Access to ring-fused homo- and heteroaromatic derivatives via an initial ring-opening of 3-nitro-4-(phenylsulfonyl)thiophene

Article abstract of DOI:10.1021/jo034264q

Within an overall ring-opening/ring-forming protocol, the (e,e)-4-methylthio-2-nitro-3-phenylsul fonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)-thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn β-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.

Full text of DOI:10.1021/jo034264q

Access to Rin g-F u sed Hom o- a n d Heter oa r om a tic Der iva tives via
a n In itia l Rin g-Op en in g of 3-Nitr o-4-(p h en ylsu lfon yl)th iop h en e1
Lara Bianchi, Carlo Dell’Erba, Massimo Maccagno, Angelo Mugnoli, Marino Novi,
Giovanni Petrillo,* Fernando Sancassan, and Cinzia Tavani
Dipartimento di Chimica e Chimica Industriale, Universita` di Genova,
Via Dodecaneso 31, I-16146 Genova, Italy
petrillo@chimica.unige.it
Received February 28, 2003
Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsul-
fonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)-
thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor
of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or het-
eroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by
conventional methods. The key step is represented by a thermal electrocyclic rearrangement of
(E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper
geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an
irreversible, concerted syn â-elimination of methanesulfinic acid to aromatize the newly formed
cyclohexadienic ring.
CHART 1
In tr od u ction
Within the framework of the well-recognized nonben-
zenoid behavior of the thiophene heterocycle,2-4 the
initial, amine-induced, ring-opening of nitrothiophenes
12a,c,3 and 42b,4 has been shown to provide access to in-
teresting polyfunctionalized molecules such as dinitro-
butadienes 2 or nitrohexatrienes 3, and nitrobutadienes
5, respectively (Chart 1), which represent powerful build-
ing blocks amenable to further manipulation. In particu-
lar, an overall ring-opening/ring-closure procedure has
recently allowed the attainment of benzene derivatives,3a
as well as heteroaromatic compounds such as isoxa-
zoles,2a,b,5 furoxans,6 furazans,6 or pyrroles.3b
* Author to whom correspondence should be addressed. Phone: +39
10 3536121. Fax: +39 10 3536118.
(1) Synthetic Exploitation of the Ring-Opening of Nitrothiophenes,
Part XV. For part XIV, see ref 2a.
As a novel, significant example of the applicability of
such a procedure to the construction of a homoaromatic
ring starting from a 3-nitrothiophene, herein we report
on an effective transformation of 3-nitro-4-(phenylsulfo-
nyl)thiophene (6) into ring-fused aromatic derivatives
functionalized with vicinal nitro and phenylsulfonyl
groups (10).
(2) (a) Bianchi, L.; Dell’Erba, C.; Gasparrini, F.; Novi, M.; Petrillo,
G.; Sancassan, F.; Tavani, C. Arkivoc 2002, 142-158. (b) Bianchi, L.;
Dell’Erba, C.; Gabellini, A.; Novi, M.; Petrillo, G.; Tavani, C. Tetrahe-
dron 2002, 58, 3379-3385. (c) Armaroli, T.; Dell’Erba, C.; Gabellini,
A.; Gasparrini, F.; Mugnoli, A.; Novi, M.; Petrillo, G.; Tavani, C. Eur.
J . Org. Chem. 2002, 1284-1291, and previous papers in the series.
For
a survey of relevant earlier literature see: (d) Spinelli, D.;
Consiglio, G.; Dell’Erba, C.; Novi, M. In The Chemistry of Heterocyclic
Compounds, Thiophene and its Derivatives; Gronowitz, S., Ed.; J .
Wiley: New York, 1991; Vol. 44, pp 295-396. (e) Dell’Erba, C.; Novi,
M.; Petrillo, G.; Tavani, C. In Topics in Heterocyclic Systems: Synthesis,
Reactions and Properties; Attanasi, O. A., Spinelli, D., Eds.; Research
Signpost: Trivandrum, India, 1996; Vol. 1, pp 1-12. (f) Consiglio, G.;
Spinelli, D.; Dell’Erba, C.; Novi, M.; Petrillo, G. Gazz. Chim. Ital. 1997,
127, 753-769.
Resu lts a n d Discu ssion
The overall ring-to-ring transformation described in the
present paper is summarized in Scheme 1. The effective
preparation of compounds 10 takes advantage of a final,
surprisingly simple, benzene-ring forming cyclization
(step e) following ring-opening of 3-nitro-4-(phenylsulfo-
nyl)thiophene (6) (steps a and b), replacement of the
(3) (a) Dell’Erba, C.; Gabellini, A.; Mugnoli, A.; Novi, M.; Petrillo,
G.; Tavani, C. Tetrahedron 2001, 57, 9025-9031. (b) Dell’Erba, C.;
Mugnoli, A.; Novi, M.; Pani, M.; Petrillo, G.; Tavani, C. Eur. J . Org.
Chem. 2000, 903-912, and previous papers in the series.
(4) Dell’Erba, C.; Gabellini, A.; Novi, M.; Petrillo, G.; Tavani, C.;
Cosimelli, B.; Spinelli, D. Tetrahedron 2001, 57, 8159-8165.
(5) Dell’Erba, C.; Novi, M.; Petrillo, G.; Stagnaro, P. J . Heterocycl.
Chem. 1994, 31, 861-865.
(6) Armani, V.; Dell’Erba, C.; Novi, M.; Petrillo, G.; Tavani, C.
Tetrahedron 1997, 53, 1751-1758.
10.1021/jo034264q CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/31/2003
5254
J . Org. Chem. 2003, 68, 5254-5260

Ring-Opening of 3-Nitro-4-(phenylsulfonyl)thiophene
SCHEME 1a
much akin to that reported for the 2-X-4-nitrothiophenes
4.2b,4 The assignment of the (E,E)-configuration to 7 is
founded on an X-ray single-crystal structure determina-
tion.7
It is interesting to note that the amine attack on 6 is
chemoselectively directed toward the C(2) atom, while
reactions with arenethiolates on the same substrate have
been reported8 to lead to a mixture of cine-substitution
products resulting from attack of the nucleophile to C(2)
(main pathway) or C(5).
The replacement of the pyrrolidino group of 7 with an
aryl moiety has been accomplished by means of a
procedure already applied with success to butadienes
derived from ring-opening of 12b and 4.9,10 In tight analogy
with the latter cases, only the nitroenamine system
undergoes attack by the Grignard reagent, the yields of
the resulting aryl derivatives 8 being excellent through-
out (Table 1).
a
Reagents and conditions: (a) 6 (1.1 mmol), pyrrolidine (2 mol
equiv), AgNO3 (2 mol equiv), in absolute ethanol (10 mL), 40 °C,
15 h; (b) MeI (10 mmol), rt, 4 h; (c) [7]: ca. 0.08 M in THF;
ArMgBr: 1.1 mol equiv; 0 °C; then, H3O+ quenching; (d) [8]: 0.07
M in CH2Cl2; m-chloroperbenzoic acid: 2 mol equiv; rt; (e) [9]: 5
× 10-3 M in dry p-xylene; reflux, 1-70 h.
