DEMINA et al.
1808
equilibrium monomer–dimer shifts toward the mono-
meric form on raising the temperature or increasing the
solvent polarity. The observed inconsistency may be
rationalized by formation in solutions of compounds
IV and V of a relatively strong intramolecular hydro-
gen bond C=O···H–N which is destroyed on heating
and in going to more polar solvents.
atoms; the final divergence factors were R = 0.0506,
wR = 0.060. The calculations were performed using
SHELXTL software package [16].
Reaction of 3-trimethylsilyl-2-propynal (I) with
trimethylsilyl azide (III). a. A solution of 2.52 g
(20 mmol) of 3-trimethylsilyl-2-propynal (I) and 2.3 g
(20 mmol) of trimethylsilyl azide (III) in 40 ml of
anhydrous toluene was heated for 16 h at 90–95°C
under stirring. The colorless crystals were filtered off,
washed with hexane, and dried under reduced pressure.
Yield of 4-trimethylsilyl-1H-1,2,3-triazole-5-carbal-
dehyde (IV) 0.85 g (25%), mp 189°C. IR spectrum
(KBr), ν, cm–1: 3100 (NH), 1697 (C=O), 1251
[(CH3)3Si]. 1H NMR spectrum (CDCl3-), δ, ppm: 0.40 s
[9H, (CH3)3Si], 10.26 s (1H, CHO). 13C NMR spec-
trum (CDCl3), δC, ppm: –2.20 [(CH3)3Si], 140.13 (C4),
152.42 (C5), 186.52 (C=O). 29Si NMR spectrum
(CDCl3): δSi: –6.5 ppm [(CH3)3Si]. Found, %: C 42.58;
H 6.76; N 24.71; Si 16.55. C6H11N3OSi. Calculated,
%: C 42.58; H 6.55; N 24.81; Si 16.60. The filtrate was
heated for an additional 16 h, the solvent was removed
under reduced pressure, 7 ml of methanol was added to
the residue, and the mixture was heated for 1 h under
reflux. Removal of the solvent left a viscous residue
which crystallized on storage. We thus isolated an ad-
ditional portion of triazole IV, 1.7 g; overall yield 75%.
Thus, unlike most formylazoles in which the alde-
hyde group is contiguous to the NH moiety, 1,2,3-tri-
azole-5-carbaldehydes obtained by 1,3-dipolar cyclo-
addition of trimethylsilyl azide to 3-trimethylsilyl-2-
propynal and 2-propynal exist mainly in the mono-
1
meric form. According to the IR and H NMR data,
increase in the solvent polarity and temperature, as
well as trimethylsilylation, favors dimerization of
1,2,3-triazole-5-carbaldehydes to the corresponding tri-
cyclic bis-hemiaminals.
EXPERIMENTAL
The IR spectra were recorded on a Specord 75IR
instrument from samples prepared as KBr pellets, dis-
persed in mineral oil, and dissolved in CCl4, CHCl3,
1
C2H2Cl4, CH3CN, and octane. The H, 13C, and 29Si
NMR spectra were obtained on a Bruker DPX-400
spectrometer using hexamethyldisiloxane as internal
reference. The progress of reactions was monitored
by TLC on Silufol UV-254 plates using chloroform–
methanol (3:1) as eluent. 2-Propynal (II) [12], 3-tri-
methylsilyl-2-propynol [13], 3-trimethylsiloxypropyne
[14], and 3-trimethylsilyl-2-propynal [15] were syn-
thesized by known methods.
b. A mixture of 3.0 g (24 mmol) of aldehyde I and
2.76 g (24 mmol) of trimethylsilyl azide (III) was kept
for 14 days at room temperature. Mixing of the re-
actants was accompanied by spontaneous heating to
70°C. The mixture was evacuated, 10 ml of methanol
was added to the residue, and the mixture was heated
at the boiling point over a period of 1 h. We isolated
2.47 g (62%) of 4-trimethylsilyl-1H-1,2,3-triazole-5-
carbaldehyde (IV) with mp 188–189°C.
X-Ray analysis of compound IV. Colorless single
crystals of 4-trimethylsilyl-1H-1,2,3-triazole-5-carbal-
dehyde (IV) were preliminarily examined by the photo
method using RKOP, KFOR, and RRECESSION
cameras. The unit cell parameters and space group
were thus determined and were refined on a Syntex
P21 four-circle automatic diffractometer (MoKα radia-
tion, graphite monochromator, ω-scanning).
Reaction of 2-propynal (II) with trimethylsilyl
azide (III). A solution of 1.2 g (22 mmol) of 2-pro-
pynal in tetrahydrofuran was cooled to –30°C, and
2.3 g (20 mmol) of trimethylsilylazide (III) was added.
The mixture was kept for 7 days at room temperature,
the solvent was removed under reduced pressure, 5 ml
of methanol was added to the residue, and the mixture
was heated at the boiling point over a period of 1 h.
The red–brown viscous residue was dissolved in ben-
zene, and the product was precipitated with hexane.
Yield of 1H-1,2,3-triazole-4(5)-carbaldehyde (V)
1.44 g (74%); brown crystals, mp 137–138°C. IR spec-
trum (thin layer), ν, cm–1: 3100 (NH), 1700 (C=O).
1H NMR spectrum (CD3CN), δ, ppm: 8.26 s (1H,
4-H or 5-H), 10.07 s (1H, CHO), 13.4 s (1H, NH).
Single crystals of compound IV were grown from
a solution in toluene; they are stable on exposure to
air. Crystal system monoclinic, space group P21/c; unit
cell parameters: a = 11.655(4), b = 8.960(3), c =
9.503(3) Å; β = 109.90(1)°; V = 933 Å3; Z = 4; dcalc
=
1.718(2) g/cm3. Intensities of 1198 reflections with
I > 2σ(I) were measured. The structure was solved by
the direct least-squares procedure in the full-matrix
anisotropic approximation for the Si, O, C, and N
atoms and isotropic approximation for hydrogen
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 12 2004