Dipolarophilic behaviour of the thiophene ring in intramolecular nitrile imine cycloadditions

Article abstract of DOI:10.1039/a807441k

Unprecedented intramolecular nitrile imine cycloadditions onto a thiophene ring are described as a synthetic route to a number of tricyclic pyrazoline derivatives (5). Diadducts 6 and 7, which can be ascribed to a sequential intra-intermolecular cycloaddi

Full text of DOI:10.1039/a807441k

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Dipolarophilic behaviour of the thiophene ring in intramolecular
nitrile imine cycloadditions
Gianluigi Broggini, Luisa Garanti,* Giorgio Molteni and Gaetano Zecchi
Dipartimento di Chimica Organica e Industriale dell’Università and Centro CNR, Via Golgi 19,
20133, Milano, Italy
Received (in Cambridge) 23rd September 1998, Accepted 3rd November 1998
Unprecedented intramolecular nitrile imine cycloadditions onto a thiophene ring are described as a synthetic
route to a number of tricyclic pyrazoline derivatives (5). Diadducts 6 and 7, which can be ascribed to a sequential
intra–intermolecular cycloaddition pathway, are also formed.
Despite their propensity for substitution rather than addition
reactions, various five-membered heteroaromatics can behave
as dipolarophiles in intramolecular cycloadditions of 1,3-
dipoles.1 Intramolecular nitrile oxide cycloadditions to furan
and thiophene2–4 have received growing attention, in recent
years, owing to the array of latent functionalities presented by
the cycloadducts. Little is known, in this respect, about nitrile
imines. To the best of our knowledge, only two reports describe
intramolecular cycloadditions of a nitrile imine to the furan
ring,5,6 while there is a complete lack of data regarding the
thiophene ring.
We present here the first investigation about the intra-
molecular reactivity of a series of appropriately substituted
nitrile imines (4) containing the thiophene moiety.
Results and discussion
As precursors of the desired nitrile imines, we first synthesised
the hydrazonoyl chlorides
3 according to the reaction
sequence outlined in Scheme 1. Cycloaddition reactions of
3 via the labile species 4 were carried out in hot dioxane in
the presence of a two-fold molar excess of silver carbonate.
Scheme 1 Reagents and conditions: i, xylene, ∆; ii, SO2Cl2, 0 ЊC; iii, ArNϩ2 ClϪ, 0 ЊC; iv, Ag2CO3–dioxane, room temp.
J. Chem. Soc., Perkin Trans. 1, 1998, 4103–4106
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Reaction times, products, eluants and yields are summarised in
Table 1.
side-products due to a known degradative process of nitrile
imines.11
Structures 5–7 were firmly established by elemental analyses
and spectral data, including 1H NMR, IR, and MS spec-
trometry (see Table 2). 1H NMR spectra of compounds 5
parallel those reported for some analogous thienoxazolines7
and furopyrazolines.8 For diadducts 6, the relative configuration
of the hydrogens HA and HB reflects the typical cis junction of
five-membered rings. On the other hand, the stereochemical
relationship between HB and HC was proven to be anti by the
apparent lack of vicinal coupling (Jvic < 1 Hz), which finds
precedents in the literature for such a disposition in strained
polycyclic structures.9,10 Diagnostic evidence also came from
the IR spectra, where higher frequencies appeared for the
unconjugated lactone carbonyl of 7 in comparison with the
conjugated one of both 5 and 6. Oxalamides 8 are trivial
The results depicted in Scheme 1 deserve some comments
aimed at rationalising the operative reaction paths. First of all,
the intramolecular cycloaddition onto the thiophene ring to
give the tricyclic pyrazolines 5 merits attention owing to its
novelty. Plausibly, the high energy barrier due to the loss of
aromaticity is overcome by favourable entropic contributions
working in intramolecular reaction.12,13 However, both geo-
metric constraints and electronic factors must be responsible
for the regiochemical trend of the cycloaddition. In fact,
experimental results9,10 as well as theoretical calculations9,14
dealing with nitrile oxide cycloaddition on thiophene have
shown that the preferred orientation involves bond formation
between the carbon of the dipole and the α-carbon of the
heterocycle. Assuming the same preference in the case of nitrile
imines, this explains the formation of 5. To gain a deeper
insight into this point, we synthesised the hydrazonoyl chloride
11 (Scheme 2) and reacted it under the same conditions as
3; besides tarry material, unchanged 11 (65%) was recovered.