The stereochemical assignment to compounds 8 es-
sentially rests on an NMR analysis on the model com-
pound 8i (Ar ) 2-Th). Thus, NOE experiments showed
that irradiation of H(4) caused a 2.64% NOE enhance-
ment for the H(2′) and H(6′) protons of the phenylsulfonyl
group, besides a 6.62% enhancement for the SMe protons;
on the other hand, irradiation of SMe caused no ap-
preciable NOE effect for the H(2′) and H(6′) protons,
besides a 3.53% enhancement for H(4). On this basis, an
(E)-configuration can be assigned to the C(3)-C(4) vinylic
system of 8. With regard to the C(1)-C(2) vinylic system,
a likewise (E)-configuration is supported by the marked
deshielding experienced by the proton adjacent to the
nitro group, relevant δ values being higher than 8.2 ppm
throughout.4 It should also be remarked that, in those
cases where the C(3) multiplet could be observed [such
TABLE 1. Yield s of Com p ou n d s 8 a n d 9 fr om Step s c
a n d d of Sch em e 1a
Ar
8: %a
9: %a
Ph
8a : 90
8b: 98
8c: 95
8d : 90
8e: 89
8f: 67
8g: 98
8h : 98
8i: 98
8j: 77
9a : 95
9b: 98
9c: 98
9d : 92
9e: 98
9f: 81
9g: 99
9h : 99
9i: 99
9j: 98
2-MeC6H4
3-MeC6H4
4-MeC6H4
4-MeOC6H4
4-(COOMe)C6H4
1-naphthyl
2-naphthyl
2-thienyl
3-thienyl
3
a
as 8d (Ar ) p-Tol) or 8i (Ar ) 2-Th)] the J C3-H1 values
Yields of isolated products.
found (8.0 and 6.8 Hz, respectively) compare well with
3
trans J CH values (ranging from 8.2 to 11.8 Hz) previously
TABLE 2. Yield s of Rin g-F u sed Com p ou n d s 10 fr om th e
3
reported for diene-Fe(CO)3 complexes:11 cis J CH values
Oxid a tive Cycliza tion of 9 in Dr y p-Xylen ea
ranging from 3.4 to 4.6 Hz.11 Such results in particular
confirm that, also in the present case, the replacement
of the amino moiety in the nitroenamine portion with the
aryl of the Grignard reagents occurs with retention of
configuration, as already observed in other similar
cases.4,9,10a
reaction
Ar
product
10a
yield (%)b
time (h)c
Ph
96
98
93
90
81
67
88
98
90
98
48
24
17
70
24
28
1.5
1.0
20
16
2-MeC6H4
3-MeC6H4
4-MeC6H4
4-MeOC6H4
4-(COOMe)C6H4
1-naphthyl
2-naphthyl
2-thienyl
10b
10c/10c′d
10d
Th er m a l Cycliza tion of Com p ou n d s 9. The key step
of the overall 6 to 10 sequence of Scheme 1 is undoubtedly
represented by the cyclization (step e), whereby a nitro-
(phenylsulfonyl)-substituted benzene ring is obtained
through annulation accompanied by methanesulfinic acid
elimination (Scheme 2).
As a matter of fact, as a first attempt to exploit the
high degree of functionalization of compounds 9, recent
reports on the behavior of trans-1,2-bis(arylsulfonyl)-
10e
10f
10g
10h
10i
10j
3-thienyl
a
b
[9]: 5 × 10-3 M in dry p-xylene; reflux (1-70 h). Isolated
yields. c Reaction followed by TLC disappearance of substrate.
Mixture of isomeric 10c and 10c′ from which the single compo-
d
nents could not be separated in pure form: 10c/10c′ ratio ) 66/
34 (1H NMR analysis).
(7) Bianchi, L.; Fossa, P.; Maccagno, M.; Mugnoli, A.; Petrillo, G.;
Tavani, C. Z. Kristallogr., in press.
(8) Novi, M.; Guanti, G.; Dell’Erba, C.; Spinelli, D. J . Chem. Soc.,
Perkin Trans. 1 1976, 2264-2266.
(9) Dell’Erba, C.; Mele, A.; Novi, M.; Petrillo, G.; Stagnaro, P.
Tetrahedron 1992, 48, 4407-4418.
(10) (a) Dell’Erba, C.; Novi, M.; Petrillo, G.; Spinelli, D.; Tavani, C.
Tetrahedron 1996, 52, 3313-3326. (b) Dell’Erba, C.; Mugnoli, A.; Novi,
M.; Pertici, M.; Petrillo, G.; Tavani, C. Eur. J . Org. Chem. 1999,
431-435.
(11) Adams, C. M.; Cerioni, G.; Hafner, A.; Kalchhauser, H.; von
Philipsborn, W.; Prewo, R.; Schwenk, A. Helv. Chim. Acta 1988, 71,
1116-1142.
pyrrolidino moiety of 7 (step c), and oxidation of the
methylthio group of 8 (step d). Yields of compounds 8 and
9 are collected in Table 1; cyclization yields are collected
in Table 2.
In particular, it should be noted that the ring-opening
of 6 effectively occurs in the presence of silver ions,
leading (after methylation of the envisageable, although
nonisolated, intermediate silver thiolate) to the appeal-
ingly functionalized butadiene 7, an outcome undoubtedly
J . Org. Chem, Vol. 68, No. 13, 2003 5255

Bianchi et al.
SCHEME 2
SCHEME 3
From a practical point of view, it should be stressed
that the protocol herein allows the access to, e.g.,
polysubstituted naphthalenes or phenanthrenes which
are difficult, if not impossible, to prepare through con-
ventional synthetic methodologies, such as those based
on electrophilic aromatic substitutions. As a matter of
fact the general approach hinging on the cycloaddition
(inter- or intramolecular) of suitable precursors is fre-
quently exploited, e.g., for the synthesis of properly
substituted naphthalene moieties, whose interest in the
biological and/or pharmaceutical fields is, on the other
hand, well-known.13
ethylenes as valuable dienophiles12 suggested the em-
ployment of 9 in Diels-Alder processes. Surprisingly
enough, from the model reaction of 9d with 1,3-cyclo-
hexadiene in refluxing toluene for 1 day, the workup led
to the isolation, besides some recovered substrate, of a
main product that was identified as 6-methyl-2-nitro-3-
(phenylsulfonyl)naphthalene (10d ). The formation of 10d
was found to be independent of the presence of cyclo-
hexadiene, efficiently occurring when heating 9d alone
at reflux in the same solvent.
From a mechanistic point of view, for the present
cyclization we can envisage an initial electrocyclic rear-
rangement, eventually followed by an irreversible meth-
anesulfinic acid elimination (Scheme 3).14
Within this framework, an aspect that is surely in-
triguing is represented by the unprecedented mildness
of the experimental conditions (reflux in p-xylene) neces-
sary to perform the cyclization on compounds 9. As a mat-
ter of fact, e.g., the benzocyclization of 1-aryl-1,3-butadi-
enes has been reported13b,15 until recently to occur in
much harsher thermal conditions such as flash vacuum
pyrolysis,15a or with acid catalysis13b or photostimulation.15b
Further examples of the participation of two π-electrons
of an aromatic ring in an electrocyclization process are
essentially confined to the photochemical conversions,
under oxidizing conditions, of stilbenes16a or heterostil-
benes16b to phenanthrenes or heterophenanthrenes, re-
spectively, or of styrylanthracenes to more complex fused
systems.16c
The synthetic interest of such an outcome prompted
us to extend the process to the whole series of 9 in our
hands after optimization of the experimental conditions,
eventually selecting the higher boiling p-xylene for the
initially employed toluene. The results of Table 2 clearly
show that operatively simple, relatively mild reaction
conditions meet with results which are excellent through-
out; it should be noticed that the prompt reactivity of the
naphthyl derivatives 9g,h (reaction complete within 1.5
and 1 h, respectively) indicates they are particularly
suitable systems.
Most likely a number of factors concur to the facility
of the overall process herein, namely (a) a proper con-
figuration, hence a proper spatial arrangement of the
molecule, which brings to the correct distance the two
carbon atoms involved in the formation of the new bond,
(b) favorable electronic effects of the substituents on the
As expected, with the phenyl- (9a ) and the 4-substi-
tuted phenyl derivatives (9d -f) cyclization concerns at
one of the two (equivalent) positions ortho to the buta-
diene system, while the 2-methyl group of 9b directs the
cyclization onto the free 6-position; interestingly, with
the 3-tolyl derivative 9c it was possible to isolate a
mixture of the two nonseparable isomeric products cor-
responding to cyclization at the 6-position (10c) or at the
2-position (10c′) of the aromatic ring, some regioselec-
tivity showing up in the sizable preference (10c/10c′ )
66/34) for the less hindered 6-position.
