SMQ-V047 N-002_ligas_size.pdf - Journal of the Mexican Chemical ...

204 Rev. Soc. Quím. Méx. Vol. 47, Núm. 2 (2003) Erick Cuevas Yañez et al.
Table 2. Selected bond distances (Å) and angles (°) for 1.
Bond
Distance (Å)
S1-C13 1.689(8)
O1-C1 1.221(9)
O2-C9 1.440(8)
N1-C2 1.316(9)
C1-C3 1.483(9)
C3-C4 1.409(9)
C3-C8 1.407(10)
C4-C5 1.370(9)
S1-C10 1.707(9)
O2-C4 1.366(9)
N1-N2 1.117(8)
C1-C2 1.433(12)
C9-C10 1.487(10)
C11-C12 1.419(11)
Fig. 2. ORTEP representation for compound 1.
because there are not overwhelming evidences about the reaction
mechanism. The McKervey group [7-9] found that varying
the catalyst they could modify the course of this kind of
reactions to obtain both chromanones and benzofuranones.
However, the five-membered ring formation and subsequent
Stevens rearrangement is more common in these processes
[10].
Treatment of diazoketone 1 with rhodium (II) acetate in
dichloromethane at room temperature under inert atmosphere
gave a reaction product whose physical and spectroscopic
constants did not correspond to those expected for chromanone
8 as have been reported previously [11, 12]. In this way,
spectroscopic data indicated that the compound obtained was
thienylmetylbenzofuranone 10. Additionally, Gefflaut and
Périe [13] informed a similar cyclization process when the
diazoketone derived from 2-benzyloxybenzoic acid reacted
with catalytic rhodium (II) acetate. Therefore, in this case the
carbenoid 7 derived from the diazoketone 1 reacted in an
intramolecular way with the phenoxy oxygen to generate a
five-membered ring and also an oxonium ylide which is
kinetically favored and is rearranged later to the benzofuranone
10.
In conclusion, this work presents the first synthesis of the
2-diazo-1-[2-(thiophen-2-ylmethoxy)-phenyl]-ethanone 1 and
its intramolecular cyclization to the benzofuranone 10, which
expands the possibilities to carry out reactivity studies with
transition metals and to synthesize some derivatives from this
molecule.
Experimental section
Bond Angle (°)
C13-S1-C10 92.0(5)
N2-N1-C2 177.0(10)
O1-C1-C3 121.6(8)
N1-C2-C1 115.0(8)
C8-C3-C1 116.4(6)
O2-C4-C5 124.0(7)
C5-C4-C3 120.6(7)
C11-C10-C9 126.1(8)
C9-C10-S1 122.3(6)
C4-O2-C9 117.4(5)
O1-C1-C2 121.0(6)
C2-C1-C3 117.3(7)
C8-C3-C4 117.9(6)
C4-C3-C1 125.7(7)
O2-C4-C3 115.4(6)
O2-C9-C10 108.2
C11-C10-S1 111.5(6)
The starting materials were purchased from Aldrich Chemical
Co. and were used without further purification. Solvents were
distilled before use, ether and tetrahydrofuran (THF) were
dried over sodium using benzophenone as indicator. Diazomethane
was prepared from N-methyl-N-nitroso-p-toluenesulfonamide
(Diazald ®) using a minimum amount of water and
ethanol as co-solvent, and dried over KOH pellets before use.
Silica gel (230-400 mesh) and neutral alumina were purchased
from Merck. Silica plates of 0.20 mm thickness were used for
thin layer chromatography. Melting points were determined
with a Fisher-Johns melting point apparatus and they are
uncorrected. 1 H and 13 C NMR spectra were recorded using a
Varian Gemini 200, chemical shifts (d) are given in ppm relative
to TMS as internal standard (0.00). For analytical purposes,
mass spectra were recorded on a JEOL JMS-5X 10217 in
the EI mode, 70 eV, 200 °C via direct inlet probe. Only molecular
and parent ions (m/z) are reported. IR spectra were
recorded on a Nicolet Magna 55-X FT instrument. For X-Ray
diffraction studies, crystals of compound 1 were obtained by
slow evaporation of a dilute ethanol solution, and reflections
were acquired with a Nicolet P3 / F diffractometer. Three
standard reflections every 97 reflections were used to monitor
crystal stability. The structure was solved by direct methods,
missing atoms were found by difference-Fourier synthesis,
and refined on F2 by a full-matrix least-squares procedure
using an isotropic displacement parameters using SHELX-97.