The preparation of N-alkyl acyclic imides
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An optimized method for the preparation of a little known class of compounds, acyclic imides, is described. First, the N-metalation of selected secondary am des was examined, using various bases and solvents. The most efficient metalating agent was found to be butyllithium in tetrahydrofuran. The N-lithiated amides were then acylated at -60 °C, with an acid chloride or anhydride to afford the corresponding acyclic imide in high yields. A total of 14 acyclic imides were prepared in this manner, most of them being new compounds. Among the two workup procedures examined, aqueous and nonaqueous, the latter was found to be more efficient. Compared to the literature procedures, this novel method appears to be superior in yields, purity and the time required for the preparaton. In view of the fact that acyclic imides are considerably reactive, they may become useful intermediates in synthesis.