1
The H and 13C NMR spectra were taken on a Bruker AM-300 spectrometer at 300 and 75 MHz,
respectively, in CDCl3. The solvent signals served as the internal chemical shift reference. We used a
commercial sample of thiirane 2a obtained from Aldrich, while thiirane 2b was prepared according to Schuets
[5] and thiirane 2c was prepared according to Stewart [6].
2,3-Dihydrothiazolo[3,2-a]benzimidazole (3a). A solution of 2-chlorobenzimidazole 1 (1.52 g,
10 mmol), NaOH (0.40 g, 10 mmol), and thiirane 2a (0.60 g, 10 mmol) in DMF (30 ml) was heated at 45-50°C
for 1 h and then at reflux for 1 h. The mixture was diluted with a 10-fold amount of water and extracted with
two 50 ml portions of ethyl acetate. Then, the ethyl acetate was evaporated off to give 0.73 g (41%) compound
1
3a, mp 98-99°C (hexane). H NMR spectrum, δ, ppm: 3.88-4.00 (2H, m, SCH2); 4.23-4.35 (2H, m, NCH2);
7.17-7.31 (3H, m, 3CH benzimidazole); 7.60-7.68 (1H, m, CH benzimidazole). Found, %: C 61.52; H 4.68;
N 15.64. C9H8N2S. Calculated, %: C 61.33; H 4.58; N 15.90.
2-(Methoxymethyl)-2,3-dihydrothiazolo[3,2-a]benzimidazole (3b). A solution of 2-chlorobenz-
imidazole 1 (1.52 g, 10 mmol), KOH (0.56 g, 10 mmol) and thiirane 2b (1.04 g, 10 mmol) in DMF (30 ml) was
heated at reflux for 1 h and then diluted with a five-fold amount of water. The mixture was extracted with two
50 ml portions of ether. Then, the ether was evaporated off to give 0.79 g (36%) compound 3b, mp 64-66°C
1
3
(ether). H NMR spectrum, δ, ppm (J, Hz): 3.41 (3H, s, OCH3); 3.64 (2H, d, J = 7.2, 2-CH2); 4.24 (2H, d,
3J = 5.8, NCH2); 4.46-4.56 (1H, m, SCH); 7.10-7.25 (3H, m, 3CH benzimidazole); 7.57-7.62 (1H, m,
CH benzimidazole). 13C NMR spectrum, δ, ppm: 45.96 (C-3); 50.68 (C-2); 59.19 (OCH3); 74.09 (2-CH2);
108.79 (C-5); 118.78 (C-8); 121.89 (C-6, C-7); 133.94 (C-4a); 149.28 (C-8a); 157.63 (C-9a). Found, %:
C 59.91; H 5.58; N 12.88. C11H12N2OS. Calculated, %: C 59.97; H 5.49; N 12.72.
2-(1-Piperidinylmethyl)-2,3-dihydrothiazolo[3,2-a]benzimidazole (3c) was obtained analogously to
compound 3b using thiirane 2c (1.57 g, 10 mmol). Water was added until a precipitate formed. The precipitate
was filtered off, washed with water, and dried to give 1.34 g (49%) compound 3c, mp 138-139°C (hexane).
1H NMR spectrum, δ, ppm (J, Hz): 1.38-1.50 (2H, m, CCH2); 1.52-1.62 (4H, m, 2CCH2); 2.35-2.50 (4H, m,
3
2
3
2
N(CH2)2); 2.65 (1H, dd, J = 7.7, J = 12.7, 2-CH2); 2.70 (1H, dd, J = 7.9, J = 12.7, 2-CH2); 4.08 (1H, dd,
3J = 6.3, 2J = 10.4, NCH2); 4.22 (1H, dd, 3J = 7.3, 2J = 10.4, NCH2); 4.50-4.60 (1H, m, SCH); 7.08-7.20 (3H, m,
3CH benzimidazole); 7.55-7.60 (1H, m, CH benzimidazole). 13C NMR spectrum, δ, ppm: 24.15 (CH2); 25.86
(2CH2); 47.12 (C-3); 50.61 (C-2); 54.78 (N(CH2)2); 62.69 (2-CH2); 108.72 (C-5); 118.49 (C-8); 121.64 (C-7);
121.88 (C-6); 133.80 (C-4a); 148.91 (C-8a); 158.21 (C-9a). Found, %: C 65.78; H 6.93; H 15.53. C15H19N3S.
Calculated, %: C 65.90; H 7.00; N 15.37.
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