Toluene → 17-(tert-Butoxy)-17-oxoheptadecanoic acid

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Reaction Steps

The crude heptadecanedioic acid (0.99 g, 3.3 mmol) was dissolved in toluene (15 ml) at 115° C. N,N-dimethylformamide di-tert-butylacetale (0.79 ml, 3.3 mmol) was added dropwise over 10 min. After refluxing for 1 h more N,N-dimethylformamide di-tert-butylacetale (0.79 ml) was added over 10 min. After refluxing for another 1 h, a last eq of N,N-dimethylformamide di-tert-butylacetale (0.79 ml) was added over 10 min. Reflux was continued for 1 h. On cooling to RT a precipitate appeared, this was filtered off (diacid). The mother liqueour was extracted with water (25 ml) and DCM (25 ml). The organic layer was dried and concentrated. The residue was purified by flash chromatography using DCM/MeOH 15:1 as eluent. Heptadecanedioic acid mono-tert-butyl ester was isolated in 33% yield (0.330 g). HPLC-MS: 379 (M+Na), rt 6.11. 1H-NMR (DMSO-d6): δ 1.22 (br s, 22H), 1.39 (s, 9H), 1.47 (m, 4H), 2.16 (t, 2H), 2.19 ppm (t, 2H).

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