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triethylamine was added dropwise. When the addition
was complete, the mixture was stirred for 2 h at
100 C, cooled to 5 C, and filtered. The filtrate was
distilled to isolate silylamine IIn or IIo (yield 92
93%) as the last fraction.
added to 1 mol of compound VIIIb or VIIIt, and the
mixture was kept for 3 days with occasional stirring.
The mixture was filtered, and excess chlorotrimethyl-
silane and HMDS were distilled off from the filtrate
under reduced pressure to obtain carbamate mixture
VIIIb/IXb (3:7) or VIIIt/IXt (1:3).
Phosgenation of silylamines (general procedure).
A solution of silylamine mixture IIa/IIIa IId/IIId
(calculated per mole of amine Ia Id) or 1 mol of
compound IIe IIo in 200 ml of toluene was added
dropwise to a solution of 109 g of COCl2 in 380 ml
of toluene under stirring at 0 C. When the addition
was complete, chlorotrimethylsilane and toluene were
distilled off up to a vapor temperature of 105 C.
Toluene and the resulting isocyanate were distilled
off from the residue under reduced pressure, and the
distillate was repeatedly distilled to remove toluene;
in the synthesis of isocyanates VIa VId, the distilla-
tion was performed using a rectification column. We
thus isolated mixture IVa/VIa (7:13), isocyanates
VIb VId and VIm VIo or inseparable mixtures
VIe/VIIe VIj/VIIj which contained 5 6% of cyana-
tes VIIe VIIh and VIIj or 35% of cyanate VIIi. By
heating mixture IVa/VIa for 4 h at 140 C we ob-
tained pure isocyanate VIa. Listed below are com-
pound no., n2D0: VIa, 1.4200; VIb, 1.4105; VIc,
1.4190; VId, 1.4180; VIe, 1.5260; VIf, 1.4328; VIg,
1.5224; VIh, 1.5052; VIj, 1.4300; VIk, 1.5222; VIl,
1.5270; VIm, 1.5350; VIn, 1.4470; VIo, 1.4552.
Pyrolysis of silyl carbamates in the presence of
trichloro(phenyl)silane (general procedure). Silyl
carbamate VIIIn VIIIs, 1 mol, or carbamate mixture
VIIIb/IXb (3:7), VIIIt/IXt (1:3), or VIIIu/IXu
VIIIw/IXw (1:1) equivalent to 1 mol of initial amine
was added dropwise to 1 mol of trichloro(phenyl)-
silane. An additional 1 mol of trichloro(phenyl)silane
was added to the mixture, and it was gradually heated
under stirring to 200 C with simultaneous removal of
volatile substances by distillation into a receiver
cooled to 5 C. The distillate was subjected to re-
ctification until 96 99% purity (according to the GLC
1
and H NMR data) of the isolated product. Yield of
isocyanates VIn VIs 50 65%, of VIb, 60%, of VIt,
52%, and of VIu VIw, 50%. Compound VIv was
isolated as a mixture with chlorotrimethylsilane. To
remove the latter, mixture Me3SiCl/VIv was diluted
with a double volume of toluene and cooled to 2 C,
and an equimolar mixture of 1-butanol and triethyl-
amine (equivalent to the chlorotrimethylsilane) in an
equal volume of toluene, cooled to 0 C, was added
dropwise. The mixture was stirred for 1 h and filtered,
and the filtrate was distilled through a rectification
column to isolate 48% of isocyanate VIv with a purity
higher than 96%. Below are listed compound no., n2D0:
VIp, 1.3820; VIq, 1.3940; VIr, 1.4000; VIs, 1.4110;
VIt), 1.4170; VIv, 1.3803; VIw, 1.4492.
N-Siloxycarbonylation of free amines (general
procedure). A mixture of 2 mol of amine Ib or In It
and 200 g of HMDS was heated to 40 C, and dry
carbon dioxide was bubbled through the solution over
a period of 3 h, maintaining the temperature (the reac-
tion was accompanied by heat evolution) at 55 60 (Ib,
Ip It), 63 65 (In), or 70 80 C (Io) to avoid clogging
of the bubbler. The mixture was cooled, and excess
HMDS was distilled off at 50 C (5 mm) to leave
carbamate VIIIb or VIIIn VIIIt containing 96 98%
of the main substance.
Pyrolysis of carbamate VIIIt. Compound VIIIt,
0.2 mol, was heated for 3 h at 150 160 C. GLC
analysis showed formation and accumulation of car-
bamate IXt in the temperature range from 120 to
150 C. The mixture was cooled, 30 ml of hexane was
added, and the precipitate was filtered off and washed
with hexane to isolate 7.7 g (55%) of N,N -diallylurea
(X).
N-Siloxycarbonylation of ammonium salts
(general procedure). A suspension of 2 mol of com-
pound XIIb or XIIu XIIw and 200 g of HMDS in
200 ml of anhydrous toluene was kept for 3 h at
80 90 C while bubbling carbon dioxide through the
mixture. The mixture was cooled and filtered, and
excess HMDS and the solvent were distilled from the
filtrate to isolate carbamate mixture VIIIb/IXb or
VIIIu/IXu VIIIw/IXw at a ratio of 1:1. Yield 88
90%, calculated on the initial amine hydrochloride.
N,N -Bis(cyclopropylmethyl)urea (XI). N-Methyl-
N-nitrosourea, 16.48 g, was added to a mixture of
60 ml of 40% aqueous potassium hydroxide and
300 ml of diethyl ether. The ether layer solution was
separated by decanting, dried for 2 h over solid KON,
and mixed with 30 ml of methanol, the mixture was
added to 5.6 g of urea X, and the resulting mixture
was stirred. When gaseous products no longer evolved
( 1 h), 10 ml of acetic acid was added, the solvent
was distilled off, and the residue was recrystallized
from ethanol. Yield 5.7 g (85%).
N-Silylation of silylcarbamates VIIIb and VIIIt.
Chlorotrimethylsilane, 163 g, and HMDS, 80 g, were
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 3 2006