Syntheses of 12‐aminododecanoic and 11‐aminoundecanoic acids from vernolic acid

Abstract 12‐Aminododecanoic acid and 11‐aminoundecanoic acid, monomer precursors for nylon‐12 and nylon‐11, respectively, have been synthesized from vernolic ( cis ‐12,13‐epoxy‐ cis ‐9‐octadecenoic) acid via a reaction sequence that includes the formation of 12‐oxododecanoic acid oxime. Saponification of vernonia oil, followed by a low‐temperature recrystallization at −20°C, gave 51% vernolic acid (97% purity, m.p. 23–25°C). Hydrogenation afforded cis ‐12,13‐epoxystearic acid (m.p. 52–54°C, lit. m.p. 52–54°C), which upon oxidation with periodic acid in tertiary butyl alcohol gave 12‐oxododecanoic acid with an isolated yield of 71.0%. Reaction of the oxoacid with hydroxylamine hydrochloride gave 12‐oxododecanoic acid oxime, which was catalytically reduced to give 12‐aminododecanoic acid with a yield greater than 85% and a melting point of 184–186°C (lit. m.p. 185–187°C). 11‐Aminoundecanoic acid was prepared from the 12‐oxododecanoic acid oxime via a three‐step reaction sequence that involved a Beckmann rearrangement, Hofmann degradation, and hydrolysis. Thus, the aldoxime acid was hydrolyzed in the presence of nickel acetate tetrahydrate to give 11‐carbamoylundecanoic acid (48% yield, m.p. 129–131°C, lit. m.p. 129–130°C). The amide was then treated with a solution of sodium methoxide and bromine at 70–80°C to give 11‐(methoxycarbonylamino)undecanoic acid at 75% yield (m.p. 84–86°C; elemental analysis, calculated for C 13 H 25 NO 4 : C, 60.19; H, 9.73; N, 5.40; O, 24.68%; found C, 60.02; H, 9.81; N, 5.26; O, 24.91%), which upon alkaline hydrolysis and subsequent neutralization gave 11‐aminoundecanoic acid at 34% yield (m.p. 189–192°C, lit. m.p. 190°C). Mass spectrometric and 13 C nuclear magnetic resonance data of the previously unreported 11‐(methoxycarbonylamino)undecanoic acid is provided.