2
022 J . Org. Chem., Vol. 66, No. 6, 2001
Prakash et al.
2-Th iocya n a toa cetop h en on e (10a ). Oil (210 mg, 60%).7
at the R-position are mostly unstable owing to their
further cyclization reactions.
1
H NMR (CDCl
3
, 300 MHz, δ): 4.75 (s, 2H, COCH
2
SCN), 7.51-
7
2
.56 (m, 2H), 7.65-7.70 (m, 1H), 7.93-7.97 (m, 2H). IR (νmax):
-
1
155 (SCN str.), 1712 (CdO str.) cm
.
Exp er im en ta l Section
2-(2-Th iocya n a toa cetyl)fu r a n (10b). Colorless crystalline
1
3
solid (155 mg, 46%), mp 101-103 °C. H NMR (CDCl , 300
Gen er a l. Melting points were taken in open capillaries and
MHz, δ): 4.44 (s, 2H, COCH SCN), 6.64 (dd, 1H, J ) 3.6, 1.2
2
1
are uncorrected. H NMR spectra were recorded on a Brucker
Hz, 4-furyl proton), 7.37 (d, 1H, J ) 3.6 Hz, 3-furyl proton),
3
00 MHz instrument using TMS as an internal standard. IR
7.67 (d, 1H, J ) 1.2 Hz, 5-furyl proton). IR (ν ): 2158 (SCN
max
-
1
+
spectra were recorded on a Perkin-Elmer 1800 IR spectropho-
tometer. Mass spectra were recorded on Kratos MS-50 mass
spectrometer. Most of the chemicals were obtained from
str.), 1651 (CdO str.) cm . MS (m/z, CI): 168 (M + 1, 100),
140 (12.5), 122 (7.7), 111(31), 109 (22.3). Found: C, 50.27; H,
2.94; N, 8.32; S, 19.23. C H NO S requires C, 50.30; H, 2.99;
7
5
2
3
5
commercial suppliers. Enol silyl ethers 9a -d and ketene silyl
N, 8.38; S, 19.16.
3
6
37,38
acetals 11a -d , R-substituted 1,3-indandiones (22a -e),
2-(2-Th iocya n a toa cetyl)th iop h en e (10c). Light brown
3
9
41
and (dichloroiodo)benzene were prepared according to the
literature methods. The structures of all new thiocyanato
derivatives were confirmed by their spectral data and elemen-
tal analyses, whereas the products known in the literature
were characterized by the comparison of melting points and
crystalline solid (235 mg, 64%), mp 89-91 °C (lit. mp 88 °C).
1
H NMR (CDCl , 300 MHz, δ): 4.56 (s, 2H, COCH SCN), 7.21
3
2
(dd, 1H, J ) 4.8, 3.9 Hz, 4-furyl proton), 7.77-7.80 (m, 2 H, 3-
and 5-thienyl protons). IR (ν ): 2160 (SCN str.), 1645 (CdO
max
str.) cm-1
.
1
spectral (IR and H NMR) data. The IR spectra of all of the
2
-(2-Th iocya n a toa cetyl)p yr id in e (10d ). Light brown oil
products showed a characteristic sharp SCN absorption band
(
230 mg, 65%) decomposed to dark colored mixture on stand-
ing. Unstability prevented obtaining an analytical sample of
this product. Spectral data were obtained on almost pure
-
1
at ˜2160 cm . A downfield shift of the R-proton with respect
1
to the substrate was observed in the H NMR spectra of the
products. This property was used for monitoring the progress
of the reaction and determining the yields of the products in
the cases of enolizable thiocayanato â-dicarbonyl compounds,
which were unstable. In most such cases, the reactions were
sample after removing iodobenzene through column chroma-
1
tography. H NMR (CDCl
3
2
, 300 MHz, δ): 5.12 (s, 2H, COCH -
SCN), 7.26-7.53 (m, 1H,pyridyl), 7.77-7.89 (m 1H, pyridyl),
.09-8.20 (m, 1H, pyridyl), 8.67 (dd, 1H, J ) 4.2, 1.8 Hz,
pyridyl). IR (νmax): 2165 (weak) (SCN str.), 1719 (CdO str.)
