Nitrosoalkenes: Synthesis and Properties of Nitrosoderivatives of a Vinylogous Tetrathiafulvalene

Full text of DOI:10.1021/jo962209u

2616
J . Org. Chem. 1997, 62, 2616-2618
Sch em e 1
Nitr osoa lk en es: Syn th esis a n d P r op er ties
of Nitr oso Der iva tives of a Vin ylogou s
Tetr a th ia fu lva len e
Yvette A. J ackson,† J ames P. Parakka,
M. V. Lakshmikantham, and Michael P. Cava*
The University of Alabama, Department of Chemistry,
Box 870336, Tuscaloosa, Alabama 35487-0336
Received November 26, 1996
In tr od u ction
The chemistry of nitrosoalkenes is much less developed
than that of nitrosoarenes and nitrosoalkanes.1 Nitroso-
alkenes are generally unstable,2 and their generation has
usually been established by trapping with an appropriate
Diels-Alder diene. A few stable, crystalline monomeric
nitrosoalkenes have been reported, however,3-8 almost
all of which are nitrosodithiafulvenes or -diselenaful-
venes, systems in which the nitroso group is stabilized
by electron donation of the chalcogen atoms.
We now report the synthesis of the first nitroso
derivatives (3, 16, and 17) of a vinylogous tetrathiaful-
valene (18) and some novel properties of these com-
pounds.
Resu lts a n d Discu ssion
The intensely purple compound 3 was obtained in good
yield by the Wittig reaction of the ylide of phosphonium
salt 29 with the readily prepared 2-(nitrosoformylmeth-
ylene)-4,5-dicarbomethoxy-1,3-dithiole (1)7 in the pres-
ence of triethylamine at rt. No product derived from ylide
attack at the nitroso group of 1 was detected.
Careful treatment of 3 with 1 mol equiv of tribu-
tylphosphine at rt led to an immediate reaction with the
formation of the novel red imine 4 in 57% yield. The
reaction also yielded the vinylic nitrile 5, a product of
the reductive cleavage of the starting nitroso compound
3. This result parallels our work with 2-(nitrosophenyl-
methylene)-4,5-dicarbomethoxy-1,3-dithiole (7) which was
reported earlier.10 Deoxygenation of 7 was postulated to
lead to a nitrene, which fragmented to produce benzoni-
trile and tetrakis(carbomethoxy)tetrathiafulvalene (9),
via carbene 8.
Sch em e 2
By analogy, the formation and fragmentation of nitrene
10 should lead to the nitrile 5 and the carbene 8. In
† On leave from the Department of Chemistry, University of the
West Indies, Kingston 7, J amaica, West Indies.
(1) Cameron, M.; Gowenlock,. B. G.; Vasapollo, G. Chem. Soc. Rev.
1990, 19, 355.
(2) Gilchrist, T. L. Chem. Soc. Rev. 1983, 12, 53.
(3) Wieser, K.; Berndt, A. Angew. Chem., Int. Ed. Engl. 1975, 14,
70.
(4) Lakshmikantham, M. V.; Cava, M. P. J . Org. Chem. 1981, 46,
3246.
(5) Lakshmikantham, M. V.; Cava, M. P.; Albeck, M.; Engman, L.;
Wudl, F.; Aharon-Shalom, E. J . Chem. Soc., Chem. Commun. 1981,
828.
(6) Lakshmikantham, M. V.; J ackson, Y. A.; Cava, M. P. J . Org.
Chem. 1988, 53, 3529.
(7) Gowenlock, B. G.; Orrell, K. G.; Sik, V.; Vasapollo, G.; Lakshmi-
kantham, M. V.; Cava, M. P. Polyhedron 1994, 13, 675.
(8) Chesney, A.; Bryce, M. R.; Chalton, M. A.; Batsanov, A. S.;
Howard, J . A. K.; Fabre, J . M.; Binet, L.; Chakroune, S. J . Org. Chem.
1996, 61, 2877.
contrast to the earlier case of 7 (Scheme 1), carbene 8
couples preferentially with nitrene 10, rather than
dimerizing to tetraester 9. Interestingly enough, no trace
of the azo derivative 11, a plausible dimerization product
of nitrene 10, was detected, and only traces of the
tetraester 9 were found (Scheme 2).
It would appear that nitrene 10 may have a longer
lifetime than usual, allowing it to act as an efficient trap
for carbene 8. Stabilization of 10 could be achieved by
sulfur participation, as in the resonance contributor 10a .
The intermediacy of the carbene 8 was established by
(9) Sato, M.; Gonella, N. C.; Cava, M. P. J . Org. Chem. 1979, 44,
930.
(10) Cava, M. P.; Lakshmikantham, M. V. J . Heterocycl. Chem. 1980,
17, S-39.
