Structure of N-Aryl Selenoacetamide in Solutions and in the Solid State

Full text of DOI:10.1021/jo971222r

374
J . Org. Chem. 1998, 63, 374-376
Ta ble 1. Syn th esis of N-Ar yl Selen oa m id es 1 a n d th e
Str u ctu r e of N-Ar yl Selen oa ceta m id es in
Ra tio of E- a n d Z-Isom er sa
Solu tion s a n d in th e Solid Sta te
ratio of E:Z
yieldb ratio of E:Z
compd (%)
isomers of
Toshiaki Murai,* Naoko Niwa, Tatsuya Ezaka, and
Shinzi Kato*
entry
1
Ar
isomersc CH3C(S)NHArc,d
C6H5
1a
1b
59
31
71
61:39
65:35
64:36
23:77f
17:83g
14:86h
17:83i
49:51
48:52
36.5:63.5
42.5:57.5
44:56
Department of Chemistry, Faculty of Engineering,
Gifu University, Yanagido, Gifu 501-11, J apan
2e C6H4-CH3-4
3
4
5
6
7
C6H4-OCH3-4 1c
Received J uly 7, 1997
Synthesis and synthetic applications of selenium coun-
terparts of amides, i.e., selenoamides, have been widely
developed in recent years.1,2 On the contrary, little is
known about their structures. There has been several
reports on the X-ray molecular structure analyses of only
tertiary selenoamides3-5 and selenoformamides.6 No
structural studies have been reported on secondary
selenoamides except for one case7 despite their potential
importance related to those on well-known ordinary
amides8 and thioamides.9 Herein we report the structure
of N-aryl selenoacetamides in solutions and in the solid
state.
8j C6H4-Cl-4
1d
1e
19
34
30:70
28.5:71.5
9
C6H4-Br-4
a
Synthesis of 1 was carried out as follows: (trimethylsilyl)-
acetylene (2 mmol), n-BuLi (2 mmol), Se (2 mmol), CH3CO2H (2
mmol), arylamine (2 mmol), KF (2 mmol), CH3OH (5 mL), and
b
d
THF (5 mL). Isolated yield. c In CDCl3, ref 9c. The Ar group is
identical to that of 1 in each entry. e 4-CH3C6H4NH2‚HCl was used
instead of CH3CO2H and 4-CH3C6H4NH2. f In THF-d8. g In acetone-
d6. In CD3OD. i In CD3CN. j 4-ClC6H4NH2‚HCl was used instead
of CH3CO2H and 4-ClC6H4NH2.
h
selenium, acetic acid, and arylamines followed by the
reactions with potassium fluoride in moderate to good
yields (eq 1).2o The selenoamides 1 existed as a stereo-
isomeric mixture (eq 2). The yields of 1 and the ratios
N-Aryl selenoamides 1 were synthesized from the
reactions of (trimethylsilyl)acetylene, n-butyllithium,
(1) For reviews: (a) Ogawa, A.; Sonoda, N. In Comprehensive
Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon Press:
Oxford, U.K., 1991; Vol. 6, p 476. (b) Ogawa, A.; Sonoda, N. Rev.
Heteroatom Chem. 1994, 10, 43. (c) Dell, C. P. In Comprehensive
Organic Functional Group Transformations; Katritzky, A. R., Meth-
Cohn, O., Rees, C. W., Eds.; Pergamon: Oxford, U.K., 1995; Vol. 5, p
565.
n
–
(2) For recent examples: (a) Ishihara, H.; Yoshimi, M.; Hara, N.;
Ando, H.; Kato, S. Bull. Chem. Soc. J pn. 1990, 63, 835. (b) Ishihara,
H.; Yoshimi, M.; Kato, S. Angew. Chem., Int. Ed. Engl. 1990, 29, 530.
(c) Sekiguchi, M.; Ogawa, A.; Fujiwara, S.; Ryu, I.; Kambe, N.; Sonoda,
N. Chem. Lett. 1990, 913. (d) Shimada, K.; Hikage, S.; Takeishi, Y.;
Takikawa, Y. Chem. Lett. 1990, 1403. (e) Sekiguchi, M.; Ogawa, A.;
Fujiwara, S.; Ryu, I.; Kambe, N.; Sonoda, N. Chem. Lett. 1990, 2053.
