Synthesis and Diels-Alder Reactions of Butadienylpyridinium Bromides

Article abstract of DOI:10.1021/jo971181z

1-(3-Sulfolen-3-yl)pyridinium bromide (5) and 1-(3-methyl-2-sulfolen-4-yl)pyridinium bromide (35) have been prepared and served as the stable precursors for the cation-substituted dienes 6a and 32a, respectively. Compounds 6a and 32a are reactive dienes in the Diels-Alder reactions with a number of electron-poor dienophiles. Some [4 + 2] cycloadditions of 6a and 32a can take place in water.

Full text of DOI:10.1021/jo971181z

7812
J . Org. Chem. 1997, 62, 7812-7819
Syn th esis a n d Diels-Ald er Rea ction s of Bu ta d ien ylp yr id in iu m
Br om id es
Shwu-J iuan Lee,* Chiou-Bih Tzeng, Yung-I Liu, Chao-J ung Chien, and Ta-shue Chou
Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115, Republic of China
Received J une 30, 1997X
1-(3-Sulfolen-3-yl)pyridinium bromide (5) and 1-(3-methyl-2-sulfolen-4-yl)pyridinium bromide (35)
have been prepared and served as the stable precursors for the cation-substituted dienes 6a and
32a , respectively. Compounds 6a and 32a are reactive dienes in the Diels-Alder reactions with
a number of electron-poor dienophiles. Some [4 + 2] cycloadditions of 6a and 32a can take place
in water.
In tr od u ction
Resu lts a n d Discu ssion
3-Sulfolenes have been widely used as stable precur-
sors for synthetically useful 1,3-dienes.1 Electron-poor
dienes such as 2-(methoxycarbonyl)- (1a ),1b 2-nitro- (1b),1c
2-(arylsulfonyl)- (1c),1d,e and 2-cyano- (1d )1f 1,3-buta-
dienes may be generated in situ by thermolysis of the
corresponding 3-sulfolenes 2a -d , and their [4 + 2]
cycloaddition reactions with electron-deficient dienophiles
have been successful.1 These electron-poor dienes are
also dienophilic, so they dimerize in a [4 + 2] cycloaddi-
tion manner in the absence of a dienophile. The intro-
duction of a positively charged substituent at the 2-po-
sition of 1,3-butadienes would make them more electron-
deficient and could influence both the reactivity and the
mode of cycloaddition reactions. However, the cycload-
dition reactions of 1,3-butadienes bearing a cationic sub-
stituent are hardly known. It was reported that buta-
dienylphosphonium salts 3 do not undergo cycloaddition
reactions with maleic anhydride or tetracyanoethylene,2
but they react well with ketone enolates. The cycload-
ducts were formed via a conjugate addition and intramo-
lecular Wittig reaction sequence.3 Butadienylsulfonium
salts 4 are known to react with enolates to produce
dihydroarene oxides via a nonconcerted mechanism.4 In
this paper, we report the details of the preparation of
1-(3-sulfolen-3-yl)pyridinium bromide (5) and 1-(3-meth-
yl-2-sulfolen-4-yl)pyridinium bromide (35) as the stable
precursors for the positively charged dienes 6a and 32a
and the success of their Diels-Alder reactions.5
Treatment of the known 3,4-dibromosulfolane with
pyridine at ambient temperature gave compound 5 in
40% yield.6 Thermolysis of compound 5 in acetonitrile
at 140 °C for 1 h caused SO2 extrusion and gave 6a in
quantitative yield (eq 1). Diene 6a is a reasonably stable
compound which can be stored at room temperature for
over 1 month without appreciable decomposition. De-
spite its stability, an analytically pure sample of bromide
salt 6a could not be obtained due to its oiliness. The
diene 6a was thus treated with aqueous NaPF6 for
counterion exchange so that it could be purified and
characterized more easily by recrystallization.
Since there is a strong electron-withdrawing pyri-
dinium attached at the 2-position, the reactions of
compound 6a with electron-rich dienophiles were first
tested. However, treatment of 6a with ethyl vinyl ether
in acetonitrile at 100 °C for 3 h resulted in no reaction,
whereas the reaction with ethyl vinyl ether or dihydro-
furan in acetonitrile at 140 °C for 1 h gave no cycload-
ducts but did yield complex mixtures. Apparently,
inverse electron demand Diels-Αlder reactions7 of 6a did
not take place.
On the other hand, reactions of the cationic species 6a
with a number of electron-deficient alkenes in acetonitrile
or water proceeded smoothly to give [4 + 2] cycloadducts
(Scheme 1 and Table 1). The cycloadducts were also
treated with aqueous NaPF6 for counterion exchange to
(1) (a) Chou, T. S.; Tso, H. H. Org. Prep. Proc. Int. 1989, 21, 257.
(b) McIntosh, J . M.; Sieler, R. A. J . Org. Chem. 1978, 43, 4431. (c)
Berestovitskaya, V. M.; Speranskii, E. M.; Perekalin, V. V. Zh. Org.
Khim. 1979, 15, 185. (d) Chou, T. S.; Hung, S. C.; Tso, H. H. J . Org.
Chem. 1987, 52, 3394. (e) Chou, T. S.; Hung, S. C. J . Org. Chem. 1988,
53, 3020. (f) Baraldi, P. G.; Barco, A.; Benetti, S.; Manfredini, S.; Pollini,
G. P.; Simoni, D.; Zanirato, V. Tetrahedron 1988, 44, 6451.
(2) Ford, J . A.; Wilson, C. V. J . Org. Chem. 1961, 26, 1433.
(3) (a) Fuchs, P. L. Tetrahedron Lett. 1974, 4055. (b) Buchi, G.;
Pawlak, M. J . Org. Chem. 1975, 40, 100.
(4) Garst, M. E. J . Org. Chem. 1979, 44, 1578.
(5) The preliminary results of this approach have been published
as a communication, see: Lee, S. J .; Chien, C. J .; Peng, C. J .; Chao, I.;
Chou, T. S. J . Org. Chem. 1994, 59, 4367.
(6) (a) Bailey, W. J .; Cummins, E. W. J . Am. Chem. Soc. 1954, 76,
1932. (b) Ellis, F.; Sammes, P. G.; Hursthouse, M. B.; Neidle, S. J .
Chem. Soc., Perkin Trans. 1 1972, 1560.
X Abstract published in Advance ACS Abstracts, October 1, 1997.
(7) Sauer, J . Angew. Chem., Int. Ed. Engl. 1967, 6, 16.
S0022-3263(97)01181-X CCC: $14.00 © 1997 American Chemical Society

Reactions of Butadienylpyridinium Bromides
J . Org. Chem., Vol. 62, No. 22, 1997 7813
Sch em e 1
facilitate their purification and characterization by re-
crystallization. The cycloadditions with N-phenylmale-
imide, dimethyl fumarate, and methyl vinyl ketone (e.g.
entries 1, 4, and 8 of Table 1) were completed in
acetonitrile at 140 °C in 1 h. In fact, the reactions can
be performed at even lower temperatures. For example,
reaction of 6a with N-phenylmaleimide at room temper-
ature for 6 h or at 70 °C for 2 h produced 7a in almost
quantitative yield. It is especially interesting that the
cycloaddition reaction of 6a with the water-soluble di-
enophiles including fumaric acid, maleic acid, fumaroni-
trile, acrylic acid, propiolic acid, and acetylenedicarbox-
ylic acid took place smoothly in water as well (entries
9-14 of Table 1). Although there are some examples of
water-catalyzed Diels-Alder reactions,8 our results il-
lustrate that water can sometimes serve as a good solvent
for “organic” Diels-Alder reactions.
