Elemental iodine or diphenyl diselenide in the [bis(trifluoroacetoxy)iodo] benzene-mediated conversion of alkynes into 1,2-diketones

Article abstract of DOI:10.1002/ejoc.201001232

Both elemental iodine and diphenyl diselenides, in the presence of [bis(trifluoroacetoxy)iodo]benzene (PIFA), promote the transformation of internal alkynes into the corresponding 1,2-diketones. The reactions carried out in the presence of iodine unfortunately did not proceed with complete conversion of the starting alkynes. On the other hand, diphenyl diselenide was more efficient and gave satisfactory transformation of the starting alkynes into 1,2-diketones in better yields. The structure of the vicinal dicarbonyl compounds were confirmed by applying a subsequent condensation reaction to construct the corresponding quinoxaline derivatives. Both elemental iodine and diphenyl diselenide in the presence of [bis(trifluoroacetoxy)iodo]benzene (PIFA) promote the transformation of internal alkynes into 1,2-diketones. The structure of the products were confirmed by transformation into the corresponding quinoxaline derivatives, two of which were studied by X-ray analysis. Copyright

Full text of DOI:10.1002/ejoc.201001232

FULL PAPER
DOI: 10.1002/ejoc.201001232
Elemental Iodine or Diphenyl Diselenide in the [Bis(trifluoroacetoxy)-
iodo]benzene-Mediated Conversion of Alkynes into 1,2-Diketones
Marco Tingoli,*[a] Mauro Mazzella,[a] Barbara Panunzi,[a] and Angela Tuzi[b]
Dedicated to the memory of Professor Carlo Rosini
Keywords: Hypervalent compounds / Iodine / Selenium / Alkynes / Ketones
Both elemental iodine and diphenyl diselenides, in the pres-
ence of [bis(trifluoroacetoxy)iodo]benzene (PIFA), promote
the transformation of internal alkynes into the corresponding
1,2-diketones. The reactions carried out in the presence of
iodine unfortunately did not proceed with complete conver-
sion of the starting alkynes. On the other hand, diphenyl dis-
elenide was more efficient and gave satisfactory transforma-
tion of the starting alkynes into 1,2-diketones in better yields.
The structure of the vicinal dicarbonyl compounds were con-
firmed by applying a subsequent condensation reaction to
construct the corresponding quinoxaline derivatives.
the chosen nucleophile. For instance, iodo- or (phenyl-
seleno)fluorination of terminal or internal alkynes produce
the corresponding unsaturated derivatives with (E) configu-
ration at the resulting double bond.[3] A different result is
observed when electrophilic selenium is prepared in the
presence of oxygen-containing nucleophiles. Working in an-
hydrous methanol, α-oxo acetals and α-oxo ketals were iso-
lated in good yields.[5] Meanwhile, more recently, use of a
3:1 mixture of H2O/CH3CN directed the reaction towards
the corresponding unprotected 1,2-dicarbonyl derivatives.[6]
These two examples have common features due to the pres-
ence of the large excess of (NH4)2S2O8 employed, which is
able to generate electrophilic selenium species in situ and to
promote the transformation of the initial addition product
intermediate into the final 1,2-dicarbonyl derivative.
Vicinal diketones are interesting precursors that have
been proposed in the literature as versatile intermediates for
the synthesis of biologically active heterocyclic com-
pounds.[7] Many synthetic methods have been recently re-
ported for the preparation of such building blocks, but they
are preferentially obtained through the direct oxidation of
substituted alkynes, which are easily available through the
Sonogashira coupling reaction.[8] The cited oxidation has,
for instance, been performed by employing permanganate
or Oxone in tetrahydrofuran (THF),[9a] or by using more
hazardous transition-metal-catalyzed oxidation (Wacker-
type).[10] Furthermore, an interesting approach to the syn-
thesis of α-diketones through the reactions of alkynes with
N-iodosuccinimide in CH3CN/H2O has been recently pro-
posed.[11]
Introduction
The discovery and application of new oxidation reactions
promoted by hypervalent iodine species,[1] in the presence
of elemental iodine or diphenyl diselenides, have been ex-
tensively studied in our laboratory. Using these oxidation
reactions we have been able to generate electrophilic iodon-
ium and selenium species in situ that, starting from simple
alkenes and in the presence of different nucleophiles, pro-
duce oxyselenenylated derivatives[2a] or iodohydrins,[2b] and
undergo phenylselenofluorination and iodofluorination re-
actions of unsaturated compounds.[3] In the case of terminal
alkenes, all the reactions proceed in a Markovnikov fashion.