(13) (a) de Koning, C. B.; Rousseau, A. L.; van Otterlo, W. A. L.
Tetrahedron 2003, 59, 7-36 and references therein. (b) Kajikawa, S.;
Nishino, H.; Kurosawa, K. Tetrahedron Lett. 2001, 42, 3351-3354.
(14) Cossu, S.; Cuomo, G.; De Lucchi, O.; Maggini, M.; Valle, G. J .
Org. Chem. 1996, 61, 153-158.
(15) (a) Valkovich, P. B.; Conger, J . L.; Castiello, F. A.; Brodie, T.
B.; Weber, W. P. J . Am. Chem. Soc. 1975, 97, 901-902. Banciu, M.
D.; Brown, R. F. C.; Coulston, K. J .; Eastwood, F. W.; Macrae, T. Aust.
J . Chem. 1998, 51, 695-701. Padwa, A.; Caruso, T.; Nahm, S.;
Rodriguez, A. J . Am. Chem. Soc. 1982, 104, 2865-2871. (b) Olsen, R.
J .; Minniear, J . C.; Mack Overton, W.; Sherrick, J . M. J . Org. Chem.
1991, 56, 989-991.
(16) (a) Lewis, F. D.; Kurth, T. L.; Kalgutkar, R. S. Chem. Commun.
2001, 1372-1373. Mallory, F. B.; Mallory, C. W. In Organic Reactions;
J ohn Wiley & Sons: New York, 1984. Doyle, T. D.; Benson, W. R.;
Filipescu, N. J . Am. Chem. Soc. 1976, 98, 3262-3267. Liu, L.; Yang,
B.; Katz, T. J .; Poindexter, M. K. J . Org. Chem. 1991, 56, 3769-3775.
Rodier, J .-M.; Myers, A. B. J . Am. Chem. Soc. 1993, 115, 10791-10795.
Caldwell, R. A.; Mizuno, K.; Hansen, P. E.; Vo, L. P.; Frentrup, M.;
Ho, C. D. J . Am. Chem. Soc. 1981, 103, 7263-7269. (b) Lewis, F. D.;
Kalgutkar, R. S.; Yang, J .-S. J . Am. Chem. Soc. 2001, 123, 3878-3884.
Irie, M. Chem. Rev. 2000, 100, 1685-1716. Rawal, V. H.; J ones, R. J .;
Cava, M. P. Tetrahedron Lett. 1985, 26, 2423-2426. (c) Karatsu, T.;
Kitamura, A.; Zeng, H.; Arai, T.; Sakuragi, H.; Tokumaru, K. Bull.
Chem. Soc. J pn. 1995, 68, 920-928.
Of particular relevance is the possibility of obtaining,
in similar excellent yields, isomeric nitro(phenylsulfonyl)
phenanthrenes (10g,h ) and benzothiophenes (10i,j) sim-
ply by means of an appropriate choice of the Grignard
reagent for step c of Scheme 1. Interestingly enough, the
formation of 10h from 9h as the sole product is the result
of a complete regioselectivity, annulation exclusively
occurring at the naphthalene R-position adjacent to the
butadiene chain.
(12) Cossu, S.; De Lucchi, O.; Fabbri, D.; Licini, G.; Pasquato, L.
Org. Prep. Proc. Int. 1991, 23, 573-592. De Lucchi, O.; Pasquato, L.
Tetrahedron 1988, 44, 6755-6794.
5256 J . Org. Chem., Vol. 68, No. 13, 2003

Ring-Opening of 3-Nitro-4-(phenylsulfonyl)thiophene
butadiene chain, and (c) the possibility of an irreversible
aromatization due to a favorable â-elimination of meth-
anesulfinic acid, which prevents the possibility of isolat-
ing any reaction intermediate.
advantage of its stereochemistry, which allows a con-
certed syn â-elimination.
Exp er im en ta l Section
As far as the former factor above is concerned, the
(E,E)-configuration of compounds 9 allows the molecule
to attain the s-cis conformation (A) required for intramo-
lecular cyclization.
Gen er a l. Unless differently specified, 1H NMR and 13C
NMR spectra were recorded at 200 and 50 MHz, respectively;
chemical shifts (TMS as internal reference) are reported as δ
ppm. Melting points are uncorrected. Silica gel 230-400 mesh
was used for column chromatography, all solvents being
distilled before use. Tetrahydrofuran (THF) was purified by
standard methods and distilled over potassium benzophenone
ketyl before use. 3-Nitro-4-(phenylsulfonyl)thiophene (6) was
synthesized as previously reported18a from methyl 3-bromo-2-
thiophenecarboxylate, which was in turn obtained by the
action of diazomethane on the corresponding acid.18b Com-
mercial 2- and 3-bromothiophene as well as 1- and 2-bro-
monaphthalene were used as received after drying over
molecular sieves (4 Å) or (for the latter) over P2O5 under
vacuum; methyl 4-iodobenzoate was prepared from the corre-
sponding commercial acid by reaction with diazomethane in
ether. All other commercially available reagents were used as
received.
Rin g-Op en in g of 3-Nitr o-4-(p h en ylsu lfon yl)th iop h en e
(6). A suspension of 3-nitro-4-(phenylsulfonyl)thiophene (0.3
g, 1.1 mmol) in absolute ethanol (10 mL), under argon and
magnetic stirring, was heated to 40 °C and 0.38 g (2.2 mmol)
of silver nitrate was added; after 15 min pyrrolidine (0.18 mL,
2.2 mmol) was introduced and the reaction mixture was kept
overnight at 40 °C under magnetic stirring. The reaction
mixture was cooled to room temperature and MeI (0.62 mL,
10 mmol) was added; after 4 h under magnetic stirring, the
reaction was diluted with acetone and filtered from a gray
precipitate, which was washed with acetone. The clear filtrate
was evaporated under reduced pressure to leave a residue that
was dissolved in dichloromethane and chromatographed on a
With regard to the substituent effects in the butadiene
moiety, it should be stressed that no significant reaction
has been observed on the sulfide 8d either in the same
experimental conditions used for 9d or in the presence
of DDQ, which should be able to perform dehydrogena-
tion of the newly formed ring: thus, the presence of the
methylsulfonyl group at C(4) seems essential17 not simply
to accomplish rearomatization (providing a good leaving
group for the final elimination step), but also for the
cycloaddition step itself.
Finally, thanks to the disrotatory nature of the thermal
electrocyclization process herein, the starting (E)-config-
uration of the C(3)-C(4) double bond most likely leads
to a cyclohexadiene intermediate (see Scheme 3) where
the SO2Me group and the adjacent ring hydrogen are
cis: such a relative position justifies, in the neutral
reaction conditions employed, an easy, concerted syn
â-elimination as schematized in B.
silica gel column (eluants: dichloromethane and then
a
gradient of the latter with ethyl acetate). Unreacted thiophene
derivative (10) was eluted first (18 mg, 6%), followed by the
product (7) (0.34 g, 87%).
4-Met h ylt h io-2-n it r o-3-p h en ylsu lfon yl-1-p yr r olid in o-
1,3-bu tadien e (7). Yellowish solid, mp 190.6-191.2 °C (EtOH);
νmax (Nujol) 1611, 1572, 1403, 1295, 1265, 1238, 1140, 1086
cm-1; 1H NMR (CDCl3) δ 1.99 (4H, m), 2.52 (3H, s), 3.32 (1H,
m), 3.72 (2H, m), 4.05 (1H, m), 7.51 (3H, m), 7.83 (2H, m),
8.13 (1H, s), 8.66 (1H, s); 13C NMR (CDCl3) δ 17.35, 24.45,
26.04, 47.56, 55.79, 112.32, 127.04, 128.30, 128.96, 133.41,
140.09, 148.48, 155.03. Anal. Calcd for C15H18N2O4S2: C, 50.8;
H, 5.1; N, 7.9. Found: C, 50.7; H, 5.2; N, 8.0.
