PAPER
Novel Approach to C-Trimethylsilyl-1,3-azoles
1281
13C NMR (DMSO-d6): d = –0.98, 35.15, 123.70, 124.23, 139.72.
13C NMR (C6D6): d = –2.26, 123.46, 128.67, 129.45, 137.50,
165.23, 170.34.
Anal. Calcd for C7H15BrN2Si (235.20): C, 35.75; H, 6.43; N, 11.91.
Found: C, 35.44; H, 6.22; N, 11.81.
Anal. Calcd for C11H13ClN2OSi (252.78): C, 52.27; H, 5.18; N,
11.08. Found: C, 52.25; H, 5.30; N, 11.19.
C-Trimethylsilylazoles; General Procedure
Bromotrimethylsilane (61.2 g, 0.4 mol) was added to a solution of
appropriate 1,3-azole 3, 5, 6, 9 (0.2 mol) and Et3N (55.2 mL, 0.4
mol) in pyridine–toluene mixture (200 mL, 1:1). The reaction mix-
ture was left for 24 h at r.t. The precipitated triethylamine hydrobro-
mide was filtered off and washed with toluene. The combined
filtrate and the washings were evaporated in vacuo, hexane was
added to the residual oil and the mixture was allowed to stand for
24 h. Then, the hexane solution was filtered, the solvent was re-
moved and the residue was either distilled under reduced pressure
(compounds 4a–c, 7a, 8a, 10) or crystallized (compounds 7b and
7c) to give target silylazoles.
2-(4-Fluorophenyl)-5-trimethylsilyl-1,3,4-oxadiazole (7c)
Mp 92–94 °C.
1H NMR (C6D6): d = 0.27 (s, 9 H), 6.72 (tt, J = 1.8, 8.4 Hz, 2 H),
7.86 (m, 2 H).
13C NMR (C6D6): d = –2.26, 116.29 (JCF = 21.9 Hz), 121.28 (JCF
3.2 Hz), 129.61 (JCF = 8.5 Hz), 164.68 (JCF = 251.1 Hz), 165.07,
170.17.
=
19F NMR (C6D6): d = –108.016.
Anal. Calcd for C11H13FN2OSi (236.32): C, 55.91; H, 5.54; N,
11.85. Found: C, 56.10; H, 5.34; N, 12.03.
5-Phenyl-2-trimethylsilyloxazole (4a)5
Bp 123–125 °C/25 Torr.
1H NMR (C6D6): d = 0.31 (s, 9 H), 7.01 (t, J = 7.5 Hz, 1 H), 7.10 (t,
J = 7.5 Hz, 2 H), 7.36 (s, 1 H), 7.52 (t, J = 7.5 Hz, 2 H).
13C NMR (C6D6): d = –1.95, 123.14, 124.76, 128.33, 128.93,
129.00, 153.56, 169.98.
2-Phenyl-5-trimethylsilyl-1,3,4-thiadiazole (8a)
Bp 131–133 °C/0.4 Torr.
1H NMR (C6D6): d = 0.28 (s, 9 H), 7.01–7.09 (m, 3 H), 7.98–8.04
(m, 2 H).
13C NMR (C6D6): d = –0.85, 128.71, 129.35, 130.88, 130.91,
169.91, 170.74.
Anal. Calcd for C12H15NOSi (217.35): C, 66.32; H, 6.96; N, 6.44.
Found: C, 66.48; H, 6.73; N, 6.69.
Anal. Calcd for C11H14N2SSi (234.40): C, 56.37; H, 6.02; N, 11.95.
Found: C, 56.30; H, 6.14; N, 12.08.
2-[2-(Trimethylsilyl)-1,3-oxazol-5-yl]pyridine (4b)
Bp 152–153 °C/10 Torr; mp 51–53 °C.
1H NMR (C6D6): d = 0.31 (s, 9 H), 6.56 (ddd, J = 0.9, 4.8, 7.7 Hz, 1
H), 7.06 (td, J = 1.7, 7.7 Hz, 1 H), 7.41 (d, J = 8.0 Hz, 1 H), 8.08 (s,
1 H), 8.41 (d, J = 4.0 Hz, 1 H).
1-Methyl-5-trimethylsilyl-1,2,4-triazole (10)
Bp 82–84 °C/30 Torr.
