consumed (TLC). Then pyridine was added (0.17 ml, 2 mmol)
and the mixture stirred for a further 1 h, filtered and the crude
product purified by column chromatography (light petroleum–
dichloromethane, 8:2) to give the title compound (0.187 g,
74%) as yellow needles, mp 152 ЊC (from light petroleum);
νmax(KBr)/cmϪ1 3086, 2229 (CN), 1570, 1494, 1411, 1237, 1014
(300 W). The initial temperature (infra-red measurement)
was constant over a period of 15 to 30 s followed by a sharp
increase over a period of 1 min. The irradiation was stopped
2 min later. After cooling, the brown reaction mixture was
purifed by column chromatography as above.
The following isothiocyanates were prepared by the method
indicated.
and 873; δH(400 MHz, CDCl3) 7.28 (2H, d, J 8.50 Hz, Harom
)
and 7.76 (2H, d, J 8.60 Hz, Harom); m/z 253 (Mϩ, 3%), 192
(Mϩ Ϫ ClCN, 15), 160 (Mϩ Ϫ ClCNS, 51).
Phenyl isothiocyanate. A colourless oil (54%, method A);
᎐ ᎐
νmax(KBr)/cmϪ1 2973, 2924, 2062 (N᎐C᎐S), 1591, 1488, 1451,
1252, 927 and 750; δH(400 MHz, CDCl3) 7.23 (2H, d, J 8.39 Hz,
Harom), 7.29 (2H, d, J 7.59 Hz, Harom) and 7.36 (1H, t, J 8.40 Hz,
Harom); δC(100 MHz, CDCl3) 125.73, 127.29, 129.53, 131.21 and
136.12.
N-Arylcyanothioformanilides 6
N-(Cyanothioformyl)-4,5-dimethoxyanthranilonitrile 6g4b and
N-(4-methoxyphenyl)cyanothioformamide 6d6 were prepared
following procedures previously described.
2-Fluorophenyl isothiocyanate. A colourless oil (50%, method
᎐ ᎐
N-(Cyanothioformyl)-2,3-dihydro-1,4-benzodioxin-6-amine
6h. Stirring of the imine 2h (0.286 g, 1 mmol) with triphenyl-
phosphine (0.536 g, 2 mmol) in dichloromethane (10 ml) at
room temperature for 1 h, followed by column chromatography
(light petroleum–dichloromethane), gave the title compound
(0.176 g, 80%) as red needles, mp 118 ЊC (from ethanol) (Found:
C, 54.37; H, 3.29; N, 12.48. C10H8N2O2S requires C, 54.58; H,
3.66; N, 12.73%); νmax(KBr)/cmϪ1 3258, 3088, 2229 (CN), 1726,
1604, 1503, 1401, 1297, 1065, 845 and 754; δH(400 MHz,
CDCl3) 4.29 (4H, m, OCH2CH2O), 6.89 (1H, d, J 9.00 Hz,
Harom), 7.18 (1H, dd, J 3.00 and 9.00 Hz, Harom) and 7.52 (1H, d,
J 3.00 Hz, Harom); δC(100 MHz, CDCl3); m/z 220 (Mϩ, 23%), 193
(Mϩ Ϫ HCN, 100), 137 (Mϩ ϩ 2 Ϫ C2HN2S, 60) and 109
(Mϩ ϩ 2 Ϫ C2HN2S Ϫ C2H4, 37).
A); νmax(KBr)/cmϪ1 2923, 2851, 2033 (N᎐C᎐S), 1607, 1598,
1496, 1458, 1265, 1212, 942 and 809; δH(400 MHz, CDCl3)
7.08–7.25 (4H, m, Harom).
2-Cyanophenyl isothiocyanate. Colourless needles (55%,
method A) (76%, method C) (55%, method D), mp 64 ЊC (from
light petroleum) (Found: C, 60.28; H, 2.72; N, 17.32. C8H4N2S
requires C, 60.05; H, 2.52; N, 17.51%); νmax(KBr)/cmϪ1 2229
(CN), 2111 (N᎐C᎐S), 1651, 1588, 1483, 1445, 1283, 955 and
᎐ ᎐
761; δH(400 MHz, CDCl3) 7.35 (1H, td, J 1.50 and 7.78 Hz,
Harom), 7.36 (1H, dd, J 1.50 and 7.99 Hz, Harom), 7.60 (1H, td,
J 1.50 and 8.05 Hz, Harom), 7.64 (1H, dd, J 1.50 and 7.99 Hz,
Harom); δC(100 MHz, CDCl3) 109.68, 115.48, 115.82, 127.65,
133.45, 133.95, 134.80 (NCS) and 141.08; m/z 160 (Mϩ, 100%),
133 (Mϩ Ϫ HCN, 2) and 102 (Mϩ Ϫ N᎐C᎐S, 40).
᎐ ᎐
4-Methoxyphenyl isothiocyanate. A colourless oil (44%,
method A) (93%, method B) (75%, method C) (57%, method
D) (57%, method E); νmax(KBr)/cmϪ1 2923, 2846, 2108
Aryl isothiocyanates: typical procedures from N-arylimino-4-
chloro-5H-1,2,3-dithiazoles 2 and cyanothioformanilides 6
Method A. Under an argon atmosphere, a solution of ethyl-
magnesium bromide (2 mmol, 1 in THF) was added dropwise
to a solution of the imino-1,2,3-dithiazole 2 (1 mmol) in boiling
THF (5 ml). The brown mixture obtained was heated for about
1 h, the reaction being followed by TLC. After addition of
dichloromethane (20 ml) the solution was washed with water,
the organic layer was dried over sodium sulfate and the solvent
evaporated. The crude product was then purified by column
chromatography with light petroleum–dichloromethane as the
eluent.