(f) Segi, M.; Kojima, A.; Nakajima, T.; Suga, S. Synlett 1991, 105. (g)
Sekiguchi, M.; Ogawa, A.; Kambe, N.; Sonoda, N. Chem. Lett. 1991,
315. (h) Okuma, K.; Ikari, K.; Ohta, H. Chem. Lett. 1992, 131. (i) Lai,
L.-L.; Reid, D. H. Synthesis 1993, 870. (j) Takikawa, Y.; Watanabe,
H.; Sasaki, R.; Shimada, K. Bull. Chem. Soc. J pn. 1994, 67, 876. (k)
Shimada, K.; Akimoto, S.; Itoh, H.; Nakamura, H.; Takikawa, Y. Chem.
Lett. 1994, 1743. (l) Takikawa, Y.; Yamaguchi, M.; Sasaki, T.; Ohnishi,
K.; Shimada, K. Chem. Lett. 1994, 2105. (m) Otten, P. A.; Gen, A. Recl.
Trav. Chim. Pays-Bas 1994, 113, 499. (n) An, D.-L.; Toyota, K.;
Yasunami, M.; Yoshifuji, M. Chem. Lett. 1995, 199. (o) Murai, T.;
Ezaka, T.; Niwa, N.; Kanda, T.; Kato, S. Synlett 1996, 865. (p) Murai,
T.; Ezaka, T.; Kanda, T.; Kato, S. J . Chem. Soc., Chem. Commun. 1996,
1809. (q) Murai, T.; Ezaka, T.; Ichimiya, T.; Kato, S. Synlett 1997, 775.
(3) For R,â-unsaturated selenoamides: (a) Fischer, H.; Tiriliomis,
A.; Gerbing, U.; Huber, B.; Mu¨ller, G. J . Chem. Soc., Chem. Commun.
1987, 559. (b) Fischer, H.; Gerbing, U.; Tiriliomis, A.; Mu¨ller, G.; Huber,
B.; Riede, J .; Hofmann, J .; Burger, P. Chem. Ber. 1988, 121, 2095.
(4) For diselenoamide: Nakayama, J .; Mizumura, A.; Akiyama, I.;
Nishio, T.; Iida, I. Chem. Lett. 1994, 77.
(5) For aromatic selenoamides: (a) Murai, T.; Mizutani, T.; Kanda,
T.; Kato, S. Heteroatom Chem. 1995, 6, 241. (b) Otten, P. A.; Gorter,
S.; Gen, A. Chem. Ber. 1997, 130, 49.
(6) Li, G. M.; Zingaro, R. A.; Segi, M.; Reibenspies, J . H.; Nakajima,
T. Organometallics 1997, 16, 756.
(7) The N-phenylselenoacetamide 1a has been reported to exist
predominantly as a Z-isomer on the basis of infrared spectroscopy,
see: Rae, I. D.; Wade, M. J . Int. J . Sulfur Chem. 1976, 8, 519.
(8) (a) Eliel, E. L.; Wilen, S. H.; Mander, L. N. In Stereochemistry
of Organic Compounds; J ohn Wiley & Sons: New York, 1994; p 620.
(b) Saito, S.; Toriumi, Y.; Tomioka, N.; Itai, A. J . Org. Chem. 1995,
60, 4715. (c) Manea, V. P.; Wilson, K. J .; Cable, J . R. J . Am. Chem.
Soc. 1997, 119, 2033 and references therein.
of two isomers are listed in Table 1. The structures of
major isomers were determined by the comparison of the
chemical shifts of 1 with those of N-aryl thioamides.10
In the 1H NMR spectra the signals corresponding to N-H
proton of E-isomers were observed in the lower fields
than those of Z-isomers. On the other hand, the signals
due to a methyl group attached to the selenocarbonyl
group in E-isomers were upfield of those in Z-isomers.
