SUSTAINABLE OXIDATIVE DEPROTECTION USING GASEOUS NITROGEN DIOXIDE 147
General Procedure for the Oxidative Deprotection of TMS Ethers
No particular precautions, except vacuum tightness, were necessary when 1.00 mmol
of the pure, known TMS ethers 1a–o or triphenylmethyl TMS ether or 2-phenylethyl TMS
ether were exposed to approximately 0.6 bars of NO2/N2O4 gas from a lecture bottle in
an evacuated 100 mL flask (about 5.8 mmol calculated for NO2) at a vacuum line and at
room temperature, with occasional shaking for the times mentioned in Table 1. The formed
liquids changed their colors rapidly. After condensation of the reaction gas mixtures and
(
Me3Si)2O to a cold trap at the vacuum line all of the solid benzaldehydes or ketones
crystallized. The evaporated gases from various experiments were collected for distillative
4
separation with FTIR control and further use. The least volatile fraction was (Me3Si)2O, the
1
identity of which was secured by its H NMR, FTIR and MS spectra. The immediate purity
of the known compounds 4a–o (Table 1), 2-phenylacetaldehyde, and Ph3COH was verified
1
by VPC, TLC, and melting-point determinations. Also, H NMR spectra excluded traces
of the corresponding benzoic acids or aromatic nitrations by the not including spurious
additional peaks.
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