1H NMR (C6D6): d = 0.17 (s, 9 H), 3.33 (s, 3 H), 8.09 (s, 1 H).
13C NMR (C6D6): d = –1.47, 36.77, 151.87, 157.86.
13C NMR (C6D6): d = –1.96, 119.22, 122.49, 126.71, 136.30,
148.59, 150.20, 153.89, 171.09.
Anal. Calcd for C6H13N3Si (155.28): C, 46.41; H, 8.44; N, 27.06.
Found: C, 46.54; H, 8.35; N, 27.25.
Anal. Calcd for C11H14N2OSi (218.33): C, 60.51; H, 6.46; N, 12.83.
Found: C, 66.69; H, 6.53; N, 12.92.
N-Phenyl-N¢-(trimethylsilyl)carbodiimide (13)17
Bromotrimethylsilane (6.93 g, 52.5 mmol) was added dropwise to a
stirred solution of 1-phenyltetrazole (11, 5.116 g, 35 mmol) and
Et3N (7.32 mL, 52.5 mmol) in pyridine (35 mL) at –20 °C. The re-
action mixture was maintained at this temperature until the nitrogen
evolution stopped and then was left for 24 h at r.t. After addition of
toluene (35 mL), the precipitated triethylamine hydrobromide was
filtered off. The solvents were removed, and the residue was dis-
tilled under reduced pressure to give the title product 13 (5.974 g,
90%) as a colorless liquid; bp 129 °C/35 Torr.
IR (film): 2970, 2170 cm–1.
1H NMR (C6D6): d = 0.02 (s, 9 H), 6.86 (tt, J = 1.4, 7.0 Hz, 1 H),
7.07–7.17 (m, 4 H).
2-Trimethylsilylbenzoxazole (4c)
Bp 97–98 °C/10 Torr; mp 32–34 °C.
1H NMR (C6D6): d = 0.30 (s, 9 H), 7.04 (m, 2 H), 7.34 (d, J = 8.0
Hz, 1 H), 7.79 (s, J = 7.0 Hz, 1 H).
13C NMR (C6D6): d = –2.20, 110.85, 120.85, 124.17, 125.41,
142.42, 152.24, 172.44.
Anal. Calcd for C10H13NOSi (191.31): C, 62.78; H, 6.85; N, 7.32.
Found: C, 62.86; H, 6.74; N, 7.38.
2-Phenyl-5-trimethylsilyl-1,3,4-oxadiazole (7a)
Bp 103–104 °C/0.12 Torr; mp 44–46 °C.
1H NMR (C6D6): d = 0.22 (s, 9 H), 7.02–7.03 (m, 3 H), 8.08–8.11
(m, 2 H).
13C NMR (C6D6): d = –2.28, 125.03, 127.36, 129.13, 131.38,
166.03, 170.15.
13C NMR (CDCl3): d = 0.84, 123.01, 123.16, 128.12, 129.27,
141.02.
Anal. Calcd for C10H14N2Si (190.32): C, 63.11; H, 7.41; N, 14.72.
Found: C, 63.28; H, 7.31; N, 14.88.
Anal. Calcd for C11H14N2OSi (218.33): C, 60.51; H, 6.46; N, 12.83.
Found: C, 60.72; H, 6.38; N, 12.59.
References
(1) Lopyrev, V. A.; Larina, L. I.; Voronkov, M. G. Zh. Org.
Khim. 2001, 37, 165; Russ. J. Org. Chem. (Engl. Transl.),
2001, 37, 149.
2-(4-Chlorophenyl)-5-trimethylsilyl-1,3,4-oxadiazole (7b)
Mp 47–48 °C.
1H NMR (C6D6): d = 0.21 (s, 9 H), 6.98 (d, J = 8.7 Hz, 2 H), 7.78
(d, J = 8.7 Hz, 2 H).
(2) Dondoni, A. Synthesis 1998, 1681.
(3) (a) Carpenter, A. J.; Chadwick, D. J. Tetrahedron 1986, 42,
2351. (b) Ngochindo, R. I. J. Chem. Soc., Perkin Trans. 1
1990, 1645.
Synthesis 2006, No. 8, 1279–1282 © Thieme Stuttgart · New York