Ar ylm a gn esiu m Ha lid es. All the Grignard reagents were
THF or Et2O solutions titrated19 just before use. Commercial
solutions in THF or Et2O of phenyl-, of 2-, 3-, and 4-meth-
ylphenyl-, and of 4-methoxyphenylmagnesium bromides or
chlorides were used as received. 1-Naphthyl-, 2-naphthyl-, and
2-thienylmagnesium bromides were prepared in THF by
standard methods. 3-Thienylmagnesium bromide in THF was
synthesized by the entrainment method with 1,2-dibromoet-
hane20 in analogy with a reported procedure.21 Following a
literature procedure,22 the 4-methoxycarbonyl phenylmagne-
sium halide was obtained in THF by exchange reaction with
freshly prepared isopropylmagnesium bromide of the corre-
sponding methyl iodobenzoate.
Con clu sion s
The results reported herein depict a useful, high-
yielding, overall ring-ring interconversion whereby 3-ni-
tro-4-(phenylsulfonyl)thiophene (6) is transformed, in
generally good overall yields, into appealing ring-fused
aromatic or heteroaromatic derivatives whose substitu-
tion pattern cannot be easily achieved via conventional
methodologies. The most interesting aspects of the overall
sequence are represented by the initial transformation
of 6 into the (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-
phenylsulfonyl-1,3-butadienes 8 and by the thermal
electrocyclization step whose unprecedentedly mild con-
ditions are surely due to the concurrence of particularly
favorable geometric and electronic factors. The final,
irreversible elimination of methanesulfinic acid on the
nonisolable cyclohexadienic intermediate takes in turn
(18) (a) Novi, M.; Guanti, G.; Dell’Erba, C.; Spinelli, D. J . Chem.
Soc., Perkin Trans. 1 1976, 2264-2266. (b) Lawesson, S.-O. Acta Chem.
Scand. 1956, 10, 1020-1023.
(19) Bergbreit, D. E.; Pendergrass, E. J . Org. Chem. 1981, 46, 219-
220.
(20) Pearson, D. E.; Cowan, D.; Beckler, J . D. J . Org. Chem. 1959,
24, 504-509.
(21) Gronowitz, S.; Pettersson, K. J . Heterocycl. Chem. 1976, 1099-
1100.
(17) Preliminary results suggest that the phenylsulfonyl goup at C(3)
is, on the contrary, not essential for the cyclization process to occur.
(22) Boymond, L.; Rottla¨nder, M.; Cahiez, G.; Knochel, P. Angew.
Chem. 1998, 110, 1801-1804;
J . Org. Chem, Vol. 68, No. 13, 2003 5257

Bianchi et al.
Rea ction s of 7 w ith Ar yl Gr ign a r d Rea gen ts. To a
suspension of 4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrro-
lidino-1,3-butadiene (7; 0.354 g, 1 mmol) in THF (12 mL),
cooled to 0 °C, was slowly added by syringe the Grignard
reagent in THF (1.1 mmol) under argon and magnetic stirring.
The reaction mixture was left to reach room temperature, kept
under stirring for 15 min (the end of the reaction being judged
by TLC analysis), and eventually poured into a dichlo-
romethane-ice-HCl (1.1 mmol) mixture. After separation of
the two layers, the aqueous phase was extracted with dichlo-
romethane; the collected organic extracts were washed with
water and dried over Na2SO4. Concentration under vacuum
of the extracts gave a crude that was purified by column
chromatography over silica gel (petroleum ether/dichlo-
romethane gradients as eluent). Yields of compounds 8 are
collected in Table 1.
(E,E)-4-Meth ylth io-2-n itr o-1-p h en yl-3-p h en ylsu lfon yl-
1,3-bu ta d ien e (8a ). Yellow solid, mp 101.2-102.4 °C (EtOH);
νmax (Nujol) 1643, 1552, 1521, 1446, 1310, 1208, 1150, 1086
cm-1; 1H NMR (CDCl3) δ 2.53 (3H, s), 7.43 (8H, m), 7.77 (2H,
m), 8.27 (1H, s), 8.30 (1H, s); 13C NMR (CDCl3) δ 17.66, 125.72,
128.21, 128.99, 129.08, 129.70, 130.84, 132.13, 133.64, 139.17,
139.50, 141.15, 155.86. Anal. Calcd for C17H15NO4S2: C, 56.5;
H, 4.2; N, 3.9. Found: C, 56.7; H, 4.3; N, 4.0.
(E,E)-4-Meth ylth io-1-(1-n a p h th yl)-2-n itr o-3-p h en ylsu l-
fon yl-1,3-bu ta d ien e (8g). Yellow solid, mp 222.1-223.1 °C
(toluene); νmax (Nujol) 1642, 1521, 1446, 1307, 1243, 1141, 1082
cm-1; 1H NMR (CDCl3) δ 2.56 (3H, s), 7.07 (3H, m), 7.33 (1H,
app. t, J ) 7.7 Hz), 7.59 (5H, m), 7.85 (3H, m), 8.28 (1H, s),
9.02 (1H, s); 13C NMR (CDCl3) δ 17.82, 123.46, 125.27, 125.50,
126.58, 126.78, 127.23, 127.34, 127.89, 128.58, 128.83, 131.49,
132.04, 132.69, 133.31, 138.91, 141.13, 156.62. Anal. Calcd for
C
21H17NO4S2: C, 61.3; H, 4.2; N, 3.4. Found: C, 61.4; H, 4.3;
N, 3.3.
(E,E)-4-Meth ylth io-1-(2-n a p h th yl)-2-n itr o-3-p h en ylsu l-
fon yl-1,3-bu ta d ien e (8h ). Yellow solid, mp 131.4-132.4 °C
(EtOH); νmax (Nujol) 1643, 1621, 1598, 1548, 1519, 1446, 1344,
1309, 1177, 1144, 1084 cm-1; 1H NMR (CDCl3) δ 2.53 (3H, m),
7.35 (3H, m), 7.56 (3H, m), 7.78 (5H, m), 7.99 (1H, br s), 8.32
(1H, s), 8.48 (1H, s); 13C NMR (CDCl3) δ 17.67, 125.12, 125.99,
126.90, 127.38, 127.72, 128.21, 128.58, 128.87, 129.05, 129.10,
132.85, 133.53, 133.87, 134.84, 139.09, 139.55, 141.35, 155.93.
Anal. Calcd for C21H17NO4S2: C, 61.3; H, 4.2; N, 3.4. Found:
C, 61.5; H, 4.2; N, 3.3.
(E,E)-4-Meth yltio-2-n itr o-3-ph en ylsu lfon yl-1-(2-th ien yl)-
1,3-bu ta d ien e (8i). Yellow solid, mp 62.5-63.5 °C (EtOH);
νmax (Nujol) 1629, 1546, 1508, 1414, 1304, 1217, 1145, 1084,
1
1055 cm-1; H NMR (CDCl3) δ 2.54 (3H, s), 7.12 (1H, dd, J )
(E,E)-1-(2-Meth ylp h en yl)-4-m eth ylth io-2-n itr o-3-p h en -
ylsu lfon yl-1,3-bu ta d ien e (8b). Yellowish solid, mp 140.2-
141.8 °C (EtOH); νmax (Nujol) 1641, 1559, 1522, 1316, 1306,
3.8 and 4.9 Hz), 7.50 (4H, m), 7.65 (1H, d, J ) 4.9 Hz), 7.82
(2H, m), 8.34 (1H, s), 8.53 (1H, s); 13C NMR (CDCl3) δ 17.60,
125.31, 127.99, 128.19, 129.42, 132.94, 133.63, 134.69, 135.36,
135.96, 137.82, 139.98, 157.43. Anal. Calcd for C15H13NO4S3:
C, 49.0; H, 3.6; N, 3.8. Found: C, 49.0; H, 3.7; N, 3.7.