A different outcome was observed when iodonium or se-
lenium species were generated in the presence of alkyl aryl
ketones. Depending on the solvent employed, the selective
electrophilic aromatic substitution or the addition reaction
to the enolisable ketones is guaranteed by the selenium moi-
ety; on the other hand, regardless of which solvent was
used, electrophilic monoiodination of the aromatic ring was
always observed.[4]
The ability of both iodonium and selenium species to
react with internal C–C double bonds is well documented
and, in all cases, anti addition has been observed. When the
same chemistry is applied to alkynes, the fate of the initially
formed reactive intermediates is essentially dependent on
[a] Department of Food Science, University of Napoli “Federico II”
Via Università 100, 80055 Portici, Napoli, Italy
Fax: +39-081-775-4942
E-mail: tingoli@unina.it
[b] Department of Chemistry “Paolo Corradini”, University of
Napoli “Federico II”
Because of the demonstrated ability of hypervalent
iodine reagents to efficiency act as good alternatives to
Via Cintia, 80126 Napoli, Italy
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M. Tingoli et al.
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heavy-metal oxidants, we have assessed the use of iodonium PhSeSePh) gave more satisfactory outcomes in the transfor-
and selenium species, generated in situ from hypervalent mation of alkynes into 1,2-diketones. As depicted in
iodine compounds, in promoting the transformation of a Scheme 2 and summarized in Table 1, the transformation of
variety of alkynes into the corresponding 1,2-dicarbonyl
compounds.
a variety of acetylenic starting materials proceeded
smoothly by simply applying the same reaction conditions
described before and using analytical grade THF/H2O
(20:1), as reaction solvent.
Results and Discussion
An initial experiment was carried out with diphenylace-
tylene as a model, which was treated with a slight excess of
[bis(trifluoroacetoxy)iodo]benzene (PIFA), in the presence
of an equimolecular amount of PhSeSePh, in CH3CN/H2O
(20:1), at 40 °C. The progress of the reaction was monitored
by GC–MS analysis, which showed that, after 1 h, some
starting material was still present, together with 1,2-diphen-
ylethanedione, traces of an α-(phenylseleno) carbonyl deriv-
ative and a heterocyclic compound (m/z = 235) that was
quickly identified as 2-methyl-4,5-diphenyloxazole. The lat-
ter compound probably derived from incorporation of
CH3CN, which acts as a competitive nucleophile under the
reaction conditions, giving, after hydrolysis and subsequent
cyclization, the corresponding heterocyclic compound.[12]
After 14 h, both the starting material and the α-(phenyl-
seleno) carbonyl derivative were consumed; however, an
equimolar mixture of the cited oxazole and 1,2-diphenyl-
ethanedione, together with diphenyl diselenide and iodo-
benzene, were observed in the reaction mixture. It is some-
what surprising that such side-reactions were not reported
by other authors who used mixtures of CH3CN and water
in similar transformations of acetylenic compounds.[6,11] In
the light of these somewhat disappointing results, which
Scheme 2. Scope of the reaction.
Table 1. Conversion of alkynes into 1,2-diketones promoted by
PhI(OCOCF3)2/I2 (A) or PhSeSePh (B).
were due to the competitive reaction of the solvent,[13]
a
non-nucleophilic medium such as THF together with a
small amount of water (20:1), was subsequently chosen.
To evaluate the efficiency of these new reaction condi-
tions, we applied our protocol to the terminal and internal
alkynes, phenylacetylene and 3-hexyne, respectively. As de-
picted in Scheme 1, both of the acetylenic compounds were
transformed into the corresponding α-iodo or α-(phenyl-
seleno) carbonyl derivatives, probably by initial addition of
I+ or PhSe+ to the triple bond, followed by addition of the
easily hydrolysable trifluoroacetoxy anion or water. Only in
the case of phenylacetylene and PhSe+ was a small amount
of a compound (m/z = 134), that was recognised as phen-
ylglyoxal, found in the reaction mixture; in this case, further
oxidation of the intermediates probably took place.
[a] Yields of isolated products after column chromatography.
