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LEBEDEV et al.
gene in 80 ml of toluene, a solution of 0.2 mol of
silylamine VIIa or VIIb in 40 ml of toluene was
added dropwise with stirring at 0 C. After the addi-
tion was complete, the trimethylchlorosilane and to-
luene were distilled off until the vapor temperature
reached 105 C. The residue was distilled in a vacuum
to obtain the target products VIIIa and VIIIb.
OCH3); 4.08 q, 4.23 q (12:88, 1H, CH); 4.92 d,
5.17 d (13:87, 1H, NH). Mass spectrum (m/z): 247
([M]+ ). C10H21NO4Si. Calculated, %: molecular mass
247.36.
Ethyl 2-(trimethylsiloxycarbonylamino)-3-
1
methylbutanoate IXc. H NMR spectrum (CDCl3),
, ppm: 0.27 s, 0.29 s (88:12, 9H, SiMe3); 0.88 d,
0.95 d, 0.90 d, 0.97 d (88:12, 6H, 2CH3); 1.27 t (3H,
CH3); 2.04 m, 2.14 m (12:88, 1H, CH); 4.08 m,
4.22 m (12:88, 3H, CH + OCH2); 4.94 d, 5.18 d
(13:87, 1H, NH). Mass spectrum (m/z): 261 ([M]+ ).
C11H25NO4Si. Calculated, %: molecular mass 261.39.
Ethyl 3-isocyanato-4-methylpentanoate VIIIa.
Yield 58%, bp 76 C (1.5 mm Hg), n2D0 1.4339. H
1
NMR spectrum (CDCl3), , ppm: 0.97 q (6H, 2CH3),
1.27 t (3H, CH3), 1.77 m (1H, CH), 2.48 d (2H, CH2),
3.83 q (1H, CH), 4.17 q (2H, OCH2). Mass spectrum
(m/z): 185 ([M]+ ). C9H15NO3. Calculated: molecular
mass 185.22.
Ethyl 3-(trimethylsiloxycarbonylamino)-4-
1
methylpentanoate XIIa. H NMR spectrum (CDCl3),
, ppm: 0.25 s, 0.27 s (85:15, 9H, SiMe3); 0.91 s
(6H, 2CH3); 1.25 t (3H, CH3); 1.73 1.86 m (1H, CH);
2.39 2.55 m (2H, CH2); 3.74 m (1H, CH); 4.12 q
(2H, OCH2); 4.66 d, 5.05 d (15:85, 1H, NH). Mass
spectrum (m/z): 275 ([M]+ ). C12H25NO4Si. Calculated:
molecular mass 275.41.
3-Isocyanato-4-methylpentanoyl chloride VIIIb.
Yield 41%, bp 74 C (1.5 mm Hg), n2D0 1.4510. H
1
NMR spectrum (CDCl3), , ppm: 1.01 q (6H, 2CH3),
1.83 m (1H, CH), 3.07 d (2H, CH2), 3.93 q (1H, CH).
Mass spectrum (m/z): 175 ([M]+ ). C7H10ClNO2.
Calculated: molecular mass 175.61.
Ethyl 3-phenyl-3-(trimethylsiloxycarbonyl-
amino)propanoate XIIb. 1H NMR spectrum (CDCl3),
, ppm: 0.25 s, 0.27 s (86:14, 9H, SiMe3); 1.17 t
(3H, CH3); 2.70 2.90 m (2H, CH2); 4.07 q (2H,
OCH2); 4.98 q, 5.10 q (14:86, 1H, CH); 5.37 d,
5.67 d (14:86, 1H, NH); 7.20 7.32 m (5Harom). Mass
spectrum (m/z): 309 ([M]+ ). C15H23NO4Si. Calculated:
molecular mass 309.43.
Esterification of the acid chloride. To a solution
of 17.5 g of acid chloride VIIIb in 20 ml of dry to-
luene, 10.1 g of triethylamine was added at 0 2 C.
After that, 4.6 g of absolute ethanol was added drop-
wise. The reaction mixture was left until its tempera-
ture reached 20 C. After that, the precipitate of tri-
ethylamine hydrochloride was filtered off, and the
filtrate was distilled in a vacuum to obtain 17 g of
isocyanate VIIIa. Yield 92%.
Phosgene treatment of silylurethanes derived
from amino esters. To a solution of 0.22 mol of
phosgene in 80 ml of toluene, a solution of 0.2 mol of
urethane IXa IXc, XIIa, or XIIb in 50 ml of toluene
was added dropwise with stirring at 0 C. After the
addition was complete, the reaction mixture was
slowly heated to 50 C and kept at this temperature
until the CO2 liberation ceased. After that, the tri-
methylchlorosilane and toluene were distilled off at
50 mm Hg. Vacuum distillation of the residue (2
3 mm Hg) gave the target products XIa XIc, VIIIa,
and VIIIc in yields of 84, 81, 80, 85, and 82%,
respectively.
N-Siloxycarbonylation of the amino ester hyd-
rochlorides. A mixture of 1 mol of compound IIIa
IIIc, VIa, or VIb, 0.62 mol of hexamethyldisilazane,
and 300 ml of toluene was heated with stirring in a
CO2 flow for 5 h at 90 95 C. After completion of the
gas bubbling, the reaction mixture was cooled, and the
precipitate was filtered off. After the distillation of
excess hexamethyldisilazane and the solvent, ure-
thanes IXa IXc, XIIa, and XIIb were obtained in
99 100% yield based on the starting amino ester
hydrochloride.
Methyl
2-phenyl-2-(trimethylsiloxycarbonyl-
Methyl 2-phenyl-2-isocyanatoethanoate XIa:
bp 90 93 C (1.5 mm Hg). 1H NMR spectrum
(CDCl3), , ppm: 3.76 s (3H, OCH3), 5.07 s (1H,
CH), 7.39 m (5Harom). Mass spectrum (m/z): 191
([M]+ ). C10H9NO3. Calculated: molecular mass
191.18.
1
amino)ethanoate. H NMR spectrum, , ppm: 0.26
s, 0.28 s (83:17, 9H, SiMe3); 3.70 s, 3.72 s (16:84,
3H, OCH3); 5.17 d, 5.32 d (17:83, 1H, CH); 5.55 d,
5.70 d (17:83, 1H, NH); 7.35 m (5Harom). Mass
spectrum (m/z): 281 ([M]+ ). C13H19NO4Si. Calculated:
molecular mass 281.38.
Methyl 2-isocyanato-3-methylbutanoate XIb:
1
Methyl 2-(trimethylsiloxycarbonylamino)-3-
methylbutanoate IXb. H NMR spectrum (CDCl3),
, ppm: 0.27 s, 0.29 s (88:12, 9H, SiMe3); 0.88 d,
0.95 d, 0.90 d, 0.97 d (88:12, 6H, 2CH3); 2.04 m,
2.14 m (12:88, 1H, CH); 3.71 s, 3.73 s (12:88, 3H,
bp 61 62 C (2 mm Hg). H NMR spectrum (CDCl3),
1
, ppm: 0.86 d (3H, CH3), 0.99 d (3H, CH3), 1.27 t
(3H, CH3), 2.20 m (1H, CH), 3.87 d (1H, CH), 4.23
m (2H, OCH2). Mass spectrum (m/z): 171 ([M]+ ).
C8H13NO3. Calculated: molecular mass 171.19.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 4 2007