In addition to spectral analysis, the structure of the
vinylpyridinium-containing cycloadduct 7a was further
confirmed by chemical transformations. When 7a was
treated with sodium borohydride at 0 °C9 followed by
hydrolysis,10 the pyridinium functionality was trans-
formed into the substituted cyclohexanone 22, presum-
ably via a dihydropyridine intermediate. Therefore,
compound 6a may be considered as a water-soluble
version of 2-alkoxy-1,3-butadiene in aqueous Diels-Alder
reactions.
(8) (a) Lubineau, A.; Auge, J .; Queneau, Y. Synthesis 1994, 741. (b)
Li, C. J . Chem. Rev. 1993, 93, 2023. (c) Breslow, R. Acc. Chem. Res.
1991, 24, 159. (d) Rideout, D. C.; Breslow, R. J . Am. Chem. Soc. 1980,
102, 7816. (e) Breslow, R.; Maitra, U.; Rideout, D. Tetrahedron Lett.
1983, 24, 1901. (f) Grieco, P. A.; Garner, P.; He, Z. Tetrahedron Lett.
1983, 24, 1897.
(9) Schenker, K.; Druey, J . Helv. Chim. Acta 1959, 42, 1960.
(10) Stamhuis, E. J .; Cook, A. G. In Enamines: Synthesis, Structure,
and Reactions; Cook, A. G., Ed.; Marcel Dekker: New York, 1988;
Chapter 3.

7814 J . Org. Chem., Vol. 62, No. 22, 1997
Lee et al.
Ta ble 1. Diels-Ald er Rea ction s of Dien e 6a
Two regioisomers were obtained (para:meta ) 2:1)
when 6a was reacted with unsymmetric alkenes (entries
7, 8, and 12 of Table 1). The ratios of these two isomers
conditions
(solvent)
product
(ratio)
PF6- salt
entry
1
dienophile (equiv)
(% yielda)
1
were determined by H NMR spectral analyses. Coun-
N-phenylmaleimide
(10)
N-phenylmaleimide
(10)
N-phenylmaleimide
(10)
dimethyl fumarate
(10)
140 °C, 1 h
(CH3CN)
rt, 6 h
(CH3CN)
70 °C, 2 h
(CH3CN)
140 °C, 1 h
(CH3CN)
140 °C, 3 h
(CH3CN)
7a
7b (88)
terion exchange (NaPF6) and recrystallization of any of
the mixtures 11b/12b, 13b/14b, or 18b/19b gave the
major regioisomer as a white crystal. The structures of
the major isomers were subjected to 2D NMR COSY
experiments. The cross-peaks corresponding to the C3
methylene hydrogens with the C2 vinyl hydrogen and the
C4 methine hydrogen in the spectra indicated that these
major isomers 11b, 13b, and 18b are all “para”.11 The
structure of 18b was also unambiguously established by
X-ray crystallographic analysis.
The regiochemical assignments of 20b and 21b were
supported by their 2D NMR NOESY experiments. For
compound 20b, the NOE correlations between (1) the C2
vinyl hydrogen and the C3 methylene hydrogens, (2) the
C2 vinyl hydrogen and the ortho-hydrogens of the pyri-
dinium, (3) the C6 methylene hydrogens and the C5 vinyl
hydrogen, and (4) the C6 methylene hydrogens and the
ortho-hydrogens of the pyridinium were observed, indi-
cating their close proximity. Whereas for 21b, NOE
2
7a b
7a b
8a
3
4
8b (86)
9b (79)
10b (92)
5
dimethyl maleate
(10)
norbornene (10)
9a
6
140 °C, 1.5 h 10a
(CH3CN)
7
methyl acrylate (10) 140 °C, 1.5 h 11a + 12a 11b (55)d
(CH3CN)
140 °C, 1 h
(CH3CN)
110 °C, 4 h
(H2O)
110 °C, 22 h 16a
(H2O)
100 °C, 45 h 17a
(H2O)
(2:1)c
8
methyl vinyl ketone
(10)
fumaric acid (2)
13a + 14a 13b (57)d
(2:1)c
9
15a
15b (68)
16b (62)
17b (64)
10
11
12
13
14
maleic acid (2)
fumaronitrile (10)
acrylic acid (2)
100 °C, 9 h
(H2O)
18a + 19a 18b (33),
(1.6:1)c
19b (19)
propiolic acid (10)
100 °C, 24 h 20a + 21a 20b (33),
(H2O) 21b (32)
(5:4)c
acetylenedicarboxylic 100 °C, 24 h 20a + 21a 20b (35),
acid (10) (H2O) 21b (33)
(4:3)c
a
These are isolated yields of the hexafluorophosphate salts after
recrystallization. b Compound 7a was obtained in nearly quantita-
tive yield. The 1H NMR spectrum of which indicates the purity to
be better than 95%. c The ratio of these two regioisomers was
d
determined by 1H NMR spectral analysis. Although 11b and 13b
could be isolated in pure state by fractional crystallization, we were
unable to get a pure sample of 12b (or 14b) uncontaminated by
11b (or 13b) by this method.
literature in which acetylenedicarboxylic acid loses CO2
readily upon heating in H2O to give propiolic acid.12
Under the reaction condition, acetylenedicarboxylic acid
was first converted to propiolic acid, which then partici-
pated in the cycloaddition reaction with 6a to give 20a
and 21a .
correlations between (1) the C3 methylene hydrogens and
the C2 and C4 vinyl hydrogens and (2) ortho-hydrogens
of the pyridinium and the C6 methylene hydrogens and
the C2 vinyl hydrogen were observed.
Analytically pure samples of the cyclohexadienes 20b
and 21b could not be obtained due to their instability.
Therefore, the dienes were aromatized oxidatively with
MnO2 to 23 and 24, respectively, of which purification
and characterization were achieved.
Since substituted vinylpyridinium salts are very reac-
tive dienophiles,13 it was at first anticipated that 6a
might be a good dienophile to react only with electron-
rich dienes. However, when the thermal extrusion of SO2
from 5 was performed above a certain concentration,14
[4 + 2] dimerization of the primary product 6a would take
place to give 26 and 27, to some extent indicating that
compound 6a is also a dienophile which can react with
electron-deficient dienes. Unlike the dimerization reac-
tions of 1a -d , the C1-C2 double bond of 6a is less reac-
tive as a dienophile than the C3-C4 double bond. The
Somewhat unexpectedly, two regioisomers, 20a and
21a , were obtained (para:meta ) 4:3) when 6a was
reacted with acetylenedicarboxylic acid (entry 14 of Table
1). The anticipated cycloadduct 25 was not detected.
Their structures were confirmed by comparing with the
products obtained from the reaction of 6a with propiolic
acid. This result is consistent with a report in the
(12) Bandrowski, E. Chem. Ber. 1879, 12, 2212.
(13) (a) J ung, M. E.; Buszek, K. R. J . Org. Chem. 1985, 50,
5441. (b) J ung, W. E.; Buszek, K. R. Tetrahedron Lett. 1986, 27,
6165.
(14) Lee, S. J .; Tzeng, C. B.; Lin, S. C.; Chao, I.; Lu, H. F.; Chou, T.
S. J . Org. Chem. 1996, 61, 9293.
(11) Although 11b and 13b could be isolated in pure state by
fractional crystallization, we were unable to get a pure sample of 12b
(or 14b), uncontaminated by 11b (or 13b), by this method.

Reactions of Butadienylpyridinium Bromides
J . Org. Chem., Vol. 62, No. 22, 1997 7815
unusual site-selectivity of 6a in its dienophilic behavior
seems to originate from the steric effect of the pyridinium
ring.
