8
M. G. RASMUSSEN ET AL.
to the colorless reaction mixture over 5 min. The reaction mixture was heated to 50°C
and stirred for 24 h, cooled to RT, diluted by addition of H2O (20 mL) and extracted with
CH2Cl2 (75 mL). The organic phase was washed with H2O (3 × 50 mL), dried over MgSO4,
filtered and concentrated in vacuo. The crude product was recrystallized in a 1:2 boiling
solution of CH2Cl2/petroleum ether, which yielded the title compound 2 (3.17 g, 77%)
as bright yellow crystals. Rf (70% CH2Cl2/heptanes) = 0.69. M.p.: 128°C (Lit. [19]: 128°C
from EtOH). 13C NMR (126 MHz, CDCl3): δ = 148.28, 117.93 ppm. IR (ATR, neat): 1530,
1488, 1337, 1311, 1290, 1113, 907, 872, 834, 746, 615, 478 cm−1. The title compound was
not observed using the following methods: GC-MS, MALDI+ or ESI+.
2-Nitro-3,4-dibromothiophene (4)
A flask was charged with a solution of 3,4-dibromothiophene (3.00 g, 12.4 mmol) and
HNO3 (5 mL, 68%) in CHCl3 (10 mL). H2SO4 (5 mL, 95%) was added dropwise to the
colorless reaction mixture over 5 min. The reaction mixture was heated to 50°C and
stirred for 24 h, cooled to RT, diluted by addition of H2O (30 mL) and extracted with 1:4
CH2Cl2/petroleum ether (100 mL). The organic phase was washed with H2O (3 × 30 mL),
dried over MgSO4, filtered and concentrated in vacuo. The crude product was recrystal-
lized in a 3:1 boiling solution of CH2Cl2/petroleum ether, which yielded the title compound
4 (3.39 g, 95%) as yellow crystals. Rf (70% CH2Cl2/heptanes) = 0.66. M.p.: 110–112°C (Lit.
1
[19]: 115–116°C from EtOH). H NMR (500 MHz, CDCl3): δ = 7.62 (s, 1H) ppm. 13C
NMR (126 MHz, CDCl3): δ = 127.87, 117.93, 116.93, 116.82 ppm. IR (ATR, neat): 3094,
1529, 1489, 1386, 1311, 1291, 1113, 907, 833, 754, 746, 726 cm−1. The title compound was
not observed using the following methods: GC-MS, MALDI+ or ESI+.
2-Nitro-3,4-dicyanothiophene (5)
Method A: A flame-dried flask was charged with a mixture of 4 (10.0 g, 34.9 mmol),
CuCN (12.4 g, 139 mmol) in anhydrous DMF (100 mL), heated to 120°C and stirred for
22 h. The reaction mixture was cooled to RT and filtered through a short silica plug
(SiO2, 15–40 μm) eluted with CH2Cl2 (combined fractions 800 mL). The filtrate was
washed with sat. aqueous Na2S2O3 (500 mL), sat. aq. NaHCO3 (1000 mL) and water
(1500 mL), dried over MgSO4, filtered and concentrated in vacuo. The crude residue was
dissolved in CH2Cl2 and purified by dry column vacuum chromatography (SiO2, 0–80%
CH2Cl2/heptanes, 15% increment, 150 ml fractions), followed by flash column chromatog-
raphy (SiO2, 8% EtOAc/toluene) in addition to gravity column chromatography (SiO2, 80%
CH2Cl2/heptane) which afforded the title compound 5 (640 mg, 10%) as an off-white solid.
1
Rf (80% CH2Cl2/heptanes) = 0.22. M.p.: 195°C. H NMR (500 MHz, CDCl3): δ = 8.17
(s, 1H) ppm. 13C NMR (126 MHz, CDCl3): δ = 156.65, 138.62, 114.68, 111.79, 110.27,
108.64 ppm. IR (ATR, neat): 3113, 2246, 1546, 1519, 1451, 1339, 1174, 1060, 913, 871, 821,
780, 744, 536, 481, 452, 429, 409 cm−1. The title compound was not observed using the
following methods: GC-MS, MALDI+ or ESI+. Anal. Calcd (%) for C6HN3O2S: C, 40.23;
H, 0.56; N, 23.46; S,17.90. Found: C, 40.28; H, 0.69; N, 22.55; S, 17.76.
Method B: A flask was charged with a solution of 6 (200 mg, 1.49 mmol) and HNO3
(5 mL, 68%) in CHCl3 (10 mL). H2SO4 (5 mL, 95%) was added dropwise to the color-
less reaction mixture over 5 min. The reaction mixture was heated to 50°C and stirred
for 17 h, cooled to RT, diluted by addition of H2O (30 mL) and extracted with CH2Cl2