Nevertheless, the 1,2-diketones were produced with dif-
ferent efficiency when I2 or PhSeSePh were chosen as reac-
tion mediators. In particular, the couple PIFA/I2 appears to
be less reactive, and all attempts to enhance the conversion
yield by adding an excess of PIFA or raising the reaction
temperature, were unsuccessful. In all cases, the acetylenic
compounds employed were partially converted into the cor-
responding 1,2-diketones, (see Table 1, column A). Proba-
bly, the interaction of electrophilic iodine with the triple
bond, followed by the addition of CF3COO–, is a readily
reversible reaction, similar to the addition of hypoiodous
acid to alkenes, which is used to generate iodohydrins.[14]
Again, the chalcogenic element selenium shows more
Scheme 1. Reaction of terminal and internal alkynes under the de-
veloped conditions.
When our methodology was applied to disubstituted
alkyl-aryl- or diarylacetylenes, in spite of the unsatisfactory versatility compared with the less toxic halogen iodine.[4]
results described above, the couple PIFA/X2 (X = I2 or Thus, all the reactions that were partially promoted by I2
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Conversion of Alkynes into 1,2-Diketones
were repeated in the presence of the couple PIFA/PhSeSePh formed into the corresponding quinoxaline ring system.
and, as depicted in column B of Table 1; the starting materi- Such systems have proven to be widely useful as biologically
als were then totally consumed and vicinal diketones were active compounds.[18]
obtained in satisfactory yields. Moreover, the reaction was
not limited to the preparation of functionalised benzils, be-
cause the synthesis of some alkyl aryl 1,2-dicarbonyl com-
Table 2. Conversion of 1,2-diketones into quinoxalines promoted
by 1,2-phenylenediamine in CH3COOH at 60 °C.
pounds were also easily achieved. To learn more about the
mechanism of this transformation, the quantity of PhSe-
SePh initially added was reduced; unfortunately, the results
indicated that the reaction is not promoted by a catalytic
amount of electrophilic selenium. Nevertheless, as pointed
out before, more than 90% of diphenyl diselenide initially
added was recovered and could be recycled after the stan-
dard purification procedure.
It is noteworthy that, in the absence of both elemental
iodine and diphenyl diselenide, the direct oxidation of the
acetylenic starting materials promoted by their simple treat-
ment with a slight excess of PIFA at 40 °C, occurs slowly
and, after 24 h reaction time, at least 5% conversion into
vicinal diketones was realised (by GC–MS analysis).
According to our experimental results and to those of
others,[5,11,15] a plausible reaction mechanism for the con-
version of internal alkynes into 1,2-dicarbonyl compounds
could be proposed. It is our opinion that both the enolis-
able α-iodo or α-(phenylseleno) carbonyl derivatives, di-
rectly monitored during the progress of our reactions by
GC–MS analysis, would undergo further iodination or
phenylselenenylation reactions to produce unstable α,α-di-
iodo- or α,α-diseleno ketones. Under the reaction condi-
tions, the latter, unstable intermediates are easily hydrolysed
[a] Yields of isolated products.
to provide the desired products 2 (Table 1).
The reduced efficiency of the reactions carried out with
Because compounds 3f, 3g and 3h have not been com-
iodine could also probably be explained by the fact that
pletely characterised previously, we tried to isolate suitable
when elemental iodine is treated with PIFA a series homo-
crystals of these compounds for X-ray analysis. Thus, single
crystals of 3f and 3h were obtained by slow concentration
polyatomic iodine-containing cations can be produced to-
gether with the expected I+ species, these are particularly
of acetone solutions at ambient temperature and, as de-
stable in the presence of Lewis acids,[16] but are ineffective
picted in the Experimental Section, satisfactory results were
achieved by X-ray crystallographic analysis, which showed
the expected structure for both quinoxaline derivatives (Fig-
in the desired reactions.
Finally, as cited before, all the alkyl aryl and diaryl diket-
ones synthesised are good intermediates for the prepara-
tion of substituted heterocyclic compounds, including quin-
oxaline derivatives. To learn more about the structures of
some of the 1,2-diketones isolated, we transformed these
species into the corresponding quinoxaline derivatives by
applying a slight modification of a known methodology.[17]
Thus, simple treatment of the dicarbonyl compounds with
1,2-phenylenediamine in a solution of glacial acetic acid at
60 °C for 2 h, followed by quenching of the reaction with
ice-cold water, gave the desired quinoxaline skeletons in al-
most quantitative yields. As depicted in Scheme 3 and
Table 2, all the oxidation products 2a–h could be trans-
Figure 1. ORTEP view of 3f with ellipsoids drawn at the 30% prob-
ability level.