S0022-3263(96)02209-8 CCC: $14.00 © 1997 American Chemical Society

Notes
J . Org. Chem., Vol. 62, No. 8, 1997 2617
Sch em e 3
Sch em e 4
There is literature precedence for 1,2,5-oxadiazole
N-oxides (viz. 16b)11 and stabilization of nitroso com-
pounds of this type by nonbonded S- - -O interactions is
well known.7,8 The proton NMR spectrum of 16 leads
us to believe that the bis-nitroso compound exists in the
form 16a since there are only two singlets in its proton
NMR spectrum in a ratio of 1:1, implying a symmetrical
molecule. We have so far not succeeded in obtaining
suitable crystals of this compound so as to verify the
structure by X-ray crystallographic measurements.
Formation of 16 by this method is always accompanied
by production of the nitroso nitro analog 17. Hence,
treatment of 3 with 2 mol equiv of isoamyl nitrite
produced, after 3.5 h at rt, green crystals of compound
17 in 46% yield, and the bis-nitroso compound as a brown
powder in 25% yield. When the reaction was carried out
using 8 mol equiv of isoamyl nitrite, only a trace of 16
was formed, and the nitroso nitro compound was the
dominant product (Scheme 5).
The same compound 17 is also obtained in 83% yield
by treatment of the nitro ester 15 with excess isoamyl
nitrite, and by the reaction of ethanediylidene-2,2′-bis-
(4,5-dicarbomethoxy-1,3-dithiole) (18) with nitrous acid
or with isoamyl nitrite (Scheme 6). Formation of 17 from
18 could be shown to always proceed via the nitro
compound 15, rather than via the nitroso analog 3.
We note with interest the difference in reactivity
between the nitroso function of the aldehyde 1 and that
of the compound 3 and continue our investigations in this
area.
running the experiment in the presence of benzaldehyde.
This reaction produced imine 4, and nitrile 5 as well as
the known compound 69 in reasonable yield (Scheme 1).
Our proposal for the mechanism of this reaction is further
strengthened by the fact that the reaction is concentra-
tion dependent. Dilution decreases the yield of imine
quite significantly. When the less reactive oxygen ab-
stractor triphenylphosphine was used in the reaction,
imine 4 was obtained, but at a much slower rate.
Attempts at the formation of imine 4 by an aza-Wittig
reaction of the nitroso compound 3 with the phosphonium
salt 2 and triethylamine were unsuccessful. We also
conceived that a second mole of tributylphosphine could
form the reagent 12 which, on reaction with benzalde-
hyde, would produce imine 13. The reaction with 2 mol
of tributylphosphine, however, produced compounds 5
and 6, none of compound 13, and a very small amount of
imine 4. We also observed that use of any excess
phosphine resulted in a decrease of imine 4 (Scheme 3).
Reaction of the nitrosoester 3 with m-chloroperbenzoic
acid (m-CPBA) produced none of the analogous nitroester
15. This was, however, available in excellent yield as
shown in Scheme 4.
Thus, oxidation of compound 1 took place preferentially
at the nitroso function, and the emerald green nitroso
aldehyde was converted smoothly by m-CPBA into yel-
low-green crystals of the nitro aldehyde 14 in 76% yield.
Nitro aldehyde 14 underwent a Wittig reaction with the
ylide of phosphonium salt 2 to produce the desired 15 as
red crystals.
The reaction of 3 with isoamyl nitrite afforded a brown
compound, mp 182 °C, the analysis and mass spectrum
of which were consistent with the dinitroso structure 16.
However, true vicinal dinitroso compounds appear to be
unknown, and attempts to obtain such compounds gener-
ally lead to very stable 1,2,5-oxadiazole N-oxides.11
Exp er im en ta l Section
Gen er a l. All melting points are uncorrected. UV-visible
spectra were determined in CH2Cl2. The NMR spectra were
determined in CDCl3 at 360 MHz. Elemental analyses were
carried out by Atlantic Microlabs, Atlanta, GA.
(11) Paton, R. M. In Comprehensive Heterocyclic Chemistry; Katritz-
ky, A. R., Rees, C. W., Eds.; Pergamon Press: New York, 1984; Vol. 6,
Ch. 4.22, p 393.

2618 J . Org. Chem., Vol. 62, No. 8, 1997
Notes
spectrum, m/ z (relative intensity) 257 (100, M+). Anal. Calcd
for C9H7NO4S2: C, 42.01; H, 2.74; N, 5.44; S, 24.92. Found: C,
41.90; H, 2.67; N, 5.40; S, 24.88. When the same deoxygenation
of 3 was carried out in the presence of 1 equiv of benzaldehyde,
compounds 4, 5, and 69 were obtained in yields of 30%, 57%,
and 23%, respectively.
