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Scheme
3 Proposed process for this a-amination of aliphatic
aldehydes.
very mild conditions, affording the desired products in
moderate to good yields. Furthermore, the enamine with
readily removable protecting groups, which is confirmed as
the intermediate in this reaction, was also directly converted
into a-amino acetal via oxidative rearrangement. Further
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We gratefully acknowledge the Nanyang Technological
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Research Fund Tier 2 (No. T206B1221; T207B1220RS) for the
financial support of this research.
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Notes and references
z General procedure for the copper-catalyzed a-amination of aliphatic
aldehydes: tert-butyl hydroperoxide (B5.5 M in decane) (0.1 mL,
B0.55 mmol) was added to a mixture of CuI (38 mg, 0.2 mmol),
dibenzylamine 1a (98 mg, 0.5 mmol), and butyraldehyde 2a (54 mg,
0.75 mmol) in methanol (0.4 mL)/acetonitrile (2.0 mL) at room
temperature. The mixture was stirred at 40 1C until dibenzylamine
1a was completely converted by TLC detection. The resulting reaction
mixture was mixed with a small amount of silica gel and concentrated.
The crude product was purified by flash column chromatography
(silica gel; ethyl acetate or diethyl ether/hexane = 1 : 100) to afford
the desired product 3a as a light yellowish oil (0.125 g, 80% yield).
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c
5460 Chem. Commun., 2011, 47, 5458–5460
This journal is The Royal Society of Chemistry 2011