Scheme 3. Conversion of 1,2-diketones into quinoxalines.
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13C NMR spectra were recorded at 40 MHz with a Varian XL-200
NMR spectrometer, with TMS as internal standard at 25 °C. Mass
spectra were recorded with a GC–MS spectrometer [Shimadzu
GCMS-QP5000 (EI, 70 eV)].
ures 1 and 2). Compound 3g was obtained as a solid but
was only suitable for standard characterization by tradi-
tional techniques such as elemental analysis.
Typical Procedure for the Synthesis of 1,2-Diketones 2a–h: To a
solution of I2 (0.6 mmol) or PhSeSePh (0.6 mmol) in a mixture of
THF (analytical grade; 7 mL) and water (0.35 mL) at 40 °C, PIFA
(0.6 g, 1.1 mmol) was added. After being stirred at 40 °C for
15 min, alkyne 1 (1.0 mmol) was added in one portion. The pro-
gress of the reaction was monitored by both TLC and GC–MS
analyses. In all cases an excess of PIFA (0.3–0.4 mmol) was added
after 3 h. The reaction was quenched with water after 14 h and the
mixture extracted with MTBE (3ϫ 15 mm). The organic layer was
washed with brine, dried with anhydrous Na2SO4, filtered, and con-
centrated in vacuo. The residue was purified by column chromatog-
raphy to give diketones 2a–h.
Typical Procedure for the Synthesis of Quinoxalines 3a–h: To a solu-
tion of 1,2-diketone 2a (0.5 mmol) in glacial CH3COOH (4 mL),
1,2-phenylendiamine (0.55 mmol) was added in one portion at
60 °C. After 2 h at this temperature, the reaction mixture was
slowly added to ice-cold water (20 mL). The separated solid was
filtered, washed with cold water and dried.
Compound 2f: Pale-yellow soild; m.p. 62–65 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.95 (s, 3 H), 7.45–7.75 (m, 4 H), 7.95–
8.22 (m, 5 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 52.8, 129.3,
130, 130.2, 130.3, 132.9, 135.3, 135.5, 136.3, 166.13, 193.9 ppm.
GC–MS (EI): m/z (%) = 268 (1) [M]+, 237 (1), 163 (22), 135 (7),
105 (100), 77 (43), 51 (20).
Figure 2. ORTEP view of 3h with ellipsoids drawn at the 30% prob-
ability level.
Compound 3f: Colourless solid; m.p. 151–152 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.95 (s, 3 H), 7.28–7.42 (m, 3 H), 7.46–
7.54 (m, 2 H), 7.56–7.66 (m, 2 H), 7.76–7.86 (m, 2 H), 7.96–8.06
(m, 2 H), 8.14–8.25 (m, 2 H) ppm. 13C NMR (50 MHz, CDCl3): δ
= 52.4, 128.7, 129.3, 129.5, 129.7, 130.0, 130.1, 130.4, 130.7, 138.8,
141.4, 141.6, 143.7, 152.5, 153.8, 167.0 ppm. GC–MS (EI): m/z (%)
= 340 (100) [M]+, 290 (35), 283 (25), 272 (40).
Conclusion
In this paper we describe a simple and efficient synthesis
of functionalised benzils and alkyl-aryl-ethanediones by
taking advantage of the peculiar behaviour of electrophilic
selenium with respect to the partner iodine species. Under
the influence of PIFA, the organoselenium intermediates
that are initially formed are more efficiently transformed
into vicinal dicarbonyl compounds. It is our opinion that
this new preparation of 1,2-diketones followed by their sim-
ple transformation into quinoxaline derivatives, can be con-
sidered as a useful alternative to other methods.