(E,E)-4-Meth yltio-2-n itr o-3-ph en ylsu lfon yl-1-(3-th ien yl)-
1,3-bu ta d ien e (8j). Yellow solid, mp 59.0-60.0 °C (EtOH);
1
1226, 1152, 1086 cm-1; H NMR (CDCl3) δ 2.35 (3H, s), 2.53
(3H, s), 7.10 (2H, m), 7.38 (5H, m), 7.72 (2H, m), 8.20 (1H, s),
8.50 (1H, s); 13C NMR (CDCl3) δ 17.74, 20.11, 125.57, 126.35,
127.96, 128.06, 128.96, 129.32, 130.54, 131.52, 133.45, 138.95,
139.37, 139.51, 140.06, 156.14. Anal. Calcd for C18H17NO4S2:
C, 57.6; H, 4.6; N, 3.7. Found: C, 57.8; H, 4.7; N, 3.9.
νmax (Nujol) 1635, 1549, 1516, 1308, 1252, 1146, 1086 cm-1
;
1H NMR (CD3COCD3) δ 2.66 (3H, s), 7.13 (1H, dd, J ) 1.2
and 5.2 Hz), 7.38 (1H, dd, J ) 3.2 and 5.2 Hz), 7.55 (3H, m),
7.80 (2H, m), 8.03 (1H, dd, J ) 1.2 and 3.2 Hz), 8.39 (1H, s),
8.49 (1H, s); 13C NMR (CDCl3) δ 17.60, 126.00, 127.24, 127.42,
128.21, 129.12, 131.77, 133.70, 134.69, 134.81, 137.52, 139.56,
155.54. Anal. Calcd for C15H13NO4S3: C, 49.0; H, 3.6; N, 3.8.
Found: C, 49.2; H, 3.8; N, 3.8.
(E,E)-1-(3-Meth ylp h en yl)-4-m eth ylth io-2-n itr o-3-p h en -
ylsu lfon yl-1,3-bu ta d ien e (8c). Yellow solid, mp 108.3-109.4
°C (EtOH); νmax (Nujol) 1645, 1559, 1519, 1318, 1306, 1293,
1
1166, 1150, 1087 cm-1; H NMR (CDCl3) δ 2.30 (3H, s), 2.53
(3H, s), 7.21 (3H, m), 7.41 (4H, m), 7.77 (2H, m), 8.26 (2H, s);
13C NMR (CDCl3) δ 17.62, 21.30, 125.89, 127.60, 128.18,
128.89, 129.03, 129.60, 131.82, 133.04, 133.53, 138.59, 138.95,
139.59, 141.28, 155.73. Anal. Calcd for C18H17NO4S2: C, 57.6;
H, 4.6; N, 3.7. Found: C, 57.8; H, 4.7; N, 3.9.
Oxid a tion of Su lfid es 8 to Su lfon es 9. To a solution of
the methyl sulfide 8 (0.5 mmol) in dichloromethane (7.5 mL),
kept at room temperature and under magnetic stirring, was
added 0.26 g of 66% m-chloroperbenzoic acid (1 mmol). The
end of the reaction was judged both by disappearance of the
substrate (TLC) and by a negative KI spot-test for the peracid.
The mixture was diluted with dichloromethane, washed with
5% aqueous Na2SO3 and NaHCO3 solutions, and eventually
dried over Na2SO4. After filtration and removal of the solvent
under reduced pressure a crude residue was obtained, gener-
ally pure by 1H NMR analysis. Yields of the methylsulfonyl
derivatives 9 are reported in Table 1.
(E,E)-1-(4-Meth ylp h en yl)-4-m eth ylth io-2-n itr o-3-p h en -
ylsu lfon yl-1,3-bu ta d ien e (8d ). Yellow solid, mp 107.9-108.9
°C (EtOH); νmax (Nujol) 1640, 1605, 1524, 1446, 1313, 1213,
1
1186, 1146, 1084 cm-1; H NMR (CDCl3) δ 2.37 (3H, s), 2.52
(3H, s), 7.14 (2H, half AA′BB′, J ) 8.1 Hz), 7.46 (5H, m), 7.78
(2H, m), 8.26 (1H, s), 8.29 (1H, s); 13C NMR (CDCl3) δ 17.59,
21.66, 126.40, 127.09, 128.30, 129.06, 129.84, 131.13, 133.49,
138.39, 139.85, 141.21, 143.22, 155.39. Anal. Calcd for C18H17
-
NO4S2: C, 57.6; H, 4.6; N, 3.7. Found: C, 57.6; H, 4.7; N, 3.7.
(E,E)-1-(4-Meth oxyph en yl)-4-m eth ylth io-2-n itr o-3-ph en -
ylsu lfon yl-1,3-bu ta d ien e (8e). Yellow solid, mp 136.0-137.2
°C (EtOH); νmax (Nujol) 1643, 1600, 1551, 1525, 1322, 1309,
1268, 1179, 1147, 1087 cm-1; 1H NMR (CDCl3) δ 2.52 (3H, s),
3.85 (3H, s), 6.87 (2H, half AA′BB′, J ) 8.8 Hz), 7.44 (3H, m),
7.56 (2H, half AA′BB′, J ) 8.8 Hz), 7.80 (2H, m), 8.27 (1H, s),
8.30 (1H, s); 13C NMR (CDCl3) δ 17.58, 55.51, 114.65, 122.15,
126.03, 128.23, 129.08, 133.52, 133.61, 136.34, 139.60, 141.22,
155.42, 163.08. Anal. Calcd for C18H17NO5S2: C, 55.2; H, 4.4;
N, 3.6. Found: C, 55.4; H, 4.6; N, 3.6.
(E,E)-4-Meth ylsu lfon yl-2-n itr o-1-p h en yl-3-p h en ylsu lfo-
n yl-1,3-bu ta d ien e (9a ). Yellowish solid, mp 190.4-190.9 °C
(EtOH); νmax (Nujol) 1649, 1594, 1572, 1522, 1326, 1308, 1243,
1214, 1187, 1161, 1148, 1086, 1040, 1001 cm-1 1H NMR
;
(CDCl3) δ 3.01 (3H, s), 7.38 (7H, m), 7.56 (1H, m), 7.76 (2H,
m), 7.94 (1H, s), 8.38 (1H, s); 13C NMR (CDCl3) δ 42.50, 129.20,
129.47, 129.55, 131.17, 132.49, 135.37, 136.13, 141.83, 141.88,
146.00; 13C NMR (CD3COCD3) δ 42.73, 129.82, 130.22, 130.42,
130.52, 132.11, 133.02, 136.16, 137.29, 138.14, 141.62, 144.91,
145.05. Anal. Calcd for C17H15NO6S2: C, 51.9; H, 3.8; N, 3.6.
Found: C, 52.0; H, 4.0; N, 3.6.