No cycloaddition product was formed, which accords with the
fact that the molecular geometry precludes the regiochemistry
favoured by electronic factors.
Table 1 Treatment of hydrazonoyl chlorides 3 with silver carbonatea
Products and yields (%)b
Entry
t/h
5
6
7
8
Eluantc
The first-formed cycloadducts 5 still contain two double
a
b
c
d
e
f
3
30
20
11
10
10
14
25
18
14
28
57
23
67
16
28
15
11
10
—
—
—
—
—
—
8
15
5
—
5
18
—
—
30
—
CH2Cl2–LP (10:1)
Et2O–LP (2:1)
CH2Cl2
Et2O–hexane (2:1)
CH2Cl2
Et2O–AcOEt (10:1)
Et2O–LP (4:1)
bonds, namely the C᎐C bond of the 2,3-dihydrothiophenic ring
᎐
and the C᎐N bond of the pyrazolinic one, which are potentially
᎐
susceptible to subsequent dipolar attack. In several cases
(entries a–d), the route 5→6 is the only operative one in accord
with the usual better dipolarophilicity of carbon–carbon mul-
tiple bonds with respect to heterodipolarophiles.15 The LUMO-
dipole control of cycloadditions onto 2,3-dihydrothiophene, as
indicated by early calculations,9 well accounts for the observed
g
a 70 ЊC in dioxane. b Isolated yield by column chromatography. c LP =
light petroleum bp 40–60 ЊC.
Table 2 Physical and spectral data of cycloaddition products 5, 6 and 7
Compd.
Mpa/ЊC
152
νmax(Nujol)/cmϪ1
δH (CDCl3)
m/z (Mϩ)
1750
1770
1765
1760
1760
4.50 (1H, d, J 9.9), 4.92 (1H, d, J 9.9), 5.84 (1H, d, J 3.2), 5.94 (1H, dd, J 6.1,
3.2), 6.66 (1H, d, J 6.1), 7.15–7.40 (5H, m)
2.30 (3H, s), 4.65 (1H, d, J 9.9), 4.90 (1H, d, J 9.9), 5.82 (1H, d, J 3.2), 5.90 (1H,
dd, J 6.1, 3.2), 6.65 (1H, d, J 6.1), 7.05–7.20 (4H, m)
3.80 (3H, s), 4.65 (1H, d, J 9.2), 4.90 (1H, d, J 9.2), 5.80 (1H, d, J 3.7), 5.88 (1H,
dd, J 6.4, 3.7), 6.68 (1H, d, J 6.4), 6.85–7.20 (4H, m)
4.60 (1H, d, J 9.9), 4.90 (1H, d, J 9.9), 5.80 (1H, d, J 3.3), 5.90 (1H, dd, J 6.1,
3.3), 6.65 (1H, d, J 6.1), 7.00–7.20 (4H, m)
4.65 (1H, d, J 10.2), 4.75 (1H, d, J 10.2), 5.81 (1H, d, J 3.2), 5.90 (1H, dd, J 6.1,
3.2), 6.69 (1H, d, J 6.1), 7.10–7.35 (4H, m)
2.60 (3H, s), 4.71 (1H, d, J 9.9), 4.95 (1H, d, J 9.9), 5.90 (1H, d, J 3.2), 5.96 (1H,
dd, J 6.0, 3.2), 6.70 (1H, d, J 6.0), 7.22–7.78 (4H, m)
4.70 (1H, d, J 10.2), 4.90 (1H, d, J 10.2), 5.72 (1H, d, J 3.1), 5.85 (1H, dd, J 6.1,
3.1), 6.50 (1H, d, J 6.1), 7.20–8.30 (4H, m)
