1.6 Hz). 19F NMR (CDCl3): δ -80.32
(t, 3F, J ) 10.5 Hz), -116.65 (q, 2F, J ) 10.5 Hz), -126.65 (s,
2F). MS: 370 (M+, 100), 342 (95), 327 (8), 299 (21), 180 (73),
135 (90). HRMS: calcd for C15H9F7O3, 370.0440, found, 370.0428.

5626 J . Org. Chem., Vol. 63, No. 16, 1998
Notes
9c. Light yellow oil, 0.016 g (87%). IR (neat): 1745, 1725,
National Science Foundation (Grant 9111391). We
thank Prof. Carl Bumgardner for stimulating discussion
of these results and Dr. Yangzhen Ciringh and Dr.
Ferenc Gyenes for the technical assistance.
1611, 1462, 1227 cm-1 1H NMR (CDCl3): δ 1.54 (s, 3H), 2.57
.
(dd, 1H, J ) 17.8, 4.0 Hz), 2.75 (dd, 1H, J ) 18.0, 5.7 Hz), 3.67
(s, 3H), 3.71 (m, 1H), 7.11 (m, 2H), 7.65 (m, 2H). 19F NMR
(CDCl3): δ -80.8 (m, 3F), -109.9 (m, 2F), -124.8 (m, 2F). 13C
NMR (CDCl3): δ 22.10, 29.71, 43.87 (t, J ) 20.5 Hz), 52.52,
87.49, 113.88, 119.81, 122.72, 125.17, 138.82, 170.89, 171.29,
201.30. MS m/z: 402 (M+), 371 (9), 342 (2), 315 (3), 223 (30),
173 (15), 148 (100).
Su p p or tin g In for m a tion Ava ila ble: 1H, 13C, and 19F
NMR spectra of compounds 3a ,b-9c (32 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.
Ack n ow led gm en t. Mass spectra were obtained at
the Mass Spectrometry Laboratory for Biotechnology
the NCSU. Partial funding for the facility was obtained
from the North Carolina Biotechnology Center and the
J O971989J