When 6a was reacted with cyclopentadiene at lower
temperatures (under 100 °C), mixtures containing the
cycloadduct 28 from the reaction of 6a as the diene with
cyclopentadiene as the dienophile and 29 from the
reaction of cyclopentadiene as the diene with 6a as the
dienophile were obtained.14 The major cycloadduct 29
could be converted completely to the cycloadduct 28 by a
sigmatropic rearrangement process at 140 °C. Similar
to the dimerization reaction of 6a , it is the C3-C4 double
bond of 6a which reacted as the dienophile in the crossed
Diels-Alder reaction with cyclopentadiene.
Competitive Diels-Alder reactions were carried out by
treating 6a with mixtures of dienophiles to examine their
relative dienophilicity. The reaction of 6a with a mixture
of equal molar equivalents of N-phenylmaleimide and
norbornene in acetonitrile at 140 °C for 1 h produced 7a
as the only cycloadduct. The reaction of 6a with a
mixture of equal molar equivalents of N-phenylmaleimide
and dimethyl fumarate gave a mixture of 7a and 8a in a
catalyzed isomerization did take place to give 33 as the
intermediate under the reaction conditions. The subse-
quent extrusion of SO2 from 33 to produce 32a was
essentially irreversible since the SO2 could be trapped
by pyridine.
1
2:1 ratio. The ratio was easily determined by H NMR
spectral analysis since the vinyl proton of 7a (δ 6.42)
exhibits lower chemical shift than that of 8a (δ 6.18). The
results of these competitive studies indicate that N-
phenylmaleimide is more dienophilic than dimethyl
fumarate, even more so than norbornene toward com-
pound 6a . This trend is consistent with the results of
the Diels-Alder reactions of other electron-rich dienes.15
It thus appears that 6a behaves as a normal diene
despite its electron-deficient nature.
Treatment of an equimolar of 6a and another diene
(2,3-dimethyl-1,3-butadiene or isoprene) with N-phen-
ylmaleimide at room temperature for 1 h led to the
formation of cycloadduct 7a as the only product with
no indication of the formation of 30 or 31. This result
indicates that the dienic reactivity of 6a is substantially
higher than that of 2,3-dimethyl-1,3-butadiene and
isoprene.
Compound 32a , similar to compound 6a , was also
found to be a reactive diene in [4 + 2] cycloaddition
reactions with electron-deficient dienophiles (Scheme 2
and Table 2), but not with electron-rich dienophiles.
However, higher reaction temperatures and/or longer
reaction times are required for the completion of the
cycloaddition reactions. For example, the cycloaddition
reaction of 32a with norbornene (16 equiv), at 200 °C took
4 h to complete. The results indicate the lower dienic
reactivity of 32a than 6a . The difference in dienic
reactivity between 6a and 32a may be associated with
their conformational natures. It is obvious that 32a has
more difficulties than 6a adopting the s-cis conformation
necessary for [4 + 2] cycloaddition to take place. On the
other hand, the difference in dienophilic reactivity of
these two dienes is more distinct. Unlike compound 6a ,
compound 32a neither dimerizes nor reacts as a dieno-
phile toward dienes. Conceivably, both steric and elec-
tronic effects of the methyl substituent disfavor the
dienophilicity of the C3-C4 bond of 32a . Therefore,
replacement of the C3-hydrogen of 6a with a methyl
group has significant influences on the chemical proper-
ties in Diels-Alder reactions.
Two regioisomers were obtained (40a :41a ) 2:1 and
42a :43a ) 4:3) when 32a was treated with unsymmetric
alkenes (entries 5 and 6 of Table 2). The ratios of these
two isomers were determined by 1H NMR spectral
analyses. Counterion exchange (NaPF6) of the mixtures
allowed easy separation of the isomers by silica gel
column chromatography. The slower moving isomers on
silica gel column were the major isomers 40b and 42b.
To establish the regiochemistry of these isomers, the
2D NMR COSY (1H-1H and 1H-13C) and NOESY ex-
periments were carried out. In the 1H-1H COSY spectra
of 40b or 42b, there are cross-peaks between (1) the C3
methylene hydrogens and the C4 methine hydrogen and
(2) the C2 methyl hydrogens and the C6 methylene
hydrogens. In addition, the NMR NOESY experiments
of both 40b and 42b showed that (1) the C3 methylene
hydrogens are in proximity to the C2 methyl hydrogens
and the C4 methine hydrogen and (2) the C6 methylene
hydrogens are in proximity to the ortho-hydrogens of the
pyridinium ring. These results indicated that the meth-
We were interested in comparing the methylated
pyridinium diene 32a with 6a on the basis of their dienic
reactivities and the regioselectivity of their cycloaddition
reactions. On the basis of the same idea that inspired
the preparation of diene 6a , the desired diene 32a was
synthesized via the corresponding 3-sulfolene 33. Bro-
mination of the commercially available 3-methyl-3-sul-
folene afforded 3,4-dibromo-3-methylsulfolane (34),16 which
was treated with pyridine at ambient temperature to give
compound 35 in 52% yield. Isomerization of 35 to the
3-sulfolene 33 could not be accomplished under any of
the various conditions attempted. Fortunately, com-
pound 35 could be thermolyzed directly at 140 °C in the
presence of pyridine to give the diene 32a (eq 3). A base-
(15) Sauer, J .; Wiest, H.; Mielert, A. Chem. Ber. 1964, 97, 3183.
(16) Krug, R. C.; Yen, T. F. J . Org. Chem. 1956, 21, 1441.

7816 J . Org. Chem., Vol. 62, No. 22, 1997
Lee et al.
Sch em e 2
Ta ble 2. Diels-Ald er Rea ction s of Dien e 32a
a positively charged substituent, by way of the corre-
sponding 3-sulfolenes. The success of the Diels-Alder
reactions of these two dienes is noteworthy. Their dienic
reactivity toward electron-deficient alkenes and their
inability to undergo inverse electron demand Diels-Alder
reactions are especially interesting observations. In
addition, our study of the aqueous reactions of water-
soluble dienophiles with 6a and 32a should broaden the
scope of the long-popular Diels-Alder reaction.
conditions
(solvent)
product
(ratio)
PF6- salt
entry dienophile (equiv)
(% yield)a
1
2
3
4
5
6
7
8
N-phenylmaleimide 140 °C, 6 h
36a
36b (81)
37b (72)
38b (62)
39b (56)
(5)
(CH3CN)
140 °C, 5 h
(CH3CN)
dimethyl fumarate
(5)
37a
38a
39a
dimethyl maleate
(10)
140 °C, 15 h
(CH3CN)
norbornene (16)
200 °C, 4 h
(CH3CN)
methyl acrylate (5) 140 °C, 6 h
40a + 41a 40b (40),
(CH3CN)
(2:1)b
41b (18)
Exp er im en ta l Section
methyl vinyl ketone 140 °C, 10 h
42a + 43a 42b (35),
(10)
(CH3CN)
110 °C, 19 h
(H2O)
(4:3)b
43b (21)
Gen er a l P r oced u r e for th e Diels-Ald er Rea ction of
Com p ou n d 6a in CH3CN. A sealed tube containing a CH3-
CN (10 mL) solution of 6a (180 mg, 0.85 mmol) and a
dienophile (10 equiv) was heated for the period of time shown
in Table 1. After removal of the solvent, the residue was
dissolved in water and then was washed with ethyl acetate to
remove the excess dienophile. NaPF6 (2 equiv) was added to
the aqueous layer, and the resulting mixture was stirred at
room temperature overnight. The crude hexafluorophosphate
salt which precipitated was recrystallized from hot water to
give the pure product 7b-10b, 11b, or 13b. The yields of
Diels-Alder reactions are summarized in Table 1. The room
temperature or 70 °C Diels-Alder reactions were carried out
by stirring the reaction mixtures under nitrogen and were
worked up as described above.
fumaric acid (2.5)
44a
44b (75)
maleic acid (2.5)
110 °C, 120 h 45a
(H2O)
45b (49)
a
These are isolated yields of the hexafluorophosphate salts after
recrystallization or purification by silica gel column chromatog-
b
raphy. The ratio of these two regioisomers was determined by
1H NMR spectral analysis.
oxycarbonyl group of 40b and the acetyl group of 42b
are “para” to the pyridinium ring. Using the same
technique, the methoxycarbonyl group of 41b and the
acetyl group of 43b were found to be “para” to the methyl
group.