Sch em e 5
2,2′-(2-Nit r oet h a n ed iylid en e)b is(4,5-d ica r b om et h oxy-
1,3-d ith iole) (15). To a solution of nitro aldehyde (14, 0.38 g,
1.25 mmol) in CH2Cl2 (8 mL) was added triethylamine (0.5 mL).
To this solution was added the phosphonium salt (2, 735 mg,
1.45 mmol) in small portions, in the course of 15 min with
stirring, while the mixture was cooled in an ice bath. On
addition of the salt there was an immediate color change from
yellow-green to orange-red. The cooling bath was removed, and
the mixture was stirred for a further 20 min. Removal of the
solvent followed by addition of methanol yielded 15 as a red
powder (0.54 g, 86%): mp 132-134 °C (CH2Cl2/MeOH); UV-vis
λmax 221 nm (log ꢀ 4.98), 229 (4.99), 302 (4.84), 384 (4.90), 440
(sh, 4.64); 1H NMR 3.96, 3.95, 3.88, 3.84 (each, 3H, s), 6.17
(1H, s, H); mass spectrum, m/ z (relative intensity) 507 (15, M+),
461 (48), 243 (100). Anal. Calcd for C16H13NO10S4: C, 37.86;
H, 2.58; N, 2.76; S, 25.27. Found: C, 37.80; H, 2.57; N, 2.72; S,
25.15.
Sch em e 6
2,2′-(2,2′-Din itr osoeth a n ed iylid en e)bis(4,5-d ica r bom eth -
oxy-1,3-d ith iole) (16). To a solution of compound 3 (500 mg,
1.02 mmol) in CH2Cl2 (35 mL) was added isoamyl nitrite (0.27
mL, 2.04 mmol), and the mixture was stirred at rt under an
atmosphere of nitrogen for 3.5 h. The solvent was removed, the
residue was treated with boiling methanol, and the resultant
dark brown precipitate was collected by filtration.
2-(Nitr ofor m ylm eth ylen e)-4,5-d ica r bom eth oxy-1,3-d ith i-
ole (14). To a solution of the nitrosoaldehyde7 (1, 0.50 g, 1.73
mmol) in CHCl3 (15 mL) was added sodium bicarbonate (0.60
g). A solution of m-CPBA (48%, 0.865 g, 2.4 mmol) in CHCl3
(20 mL) was then added dropwise over 30 min to the above
mixture, with stirring at rt. The mixture was stirred at rt for a
further h after which it was diluted with CHCl3 (50 mL) and
water (20 mL). The chloroform solution was washed successively
with thiosulfate solution and water and was dried and concen-
trated. Trituration of the resultant yellow-green solid with cold
methanol produced crystalline 14 (0.40 g, 76%): mp 136-137
°C (CH2Cl2/MeOH); UV-vis λmax 207 nm (log ꢀ 3.36), 217 (3.41),
The methanol-soluble portion was concd and purified by
chromatography (SiO2, CHCl3:EtOAc 10:1) to give 17 (245 mg,
46%). The brown powder was treated successively with hot
benzene-CH2Cl2 (1:1) and hot acetone in an effort to remove
starting material, the sole contaminant. Soxhlet extraction with
CHCl3 then left behind pure 16 (135 mg, 25%): mp 182 °C; UV-
vis λmax 224 nm (log ꢀ 4.46), 244 (4.50), 329 (4.13), 468 (4.23);
1H NMR 4.04 and 4.01 (each 6H, s); mass spectrum, m/ z
(relative intensity) 520 (0.2, M+), 460 (1.5), 250 (34), 206 (88),
178 (100). Anal. Calcd for C16H12N2O10S4: C, 36.92; H, 2.32;
N, 5.38. Found: C, 36.75; H, 2.32; N, 5.25.
1
240 (3.40), 309 (3.32), 388 (3.95); H NMR 4.01 and 4.00 (each
3H, s), 10.35 (1H, s, CHO); mass spectrum, m/ z (relative
intensity) 305 (12, M+), 258 (39), 244 (100). Anal. Calcd for
C9H7NO7S2: C, 35.41; H, 2.31; N, 4.59; S, 21.01. Found: C,
35.47; H, 2.28; N, 4.56; S, 20.94.