Compound 3g: Yellow-orange solid; m.p. 158–160 °C. 1H NMR
(200 MHz, CDCl3): δ = 7.10–7.75 (m, 9 H), 7.75–7.90 (m, 2 H),
8.10–8.35 (m, 2 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 113.0,
117.0, 129.5, 129.6, 129.7, 130.2, 131.0, 131.3, 132.5, 133.8, 138.1,
141.1, 142.2, 143.2, 150.5, 153.5 ppm. C21H13N3 (307.21): calcd. C
82.07, H 4.26, N 13.67; found C 82.35, H 4.16, N 13.50. IR (neat):
ν
= 2225 (CN) cm–1.
˜
max
1
Compound 3h: Pale-yellow; m.p. 101–104 °C. H NMR (200 MHz,
CDCl3): δ = 2.4 (s, 3 H), 3.8 (s, 3 H), 6.82–6.94 (m, 2 H), 7.12–
7.21 (m, 2 H), 7.40–7.58 (m, 4 H), 7.68–7.71 (m, 2 H), 8.04–8.22
(m, 2 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 21.6, 55.5, 114.0,
129.2, 129.3, 129.8, 130.0, 131.6, 136.7, 139.0, 141.2, 141.3, 153.3,
153.7, 160.4 ppm. GC–MS (EI): m/z (%) = 326 (100) [M]+, 311
(59), 295 (15), 192 (19), 166 (21).
Experimental Section
General: All reagents were purchased from commercial sources and
used as received. Alkynes (Table 1, Entries 4–8) were prepared un-
der classical Sonogashira conditions.[8] Except for compound 2f,
the 1,2-diketone derivatives prepared by our method are known
compounds and gave spectroscopic data that are in agreement with
those reported previously: 2a, 2b and 2c are commercially available;
for 2d, 2e and 2g, see ref.[9a] and for 2h, see ref.[9b] For better charac-
terization of the dicarbonyl derivatives, their transformation into
the corresponding quinoxaline compounds were achieved by a
slight modification of a described methodology.[17] Compounds 3a–
e (Table 2) gave spectroscopic data in agreement with those pre-
viously reported.[7] Quinoxalines 3f and 3h furnished suitable single
crystals, which were promptly submitted to X-ray analysis. All the
products obtained were purified by column chromatography on sil-
ica gel by using mixtures of light petroleum and tert-butyl methyl
X-ray Structure Analysis: Single crystals of compound 3f and 3h
were obtained by slow concentration of acetone solutions at ambi-
ent temperature. Crystal and refinement data are reported in
Table 3. Crystals were mounted at 296 K (3f, colourless,
0.60ϫ0.10ϫ0.03 mm) and in flowing N2 at 173 K (3h, pale-yellow,
0.60ϫ0.20ϫ0.01 mm) with a Bruker-Nonius KappaCCD dif-
fractometer equipped with a graphite monochromator (Mo-Kα ra-
diation; λ = 0.71073 Å, CCD rotation images, thick slices, φ and ω
scans to fill asymmetric unit). Semiempirical absorption correction
(SADABS) was applied. Both of the structures were solved by di-
rect methods (SIR97 package)[19] and anisotropically refined by the
full-matrix least-squares method on F2 against all independent
1
ether (MTBE). H NMR spectra were recorded at 200 MHz, and
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Conversion of Alkynes into 1,2-Diketones
measured reflections (SHELXL program of SHELX97 pack-
age).[20] All hydrogen atoms were introduced into calculated posi-
tions and refined according to a riding model. The final refinement
converged to R1 = 0.1044, wR2 = 0.2594 for 3f and R1 = 0.0738,
wR2 = 0.1605 for 3h. In both of the two independent molecules of
3h, the difference Fourier maps showed a statistical position of the
CH3 and OCH3 groups [occupancy factor refined to 0.6307
(0.61869 for molecule primed)]. Due to the nearly coincident posi-
tions of C15A–D and O1A–D atoms, these atoms were iso-
tropically refined. The molecular structures reported in Figures 1
(3f) and 2 (3h) show that the bond lengths and angles in both com-
pounds are within normal ranges and are comparable with similar
compounds.[21–23] In compound 3f the quinoxaline ring system (N1/
plane of which makes a dihedral angle of 28.2(2)° with the C17–
C22 phenyl ring and 60.7(2)° with C9–C14 phenyl ring. A small
out-of-plane deformation [C17–C1–C8–C9 –173.6(6)°] is observed
as a consequence of the steric encumbrance of the two adjacent
phenyl rings attached to quinoxaline. In the crystal packing of 3f
(Figure 3) the molecules are joined in a tridimensional network by
weak CH···N and CH···O interactions [C20–H···N2(i) 2.701(6) Å,
144.8(5)°, (i) = –x, –y – 1/2, z – 1/2; C21–H···O2(ii) 2.668(5) Å,
141.7(5)°, (ii) = –x, y + 1/2, –z + 1/2; C19–H···N1(iii) 2.956(6) Å,
114.4(4)°, (iii) = x, y – 1, z; C16–H···O2(iv) 2.615(5) Å, 155.5(5)°,
(iv) = x, y – 1, z). Compound 3h (Figure 2) crystallized in the tri-
¯
clinic P1 space group with two molecules in the asymmetric unit.
