Abstract
A simple one-pot procedure for the preparation of imines from the corresponding aldehydes and amines, and their subsequent oxidation reaction with m-CPBA to produce synthetically useful oxaziridines is reported. The method is applicable to imines derived from both aliphatic and aromatic aldehydes and diverse alkyl amines. Short reaction times, essentially quantitative yields, very mild reaction conditions, and easy purification are the main features of the procedure reported herein.
Highlights
A simple one-pot procedure for the preparation of imines from the corresponding aldehydes and amines, and their subsequent oxidation reaction with m-chloroperbenzoic acid (m-CPBA) to produce synthetically useful oxaziridines is reported
We report here a new procedure for preparing highly valuable oxaziridines consisting in the one-pot, two-step initial preparation of imines that are subsequently oxidized with m-chloroperbenzoic acid (m-CPBA) under neat conditions
Once 1H and 13C-NMR spectroscopic analysis confirmed the complete formation of imine 3, the oxidation reaction was performed with m-CPBA to obtain the desired oxaziridine 4 (Step 2 in Scheme 1) [50]
Summary
Pivalaldehyde 1 and benzylamine 2 were chosen as starting materials in the present study. Once 1H and 13C-NMR spectroscopic analysis confirmed the complete formation of imine 3, the oxidation reaction was performed with m-CPBA to obtain the desired oxaziridine 4 (Step 2 in Scheme 1) [50]. On the other hand, when the oxidation reaction is carried out in the presence of 1.5 equiv of m-CPBA instead of 1.2 equiv, oxaziridine 4 was isolated in higher yield (87% yield, Table 1, entry 3). On the other hand, when Step 1 was carried out at ambient temperature under solvent-free conditions, in only 30 minutes it was observed by TLC that the formation of the imine was complete, which indicates that heating to reflux in DCM is not required. The same oxidizing agent but in presence of K2CO3 (entry 3) afforded quite low yield This result could be due to imine hydrolysis by water under the biphasic conditions H2O/CHCl3. Step 2 t2 (min) Yield 4 (%)a a) Isolated yield after purification by column chromatography
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