Method B. Under an argon atmosphere, a solution of ethyl-
magnesium bromide (1 mmol, 1 in THF) was added dropwise
to a solution of the cyanothioformanilide 6 (1 mmol) in boiling
THF (15 ml). The brown mixture obtained was heated for
about 30 min, the reaction being followed by TLC. After
addition of dichloromethane (20 ml) the solution was washed
with water, the organic layer dried over sodium sulfate and the
solvent evaporated. The crude product was then purified by
column chromatography as above.
Method C. A solution of the iminodithiazole 2 (1 mmol) and
triphenylphosphine (2 mmol) in undried dichloromethane (10
ml) was stirred at room temperature. The reaction was followed
by TLC and when complete the solvent was evaporated, the
residue was dried in a stream of argon for 10 min, and dissolved
in THF (5 ml). This solution was warmed to 50 ЊC and ethyl-
magnesium bromide (1 mmol, 1 in THF) was added drop-
wise. The mixture was heated for 30 min and the product was
isolated and purified as above.
Method D. A solution of the iminodithiazole 2 (0.7 mmol) in
dry THF (5 ml) was stirred at 67 ЊC for 18 h in the presence of
sodium hydride (60% dispersion in mineral oil, 1.54 mmol). The
reaction mixture was filtered and the solvent evaporated from
the filtrate. The residue was dissolved in ethyl acetate, washed
with water, dried over sodium sulfate and purified by column
chromatography as above.
(N᎐C᎐S), 1603, 1504, 1463, 1296, 1250, 1166, 929, 828 and 738;
᎐ ᎐
δH(400 MHz, CDCl3) 3.81 (3H, s, OMe), 6.85 (2H, dd, J 1.99
and 9.19 Hz, Harom), 7.17 (2H, dd, J 1.99 and 9.19 Hz, Harom);
δC(100 MHz, CDCl3) 55.53, 114.77, 123.56, 126.94, 133.86
(NCS) and 158.55.
4-Cyanophenyl isothiocyanate. Colourless needles (60%,
method A), mp 123 ЊC (from light petroleum); νmax(KBr)/cmϪ1
2226 (CN), 2140 (N᎐C᎐S), 1600, 1505, 1494, 1174, 934 and 836;
᎐ ᎐
δH(400 MHz, CDCl3) 7.31 (2H, d, J 8.80 Hz, Harom) and 7.66
(2H, d, J 8.80 Hz, Harom); δC(100 MHz, CDCl3) 110.62, 117.89,
126.48, 133.62, 136.06, and 139.63.
3,4-Dimethoxyphenyl isothiocyanate. A colourless oil (50%,
᎐ ᎐
method A); νmax(KBr)/cmϪ1 3003, 2958, 2934, 2128 (N᎐C᎐S),
1657, 1589, 1509, 1438, 1168, 1025 and 839; δH(400 MHz,
CDCl3) 3.87 (3H, s, OMe), 3.88 (3H, s, OMe) 6.74 (1H, d, J 2.40
Hz, Harom), 6.79 (1H, s, Harom) and 6.81 (1H, d, J 2.40 Hz, Harom);
δC(100 MHz, CDCl3) 55.89, 56.58, 111.23, 112.49, 113.48,
121.13, 140.27 (NCS), 150.50 and 153.44.
2-Cyano-4,5-dimethoxyphenyl isothiocyanate. Colourless
needles (46%, method A) (75%, method B) (54%, method C)
(32%, method D), mp 134 ЊC (from hexane) (Found: C, 55.10;
H, 3.88; N, 12.52. C10H8N2O2S requires C, 54.58; H, 3.66; N,
12.73%); νmax(KBr)/cmϪ1 2932, 2225 (CN), 2057 (N᎐C᎐S),
᎐ ᎐
1731, 1660, 1651, 1593, 1520, 1505, 1282, 1002 and 874; δH(400
MHz, CDCl3) 3.90 (3H, s, OMe), 3.93 (3H, s, OMe), 6.76 (1H,
s, Harom) and 6.96 (1H, s, Harom); δC(100 MHz, CDCl3) 56.46
(CH3O), 56.50 (CH3O), 101.04, 107.78, 109.44, 113.58, 115.87,
137.36 (NCS), 148.12 and 153.40; m/z 220 (Mϩ, 100%), 205
(Mϩ Ϫ CH , 47) and 162 (Mϩ Ϫ N᎐C᎐S, 15).
᎐ ᎐
3
2,3-Dihydro-1,4-benzodioxane 6-isothiocyanate. Colourless
needles (47%, method A) (92%, method B) (73%, method C)
(54%, method D) (54%, method E), mp 74 ЊC (from hexane)
(Found: C, 55.83; H, 3.51; N, 7.03. C9H7NO2S requires C,
56.00; H, 3.65; N, 7.26%); νmax(KBr)/cmϪ1 2978, 2163, 2135
(N᎐C᎐S), 1636, 1538, 1499, 1313, 1304, 1290, 1064 and 890;
᎐ ᎐
Method E. The cyanothioformanilide 6 (1 mmol) in 2,6-
lutidine (1 ml) was placed in the microwave oven in a glass vial
(10 ml) with a screw-cap lid. The irradiation was programmed
for 4 min with a delay of 5 s to obtain 100% power output
δH(400 MHz, CDCl3) 4.26 (4H, s, OCH2CH2O), 6.74 (1H, dd,
J 2.40 and 8.50 Hz, Harom), 6.76 (1H, d, J 2.40 Hz, Harom) and
6.81 (1H, d,
J 8.30 Hz, Harom); δC(100 MHz, CDCl3)
64.29, 64.31, 114.69, 117.94, 119.19, 123.00, 134.04 (NCS),
J. Chem. Soc., Perkin Trans. 1, 1998
891