4.55 (1H, d, J 10.2), 4.60 (1H, d, J 10.2), 4.90 (1H, d, J 8.5), 5.54 (1H, d, J 12.7),
5.63 (1H, d, J 12.7), 6.00 (1H, s), 6.28 (1H, d, J 8.5), 7.04 (1H, dd, J 5.2, 3.8), 7.09
(1H, d, J 3.8), 7.23 (1H, d, J 5.2), 7.27–7.43 (10H, m)
258 (14%)
272 (15%)
288 (23%)
276 (15%)
292 (19%)
300 (18%)
303 (25%)
516 (12%)
5a
5b
145
5c
5d
5e
5f
150
150
162
163
1770
1670
1770
5g
6a
191
145
1760
1700
6b
6c
180
156
1760
1700
2.30 (3H, s), 2.35 (3H, s), 4.52 (1H, d, J 10.1), 4.58 (1H, d, J 10.1), 4.86 (1H, d,
J 8.1), 5.52 (1H, d, J 12.2), 5.60 (1H, d, J 12.2), 5.98 (1H, s), 6.25 (1H, d, J 8.1),
7.04 (1H, dd, J 4.7, 3.8), 7.05–7.20 (8H, m), 7.22 (1H, d, J 3.8), 7.38 (1H, d, J 4.7)
3.75 (3H, s), 3.80 (3H, s), 4.50 (1H, d, J 10.1), 4.58 (1H, d, J 10.1), 4.80 (1H, d,
J 8.5), 5.50 (1H, d, J 12.3), 5.58 (1H, d, J 12.3), 5.92 (1H, s), 6.25 (1H, d, J 8.5),
7.02 (1H, dd, J 5.0, 3.7), 7.05–7.16 (8H, m), 7.20 (1H, d, J 3.7), 7.36 (1H, d, J 5.0)
4.55 (1H, d, J 10.1), 4.62 (1H, d, J 10.1), 4.85 (1H, d, J 8.3), 5.55 (1H, d, J 12.9),
5.60 (1H, d, J 12.9), 5.95 (1H, s), 6.29 (1H, d, J 8.3), 7.00–7.40 (11H, m)
4.55 (1H, d, J 10.2), 4.60 (1H, d, J 10.2), 4.90 (1H, d, J 8.7), 5.51 (1H, d, J 12.7),
5.62 (1H, d, J 12.7), 5.99 (1H, s), 6.25 (1H, d, J 8.7), 6.90–7.90 (11H, m)
4.41 (1H, d, J 10.8), 4.60 (1H, d, J 10.8), 5.40 (1H, d, J 12.4), 5.47 (1H, dd, J 3.0,
2.0), 5.55 (1H, dd, J 12.4), 5.60 (1H, dd, J 6.2, 3.0), 6.12 (1H, dd, J 6.2, 2.0), 7.00
(1H, dd, J 4.9, 3.9), 7.03–7.25 (8H, m), 7.18 (1H, d, J 3.9), 7.35 (1H, d, J 4.9)
2.50 (3H, s), 2.58 (3H, s), 4.40 (1H, d, J 10.8), 4.62 (1H, d, J 10.8), 5.40 (1H, d,
J 12.7), 5.58 (1H, dd, J 6.1, 2.3), 5.60 (1H, d, J 12.7), 5.64 (1H, dd, J 2.3, 2.0),
6.15 (1H, dd, J 6.1, 2.0), 7.00 (1H, dd, J 5.1, 3.5), 7.15–7.75 (10H, m)
4.45 (1H, d, J 10.9), 4.65 (1H, d, J 10.9), 5.42 (1H, d, J 12.7), 5.59 (1H, d, J 12.7),
5.61 (1H, dd, J 6.1, 3.1), 5.64 (1H, dd, J 3.1, 2.2), 6.20 (1H, dd, J 6.1, 2.2), 7.01
(1H, dd, J 5.1, 3.5), 7.20 (1H, d, J 3.5), 7.22–7.33 (4H, m), 7.38 (1H, d, J 5.1),
8.05–8.25 (4H, m)
544 (23%)
576 (18%)
1765
1690
6d
6e
7e
165
125
135
1760
1710
1760
1720
1787
1738
552 (20%)
584 (36%)
584 (31%)
7f
93
1790
1740
1680
1790
1740
600 (36%)
606 (28%)
7g
142
a From diisopropyl ether.