The two molecules are geometrically similar and are related by a
N2/C1–C8) is almost planar [maximum deviation from the mean non-crystallographic inversion centre. A statistical position of the
least-square plane is 0.038(5) Å for C8]. The two phenyl rings are
oriented differently with respect to the quinoxaline ring, the mean
methyl and methoxy groups attached to the phenyl rings was
found. A more pronounced deviation from planarity is observed in
Table 3. X-ray crystal data and structure refinement details for 3f and 3h.
3f
3h
Empirical formula
Formula mass
C22H16N2O2
340.37
C22H18N2O
326.38
T [K]
λ [Å]
Crystal system
Space group
296(2)
173(2)
0.71073
monoclinic
P21/c
0.71073
triclinic
¯
P1
Unit cell dimensions:
a [Å]
20.086(9)
10.660(2)
b [Å]
c [Å]
5.752(4)
15.034(5)
10.809(2)
17.610(4)
α [°]
β [°]
90
99.59(5)
81.63
74.62(2)
γ [°]
90
64.290(1)
1037.7(2)
V [Å3]
1712.7(15)
Z
4
4
ρcalcd. [Mg/m3]
1.320
0.086
1.321
0.076
µ [mm–1]
F(000)
712
2.06Ϫ25.01
6414/2894 [R(int) = 0.0662]
2894/237
1.051
R1 = 0.1044, wR2 = 0.2594
R1 = 0.2158, wR2 = 0.3149
0.373/–0.373
688
3.13Ϫ26.41
17514/6917 [R(int) = 0.1392]
6917/475
0.914
R1 = 0.0738, wR2 = 0.1605
R1 = 0.2302, wR2 = 0.2271
0.191/–0.278
θ range for data collection [°]
Reflections collected/unique
Data/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
R indices (all data)
Largest difference peak/hole [eA–3]
Figure 3. Crystal packing of 3f viewed along the b axis. Weak CH···N and CH···O interactions are reported as dashed lines.
Eur. J. Org. Chem. 2011, 399–404
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M. Tingoli et al.
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Figure 4. Crystal packing of 3h viewed along the (010) direction showing the stacking of molecules along the c axis.
[5] M. Tiecco, L. Testaferri, M. Tingoli, D. Chianelli, D. Bartoli,
J. Org. Chem. 1991, 56, 4529–4534.
[6] S. Santoro, B. Battistelli, B. Gjoka, C. S. Si, L. Testaferri, M.
Tiecco, C. Santi, Synlett 2010, 1402–1406.
the quinaxoline ring system [major deviation from the least square
plane is –0.079(3) Å for C8 and –0.103(3) Å for C8Ј]. At variance
with compound 3f, the two phenyl rings attached to the quinox-
aline ring system are more symmetrically disposed with respect to
the quinaxoline mean plane {dihedral angles 43.5(1)° with C9–C14,
and 39.2(1)° with C16–C21 rings [52.2(1)° and 32.1(1)° with C9Ј–
C14Ј and C16Ј–C21Ј rings]}. In the crystal structure of 3h, a major
out-of-plane deformation is observed compared with compound 3f
[C9–C1–C8–C16 14.0(6)° and C9Ј–C1Ј–C8Ј–C16Ј –11.9(6)°]. In the
crystal packing of 3h (Figure 4) parallel sheets of molecules stacked
along the c axis are formed, which are joined through a complex
tridimensional network of weak CH···N and CH···O interactions.
CCDC-780485 (3f) and -780486 (3h) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html or from
the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax: +44-1223/336-033.
[7]
a) K. P. C. Vollhardt, N. E. Schore, Organic Chemistry, 2nd ed.,
Freeman, New York, 1994, pp. 924–930; b) L. R. Hillis, R. C.
