Preparation and some spectroscopic properties ofN‐heterocyclic derivatives of a novel 1‐pyrroline C₁₈ fatty ester

A C 18 1‐pyrroline fatty ester, methyl 8‐(5‐hexyl‐2‐pyrrolin‐1‐yl)octanoate (1), was prepared from methyl iso ‐ricinoleate. The C=N bond of the pyrroline ring was oxidized by m ‐chloroperoxy‐benzoic acid to yield a mixture of oxaziridine isomers 2a,2b, which decomposed during gas chromatographic analysis to a 2,5‐disubstituted pyrrole derivative, methyl 8‐(5‐hexyl‐1 H ‐pyrrole‐2‐)octanoate (3). Compound 3 was also obtained by reaction of 2a,2b with dilute HCl in methanol. Reaction of compound 1 with iodo‐methane formed an N ‐methyl iminium iodide intermediate 4, which on reduction with sodium borohydride furnished a mixture of cis/trans‐N ‐methyl‐2,5‐disubstituted pyrrolidine derivatives, methyl 8‐( cis/trans ‐5‐hexyl‐ N ‐methyl‐pyrrolidine‐2‐)octanoates 5a,5b. Reduction of compound 1 with NaBH 4 gave a mixture of cis/trans ‐isomers of 2,5‐disubstituted pyrrolidine derivatives, methyl 8‐(5‐hexyl‐pyrrolidine‐2‐)octanoates 6a,6b. Acetylation of compounds 6a,6b with acetic anhydride furnished the corresponding N ‐acetyl pyrrolidines 7a,7b. When compound 1 was treated with perchloric acid, the corresponding iminium perchlorate derivative, methyl 8‐(5‐hexyl‐1‐pyrrolinium perchlorate‐2‐)octanoate 8 was obtained. The structures of the various derivatives were characterized by a combination of chromatographic, mass spectral and spectroscopic techniques.