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Miscellaneous reductions of oximes to amines
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Chem. Ber. 117, 856-858 (1984)
Isobornylamine
1.67g (10 mmol) camphor oxime and 5.7g (20 mmol) NiCl2*6H2O was dissolved in
100ml methanol and cooled to -30°C, and during 30 minutes 3.8g (10 mmol) NaBH4
was added in portions. The mixture was stirred for another 30 minutes and then
the cooling bath was removed and the reaction mixture worked up as usual.
Yield after sublimation at 100°C/14 mmHg 1.40g (92%).
4-tert-butyl-cyclohexylamine
1.69g (10 mmol) 4-tertbutylcyclohexanone oxime and 2.0g (13.8 mmol) MoO3 was
dissolved in 100ml methanol with cooling in an ice-bath, and 3.8g (0.1 mol)
NaBH4 was added in portions. After the exothermic reaction had subsided (1h)
the reaction mixture was worked up the usual way. After kugelrohr distillation,
the yield was 1.35 g (87%), and consisted of 75% cis and 25% trans isomers.
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JACS 111, 6228 (1989)
To a solution of the oxime (24.6 mg, 0.521 mmol) in 10% H2O-THF (30ml) were added
aluminum amalgam, which was prepared from 0.25g of granular aluminum and 2% HgCl2
(0.1ml) in 10% H2O-THF (0.5ml). The reaction mixture was stirred for 3h at room
temperature. 3ml conc NaHCO3 was added, and the reaction mixture was filtered and
the filter cake washed with ethyl acetate. The filtrate was diluted with water and
extracted with ethyl acetate. The extracts was washed with brine, dried over MgSO4
and concentrated in vacuo to give 20.34 mg (85%) of the desired amine as an oil.
[Rh: The oxime they reduce here is a large indole derivative. Use less solvent
with smaller molecules at a larger scale]
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JOC 56(15), 4706 (1991)
A solution of the oxime (11g, 19 mmol) in 250ml dry THF was treated with aluminum
foil (5g, 190 mmol) that had been cut into small pieces and immersed successively
in 2% aqueous HgCl2, distilled H2O and THF. The dark gray suspension was stirred
for 12h at room temperature, at which time TLC revealed the absence of starting
material. The suspension was filtrered and concentrated to yield 7.8g (75%) of
the product amine as a light yellow oil.
[Rh: The oxime they reduce here is a large indole derivative. Use less solvent
with smaller molecules at a larger scale]
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JACS 115, 10042 (1993)
NaBH4 (0.112 mol, 4.1g, 8 equiv,) and titanium(IV)tetrachloride (0.056 mol, 6ml,
4 equiv) were combined in a 1000ml RB flask (fitted with a rubber septum and purged
with nitrogen) and the flask was cooled in an ice-bath. Freshly distilled
dimethoxyethane (100ml) was added slowly while the flask was vented with a large
bore needle. The dioxime (0.014 mol, 4g) was added as a powder over 5 minutes. The
reaction mixture changed color over half an hour, from bright green to green-brown.
The solution was allowed to return to room temperature and was stirred for 24 hours.
The mixture waas cooled on ice, and water (200ml) was added slowly to quench the
reaction. The solution was basified with concentrated aqueous ammonia to pH 13, at
which point it became gelatinous and turned dark blue. The aqueos layer was
extracted several times with methylene chloride (total 1000ml). The organic layer
was dried over sodium sulfate, filtered and the solvent evaporated under vacuum to
give 1.7g (60%) of diamine.
[Rh: Use only 4 equivs of NaBH4 and 2 equivs of TiCl4 if your molecule only has
one oxime group to be reduced. The yields will also be higher with only one oxime]
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JOC 57, 6324 (1992)
At room temperature with stirring, Zinc dust (74 mg) was added to a solution of
the oxime (44mg, 0.185 mmol) in 2 ml glacial acetic acid. Stirring was continued
for another 15 minutes. The reaction mixture was then filtered through a sintered
glass funnel with suction. The filtrate was concentrated under vacuum to afford
the amine as an oil (37mg, 0.166 mmol, 90% yield).
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