Ronald, J. Org. Chem. 1985, 50, 470–473.
[8]
[9]
M. Pal, Synlett 2009, 2896–2912.
a) J. H. Chu, Y. J. Chen, M. J. Wu, Synthesis 2009, 2155–2162;
b) Z. Wan, C. D. Jones, D. Mitchell, J. Y. Pu, T. Y. Zhang, J.
Org. Chem. 2006, 71, 826–828.
[10]
W. Ren, Y. Xia, S. J. Ji, Y. Zhang, X. Wan, J. Zhao, Org. Lett.
2009, 11, 1841–1844.
[11]
[12]
M. Niu, H. Fu, Y. Jiang, Y. Zhao, Synthesis 2008, 2879–2882.
All the disubstituted alkynes treated in CH3CN/H2O with
PIFA and I2 or PhSeSePh, gave the corresponding oxazole, to-
gether with the 1,2-dicarbonyl derivative. The mechanism and
the applications of this reaction are under investigation in our
laboratory.
[13]
[14]
For the reaction of acetonitrile with a carbocation intermedi-
ate, see: D. M. Browne, O. Niyomura, T. Wirth, Org. Lett. 2007,
9, 3169–3171.
Acknowledgments
J. Rodriguez, J. P. Dulcere, Synthesis 1993, 1177–1205.
[15] a) S. F. Reed Jr., J. Org. Chem. 1965, 30, 2195–2198; b) V. L.
Heasley, D. F. Shellhamer, A. E. Chappell, J. M. Cox, D. J. Hill,
S. L. McGovern, C. C. Eden, C. L. Kissel, J. Org. Chem. 1998,
63, 4433–4437.
[16] J. Besida, T. A. O’Donnell, Inorg. Chem. 1989, 28, 1669–1673.
[17] Z. J. Feng, G. G. Xia, S. K. Bao, Z. S. Jun, Chin. Chem. Lett.
2009, 20, 672–675.
Financial support from the Università di Napoli “Federico II” and
the Consorzio Interuniversitario Nazionale di Metodologie e Pro-
cessi Innovativi di Sintesi (CINMPIS), Bari is gratefully acknowl-
edged. Thanks are due also to the “Centro Interdipartimentale di
Metodologie Chimico Fisiche” (CIMCF) of the University of
Naples “Federico II” for X-ray facilities.
[18] G. Lebras, J. F. Peyrat, J. D. Brion, M. Alami, W. Marsaud, C.
Radanyi, J. M. Renoir, J. Med. Chem. 2007, 50, 6189–6200.
[19] A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115.
[1] For recent reviews on the chemistry of hypervalent iodine, see:
a) V. V. Zhdankin, ARKIVOC 2009, 1, 1–62; b) T. Wirth (Ed.),
“Hypervalent Iodine Chemistry: Modern Developments in Or-
ganic Synthesis”, Top. Curr. Chem. 2003, 224.
[20] SHELXL-97: G. M. Sheldrick, Acta Crystallogr., Sect. A 2008,
64, 112–122.
[2] a) M. Tingoli, M. Tiecco, L. Testaferri, A. Temperini, Synth.
Commun. 1998, 28, 1769–1778; b) A. R. De Corso, B. Panunzi,
M. Tingoli, Tetrahedron Lett. 2001, 42, 7245–7247.
[3] a) B. Panunzi, A. Picardi, M. Tingoli, Synlett 2004, 2339–2342;
b) P. Conte, B. Panunzi, M. Tingoli, Tetrahedron Lett. 2006,
47, 3325–3328.
[21] D. Rajnikant, B. D. Madhukar, J. Sunil, K. Pryinka, Acta Crys-
tallogr., Sect. E 2006, 62, 2356–2357.
[22] K. Wozniak, T. M. Krygowsky, S. Filipek, Acta Crystallogr.,
Sect. C 1991, 47, 1326–1328.
[23] S. A. Cantalupo, H. Salvati, B. McBurney, R. Raju, N. M. Gla-
govich, G. Crundwell, J. Chem. Crystallogr. 2006, 36, 17–24.
Received: September 1, 2010
[4] B. Panunzi, L. Rotiroti, M. Tingoli, Tetrahedron Lett. 2003, 44,
8753–8756.
Published Online: November 24, 2010
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