The ratios of the isomers were determined by the relative
intensities of these methyl signals. N-Aryl selenoamides
1 were found to exist predominantly as Z-isomers in
THF-d8, acetone-d6, CD3OD, and CD3CN. As for amides,
secondary N-aryl amides have been reported to exist only
as Z-isomers.11 The predominance of Z-isomers in thio-
amides has been explained by the steric repulsion
between ortho-protons of the aromatic ring and an alkyl
group at the position R to the thiocarbonyl group in
E-isomers.10 A similar steric repulsion clearly exists in
selenoamides, and this seemed to explain the results of
entries 4-7 in Table 1. However, this does not explain
(9) (a) Walter, W.; Voss, J . In The Chemistry of Amides; Patai, S.,
Ed.; Interscience Publishers: London, 1970; p 383. (b) Duus, F. In
Comprehensive Organic Chemistry; Barton, D., Ollis, W. D., Eds.;
Pergamon Press: Oxford, U.K., 1979; Vol. 3, p 440. (c) Walter, W.;
Kubersky, H. P. Spectrochim. Acta 1970, 26A, 1155.
(10) Katritzky, A. R.; Moutou, J .-L.; Yang, Z. Synthesis 1995, 1497.
(11) (a) Itai, A.; Toriumi, Y.; Tomioka, N.; Kagechika, H.; Azumaya,
I.; Shudo, K. Tetrahedron Lett. 1989, 30, 6177. (b) Toriumi, Y.; Kasuya,
A.; Itai, A. J . Org. Chem. 1990, 55, 259.
S0022-3263(97)01222-X CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/07/1998

Notes
J . Org. Chem., Vol. 63, No. 2, 1998 375
Ta ble 2. Cr ysta l Da ta a n d Da ta Collection P a r a m eter s
of 1c
of the aromatic ring works well in the ordinary amides.
On the contrary, the aromatic ring and the SedC-N
group do not appear to be in conjugation in the seleno-
amide 1c. This also has suggested the importance of the
steric and/or electronic repulsion between the selenium
atom of the selenocarbonyl group and the aromatic ring.
Nevertheless, 1c existed as a Z-isomer in the solid state.
To confirm if two isomers of 1c interconvert within the
NMR time scale, a spin saturation transfer 1H NMR
experiment was performed.15 When the signal for ortho-
protons of the aromatic ring of E-isomer was irradiated,
the spectrum exhibited negative NOE effect in the signal
due to ortho-protons of the Z-isomer. This observation
has suggested that the interconversion of two isomers
clearly occurs at room temperature in CDCl3, although
the rotational barrier around C-N bond is believed to
become higher when the oxygen atom of amides is
replaced with the sulfur and selenium atoms.16 This was
further supported by phase-sensitive 2-D 1H NOESY
spectroscopy. Positive cross peaks were observed for
methyl, aryl, and NH protons between two isomers.
formula
formula weight
crystal system
space group
a/Å
C9H11NOSe
228.15
monoclinic
P21(No. 4)
5.552(1)
7.673(2)
10.912(1)
96.51(1)
461.8(1)
2
b/Å
c/Å
â/deg
V/Å3
Z value
d
calcd/g cm-3
1.641
40.16
µ(Mo KR)/cm-1
radiation, λ/Å
temp/°C
Mo KR, 0.71069
-80.0
residuals: R,a Rω
0.026, 0.031
b
a
b
2
R ) ∑(||Fo| - |Fc||)/∑|Fo|. Rω ) [∑ω(|Fo| - |Fc|)2/∑ωFo
]
1/2, ω
) [σ2(Fo) + p2Fo2/4]-1
.
1
Then, the H NMR spectrum of 1c dissolved in CDCl3 at
-40 °C was measured. The Z- and E-isomers existed in
a 50:50 ratio at this temperature. When the temperature
was raised to 0 °C, the ratio of two isomers ended up as
a 35:65 ratio, and this did not change even when it was
cooled to -40 °C again. Consequently, E-isomers of 1
were thermodynamically more stable than Z-isomers of
1 in CDCl3. The higher rotational barriers between E-
and Z-isomers of N-aryl thioamides have been observed8a,16
and accounted for by the preference for polar resonance
structures such as 2 compared with the case of ordinary
amides (eq 3).17 The present results have suggested that
a similar argument should not necessarily be applied to
the selenoamides.18
F igu r e 1. An ORTEP drawing of the molecular structure of
1c. Selected bond distances (Å), bond angles (deg), and twisted
angles (deg): Se1-C8 1.776(5), N1-C8 1.315(6), N1-C1
1.448(5), C8-C9 1.503(6), Se1-C8-N1 125.1(3), Se1-C8-
N1-C1 -0.2(7), C2-C1-N1-C8 -63.8(7).
the ratios of the isomers since E-isomers predominate
over Z-isomers in the case of selenoamides 1a -c in CDCl3
(entries 1-3). The ratios of E- and Z-isomers of 1 were
also compared with those of N-aryl thioamides. The
introduction of electron-withdrawing groups such as
chlorine and bromine on aromatic rings increased the
ratio of Z-isomers of both seleno- and thioamides in
CDCl3 (entries 8 and 9).