1-(1,3-Dioxo-2-p h en yl-1,3,3a ,4,7,7a -h exa h yd r oisoin d ol-
5-yl)p yr id in iu m h exa flu or op h osp h a te (7b): white solid,
mp 233-234 °C; 1H NMR (D2O, 200 MHz) δ 2.76-2.86 (m,
2H), 3.13 (d, 2H, J ) 5.1 Hz), 3.51-3.63 (m, 1H), 3.74-3.85
(m, 1H), 6.62 (t, 1H, J ) 5.2 Hz), 7.13-7.19 (m, 2H), 7.40-
7.48 (m, 3H), 8.09 (t, 2H, J ) 7.4 Hz), 8.58 (t, 1H, J ) 7.8
Hz), 8.81 (d, 2H, J ) 5.5 Hz); IR (KBr) 3131, 3048, 1700,
1472, 1381, 1198 cm-1; FABMS (m/z) calcd for C19H17N2O2 305,
found 305; calcd for PF6 145, found 145. Anal. Calcd for
C19H17F6N2O2P: C, 50.68; H, 3.81; N, 6.22. Found: C, 50.41;
H, 3.46; N, 5.98.
1-[tr a n s-4,5-Bis(m eth oxyca r bon yl)-1-cycloh exen -1-yl]-
p yr id in iu m h exa flu or op h osp h a te (8b): white solid, mp
128-130 °C; H NMR (D2O, 300 MHz) δ 2.48-2.62 (m, 1H),
2.65-2.78 (m, 1H), 2.87-2.94 (m, 2H), 3.08-3.19 (m, 1H),
1
In summary, we have demonstrated a very easy entry
to 6a and 32a , which are stable 1,3-butadienes bearing

Reactions of Butadienylpyridinium Bromides
J . Org. Chem., Vol. 62, No. 22, 1997 7817
3.26-3.37 (m, 1H), 3.72 (s, 6H), 6.34 (br s, 1H), 8.07 (t, 2H, J
) 7.1 Hz), 8.57 (t, 1H, J ) 7.7 Hz), 8.81 (d, 2H, J ) 6.0 Hz);
1H NMR (D2O, 300 MHz) δ 2.56-2.65 (m, 2H), 2.85-2.92 (m,
2H), 3.13-3.23 (m, 1H), 3.28-3.38 (m, 1H), 6.20 (br s, 1H),
7.95 (t, 2H, J ) 7.0 Hz), 8.45 (t, 1H, J ) 7.6 Hz), 8.78 (d, 2H,
J ) 6.1 Hz); IR (KBr) 3433, 3134, 3084, 1745, 1705, 1475, 1158
cm-1; FABMS (m/z) calcd for C13H14NO4 248, found 248. Anal.
Calcd for C13H14F6NO4P: C, 39.71; H, 3.59; N, 3.56. Found:
C, 39.78; H, 3.53; N, 3.46.
IR (KBr) 3154, 3085, 2956, 1724, 1434, 1304, 1175 cm-1
;
FABMS (m/z) calcd for C15H18NO4 276, found 276; calcd for
PF6 145, found 145. Anal. Calcd for C15H18F6NO4P: C, 42.77;
H, 4.31; N, 3.32. Found: C, 42.49; H, 3.90; N, 3.00.
1-[cis-4,5-Bis(m eth oxyca r bon yl)-1-cycloh exen -1-yl]p y-
r id in iu m h exa flu or op h osp h a te (9b): white solid, mp 85-
1-(t r a n s-4,5-Dicya n o-1-cycloh e xe n -1-yl)p yr id in iu m
h exa flu or op h osp h a te (17b): yellow solid, mp 155-157 °C;
1H NMR (D2O, 300 MHz) δ 2.70-2.86 (m, 2H), 2.92-3.15 (m,
2H), 3.48-3.58 (m, 1H), 3.66-3.76 (m, 1H), 6.31 (br s, 1H),
7.97 (t, 2H, J ) 7.2 Hz), 8.47 (t, 1H, J ) 7.8 Hz), 8.74 (d, 2H,
1
86 °C; H NMR (D2O, 200 MHz) δ 2.56-2.67 (m, 2H), 2.85-
2.96 (m, 2H), 3.23-3.34 (m, 1H), 3.38-3.50 (m, 1H), 3.64 (s,
6H), 6.21-6.27 (m, 1H), 7.97 (t, 2H, J ) 7.9 Hz), 8.49 (dt, 1H,
J ) 1.0, 7.7 Hz), 8.73 (d, 2H, J ) 6.5 Hz); IR (KBr) 3141, 2956,
1724, 1433, 1207 cm-1; FABMS (m/z) calcd for C15H18NO4 276,
found 276; calcd for PF6 145, found 145. Anal. Calcd for
C15H18F6NO4P: C, 42.77; H, 4.31; N, 3.32. Found: C, 42.37;
H, 3.86; N,3.00.
J ) 5.7 Hz); IR (KBr) 3139, 3089, 2251, 1633, 1478 cm-1
;
FABMS (m/z) calcd for C13H12N3 210, found 210. Anal. Calcd
for C13H12F6N3P: C, 43.96; H, 3.40; N, 11.83. Found: C, 43.48;
H, 3.45; N, 11.45.
1-(1,2,3,4,4a ,5,8,8a -Octa h yd r o-1,4-m eth a n on a p h th a len -
6-yl)p yr id in iu m h exa flu or op h osp h a te (10b): white solid,
mp 152-153 °C; H NMR (D2O, 300 MHz) δ 1.08 (d, 1H, J )
1-(4-Ca r boxy-1-cycloh exen -1-yl)p yr id in iu m h exa flu o-
r op h osp h a te (18b): white solid, mp 191-193 °C; 1H NMR
(D2O, 500 MHz) δ 1.92-2.03 (m, 1H), 2.10-2.20 (m, 1H), 2.41-
2.50 (m, 1H), 2.50-2.60 (m, 2H), 2.60-2.71 (m, 1H), 2.72-
2.82 (m, 1H), 6.26 (s, 1H), 8.01 (t, 2H, J ) 7.0 Hz), 8.50 (t, 1H,
J ) 7.8 Hz), 8.77 (d, 2H, J ) 6.3 Hz); 13C NMR (MeOH-d4,
50.3 MHz) δ 26.0, 28.0, 28.1, 38.6, 129.3, 129.4, 143.0, 144.6,
147.6, 177.8; IR (KBr) 3145, 3084, 1710, 1629, 1475, 1436,
1328, 1265, 1211 cm-1; FABMS (m/z) calcd for C12H14NO2 204,
found 204. Anal. Calcd for C12H14F6NO2P: C, 41.27; H, 4.04;
N, 4.01. Found: C, 41.0; H, 4.16; N, 3.91.