4104
J. Chem. Soc., Perkin Trans. 1, 1998, 4103–4106

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Table 3 Elemental analyses of compounds 3, 5, 6, 7, 8 and 11
Compd.
(Molecular
Formula)
C(%)
found
(required)
H(%)
found
(required)
N(%)
found
(required)
3a
53.11
(53.06)
54.48
(54.54)
51.92
(51.85)
49.93
(50.00)
47.58
(47.56)
53.60
(53.57)
46.00
(46.02)
53.05
(53.06)
60.50
(60.45)
61.69
(61.75)
58.27
(58.32)
56.48
(56.51)
53.30
(53.24)
60.01
(59.99)
51.51
(51.48)
60.39
(60.45)
61.77
(61.75)
58.35
(58.32)
56.55
(56.51)
53.20
(53.24)
53.21
(53.24)
59.91
(59.99)
51.44
(51.48)
61.01
3.82
(3.77)
4.30
(4.25)
4.11
(4.04)
3.20
(3.23)
3.10
(3.07)
3.94
(3.90)
3.02
(2.97)
3.74
(3.77)
3.88
(3.91)
4.42
(4.45)
4.13
(4.20)
3.31
(3.29)
3.44
(3.44)
4.00
(4.03)
3.04
(2.99)
3.86
(3.91)
4.41
(4.45)
4.16
(4.20)
3.33
(3.29)
3.48
(3.44)
3.44
(3.44)
3.98
(4.03)
3.02
(2.99)
4.80
9.58
(9.53)
9.13
(9.09)
8.70
(8.64)
9.05
(8.98)
8.50
(8.54)
8.30
(8.33)
12.44
(12.39)
9.49
(9.53)
10.91
(10.85)
10.33
(10.29)
9.79
(9.72)
10.11
(10.15)
9.62
(C13H11ClN2O2S)
3b
(C14H13ClN2O2S)
3c
(C14H13ClN2O3S)
3d
(C13H10ClFN2O2S)
3e
(C13H10Cl2N2O2S)
Scheme 2 Reagents and conditions: i, xylene, ∆; ii, SO2Cl2, 0 ЊC;
iii, 4-Cl-C6H4Nϩ2ClϪ, 0 ЊC.
3f
(C15H13ClN2O3S)
3g
regiochemistry. However, strongly electron-withdrawing groups
on the phenyl ring of 5 favour selectively the transformation
5→7 (entries f,g). This reversal in site preference may tenta-
tively be explained on the basis of the following consideration.
1,3-Dipolar cycloadditions onto heterodipolarophiles16 are
typically governed by the HOMO-dipole–LUMO-dipolaro-
phile interaction; they are consequently facilitated when lower-
ing the LUMO energy of the dipolarophile by means of
electron-withdrawing substituents. This may just be the case for
the substrates 5f,g. The behaviour of compound 3e, containing
the chlorine substituent, remains to be noted as a borderline
case.
Two conclusions can be drawn from the present work.
Primarily, our extension of the intramolecular nitrile imine
cycloaddition methodology to the thiophene dipolarophile
has provided interesting, strained tricyclic pyrazolines. The
observed yields, ranging from fair to good, make this protocol
valuable on a preparative scale. As a corollary, the formation of
the diadducts 7 is noteworthy, since there is no precedent in the
literature concerning the cycloaddition of nitrile imines onto
(C13H10ClN3O4S)
11
(C13H11ClN2O2S)
5a
(C13H10N2O2S)
5b
(C14H12N2O2S)
5c
(C14H12N2O3S)
5d
(C13H9FN2O2S)
5e
(C13H10ClN2O2S)
(9.56)
9.38
5f
(C15H12N2O3S)
(9.33)
13.90
(13.86)
10.83
(10.85)
10.33
(10.29)
9.69
(9.72)
10.08
(10.15)
9.61
(9.56)
9.67
(9.56)
9.36
(9.33)
13.95
(13.86)
5.13
5g
(C13H9N3O4S)
6a
(C26H20N4O4S2)
6b
(C28H24N4O4S2)
6c
(C28H24N4O6S2)
the C᎐N bond of pyrazolines.