8
3
performed in dry CDCl , and the yields were determined on
1
the basis of H NMR data of the filtrate obtained after the
filtration of reaction mixture. Unless and until mentioned, the
thiocyanation reactions were carried out by using following
general procedure.
Gen er a l P r oced u r e for Th iocya n a tion . (Dichloroiodo)-
benzene (660 mg, 2.4 mmol) was added to a suspension of lead-
-1
cm
Met h yl 2-P h en yl-2-t h iocya n a t oet h a n oa t e (12a ). Oil
290 mg, 70%). 1H NMR (CDCl
, 300 MHz, δ): 3.81 (s, 3H,
CO CH ), 5.18 (s, 1H, CHSCNHz), 7.42 (s, 5H, aromatic
protons). IR (νmax): 2158 (SCN str.), 1734 (CdO str.) cm
Met h yl 2(4-Ch lor op h en yl)-2-t h iocya n a t oet h a n oa t e
(12b). Oil (275 mg, 57%). H NMR (CDCl , 300 MHz, δ): 3.80
(s, 3H, CO CH ), 5.15 (s, 1H, CHSCN) 7.35-7.42 (m, 4H,
.
42
(
3
2
3
-
1
.
(
II) thiocyanate (970 mg, 3 mmol) in dry dichloromethane (20
1
3
mL) at 0 °C under argon. The mixture was stirred at the same
temperature for 15-20 min, and then the enol silyl ether/
ketene silyl acetal/dicarbonyl compound (2 mmol) in dry
dicholoromethane (10 mL) was added. The reaction mixture
was allowed to stir at 0 °C till the completion of reaction (1 h
at 0 °C, then 10 min at room temperature for silyl enol ethers
and silyl ketene acetal; 2-4 h at 0 °C, then 10 min at room
temperature for the remaining cases). During the progress of
the reaction, the color of the suspended mixture turned to light
yellow. The solid was filtered, and the filtrate was evaporated
in vacuo to give a crude mixture of thiocyanato derivative and
iodobenzene.
Purification was carried out by column chromatography on
silica gel using ethyl acetate-hexanes as eluant (for all liquids
a -b, 10d , 12a -d , 14, 21b-d and some solids 10b-c) or
triturating with hexane, followed by recrystallization with
hexanes (for most of the solid products 16a -b, 16d , 19b-f).
The physical, spectral, and analytical data of the products are
given herein.
2
3
aromatic protons). IR (ν ): 2158 (SCN str.), 1739 (CdO str.)
max
cm-1. MS (m/z, CI): 241/243 (M
+
+ 1, 100/33), 214/216 (75),
198/200 (63). Found: C, 50.01; H, 3.34; N, 5.82; S, 12.33; Cl,
14.73. C H NO SCl requires C, 49.69; H, 3.31; N, 5.80; S,
1
0
8
2
13.25; Cl, 14.70. p-Chlorophenylacetic acid (10%), mp 106-
108 °C (lit.43 mp 105-108 °C), was also isolated as a side
product of the reaction.
Eth yl 2(4-Tolyl)-2-th iocya n a toeth a n oa te (12c). Oil (360
1
mg, 75%). H NMR (CDCl
3
, 300 MHz, δ): 1.27 (t, 3H, J ) 7.2
), 2.37 (s, 3H, 4-CH ), 4.27 (q, 2H, J ) 7.2
), 5.14 (s, 1H, CHSCN) 7.21 (d, 2H, J ) 8.1 Hz,
Hz, OCH
2
CH
CH
3
3 6 4
C H
Hz, OCH
2
3
aromatic protons), 7.31 (d, 2H, J ) 8.1 Hz, aromatic protons).
IR (νmax): 2157 (SCN str.), 1733 (CdO str.) cm . Found: C,
61.23; H, 5.49; N, 5.89; S, 13.58. C12
H, 5.53; N, 5.96; S, 13.62.