1
10.3 Hz), 1.19 (d, 2H, J ) 7.0 Hz), 1.52 (d, 2H, J ) 8.1 Hz),
1.64 (dd, 1H, J ) 10.3, 1.7 Hz), 1.68-1.82 (m, 2H), 1.88-1.98
(m, 1H), 2.00-2.05 (m, 2H), 2.21-2.35 (m, 1H), 2.50-2.60 (m,
1H), 2.67 (dd, 1H, J ) 15.8, 8.0 Hz), 6.36-6.44 (m, 1H), 8.01
(t, 2H, J ) 7.5 Hz), 8.50 (t, 1H, J ) 7.8 Hz), 8.76 (d, 2H, J )
5.5 Hz); IR (KBr) 3139, 2949, 2868, 1629, 1472 cm-1; FABMS
(m/z) calcd for C16H20N 226, found 226; calcd for PF6 145, found
145. Anal. Calcd for C16H20F6NP: C, 51.76; H, 5.43; N, 3.77.
Found: C, 51.47; H, 5.50; N, 3.53.
1-[4-(Met h oxyca r b on yl)-1-cycloh exen -1-yl]p yr id in i-
u m h exa flu or op h osp h a te (11b): white solid, mp 138-139
°C; 1H NMR (D2O, 500 MHz) δ 1.75-1.85 (m, 1H), 1.98-2.06
(m, 1H), 2.28-2.36 (m, 1H), 2.36-2.45 (m, 2H), 2.46-2.56 (m,
1H), 2.62-2.70 (m, 1H), 3.50 (s, 3H), 6.10 (br s, 1H), 7.85 (t,
2H, J ) 7.2 Hz), 8.35 (t, 1H, J ) 7.8 Hz), 8.62 (dd, 2H, J )
5.6, 1.3 Hz); 13C NMR (D2O, 50.3 MHz) δ 25.8, 27.8, 28.1, 54.1,
129.2, 129.6, 142.8, 144.5, 147.9, 179.2; IR (KBr) 3140, 1724,
1618, 1469, 1192 cm-1; FABMS (m/z) calcd for C13H16NO2 218,
found 218; calcd for PF6 145, found 145. Anal. Calcd for
C13H16F6NO2P: C, 42.97; H, 4.44; N, 3.86. Found: C, 43.00;
H, 4.15; N, 3.57.
1-(4-Acetyl-1-cycloh exen -1-yl)p yr id in iu m h exa flu or o-
p h osp h a te (13b): white solid, mp 124-125 °C; 1H NMR (D2O,
500 MHz) δ 1.68-1.76 (m, 1H), 2.01-2.07 (m, 1H), 2.08 (s,
3H), 2.19-2.27 (m, 1H), 2.29-2.41 (m, 2H), 2.47-2.57 (m, 1H),
2.75-2.81 (m, 1H), 6.11 (br s, 1H), 7.85 (t, 2H, J ) 7.5 Hz),
8.32-8.35 (m, 1H), 8.61 (dd, 2H, J ) 5.6, 1.3 Hz); 13C NMR
(D2O, 75.4 MHz) δ 25.3, 27.0, 28.2, 29.2, 46.5, 129.4, 129.5,
142.5, 144.3, 147.8, 217.8; IR (KBr) 3120, 3080, 2923, 1690,
1620, 1418, 1350 cm-1; FABMS (m/z) calcd for C13H16NO 202,
found 202; calcd for PF6 145, found 145. Anal. Calcd for
C13H16F6NOP: C, 44.97; H, 4.64; N, 4.03. Found: C, 44.76;
H, 4.24; N, 3.79.
Gen er a l P r oced u r e for th e Diels-Ald er Rea ction of
Com p ou n d 6a in H2O. A sealed tube containing 6a (70 mg,
0.33 mmol) and a suitable amount of dienophile in H2O (10
mL) was heated for the period of time as shown in Table 1. To
the reaction mixture was then added NaPF6 (2 equiv) and the
mixture stirred at room temperature overnight. After removal
of the precipitate by filtration, the filtrate was concentrated
under reduced pressure. The residue was recrystallized from
hot water to give the pure hexafluorophosphate salt 15b-17b.
Regioisomers (18b/19b and 20b/21b) were separated individu-
ally by fractional crystallization from hot water. Compounds
18b and 21b were the isomers obtained first from the
fractional crystallization method.
X-r a y Str u ctu r e An a lysis of Com p ou n d 18b. Crystal
data: C12H14F6NO2P, molecular weight 349.21; monoclinic
system, space group P21/ c; a ) 7.162(2), b ) 16.815(7), c )
12.605(4) Å, â ) 98.00(2)°; V)1503.3(9) Å3, Z ) 4, F(000) )
704, Dcalc ) 1.543 mg m-3, µ ) 2.53 cm-1
. Of the 1966
reflections collected (2θmax ) 45), 1043 unique reflections were
considered observed (I > 2σ (I)) after Lorentz polarization and
empirical absorption corrections. The reliability factors con-
verged to R1 ) 0.099.17
1-(5-Ca r boxy-1-cycloh exen -1-yl)p yr id in iu m h exa flu o-
r op h osp h a te (19b): white solid, mp 124-126 °C; 1H NMR
(MeOH-d4, 500 MHz) δ 1.88-1.98 (m, 1H), 2.072.15 (m, 1H),
2.40-2.50 (m, 2H), 2.73-2.88 (m, 2H), 2.88-2.98 (m, 1H), 6.37
(s, 1H), 8.16 (t, 2H, J ) 7.0 Hz), 8.66 (t, 1H, J ) 7.8 Hz), 9.01
(d, 2H, J ) 5.6 Hz); 13C NMR (MeOH-d4, 75.4 MHz) δ 24.4,
24.7, 31.1, 40.0, 129.4, 130.5, 142.1, 144.8, 147.7, 177.3; IR
(KBr) 3136, 3083, 1714, 1632, 1473, 1331, 1266, 1213 cm-1
;
FABMS (m/z) calcd for C12H14NO2 204, found 204. Anal. Calcd
for C12H14F6NO2P: C, 41.27; H, 4.04; N, 4.01. Found: C, 41.10;
H, 4.07; N, 3.99.
1-(4-Car boxy-1,4-cycloh exdien -1-yl)pyr idin iu m h exaflu -
1
or op h osp h a te (20b): white solid, mp 186-188 °C; H NMR
(D2O+acetone-d6, 300 MHz) δ 3.15-3.25 (m, 2H), 3.48-3.58
(m, 2H), 6.40 (s, 1H), 6.98 (s, 1H), 8.10 (t, 2H, J ) 7.1 Hz),
8.60 (t, 1H, J ) 7.8 Hz), 8.89 (d, 2H, J ) 6.0 Hz); 13C NMR
(MeOH-d4, 75.4 MHz) δ 27.5, 30.6, 128.1, 128.4, 129.5, 134.8,
139.7, 144.8, 148.0, 169.0; IR (KBr) 1708, 1690, 1632, 1472,
1264, 1198 cm-1; FABMS (m/z) calcd for C12H12NO2 202, found
202.
1-(5-Car boxy-1,4-cycloh exdien -1-yl)pyr idin iu m h exaflu -
1
or op h osp h a te (21b): white solid, mp 181-183 °C; H NMR
(D2O+acetone-d6, 300 MHz) δ 3.15-3.30 (m, 2H), 3.38-3.48
(m, 2H), 6.34 (s, 1H), 6.99 (s, 1H), 8.12 (t, 2H, J ) 7.1 Hz),
8.60 (t, 1H, J ) 7.8 Hz), 8.92 (d, 2H, J ) 5.6 Hz); 13C NMR
(MeOH-d4, 75.4 MHz) δ 29.0, 29.2, 126.7, 128.1, 129.5, 135.7,
141.2, 144.9, 148.0, 168.7; IR (KBr) 1683, 1642, 1479, 1423,
1295 cm-1; FABMS (m/z) calcd for C12H12NO2 202, found 202.