2,2′-(2-Nitr osoeth a n ed iylid en e)bis(4,5-d ica r bom eth oxy-
1,3-d ith iole) (3). To a solution of nitrosoaldehyde (1, 3.00 g,
10.38 mmol) in CH2Cl2 (60 mL) was added triethylamine (4.0
mL). To this solution was added 4,5-dicarbomethoxy-1,3-dithiol-
2-yltributylphosphonium tetrafluoroborate9 (2, 6.06 g, 11.93
mmol) in small portions with stirring, while the mixture was
cooled in an ice bath. Addition was completed in 20 min, the
cooling bath was removed, and the mixture was stirred for a
further 1 h. The solvent was evaporated, methanol was added,
and the dark purple crystals were collected (3.84 g, 75%): mp
177-179 °C (CH2Cl2/MeOH); UV-vis λmax 220 nm (log ꢀ 4.29),
229 (4.32), 254 (4.23), 277 (4.09), 367 (4.44), 568 (3.76); 1H NMR
3.98 (6H, s), 3.87 (3H, s), 3.83 (3H, s), 6.76 (1H, s, H); mass
spectrum, m/ z (relative intensity) 491 (0.2, M+), 257 (100), 206
(31). Anal. Calcd for C16H13NO9S4: C, 39.10; H, 2.66; N, 2.85;
S, 26.09. Found: C, 39.02; H, 2.69; N, 2.78; S, 25.97.
Com p ou n d s 4 a n d 5. Tributylphosphine (0.2 mL, 8 × 10-4
mol) was added dropwise, via syringe, to a stirred solution of
the nitroso ester (3, 0.40 g, 8 × 10-4 mol) in CH2Cl2 (10 mL).
The purple solution became bright orange-red in color. The
mixture was stirred at rt for 5 min; the solvent was evaporated
at rt, methanol was added, and the resultant dark red powder
(4) was collected (0.160 g, 57%); mp 223 °C (dec); after crystal-
lization from CHCl3/MeOH mp 235-6 °C; UV-vis λmax 219 nm
(log ꢀ 4.53), 230 (4.55), 301 (4.27), 371 (4.21), 386 (sh, 4.18), 471
(4.43); 1H NMR 3.92 (6H, s), 3.88 (9H, s), 3.85 (3H, s), 7.35 (1H,
s, H); mass spectrum, m/ z (relative intensity) 693 (9, M+), 436
(20), 378 (61), 357 (51). Anal. Calcd for C23H19NO12S6: C, 39.82;
H, 2.62; N, 2.02; S, 27.73. Found: C, 39.60; H, 2.80; H, 2.03; S,
27.97.
2,2′-(2-Nitr o-2′-n itr osoeth a n ed iylid en e)bis(4,5-d ica r bo-
m eth oxy-1,3-d ith iole) (17). (a) From 15: Isoamyl nitrite (0.2
mL, 1.49 mmol) was added to a solution of the nitro ester (15,
40 mg, 7.9 × 10-5 mol) in CH2Cl2 (4 mL), and the mixture was
stirred at rt under nitrogen. On addition of isoamyl nitrite the
color of the solution changed from red through yellowish-brown
to yellowish green. After 15 min, the solvent was removed,
methanol was added, and the mixture was cooled with stirring.
Compound 17 was obtained as a green precipitate (35 mg,
83%): mp 177 °C (benzene/hexane); UV-vis λmax 219 (log ꢀ 3.56),
1
238 (3.55), 381 (sh, 3.44), 415 (3.64); H NMR 4.02, 3.99, 3.97,
3.86 (each, 3H, s); mass spectrum, m/ z (relative intensity)
536 (1.5, M+), 250 (52), 234 (55), 206 (100). Anal. Calcd for
C
16H12N2O11S4: C, 35.82; H, 2.24. Found: C, 35.76; H, 2.32.
(b) From 18: To a cold solution of 2,2′-ethanediylidenebis-
(4,5-dicarbomethoxy-1,3-dithiole) (18, 0.92 g, 1.99 mmol) in CH2-
Cl2 (25 mL) was added a solution of sodium nitrite (300 mg, 4.35
mmol) in H2O (10 mL). Excess 3 M HCl was added to the
mixture while being cooled in an ice-bath. The color of the
reaction mixture changed to light red, and TLC showed the
absence of starting material. Urea was added to quench any
traces of HNO2, the organic layer was concentrated, and the
residue was triturated with methanol. The brown crystals
obtained were purified by chromatography (SiO2, benzene:CHCl3
3:1) to produce green crystals of 17 (310 mg, 29%). Concentra-
tion of the methanol-soluble portion followed by chromatography
(SiO2, CH2Cl2) yielded (15) (400 mg, 40%).
Removal of the solvent from the methanol-soluble portion,
followed by chromatography (SiO2, CHCl3) yielded 2-(cyanom-
ethylene)-4,5-dicarbomethoxy-1,3-dithiole as yellow crystals (5,
0.098 g, 48%). Recrystallization from CHCl3-hexane yielded
shiny yellow crystals of 5: mp 108-110 °C; UV-vis λmax 205 nm
(log ꢀ 3.60), 222 (sh, 3.74), 230 (3.77), 310 (4.17), 327 (sh, 4.01)
359 (3.32); 1H NMR 3.88 (3H, s), 3.87 (3H, s), 5.24 (1H, s); mass
Ack n ow led gm en t. We thank the National Science
Foundation for a grant (CHE-9612350) supporting this
work.
J O962209U