8
they do not have functions for silicon atoms. We used the M062X functional of the M06 family, as this
functional shows an essentially lower dependence on the basis sets [29].
Mass spectra were recorded on a Shimadzu GCMS-QP5050A mass spectrometer, injector
temperature 200–250°С, helium carrier gas, detector temperature 290°С, quadrupole mass analyzer, EI
ionization (70 eV). Chromatographic separation of the studied compound samples was done on a SPB-
5 (60 m × 0.25 mm × 0.25 μm) capillary column, helium carrier gas, 0.7 ml/min flow, evaporator
temperature 230°С, 280 kPa pressure, gradient from 60 to 250°С at 10°С/min. Elemental analysis was
performed with a Thermo Scientific Flash 2000 CHNS-Analyzer. Gravimetric determination of silicon
content was carried out by the literature method [30]. Melting points were determined on a Boetius
heating bench.
4.2. Synthesis and characterization
4.2.1. Synthesis of 2-{[2-(trimethoxysilyl)ethyl]thio}-1,3-benzoxazole (1a).
Method 1. Trimethoxy(vinyl)silane (11.86 g, 0.08 mol) was added to 2-mercaptobenzoxazole 1
(10.58 g, 0.07 mol) under argon atmosphere. The reaction mixture was heated under reflux for 34 h. A
homogeneous reaction mass formed, and its temperature increased from 122 to 145 °С by the end of
the experiment. Fractional distillation under reduced pressure afforded the 14.67 g (70%) of compound
1a. The product obtained was a light yellow liquid, bp 164-167 °C (3 mmHg), nD20 1.4795.
Method 2. In an ampoule previously purged with dry argon, 2-mercaptobenzoxazole 1 (1.06 g,
0.007 mol) and trimethoxy(vinyl)silane (1.19 g, 0.008 mol) are placed. The cooled ampoule with the
reaction mixture was sealed in vacuo and placed in an oven (ES-4610). The reaction mixture was kept
at 200 °C for 1 h. Fractional distillation under reduced pressure afforded the 1.8 g (86%) of compound
20
1a, a light yellow liquid, bp 164–167 °C (3 mmHg), nD 1.4795. FTIR (ν, cm–1): 805, 1088, 1189
1
(Si(OMe)3), 748, 1011, 1126, 1281, 1499, 1597 (benzoxazole), 2841 (Si(OMe)3). Н NMR (CDCl3,
3
ppm): δ 1.25 (m, 2Н, CH2Si); 3.38 (m, 2Н, SCH2); 3.58 (s, 9H, OCH3); 7.15 (dd, 1H, H-5, J5-6 = 7.5
Hz, 3J5-4 = 7.6 Hz); 7.20 (dd, 1H, H-6, 3J6-5 = 7.4 Hz, 3J6-7= 7.8 Hz); 7.36 (d, 1Н, Н-7, 3J6-7 = 7.8 Hz);
3
7.54 (d, 1Н, Н-4, J4-5 = 7.6 Hz). 13C NMR (СDCl3, ppm): δ 10.38 (CH2Si); 26.95 (SCH2); 50.94
(OCH3); 109.40 (С-7); 117.97 (С-4); 123.36 (С-6); 123.81 (С-5); 141.73 (С-3а); 151.43 (С-7а);
29
15
164.57 (С-2). Si NMR (СDCl3, ppm): δ -46.1. N NMR (CDCl3, ppm): δ -146.0. MS m/z (Irel, %):
299 [M]+ (6), 271 [M–CH2CH2]+ (5), 266 [M−S–H]+ (6), 240 [M–SCH2CH2+H]+ (4), 239 [M–
SCH2CH2]+ (11), 238 [M–SCH2CH2–H]+ (18), 208 [M–SCH2CH2–OMe]+ (4), 151 [M–
CH2CH2Si(OMe)3+H]+ (51), 133 [M–SCH2Si(OMe)3+H]+ (6), 122 [M–C6H4NOCSCH2CH2+H]+ (18),
121 [Si(OMe)3]+ (100), 118 [M–SCH2CH2Si(OMe)3]+ (8), 107 [Si(OMe)3–Me+H]+ (6), 91 [Si(OMe)3–
OMe+H]+ (62), 90 [Si(OMe)3–OMe]+ (8), 75 [Si(OMe)3–OMe–Me]+ (6), 61 [Si(OMe)3–OMe–