1-(4-Ca r boxyp h en yl)p yr id in iu m h exa flu or op h osp h a te
(23): A mixture of 20b (17.7 mg, 0.05 mmol) and MnO2 (20
mg, 0.23 mmol) in H2O (5 mL) was refluxed at 100 °C for 3 h.
The resulting mixture was filtered and the filtrate was
concentrated under reduced pressure to give a solid residue.
The residue was then recrystallized from acetone to give
compound 23 as white crystal in 62% yield: mp 193-195 °C;
1-(tr a n s-4,5-Dica r boxy-1-cycloh exen -1-yl)p yr id in iu m
h exa flu or op h osp h a te (15b): white solid, mp 167-168 °C;
1H NMR (D2O, 300 MHz) δ 2.35-2.50 (m, 1H), 2.55-2.68 (m,
1H), 2.73-2.82 (m, 2H), 2.88-3.0 (m, 1H), 3.04-3.15 (m, 1H),
6.22 (br s, 1H), 7.94 (t, 2H, J ) 7.1 Hz), 8.44 (t, 1H, J ) 7.9
Hz), 8.70 (d, 2H, J ) 6.4 Hz); IR (KBr) 3134, 3085, 1696, 1632,
1474 cm-1; FABMS (m/z) calcd for C13H14NO4 248, found 248.
Anal. Calcd for C13H14F6NO4P: C, 39.71; H, 3.59; N, 3.56.
Found: C, 39.76; H, 3.82; N, 3.30.
(17) The authors has deposited atomic coordinates for this structure
with the Cambridge Crystallographic Data Centre. The coordinates
can be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.
1-(cis-4,5-Dica r b oxy-1-cycloh e xe n -1-yl)p yr id in iu m
h exa flu or op h osp h a te (16b): white solid, mp 183-185 °C;

7818 J . Org. Chem., Vol. 62, No. 22, 1997
Lee et al.
1H NMR (D2O+acetone-d6, 300 MHz) δ 7.61 (d, 2H, J ) 6.8
Hz), 7.94 (d, 2H, J ) 6.8 Hz), 8.10 (t, 2H, J ) 6.8 Hz), 8.60 (t,
1H, J ) 6.4 Hz), 9.00 (d, 2H, J ) 5.5 Hz); 13C NMR (MeOH-
d4, 75.4 MHz) δ 125.4, 129.4, 132.4, 137.0, 145.3, 146.2, 148.1,
171.4; IR (KBr) 3429, 1712, 1629, 1470, 1257 cm-1; FABMS
(m/z) calcd for C12H10NO2 200, found 200. Anal. Calcd for
C12H10F6NO2P: C, 41.76; H, 2.92; N, 4.06. Found: C, 41.45;
H, 3.05; N, 4.31.
temperature for 14 h. The resulting precipitate was collected
by filtration, and the filtrate was extracted with CH2Cl2. The
organic layers were concentrated under reduced pressure to
give a solid residue. The combined solids were then recrystal-
lized from hot water to give 32b in 64% yield as pale greenish
needle crystal: mp 128-129 °C. 1H NMR (acetone-d6, 200
MHz) δ 2.16 (s, 3H), 4.58 (s, 1H), 5.41 (s, 1H), 5.97 (s, 1H),
6.04 (s, 1H), 8.34 (t, 2H, J ) 7.1 Hz), 8.86 (t, 1H, J ) 7.8 Hz),
9.04 (d, 2H, J ) 5.1 Hz); IR (KBr) 3134, 3079, 1624, 1606,
1467, 1390, 1195 cm-1; FABMS (m/z) calcd for C10H12N 146,
found 146. Anal. Calcd for C10H12F6NP: C, 41.25; H, 4.15; N,
4.81. Found: C, 41.45; H, 4.21; N, 4.59.
1-(3-Ca r boxyp h en yl)p yr id in iu m h exa flu or op h osp h a te
(24): This compound was obtained from the oxidation of 21b
by MnO2 in 82% yield by the same procedure used for 23 as a
1
white solid: mp 174-176 °C; H NMR (D2O+acetone-d6, 300
MHz) δ 7.68-7.78 (m, 1H), 7.80-7.88 (m, 1H), 8.12-8.18 (m,
2H), 8.25 (t, 2H, J ) 6.8 Hz), 8.73 (t, 1H, J ) 7.9 Hz), 9.12 (d,
2H, J ) 6.3 Hz); 13C NMR (MeOH-d4, 75.4 MHz) δ 126.8, 129.6,
129.8, 132.1, 133.6, 135.0, 144.6, 146.3, 148.3, 167.5; IR (KBr)
3405, 1707, 1634, 1619, 1421, 1314 cm-1; FABMS (m/z) calcd
for C12H10NO2 200, found 200. Anal. Calcd for C12H10F6-
NO2P: C, 41.76; H, 2.92; N, 4.06. Found: C, 42.01; H, 2.99;
N, 3.83.
Gen er a l P r oced u r e for th e Diels-Ald er Rea ction of
Com p ou n d 32a in CH3CN. A sealed tube containing a
suitable amount of 32a and a dienophile in CH3CN was heated
for the period of time as shown in Table 2. After removal of
the solvent, the residue was dissolved in water and then was
washed with ethyl acetate to remove the excess of dienophile.
NaPF6 (2 equiv) was added to the aqueous layer, and the
resulting mixture was stirred at room temperature overnight.
The resulting crude hexafluorophosphate salt was purified by
silica gel column chromatography (CH2Cl2/MeOH) to give the
pure product 36b-39b. Regioisomers (40b/41b and 42b/43b)
were separated individually by silica gel column chromatog-
raphy (CH2Cl2/MeOH ) 9:1). Compounds 40b and 42b were
the slower moving isomers collected from the silica gel column.
2-P h en yl-h exa h yd r oisoin d olin e-1,3,5-tr ion e (22). To a
solution of compound 7a (330 mg, 0.86 mmol) in CH3CN (10
mL) was added NaBH4 (38.9 mg, 1.03 mmol) and MeOH (0.8
mL). The resulting mixture was stirred at room temperature
for 20 min and then quenched with water. The mixture was
extracted with CH2Cl2 and the combined organic layers were
concentrated under reduced pressure. To a solution of the
crude residue in THF (5 mL) was added 2% HCl aqueous
solution (5 mL). The resulting mixture was stirred at room
temperature for 2 h. The mixture was extracted with CH2Cl2
and the combined organic layers were dried (Na2SO4) and
concentrated under reduced pressure. The crude material was
purified by HPLC (1:5 n-hexane/EtOAc) to give compound 22
(107 mg, 52%) as a white solid: mp 138-140 °C; 1H NMR
(CDCl3, 300 MHz) δ 2.22-2.50 (m, 4H), 2.75-2.92 (m, 2H),
3.28-3.36 (m, 1H), 3.40-3.50 (m, 1H), 7.25-7.32 (m, 2H),
7.38-7.55 (m, 3H); IR (KBr) 3219, 1704, 1494, 1385, 1188
cm-1; MS (m/z) 293 (M+, 100), 202, 188, 173, 119, 96, 68, 54.
Anal. Calcd for C14H13NO3: C, 69.12; H, 5.39; N, 5.76.
Found: C, 68.81; H, 5.38; N, 5.70.