(E,E)-1-(2-Met h ylp h en yl)-4-m et h ylsu lfon yl-2-n it r o-3-
p h en ylsu lfon yl-1,3-bu ta d ien e (9b). Yellow solid, mp 179.4-
181.0 °C (EtOH); νmax (Nujol) 1655, 1596, 1529, 1447, 1323,
1229, 1151, 1085, 1030 cm-1; 1H NMR (CDCl3) δ 2.34 (3H, s),
2.98 (3H, s), 7.14 (2H, m), 7.27 (1H, d, J ) 7.4 Hz), 7.37 (3H,
m), 7.54 (1H, m), 7.70 (2H, m), 7.87 (1H, s), 8.60 (1H, s); 13C
NMR (CDCl3) δ 20.15, 42.30, 126.61, 128.59, 129.12, 129.41,
130.89, 131.96, 135.13, 136.16, 136.49, 139.58, 139.97, 142.08,
145.63; 13C NMR (CD3COCD3) δ 20.10, 42.59, 127.04, 129.08,
129.87, 129.92, 130.47, 131.70, 132.48, 135.98, 137.96, 138.37,
(E,E)-1-[4-(Meth oxyca r bon yl)p h en yl]-4-m eth ylth io-2-
n itr o-3-p h en ylsu lfon yl-1,3-bu ta d ien e (8f). Yellow solid, mp
162.0-163.0 °C (EtOH); νmax (Nujol) 1713, 1649, 1551, 1530,
1377, 1310, 1284, 1217, 1194, 1184, 1150, 1115, 1088 cm-1
;
1H NMR (CDCl3) δ 2.54 (3H, s), 3.94 (3H, s), 7.41 (3H, m),
7.53 (2H, half AA′BB′, J ) 8.6 Hz), 7.76 (2H, m), 7.96 (2H,
half AA′BB′, J ) 8.6 Hz), 8.29 (2H, s); 13C NMR (CDCl3) δ
17.76, 52.47, 125.21, 128.18, 129.18, 129.96, 130.30, 132.62,
133.74, 133.93, 139.29, 139.59, 141.02, 156.38, 166.03. Anal.
Calcd for C19H17NO6S2: C, 54.4; H, 4.1; N, 3.3. Found: C, 54.4;
H, 4.2; N, 3.4.
5258 J . Org. Chem., Vol. 68, No. 13, 2003

Ring-Opening of 3-Nitro-4-(phenylsulfonyl)thiophene
139.87, 140.65, 144.58, 145.12. Anal. Calcd for C18H17NO6S2:
C, 53.1; H, 4.2; N, 3.4. Found: C, 53.3; H, 4.4; N, 3.5.
(E,E)-1-(3-Met h ylp h en yl)-4-m et h ylsu lfon yl-2-n it r o-3-
p h en ylsu lfon yl-1,3-bu ta d ien e (9c). Yellow solid, mp 175.3-
176.7 °C (EtOH); νmax (Nujol) 1650, 1579, 1520, 1325, 1242,
(CDCl3) δ 3.05 (3H, s), 7.11 (1H, dd, J ) 4.0 and 5.0 Hz), 7.48
(3H, m), 7.63 (2H, m), 7.84 (2H, m), 7.96 (1H, s), 8.55 (1H, s);
13C NMR (CDCl3) δ 42.62, 128.52, 129.49, 129.58, 132.69,
135.20, 135.36, 135.64, 136.55, 138.37, 142.81, 146.08; 13C
NMR (CD3COCD3) δ 42.67, 129.25, 130.22, 130.53, 133.85,
134.03, 135.52, 136.09, 136.74, 138.70, 139.70, 145.37, 145.68.
Anal. Calcd for C15H13NO6S3: C, 45.1; H, 3.3; N, 3.5. Found:
C, 45.2; H, 3.4; N, 3.5.
(E,E)-4-Met h ylsu lfon yl-2-n it r o-3-p h en ylsu lfon yl-1-(3-
th ien yl)-1,3-bu ta d ien e (9j). Yellow solid, mp 155.0-155.3
°C (EtOH); νmax (Nujol) 1649, 1595, 1519, 1321, 1252, 1180,
1160, 1147, 1087, 1042 cm-1; 1H NMR (CDCl3) δ 3.02 (3H, s),
7.17 (1H, dd, J ) 1.5 and 5.1 Hz), 7.30 (1H, dd, J ) 2.9 and
5.1 Hz), 7.46 (2H, m), 7.63 (1H, m), 7.81 (3H, m), 7.91 (1H, s),
8.38 (1H, s); 13C NMR (CDCl3) δ 42.62, 127.24, 127.77, 129.50,
129.54, 131.31, 133.78, 135.44, 135.50, 135.74, 136.19, 141.48,
146.28. Anal. Calcd for C15H13NO6S3: C, 45.1; H, 3.3; N, 3.5.
Found: C, 45.3; H, 3.4; N, 3.7.
1
1182, 1160, 1149, 1087, 1042 cm-1; H NMR (CDCl3) δ 2.31
(3H, s), 3.02 (3H, s), 7.24 (4H, m), 7.39 (2H, m), 7.55 (1H, m),
7.75 (2H, m), 7.93 (1H, s), 8.35 (1H, s); 13C NMR (CDCl3) δ
21.24, 42.50, 128.03, 129.09, 129.45, 132.05, 133.38, 135.20,
135.35, 136.24, 138.90, 141.85, 141.99, 146.10; 13C NMR (CD3-
COCD3) δ 21.14, 42.74, 129.36, 129.75, 130.18, 130.37, 130.47,
132.36, 133.83, 136.04, 137.26, 138.29, 139.49, 141.56, 144.92,
145.24. Anal. Calcd for C18H17NO6S2: C, 53.1; H, 4.2; N, 3.4.
Found: C, 53.3; H, 4.4; N, 3.5.
(E,E)-1-(4-Met h ylp h en yl)-4-m et h ylsu lfon yl-2-n it r o-3-
p h en ylsu lfon yl-1,3-bu ta d ien e (9d ). Whitish solid, mp 212.3-
212.7 °C (toluene); νmax (Nujol) 1657, 1605, 1523, 1334, 1317,
1
1311, 1191, 1165, 1154, 1144, 1087 cm-1; H NMR (CDCl3) δ
2.37 (3H, s), 3.01 (3H, s), 7.15 (2H, half AA′BB′, J ) 8.3 Hz),
7.41 (4H, m), 7.58 (1H, m), 7.77 (2H, m), 7.93 (1H, s), 8.37
(1H, s); 13C NMR (CDCl3) δ 21.75, 42.52, 126.43, 129.48,
129.51, 130.03, 131.56, 134.43, 135.21, 136.34, 141.69, 142.15,
143.92, 146.39. Anal. Calcd for C18H17NO6S2: C, 53.1; H, 4.2;
N, 3.4. Found: C, 53.1; H, 4.3; N, 3.5.
Cycliza tion of Su lfon es 9 to th e Nitr o(p h en ylsu lfon yl)
Der iva tives 10. 1-Aryl-4-methylsulfonyl-2-nitro-3-phenylsul-
fonyl-1,3-butadienes 9 (0.1 mmol) were dissolved in dry
p-xylene (20 mL) and the solution refluxed until TLC showed
complete disappearance of the substrate (1-70 h). The solvent
was evaporated under reduced pressure and the residue
purified either by column chromatography or by crystalliza-
tion. Yields of the nitro(phenylsulfonyl) derivatives 10 are
reported in Table 2.
3-Nitr o-2-(ph en ylsu lfon yl)n aph th alen e (10a). White solid,
mp 230.5-231.6 °C (toluene); νmax (Nujol) 1535, 1349, 1319,
1152, 1134, 1120, 1086 cm-1; 1H NMR (CDCl3) δ 7.59 (3H, s),
7.83 (2H, m), 8.03 (3H, m), 8.16 (1H, m), 8.38 (1H, s), 9.01
(1H, s); 13C NMR (CDCl3) δ 126.16, 127.95, 128.94, 129.08,
129.80, 130.66, 131.20, 131.34, 133.07, 133.39, 133.71, 134.64,
141.10, 144.61. Anal. Calcd for C16H11NO4S: C, 61.3; H, 3.5;
N, 4.5. Found: C, 61.6; H, 3.7; N, 4.6.