᎐
6d
(C26H18F2N4O4S2)
6e
Experimental
(C26H20Cl2N4O4S2)
7e
Mps were determined on a Büchi apparatus and are uncor-
rected. IR Spectra were recorded on a FT IR Perkin-Elmer 1725
X spectrophotometer. Mass spectra were determined with a
VG-70EQ apparatus. 1H NMR Spectra were taken on a Bruker
AC 300 instrument in CDCl3 solutions; chemical shifts are
given as ppm from tetramethylsilane; J values are given in Hz.
Compounds 3, 5–8 and 11 gave satisfactory elemental analyses,
which are given in Table 3.
(C26H20Cl2N4O4S2)
7f
(C30H24N4O6S2)
7g
(C26H18N6O8S2)
8b
(C14H13NO3S)
8c
(C14H13NO4S)
8f
(C15H13NO4S)
(61.08)
57.70
(57.72)
59.44
(4.76)
4.44
(4.50)
4.29
(5.09)
4.86
(4.81)
4.58
General procedure for the preparation of thienyl acetoacetates 1
and 9
(59.39)
(4.32)
(4.62)
A solution of 2- or 3-hydroxymethylthiophene (11.4 g, 0.1 mol)
in xylene (20 ml) was treated with 2,2,6-trimethyl-4H-1,3-
dioxin-4-one (14.2 g, 0.1 mol). The mixture was refluxed for
1.5 h. Evaporation of the solvent under reduced pressure gave
crude 1 or 9 as undistillable oil not analytically pure.
g, 25 mmol) and sodium hydrogen carbonate (2.10 g, 25 mmol)
in dry chloroform (40 ml), on keeping the temperature in the
range 0–5 ЊC. After 1.5 h at room temperature, chloroform (80
ml) was added, and the mixture was washed with water (25 ml).
The organic layer was dried over sodium sulfate and the solvent
was removed under reduced pressure to afford 2 or 10 in the
crude state.
Compound 1. (19.6 g, 99%) νmax/cmϪ1 (neat) 1742, 1716;
δH 2.17 (3H, s), 3.41 (2H, s), 5.26 (2H, s), 6.86–7.38 (3H, m);
m/z 198 (Mϩ).
Compound 2. (3.77 g, 65%) νmax/cmϪ1 (neat) 1755, 1732;
δH 2.30 (3H, s), 4.75 (1H, s), 5.48 (2H, s), 6.90–7.40 (3H, m).
Compound 9. (19.6 g, 99%) νmax/cmϪ1 (neat) 1740, 1716;
δH 2.18 (3H, s), 3.45 (2H, s), 5.15 (2H, s), 7.02–7.36 (3H, m);
m/z 198 (Mϩ).
Compound 10. (4.06 g, 70%) νmax/cmϪ1 (neat) 1760, 1730;
δH 2.30 (3H, s), 4.77 (1H, s), 5.25 (2H, s), 7.00–7.35 (3H, m).