1-(1,3-Dioxo-6-m et h yl-2-p h en yl-1,3,3a ,4,7,7a -h exa h y-
dr oisoin dole-5-yl)pyr idin iu m h exaflu or oph osph ate (36b):
white solid, mp 246-248 °C. 1H NMR (D2O + acetone-d6
,
300 MHz) δ 1.67 (s, 3H), 2.70 (dd, 1H, J ) 3.9, 16 Hz), 2.83
(dd, 1H, J ) 7.9, 16 Hz), 2.95 (dd, 1H, J ) 3.3, 16 Hz), 3.06-
3.15 (m, 1H), 3.52-3.60 (m, 1H), 3.65-3.74 (m, 1H), 7.18-
7.22 (m, 2H), 7.35-7.48 (m, 3H), 8.18 (t, 2H, J ) 7.0 Hz), 8.65
(t, 1H, J ) 8.0 Hz), 8.67-8.72 (m, 2H); IR (KBr) 3125, 3082,
1700, 1471, 1381, 1196 cm-1; FABMS (m/z) calcd for C20H19N2O2
319, found 319. Anal. Calcd for C20H19F6N2O2P: C, 51.73; H,
4.12; N, 6.03. Found: C, 51.43; H, 4.12; N, 5.87.
1-[tr a n s-4,5-Bis(m et h oxyca r b on yl)-2-m et h yl-1-cyclo-
h exen -1-yl]p yr id in iu m h exa flu or op h osp h a te (37b): white
solid, mp 119-121 °C. 1H NMR (acetone-d6 + D2O, 300 MHz)
δ 1.43 (s, 3H), 2.40-2.62 (m, 2H), 2.70-2.80 (m, 2H), 3.00-
3.10 (m, 1H), 3.14-3.24 (m, 1H), 3.62 (s, 3H), 3.65 (s, 3H), 8.12
(t, 2H, J ) 6.8 Hz), 8.60 (t, 1H, J ) 7.8 Hz), 8.75 (d, 2H, J )
6.0 Hz); IR (neat) 2959, 1734, 1629, 1475, 1439 cm-1; FABMS
(m/z) calcd for C16H20NO4 290, found 290. Anal. Calcd for
C16H20F6NO4P: C, 44.15; H, 4.63; N, 3.22. Found: C, 44.35;
H, 4.51; N, 2.82.
1-[cis-4,5-Bis(m eth oxycar bon yl)-2-m eth yl-1-cycloh exen -
1-yl]p yr id in iu m h exa flu or op h osp h a te (38b): yellowish oil;
1H NMR (D2O, 300 MHz) δ 1.23 (s, 3H), 2.36-2.48(m, 2H),
2.58-2.70 (m, 2H), 3.10-3.18 (m, 1H), 3.24-3.32 (m, 1H), 3.48
(s, 6H), 7.92 (t, 2H, J ) 7.0 Hz), 8.40 (t, 1H, J ) 7.8 Hz), 8.47
(d, 2H, J ) 5.8 Hz); IR (neat) 2953, 1732, 1626, 1473, 1438
cm-1; FABMS (m/z) calcd for C16H20NO4 290, found 290. Anal.
Calcd for C16H20F6NO4P: C, 44.15; H, 4.63; N, 3.22. Found:
C, 44.20; H, 4.48; N, 3.02.
3,4-Dibr om o-3-m eth ylsu lfola n e (34). This compound
was obtained from the bromination of 3-methyl-3-sulfolene in
16
CHCl3 as a white solid: mp 127-128 °C (lit.16 126-127 °C);
1H NMR (CDCl3, 200 MHz) δ 2.17 (s, 3H), 3.64 (dd, 1H, J )
3.4, 14.3 Hz), 3.73 (s, 2H), 4.25 (dd, 1H, J ) 6.2, 14.4 Hz),
4.94 (dd, 1H, J ) 3.4, 6.4 Hz); IR (KBr) 3000, 2932, 1400, 1306,
1294, 1237, 1182, 1139 cm-1; MS (m/z) 293 (M+), 291, 289, 213,
211 149, 147, 67 (100). Anal. Calcd for C5H8BrO2S: C, 20.57;
H, 2.76. Found: C, 20.57; H, 2.70.
1-(3-Meth yl-2-su lfolen -4-yl)p yr id in iu m br om id e (35): A
mixture of 34 (5.1 g, 17.12 mmol) and dry pyridine (45 mL)
was stirred at room temperature for 85 h. The yellow
precipitate that formed was collected, washed with benzene,
and then recrystallized from hot ethanol-methanol (3:2) to give
compound 35 in 52% yield6b as white needle crystal: mp 215-
216 °C; 1H NMR (D2O, 300 MHz) δ 1.90 (s, 3H), 3.93 (dd, 1H,
J ) 2.6, 15.5 Hz), 4.31 (dd, 1H, J ) 8.8, 15.5 Hz), 6.25 (d, 1H,
J ) 8.7 Hz), 7.24 (s, 1H), 8.20 (t, 2H, J ) 7.1 Hz), 8.69 (t, 1H,
J ) 7.5 Hz), 8.91 (d, 2H, J ) 5.7 Hz); IR (KBr) 3028, 2962,
2897, 1619, 1290, 1264, 1146, 1098 cm-1; FABMS (m/z) calcd
1-(1,2,3,4,4a ,5,8,8a -Octa h yd r o-7-m eth yl-1,4-m eth a n on -
a p h th a len -6-yl)p yr id in iu m h exa flu or op h osp h a te (39b):
1
yellowish oil; H NMR (MeOH-d4, 300 MHz) δ 1.13 (d, 1H, J
) 10.3 Hz), 1.28 (dd, 2H, J ) 7.2, 1.6 Hz), 1.59 (d, 2H, J ) 9.0
Hz), 1.64 (s, 3H), 1.76 (d, 1H, J ) 10.3 Hz), 1.80-1.92 (m, 1H),
1.94-2.15 (m, 4H), 2.30-2.45 (m, 2H), 2.51 (dd, 1H, J ) 15.1,
7.2 Hz), 8.22 (t, 2H, J ) 7.0 Hz), 8.67 (t, 1H, J ) 7.7 Hz), 8.87
(d, 2H, J ) 5.8 Hz); IR (neat) 3116, 2951, 2872, 1625, 1472
cm-1; FABMS (m/z) calcd for C17H22N 240, found 240. FAB-
HRMS calcd for C17H22N 240.1752, found 240.1753.
1-(4-Meth oxyca r bon yl-2-m eth yl-1-cycloh exen -1-yl)p y-
r id in iu m h exa flu or op h osp h a te (40b): colorless oil; 1H
NMR (MeOH-d4, 500 MHz) δ 1.52 (s, 3H), 1.98-2.08 (m, 1H),
2.22-2.28 (m, 1H), 2.53-2.61 (m, 3H), 2.62-2.72 (m, 1H),
2.86-2.94 (m, 1H), 3.73 (s, 3H), 8.21 (t, 2H, J ) 7.0 Hz), 8.69
(t, 1H, J ) 7.8 Hz), 8.90 (d, 2H, J ) 6.3 Hz); IR (neat) 3132,
3081, 2956, 1731, 1628, 1474, 1439 cm-1; FABMS (m/z) calcd
for C10H12NO2S 210, found 210. Anal. Calcd for C10H12
BrNO2S: C,41.53; H, 4.19; N, 4.85. Found: C, 41.14; H, 4.09;
N, 4.56.
-
1-(3-Meth yl-1,3-bu tadien -2-yl)pyr idin iu m br om ide (32a).