(E,E)-1-(4-Meth oxyp h en yl)-4-m eth ylsu lfon yl-2-n itr o-3-
p h en ylsu lfon yl-1,3-bu ta d ien e (9e). Yellow solid, mp 200.2-
201.4 °C (EtOH); νmax (Nujol) 1656, 1593, 1510, 1332, 1318,
1
1301, 1272, 1176, 1154, 1140 cm-1; H NMR (CDCl3) δ 3.01
(3H, s), 3,86 (3H, s), 6.87 (2H, half AA′BB′, J ) 9.2 Hz), 7.46
(4H, m), 7.59 (1H, m), 7.80 (2H, m), 7.92 (1H, s), 8.37 (1H, s);
13C NMR (CDCl3) δ 42.55, 55.60, 114.88, 121.67, 129.52,
132.63, 134.06, 135.28, 136.42, 141.55, 142.10, 146.70, 163.49.
Anal. Calcd for C18H17NO7S2: C, 51.1; H, 4.1; N, 3.3. Found:
C, 51.2; H, 4.2; N, 3.3.
(E,E)-1-[4-(Meth oxycar bon yl)ph en yl]-4-m eth ylsu lfon yl-
2-n itr o-3-p h en ylsu lfon yl-1,3-bu ta d ien e (9f). Yellow solid,
mp 188.3-189.9 °C (EtOH); νmax (Nujol) 1720, 1650, 1595,
1530, 1327, 1311, 1289, 1161, 1151, 1117, 1087, 1044, 1017
5-Meth yl-3-n itr o-2-(p h en ylsu lfon yl)n a p h th a len e (10b).
Yellow solid, mp 246.6-248.2 °C (toluene); νmax (Nujol) 1536,
1353, 1308, 1149, 1130, 1069 cm-1 1H NMR (CD3SOCD3) δ
;
1
cm-1; H NMR (CDCl3) δ 3.06 (3H, s), 3.94 (3H, s), 7.47 (5H,
2.72 (3H, s), 7.75 (5H, m), 8.01 (2H, m), 8.28 (2H, d, J ) 7.4
Hz), 8.69 (1H,s), 9.17 (1H, s); 13C NMR (CD3SOCD3) δ 18.55,
122.74, 127.32, 128.19, 129.01, 129.36, 130.40, 131.83, 132.69,
132.91, 133.84, 135.00, 136.60, 140.66, 143.77. Anal. Calcd for
m), 7.74 (2H, m), 7.96 and 7.97 [3H, half AA′BB′ (J ) 8.4 Hz)
and s partly overlapped], 8.39 (1H, s); 13C NMR (CDCl3) δ
42.55, 52.55, 129.45, 129.65, 130.11, 130.67, 132.91, 133.29,
135.46, 135.89, 137.33, 140.15, 142.28, 145.21, 165.81. Anal.
Calcd for C19H17NO8S2: C, 50.5; H, 3.8; N, 3.1. Found: C, 50.8;
H, 3.9; N, 3.2.
C
17H13NO4S: C, 62.4; H, 4.0; N, 4.3. Found: C, 62.2; H, 4.3;
N, 4.3.
6-Meth yl-3-n itr o-2-(p h en ylsu lfon yl)n a p h th a len e (10c)
(E,E)-4-Meth ylsu lfon yl-1-(1-n a p h th yl)-2-n itr o-3-p h en -
ylsu lfon yl-1,3-bu ta d ien e (9g). Yellow solid, mp 154.7-155.9
°C dec (EtOH); νmax (Nujol) 1657, 1593, 1524, 1318, 1239, 1141,
1082 cm-1; 1H NMR (CDCl3) δ 3.12 (3H, s), 6.94 (3H, m), 7.36
(1H, apparent t, J ) 7.7 Hz), 7.47 (2H, m), 7.57 (3H, m), 7.80
(3H, m), 8.01 (1H, s), 9.06 (1H, s); 13C NMR (CDCl3) δ 42.40,
123.67, 125.35, 126.53, 126.86, 127.46, 127.75, 128.73, 128.84,
128.90, 129.99, 131.39, 132.30, 133.34, 133.75, 135.46, 138.60,
142.85, 145.00. Anal. Calcd for C21H17NO6S2: C, 56.9; H, 3.9;
N, 3.2. Found: C, 56.7; H, 3.8; N, 3.3.
an d 1-Meth yl-6-n itr o-7-(ph en ylsu lfon yl)n aph th alen e (10c′).
The isomers 10c and 10c′ were obtained as a solid mixture
(10c/10c′ 66/34) from which the single components could not
be separated in pure form. Assignments of H NMR signals
were done on the basis of NOE and NOEDiff experiments.
1
White solid mixture; νmax (Nujol) 1535, 1351, 1313, 1155, 1125,
1
1087 cm-1; H NMR (mixture, CDCl3) δ 2.61 (3H10c, s), 2.88
(3H10c′, s), 7.63 (4H10c + 5H10c′, m), 7.79 (1H10c, s), 7.87 (1H10c′
,
d, J ) 7.8 Hz), 8.02 (2H10c′ + 3H10c, m), 8.27 (1H10c′, s), 8.37
(1H10c′, s), 8.94 (1H10c, s), 9.14 (1H10c′, s); 13C NMR (CDCl3),
11 quaternary carbon lines out of the 12 expected for the two
isomers were resolved, δ 130.31, 130.78, 132.51, 134.04, 134.21,
137.22, 141.20, 141.30, 142.13, 144.40, 144.78; 14 CH carbon
lines out of the 16 expected for the two isomers were resolved,
δ 125.52, 126.70, 127.41, 127.92, 128.09, 128.92, 129.54,
131.07, 131.12, 131.31, 131.40, 132.96, 133.31, 134.35; both
CH3 carbon lines expected for the two isomers (the ratio was
about 63:37) were resolved, δ 19.46, 22.04. Anal. Calcd for
(E,E)-4-Meth ylsu lfon yl-1-(2-n a p h th yl)-2-n itr o-3-p h en -
ylsu lfon yl-1,3-bu ta d ien e (9h ). Yellow solid, mp 188.9-190.0
°C (EtOH); νmax (Nujol) 1647, 1625, 1591, 1515, 1325, 1307,
1
1273, 1239, 1190, 1158, 1146, 1085 cm-1; H NMR (CDCl3) δ
3.04 (3H, s), 7.31 (3H, m), 7.44 (1H, dd, J ) 2.0 and 8.8 Hz),
7.57 (2H, m), 7.77 (5H, m), 7.95 (1H, br s), 8.01 (1H, s), 8.55
(1H, s); 13C NMR (CDCl3) δ 42.55, 125.21, 126.67, 127.19,
127.74, 128.96, 129.03, 129.14, 129.41, 132.74, 134.31, 134.78,
135.07, 136.16, 141.92, 142.10, 146.14; 13C NMR (CD3COCD3)
δ 42.86, 126.60, 127.89, 128.08, 128.55, 129.54, 129.61, 129.96,
130.19, 130.39, 133.72, 134.75, 135.61, 135.76, 137.39, 138.28,
141.65, 145.18, 145.25. Anal. Calcd for C21H17NO6S2: C, 56.9;
H, 3.9; N, 3.2. Found: C, 57.0; H, 4.0; N, 3.4.
C
17H13NO4S: C, 62.4; H, 4.0; N, 4.3. Found: C, 62.6; H, 4.2;
N, 4.4.
6-Meth yl-2-n itr o-3-(p h en ylsu lfon yl)n a p h th a len e (10d ).
White solid, mp 269.0-270.3 °C (p-xylene/petroleum ether, bp
40-60 °C); νmax (Nujol) 1617, 1528, 1341, 1307, 1289, 1156,
1
(E,E)-4-Met h ylsu lfon yl-2-n it r o-3-p h en ylsu lfon yl-1-(2-
th ien yl)-1,3-bu ta d ien e (9i). Yellow solid, mp 193.2-193.6
°C dec (EtOH); νmax (Nujol) 1643, 1592, 1518, 1413, 1327, 1314,
1145, 1121, 1086 cm-1; H NMR (CDCl3) δ 2.64 (3H, s), 7.59
(4H, m), 7.97 (4H, m), 8.37 (1H, s), 8.92 (1H, s); (CD3SOCD3)
δ 2.59 (3H, s), 7.73 (4H, m), 7.91 (2H, m), 8.19 (2H, m), 8.74
(1H, s), 9.07 (1H, s); 13C NMR (CD3SOCD3) δ 21.38, 125.92,
1292, 1257, 1217, 1158, 1147, 1086, 1053 cm-1 1H NMR
;
J . Org. Chem, Vol. 68, No. 13, 2003 5259

Bianchi et al.