Crude 2 or 10 was dissolved in cold methanol (45 ml), and
sodium acetate (2.72 g, 20 mmol) was added. A cold aqueous
solution of the appropriate aryldiazonium chloride (16.3 mmol
for 2, 17.5 mmol for 10) was added dropwise under vigorous
stirring and ice-cooling. The mixture was allowed to stand
General procedure for the preparation of hydrazonoyl chlorides 3
and 11
A solution of sulfuryl chloride (3.35 g, 25 mmol) in dry chloro-
form (5 ml) was slowly added (2 h) to a mixture of 1 or 9 (4.95
J. Chem. Soc., Perkin Trans. 1, 1998, 4103–4106
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overnight under stirring at room temperature. The solvent was
partly removed under reduced pressure and the resulting
mixture was extracted with diethyl ether (150 ml). The organic
layer was washed firstly with 5% aqueous sodium hydrogen
carbonate (50 ml), then with water (100 ml), and dried over
sodium sulfate. Evaporation of the solvent and subsequent
crystallisation of the residue from diisopropyl ether gave the
hydrazonoyl chlorides 3 or 11 in the pure state.
treated with silver carbonate (2.76 g, 10.0 mmol), and the mix-
ture was stirred in the dark at 70 ЊC for the time indicated in
Table 1. The undissolved material was filtered off, the solvent
was evaporated and then the residue was chromatographed on
a silica gel column. Eluents, products and yields are given in
Table 1. Physical and spectral data of compounds 5–7 are given
in Table 2. Side products 8 had the following characteristic
data.
Compound 3a. (3.31 g, 45%) Mp 90 ЊC; νmax/cmϪ1 (Nujol)
3276, 1700; δH (CDCl3) 5.50 (2H, s), 7.00 (1H, dd, J 5.6, 3.2),
7.13 (1H, d, J 3.2), 7.15–7.30 (5H, m), 7.35 (1H, d, J 5.6), 8.35
(1H, br s); m/z 294 (Mϩ).
Compound 8b. Mp 136 ЊC; νmax/cmϪ1 (Nujol) 3356, 1710,
1660; δH (CDCl3) 2.28 (3H, s), 5.51 (2H, s), 6.89–7.35 (7H, m),
12.60 (1H, br s); m/z 275 (Mϩ).
Compound 8c. Mp 141 ЊC; νmax/cmϪ1 (Nujol) 3352, 1710,
1665; δH (CDCl3) 3.80 (3H, s), 5.50 (2H, s), 6.90–7.30 (7H, m),
12.54 (1H, br s); m/z 291 (Mϩ).
Compound 3b. (3.08 g, 40%) Mp 125 ЊC; νmax/cmϪ1 (Nujol)
3270, 1710; δH (CDCl3) 2.30 (3H, s), 5.50 (2H, s), 6.95 (1H, dd,
J 4.8, 3.7), 7.10 (1H, d, J 3.7), 7.15–7.25 (4H, m), 7.30 (1H, d,
J 4.8), 8.30 (1H, br s); m/z 308 (Mϩ).
Compound 8f. Mp 158 ЊC; νmax/cmϪ1 (Nujol) 3360, 1710,
1670; δH (CDCl3) 2.52 (3H, s), 5.52 (2H, s), 7.00–7.90 (7H, m),
12.75 (1H, br s); m/z 303 (Mϩ).
Compound 3c. (3.24 g, 40%) Mp 90 ЊC; νmax/cmϪ1 (Nujol)
3270, 1700; δH (CDCl3) 3.80 (3H, s), 5.50 (2H, s), 6.85 (1H, dd,
J 4.9, 3.8), 7.08 (1H, d, J 3.8), 7.10–7.20 (4H, m), 7.31 (1H, d,
J 4.9), 8.25 (1H, br s); m/z 324 (Mϩ).
References
1 (a) A. Padwa, in 1,3-Dipolar Cycloaddition Chemistry, ed. A. Padwa,
Wiley-Interscience, New York, 1984, vol. 2, ch. 12; (b) G. Zecchi,
Trends in Heterocyclic Chemistry, 1991, 2, 85.
2 R. Annunziata, M. Cinquini, F. Cozzi and L. Raimondi,
Tetrahedron Lett., 1989, 30, 5013.
Compound 3d. (2.73 g, 35%) Mp 115 ЊC; νmax/cmϪ1 (Nujol)
3275, 1700; δH (CDCl3) 5.50 (2H, s), 6.90–7.30 (6H, m), 7.35
(1H, d, J 5.3), 8.35 (1H, br s); m/z 312 (Mϩ).