Exp er im en ta l Section
The molecular structure of the N-(4-methoxyphenyl)se-
lenoacetamide (1c) was determined by the X-ray diffrac-
tion study. The crystal data and data collection param-
eters are listed in Table 2.12 The X-ray molecular
structure of 1c is shown in Figure 1 with selected bond
distances, angles, and twisted angles. The bond distance
in the selenocarbonyl group CdSe is 1.776(5) Å, which
is shorter than those of the reported tertiary seleno-
amides3-5 and selenoformamides.6 The C(Se)-N single
bond (1.315(6) Å) is similar to those of the reported
selenoamides.3-6 These bond distances are also shorter
than those of selenoformamide (HC(Se)NH2) (CdSe,
1.783 Å; C-N, 1.345 Å) determined by molecular orbital
calculations.13 Noteworthy is that the aromatic ring on
the nitrogen atom is deviated from the plane of SedC-N
by 63.8(7)°. Molecular orbital calculations have indicated
the phenyl ring of the N-phenylacetamide are in the same
plane of OdC-N.8b Likewise, the torsion angle of C-N-
C-C of the N-(4-methoxyphenyl)acetamide was reported
to be 20.3°.14 Accordingly, the resonance stabilizing effect
All reactions were carried out under an argon atmosphere.
Melting points were uncorrected. IR spectra were recorded in
KBr pellets. 1H and 13C NMR spectra were measured at 400
and 100 MHz, respectively. As for 1c, NOE difference and
phase-sensitive 2-D 1H NOESY spectra were also measured at
400 MHz. Diethyl ether was distilled from sodium benzophe-
none ketyl prior to use.
Gen er a l P r oced u r e for Syn th esis of N-Ar yl Selen oa cet-
a m id es 1. To an Et2O solution (5 mL) of lithium alkynesele-
nolate generated from (trimethylsilyl)acetylene (0.28 mL, 2
mmol), n-butyllithium (1.6 M hexane solution, 1.25 mL, 2 mmol),
and selenium (0.158 g, 2 mmol) was added acetic acid (0.11 mL,
2 mmol) at -78 °C, and the solution was stirred for 5 min. Then,
to the solution was added arylamine (2 mmol) at this temper-
ature. After the mixture was stirred for 0.5-1 h at room
temperature, methanol (5 mL) and potassium fluoride (0.116 g,
2 mmol) were added, and the solution was further stirred for 30
min. The mixture was poured into a saturated aqueous solution
of NH4Cl and extracted with Et2O three times. The combined
organic layers were dried over MgSO4 and concentrated. The
(15) Sanders, J . K. M.; Hunter, B. K. In Modern NMR Spectroscopy;
Oxford University Press: Oxford, 1993; p 222.
(12) The details of the X-ray molecular structure analysis are
available: see, Supporting Information.
(13) Dapprich, S.; Frenking, G. Chem. Phys. Lett. 1993, 205, 337.
(14) Haisa, M.; Kashino, S.; Ueno, T.; Shinozaki, N.; Matsuzaki, Y.
Acta Crystallogr. 1980, B36, 2306.
(16) (a) Hampson, P.; Mathias, A. Molecular Physics 1967, 13, 361.
(b) Walter, W.; Schaumann, E.; Voss, J . Org. Magn. Res. 1971, 3, 733.
(17) Wiberg, K. B.; Rablen, P. R. J . Am. Chem. Soc. 1995, 117, 2201.
(18) Guziec, F. S., J r. In Organoselenium Chemistry; Liotta, D., Ed.;
Wiley-Intersciense: New York, 1987; p 319.

376 J . Org. Chem., Vol. 63, No. 2, 1998
Notes
1
residue was purified by silica gel column chromatography using
n-hexane-CH2Cl2 as eluent to afford the N-aryl selenoacet-
amides 1.