A mixture of compound 35 (409 mg, 1.41 mmol) and pyridine
(0.55 g, 7 mmol) in CH3CN (14 mL) was heated in a sealed
tube at 140 °C for 4 h. The solvent was then removed under
reduced pressure to afford 32a in nearly quantitative yield as
a greenish oil: 1H NMR (D2O, 200 MHz) δ 1.93 (s, 3H), 4.30
(s, 1H), 5.18 (s, 1H), 5.52 (s, 1H), 5.72 (s, 1H), 7.98 (t, 2H, J )
7.1 Hz), 8.52 (t, 1H, J ) 7.8 Hz), 8.69 (d, 2H, J ) 6.7 Hz). 13C
NMR (MeOH-d4, 50.3 MHz) δ 20.0, 117.8, 118.8, 129.5, 139.7,
146.4, 148.5, 151.1.
1-(3-Meth yl-1,3-bu ta d ien -2-yl)p yr id in iu m h exa flu or o-
p h osp h a te (32b): A solution of 32a (283 mg, 1.25 mmol) and
NaPF6 (419 mg, 2.5 mmol) in H2O (12 mL) was stirred at room
for C14H18NO2 232, found 232. FABHRMS calcd for C14H18
NO2 232.1337, found 232.1338.
-

Reactions of Butadienylpyridinium Bromides
J . Org. Chem., Vol. 62, No. 22, 1997 7819
1-(5-Meth oxyca r bon yl-2-m eth yl-1-cycloh exen -1-yl)p y-
r id in iu m h exa flu or op h osp h a te (41b): yellowish oil; 1H
NMR (MeOH-d4, 500 MHz) δ 1.50 (s, 3H), 1.93-2.02 (m, 1H),
2.122.19 (m, 1H), 2.32-2.46 (m 2H), 2.70-2.83 (m, 2H), 2.98-
3.05 (m, 1H), 3.74 (s, 3H), 8.22 (t, 2H, J ) 7.0 Hz), 8.70 (t, 1H,
J ) 7.8 Hz), 8.92 (d, 2H, J ) 5.4 Hz); IR (neat) 3132, 3081,
2956, 1731, 1628, 1474, 1439 cm-1; FABMS (m/z) calcd for
C14H18NO2 232, found 232. FABHRMS calcd for C14H18NO2
232.1337, found 232.1339.
1-(4-Ace t yl-2-m e t h yl-1-cycloh e xe n -1-yl)p yr id in iu m
h exa flu or op h osp h a te (42b): yellowish oil; 1H NMR (MeOH-
d4, 500 MHz) δ 1.52 (s, 3H), 1.86-1.95 (m, 1H), 2.22-2.26 (m,
1H), 2.27 (s, 3H), 2.44-2.48 (m, 2H), 2.50-2.58 (m, 1H), 2.61-
2.73 (m, 1H), 2.94-3.01 (m, 1H), 8.19 (t, 2H, J ) 7.0 Hz), 8.68
(t, 1H, J ) 7.8 Hz), 8.86 (d, 2H, J ) 6.0 Hz); 13C NMR (DMSO-
d6, 50.3 MHz) δ 18.0, 24.8, 28.6, 29.6, 31.9, 45.8, 129.1, 133.4,
135.9, 145.6, 147.0, 210.6; IR (neat) 3656, 3131, 2933, 1707,
1629, 1473 cm-1; FABMS (m/z) calcd for C14H18NO 216, found
216.
mixture was concentrated under reduced pressure. The
residue was recrystallized from hot water to give the pure
hexafluorophosphate salt 44b or 45b.
1-(tr a n s-4,5-Dica r boxy-2-m eth yl-1-cycloh exen -1-yl)p y-
r id in iu m h exa flu or op h osp h a te (44b): white solid, mp
228-230 °C. 1H NMR (acetone-d6 + D2O, 300 MHz) δ 1.53 (s,
3H), 2.45-2.70 (m, 2H), 2.70-2.92 (m, 2H), 3.02-3.12 (m, 1H),
3.13-3.26 (m, 1H), 8.23 (t, 2H, J ) 7.0 Hz), 8.71 (t, 1H, J )
7.8 Hz), 8.87 (d, 2H, J ) 6.0 Hz); 13C NMR (MeOH-d4, 75.4
MHz) δ 17.7, 32.3, 32.9, 42.0, 42.8, 130.0, 135.1, 135.6, 146.1,
148.0, 177.5, 178.1; IR (KBr) 3493, 2922, 1723, 1678, 1469,
1429 cm-1; FABMS (m/z) calcd for C14H16NO4 262, found 262.
Anal. Calcd for C14H16F6NO4P: C, 41.29; H, 3.96; N, 3.44.
Found: C, 41.65; H, 4.37; N, 3.34.
1-(cis-4,5-Dica r boxy-2-m eth yl-1-cycloh exen -1-yl)p yr i-
d in iu m h exa flu or op h osp h a te (45b): white solid, mp 230-
232 °C. 1H NMR (D2O, 300 MHz) δ 1.35 (s, 3H), 2.50-2.57
(m, 2H), 2.76 (br s, 2H), 3.15-3.24 (m, 1H), 3.26-3.35 (m, 1H),
8.01 (t, 2H, J ) 7.0 Hz), 8.49 (t, 1H, J ) 7.9 Hz), 8.60 (d, 2H,
1-(5-Ace t yl-2-m e t h yl-1-cycloh e xe n -1-yl)p yr id in iu m
h exa flu or op h osp h a te (43b): yellowish oil; 1H NMR (MeOH-
d4, 500 MHz) δ 1.48 (s, 3H), 1.85-1.93 (m, 1H), 2.17-2.24 (m,
1H), 2.27 (s, 3H), 2.29-2.36 (m 1H), 2.40-2.49 (m, 1H), 2.58-
2.65 (m, 1H), 2.692.77 (m, 1H), 3.06-3.13 (m, 1H), 8.21 (t, 2H,
J ) 7.0 Hz), 8.70 (t, 1H, J ) 7.8 Hz), 8.92 (d, 2H, J ) 6.0 Hz);
13C NMR (DMSO-d6, 50.3 MHz) δ 17.7, 24.0, 28.3, 30.0, 31.1,
46.6, 129.1, 134.0, 135.1, 145.6, 147.0, 209.8; IR (neat) 2927,
J ) 6.0 Hz); IR (KBr) 3500, 2911, 1725, 1676, 1469, 1430 cm-1
;
FABMS calcd for C14H16NO4 262.1079, found 262.1083.
Ack n ow led gm en t. We thank Dr. K. -J . Lin for
collecting the single crystal X-ray diffraction data, Ms.
S. C. Lin for compiling the 2D NMR spectra, Mr. W. F.
Chen for collecting the mass spectra, and the National
Science Council of the Republic of China for financial
support.
2853, 1706, 1625, 1473 cm-1; FABMS (m/z) calcd for C14H18
-
NO 216, found 216. Anal. Calcd for C14H18F6NOP: C, 46.55;
H, 5.02; N, 3.88. Found: C, 46.94; H, 5.27; N, 3.35.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra of
all new compounds; 13C NMR spectra of 18b-21b, 23, 24, and
Gen er a l P r oced u r e for th e Diels-Ald er Rea ction of
Com p ou n d 32a in H2O. A sealed tube containing 32a (54.4
mg, 0.24 mmol) and a suitable amount of dienophile in H2O
(12 mL) was heated for the period of time as shown in Table
2. After removal of the solvent, the residue was washed with
ethyl ether (entry 7) or acetone (entry 8) to remove the excess
of dienophile. Then the residue was dissolved in water and
NaPF6 (2 equiv) was added to the solution. The resulting
mixture was stirred at room temperature for overnight. The
1
42b-44b; H-1H COSY spectra of 18b-21b, and 40b-43b;
NOESY spectra of 20b, 21b, and 40b-43b; and the ORTEP
drawing of 18b (57 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.
J O971181Z