-
1
8
2
H13NO S requires C, 61.28;
Meth yl 2(4-An isyl)-2-th iocya n a toeth a n oa te (12d ). Oil
1
(400 mg, 85%). H NMR (CDCl , 300 MHz, δ): 3.81 (s,
3
CO CH ), 3.82 (s, 3H, 4-CH OC H ), 5.16 (s, 1H, CHSCN) 6.92
2
3
3
6
4
2
-Th iocya n a tocyclop en ta n on e (8a ). Pale yellow oil (180
(d, 2H, J ) 9.0 Hz, aromatic protons), 7.35 (d, 2H, J ) 9.0 Hz,
4
0 1
aromatic protons). IR (ν ): 2157 (SCN str.), 1734 (CdO str)
mg, 66%). H NMR (CDCl
3
, 300 MHz, δ): 1.86-2.44 (m, 5H),
max
-
1
2
.60-2.66 (m, 1H), 3.75 (t 1H J ) 8.7 Hz, COCHSCN). IR
cm . Found: C, 55.69; H, 4.56; N, 5.93; S, 13.71. C11
requires C, 55.70; H, 4.64; N, 5.91; S, 13.50.
3
H11NO S
max): 2156 (SCN str.), 1750 (CdO str.) cm-
1
(ν
.
5
-Th iocya n a to-2-(5H)-fu r a n on e (14). Oil (155 mg, 55%).
2
-Th iocya n a tocycloh exa n on e (8b). Pale yellow oil (210
1
4
0 1
H NMR (CDCl , 300 MHz, δ): 6.32 [dd, 1H, J ) 1.8, 1.5 Hz,
3
mg, 68%). H NMR (CDCl
3
, 300 MHz, δ): 1.68-1.79 (m, 2H),
C(5)-H], 6.56 [dd, 1H, J ) 5.4, 1.8 Hz, C(3)-H], 7.53 [dd, 1H, J
5.4, 1.8 Hz, C(4)-H]. IR (νmax): 2162 (SCN str.), 1796 (CdO
1
2
5
.90-2.04 (m, 2H), 2.11-2.21 (m, 1H), 2.38-2.49 (m, 1H),
)
.60-2.66 (m, 1H), 2.71-2.82 (m, 1H) 4.26 (dd, 1H J ) 6.3,
.4 Hz, COCHSCN). IR (νmax): 2155 (SCN str.), 1712 (CdO
-
1
5 3
str.) cm . Found: C, 42.78; H, 2.21; N, 9.87; S, 22.58. C H -
-
1
NO
2
S requires C, 42.55; H, 2.13; N, 9.91; S, 22.69.
str.) cm
.
3
-Th iocya n a top en ta n e-2,4-d ion e (16a ). Pale yellow crys-
2
2
talline needles (280 mg, 90%), mp 79-80 °C (lit. mp 78-81
C). H NMR (CDCl
(
35) House, H. O.; Czuba, L. J .; Gall, M.; Olmstead, D. J . Org. Chem.
969, 34, 2324.
36) Ainsworth, C.; Chen, F.; Kuo, Y. J . Organomet. Chem. 1972,
6, 59.
1
°
3
3
, 300 MHz, δ): 2.51 (s 6H, 2 x CH ), 17.08
1
(
4
(41) Singh, S. P.; Sehgal, S.; Dhawan, S. N. Indian J . Chem. 1987,
26B, 151.
(42) Gagnon, P. E.; Boivin, J . L.; Brown, J . L. Can. J . Chem. 1959,
37, 1597.
(43) Prakash, O.; Goyal, S.; Moriarty, R. M.; Khosrowshahi, J . S.
Indian J . Chem. 1990, 29B, 304. Aldrich Catalog of Fine Chemicals,
Aldrich: Milwaukee, 2000; catalog no. 13926-2.
(
(
37) Bailey, D. M.; J ohnson, R. E. J . Org. Chem. 1970, 35, 3574.
38) Crabb, T. A.; Roxburgh, C. J .; Newton, R. F. J . Chem. Soc.,
Perkin Trans. 1 1989, 2431.
39) Lucas, H.; Kennedy, E. R Organic Syntheses; Wiley: New York,
955; Collect. Vol. III, p 482.
40) Morrison, G. A. J . Chem. Res., Miniprint 1981, 2901.
(
1
(