1375, 1136, 1091, 1013, 858, 822, 740, 588, 511 cm-1; H NMR
(CDCl3) δ 2.27, 2.50 (s, 3H), 6.80-7.50 (m, 4H), 9.73 (br, 1H);
13C NMR (CDCl3) δ 34.0, 40.7, 125.7, 126.0, 129.3, 129.9, 132.9,
134.1, 136.9, 138.2, 206.1, 208.4; MS m/z 233 (M+). Anal. Calcd
for C8H8ClNSe: C, 41.32; H, 3.47. Found: C, 41.40; H, 3.51.
N-(4-Br om oph en yl)eth an eselen oam ide (1e):19 yellow solid,
mp 138-141 °C; IR (KBr) 3136, 3092, 2966, 1531, 1482, 1376,
N-P h en yleth a n eselen oa m id e (1a ): yellow solid, mp 82-
84 °C; IR (KBr) 3108, 1492, 1445, 1381, 1136, 968, 767, 713,
570, 506 cm-1; 1H NMR (CDCl3) δ 2.51, 2.73 (s, 3H), 7.10-7.70
(m, 5H), 10.25 (br, 1H); 13C NMR (CDCl3) δ 33.8, 40.2, 124.4,
124.5, 127.5, 128.1, 128.9, 129.6, 138.3, 139.7, 205.3, 207.3; MS
m/z 199 (M+). Anal. Calcd for C8H9NSe: C, 48.50; H, 4.58.
Found: C, 48.36; H, 4.38.
1137, 1066, 1010, 854, 813, 587, 516 cm-1; H NMR (CDCl3) δ
1
2.48, 2.72 (s, 3H), 7.00-7.70 (m, 4H), 9.26, 10.55 (br, 1H); 13C
NMR (CDCl3) δ 34.0, 40.9, 125.9, 126.2, 132.3, 133.0, 137.3,
206.0, 208.7; MS m/z 277 (M+). Anal. Calcd for C8H8BrNSe: C,
34.69; H, 2.91. Found: C, 34.61; H, 3.00.
N-(4-Meth ylph en yl)eth an eselen oam ide (1b):19 yellow solid,
mp 103-106 °C; IR (KBr) 3142, 3103, 2959, 2361, 2344, 1534,
1
1507, 1376, 1133, 812, 706, 586, 514 cm-1; H NMR (CDCl3) δ
Ack n ow led gm en t. This work was supported par-
tially by Grant-in-Aid for Scientific Research (B) (No.
08455414), Development Research (No. 09355032), and
Scientific Research on Priority Areas (No. 09239220)
from Ministry of Education, Science, Sports and Cul-
ture, J apan.
2.30, 2.33 (s, 3H), 2.47, 2.71 (s, 3H), 7.00-7.50 (m, 4H), 10.51
(br, 1H); 13C NMR (CDCl3) δ 21.1, 21.2, 33.7, 40.2, 124.4, 129.6,
130.2, 136.0, 138.4, 205.3, 207.4; MS m/z 213 (M+). Anal. Calcd
for C9H11NSe: C, 50.95; H, 5.23. Found: C, 51.22; H, 5.25.
N-(4-Meth oxyph en yl)eth an eselen oam ide (1c): yellow solid,
mp 127-128 °C; IR (KBr) 3167, 3010, 1612, 1534, 1510, 1376,
1300, 1255, 1171, 1133, 1030, 827, 684, 588 cm-1 1H NMR
;
(CDCl3) δ 2.46, 2.75 (s, 3H), 3.80, 3.81 (s, 3H), 6.80-7.60 (m,
4H), 9.21, 10.29 (br, 1H); 13C NMR (CDCl3) δ 33.6, 39.9, 55.4,
55.5, 114.1, 114.7, 116.5, 126.0, 131.5, 132.8, 158.6, 159.2, 205.3,
207.6; MS m/z 229 (M+). Anal. Calcd for C9H11NOSe: C, 47.38;
H, 4.86. Found: C, 47.21; H, 4.74.
N-(4-Ch lor op h en yl)eth a n eselen oa m id e (1d ): yellow solid,
mp 105-108 °C; IR (KBr) 3140, 3099, 2968, 2366, 1534, 1487,
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
crystallographic data, final atomic coordinates, and equivalent
isotropic thermal parameters, bond distances, bond angles, and
torsion angles (13 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
(19) Cohen, V. I. J . Org. Chem. 1977, 42, 2645.
J O971222R