127.24, 128.81, 128.96, 129.30, 129.50, 131.59, 132.72, 133.58,
133.71, 133.91, 139.84, 141.06, 143.19. Anal. Calcd for C17H13
2-Nitr o-3-(p h en ylsu lfon yl)p h en a n th r en e (10h ). Yellow-
ish solid, mp 318.0-318.6 °C (p-xylene); νmax (Nujol) 1530,
-
1
1357, 1318, 1306, 1240, 1154, 1084 cm-1; H NMR (CDCl3) δ
NO4S: C, 62.4; H, 4.0; N, 4.3. Found: C, 62.7; H, 4.1; N, 4.0.
6-Meth oxy-2-n itr o-3-(ph en ylsu lfon yl)n aph th alen e (10e).
Yellowish solid, mp 273.9-275.2 °C (dichloromethane-
petroleum ether, bp 80-100 °C); νmax (Nujol) 1618, 1532, 1502,
1343, 1306, 1252, 1151, 1138, 1119, 1084, 1029 cm-1; 1H NMR
(400 MHz, CDCl3) δ 4.02 (3H, m), 7.41 (1H, d, J ) 2.2 Hz),
7.45 (1H, dd, J ) 2.2 and 9.1 Hz), 7.59 (3H, m), 7.93 (1H, d, J
) 9.1 Hz), 8.00 (2H, m), 8.38 (1H, s), 8.90 (1H, s); 13C NMR
(100 MHz, CDCl3) δ 55.83, 107.58, 124.14, 126.46, 127.83,
128.76, 128.87, 130.61, 131.99, 132.94, 133.24, 135.23, 141.27,
146.79, 161.37. Anal. Calcd for C17H13NO5S: C, 59.5; H, 3.8;
N, 4.1. Found: C, 59.3; H, 4.0; N, 4.2.
7.58 (3H, m), 7.87 (3H, m), 8.05 (4H, m), 8.41 (1H, s), 8.90
(1H, dd, J ) 1.2 and 8.4 Hz), 9.78 (1H, s); 13C NMR (100 MHz,
DMF-d7) δ 124.93, 126.53, 126.58, 128.73, 129.25, 129.32,
129.93, 129.98, 130.00, 130.08, 131.39, 132.08, 133.48, 133.93,
134.63, 135.38, 141.98, 146.14. Anal. Calcd for C20H13NO4S:
C, 66.1; H, 3.6; N, 3.8. Found: C, 66.3; H, 3.8; N, 3.8.
6-Nitr o-5-(ph en ylsu lfon yl)ben zo[b]th ioph en e (10i). Yel-
low solid, mp 190.1-190.5 °C (toluene/petroleum ether, bp 40-
60 °C); νmax (Nujol) 1550, 1525, 1449, 1356, 1310, 1240, 1205,
1149, 1100, 1065 cm-1 1H NMR (CDCl3) δ 7.58 [4H in all,
;
partly overlapped m and d (J ) 5.5 Hz)], 7.92 (1H, d, J ) 5.5
Hz), 8.00 (2H, dd, J ) 1.6 and 8.0 Hz), 8.41 (1H, s), 8.91(1H,
Meth yl 6-Nitr o-7-(p h en ylsu lfon yl)n a p h th a len e-2-ca r -
boxyla te (10f). Yellowish solid, mp 258.5-259.8 °C (EtOH);
νmax (Nujol) 1709, 1535, 1356, 1326, 1281, 1229, 1158, 1107,
1086 cm-1; 1H NMR (CDCl3) δ 4.05 (3H, s), 7.60 (3H. m), 8.02
and 8.09 [3H in all, partly overlapping m and d (J ) 8.8 Hz)],
8.37 and 8.39 [2H in all, partly overlapping d (J ) 1.4 Hz)
and dd (J ) 1.4 and 8.8 Hz)], 8.88 (1H, s), 9.10 (1H, s); 1H
NMR (400 MHz, DMF-d7) δ 4.01 (3H, s), 7.72 (3H, m), 8.13
(2H, m), 8.25 (1H, dd, J ) 1.6 and 8.7 Hz), 8.43 (1H, d, J )
8.7 Hz), 8.85 (1H, s), 9.13 (1H, s), 9.47 (1H, s); 13C NMR (CDCl3)
δ 52.92, 125.57, 128.18, 129.08, 129.36, 130.54, 131.91, 132.12,
132.43, 133.69, 135.73, 135.91, 140.75, 165.66; 13C NMR (100
MHz, DMF-d7) δ 58.09, 131.37, 133.58, 135.15, 135.59, 135.79,
136.86, 137.09, 137.96, 138.19, 139.73, 141.97, 142.22, 146.78,
151.58, 171.29. Anal. Calcd for C18H13NO6S: C, 58.2; H, 3.5;
N, 3.8. Found: C, 58.3; H, 3.6; N, 3.8.
s); 13
C NMR (CDCl3) δ 120.24, 124.75, 127.61, 127.93, 128.93,
131.36, 133.38, 134.07, 141.15, 141.33, 143.48, 144.15. Anal.
Calcd for C14H9NO4S2: C, 52.6; H, 2.8; N, 4.4. Found: C, 52.5;
H, 2.9; N, 4.2.
5-Nit r o-6-(p h en ylsu lfon yl)b en zo[b]t h iop h en e (10j).
White solid, mp 174.6-175.6 °C (toluene); νmax (Nujol) 1551,
1521, 1449, 1352, 1310, 1292, 1154, 1123, 1085, 1069 cm-1
;
1H NMR (CDCl3) δ 7.57 (4H, m), 7.95 and 8.00 [3H in all, partly
overlapping d (J ) 5.4 Hz) and m], 8.29 (1H, s), 8.98 (1H, s);
13C NMR (CDCl3) δ 120.48, 124.45, 126.96, 127.98, 128.98,
130.14, 133.44, 135.06, 141.14, 142.14, 142.39, 145.41. Anal.
Calcd for C14H9NO4S2: C, 52.6; H, 2.8; N, 4.4. Found: C, 52.9;
H, 2.9; N, 4.3.
3-Nitr o-2-(p h en ylsu lfon yl)p h en a n th r en e (10g). Yellow
solid, mp 261.1-262.2 °C (toluene); νmax (Nujol) 1526, 1504,
Ack n ow led gm en t. Financial support was provided
by grants from Universita` di Genova and Ministero
dell’Istruzione, dell’Universita` e della Ricerca (MIUR,
PRIN-2001). In the framework of the collaboration for
the PRIN-2001 funding, 400-MHz NMR spectra were
kindly recorded at the Trieste Research Unit.
1
1339, 1308, 1239, 1147, 1085 cm-1; H NMR (CDCl3) δ 7.57
(3H, m), 7.80 (2H, m), 7.96 and 8.04 [5H in all, partly
overlapped d (J ) 8.8 Hz) and m], 8.64 (1H, m), 9.00 (1H, s),
9.14 (1H, s); 13C NMR (CDCl3) δ 121.08, 123.47, 126.06, 128.09,
128.51, 129.00, 129.17, 129.29, 129.51, 131.86, 132.10, 132.88,
133.21, 133.33, 133.48, 133.74, 141.09, 145.18. Anal. Calcd for
C
20H13NO4S: C, 66.1; H, 3.6; N, 3.9. Found: C, 66.0; H, 3.8;
N, 3.8.
J O034264Q
5260 J . Org. Chem., Vol. 68, No. 13, 2003