3 D. Prajapati and J. S. Sandhu, Synthesis, 1988, 342.
4 D. Prajapati, P. Bhuyan and J. S. Sandhu, J. Chem. Soc., Perkin
Trans. 1, 1988, 607.
5 O. Tsuge, K. Ueno and S. Kanemasa, Chem. Lett., 1984, 285.
6 G. Broggini, G. Molteni and G. Zecchi, J. Chem. Res. (S), 1998,
812.
Compound 3e. (3.28 g, 40%) Mp 115 ЊC; νmax/cmϪ1 (Nujol)
3270, 1700; δH (CDCl3) 5.50 (2H, s), 7.01 (1H, dd, J 5.0, 3.6),
7.10–7.30 (4H, m), 7.19 (1H, d, J 3.6), 7.30 (1H, d, J 5.0), 8.30
(1H, br s); m/z 328 (Mϩ).
7 A. Hassner, K. S. K. Murthy, A. Padwa, U. Chiacchio, D. C. Dean
and A. M. Schoffstall, J. Org. Chem., 1989, 54, 5277.
8 L. Garanti, A. Sala and G. Zecchi, J. Org. Chem., 1977, 42, 1389.
9 P. Caramella, G. Cellerino, P. Grünanger, F. Marinone Albini,
M. and R. Re Cellerino, Tetrahedron, 1978, 34, 3545.
10 P. L. Beltrame, M. G. Cattania, V. Redaelli and G. Zecchi, J. Chem.
Soc., Perkin Trans. 1, 1977, 706.
Compound 3f. (4.70 g, 56%) Mp 98 ЊC; νmax/cmϪ1 (Nujol)
3260, 1710, 1700; δH (CDCl3) 2.95 (3H, s), 5.40 (2H, s), 6.90–
7.20 (7H, m), 8.25 (1H, br s); m/z 336 (Mϩ).
Compound 3g. (2.88 g, 34%) Mp 152 ЊC; νmax/cmϪ1 (Nujol)
3270, 1700; δH (CDCl3) 5.50 (2H, s), 7.08 (1H, dd, J 5.3, 3.2),
7.18 (1H, d, J 3.2), 7.20–7.35 (4H, m), 7.40 (1H, d, J 5.3), 8.60
(1H, br s); m/z 339 (Mϩ).
11 G. Broggini, L. Bruché, L. Garanti and G. Zecchi, J. Chem. Soc.,
Perkin Trans. 1, 1994, 433.
12 M. I. Page and W. P. Jencks, Proc. Natl. Acad. Sci. USA, 1971, 68,
1678.
Compound 11. (6.47 g, 88%) Mp 110 ЊC; νmax/cmϪ1 (Nujol)
3260, 1720; δH (CDCl3) 5.35 (2H, s), 7.12–7.18 (2H, m), 7.20
(1H, s), 7.26–7.31 (2H, m), 7.33 (1H, dd, J 5.0, 2.5), 7.40 (1H, d,
J 5.0), 8.30 (1H, br s); m/z 294 (Mϩ).
13 G. Illuminati and L. Mandolini, Acc. Chem. Res., 1981, 14, 95.
14 L. Bonati, T. Benincori, G. Zecchi and D. Pitea, J. Chem. Soc.,
Perkin Trans. 2, 1991, 1243.
15 A. Eckell, R. Huisgen, R. Sustmann, G. Wallbillich, D. Grashey
and E. Spindler, Chem. Ber., 1967, 100, 2192.
16 G. Bianchi, C. De Micheli and R. Gandolfi, in The Chemistry of
Double-Bonded Functional Groups, ed. S. Patai, Wiley, New York,
1977, vol. 2, ch. 6, 379.
General procedure for the treatment of hydrazonoyl chlorides 3 or
11 with silver carbonate
A solution of 3 or 11 (5.0 mmol) in dry dioxane (250 ml) was
Paper 8/07441K
4106
J. Chem. Soc., Perkin Trans. 1, 1998, 4103–4106