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Ultrasound in Fatty Acid Chemistry: Synthesis of a 1-pyrroline Fatty Acid Ester Isomer From Methyl Ricinoleate

Ultrasound in Fatty Acid Chemistry: Synthesis of a 1-pyrroline Fatty Acid Ester Isomer From Methyl Ricinoleate

M S Lie Ken Jie, M S Syed-Rahmatullah, C K Lam, P Kalluri

Lipids. 1994 Dec;29(12):889-92.

PMID: 7854016

Abstract:

A novel 1-pyrroline fatty acid ester isomer (viz. 8-5-hexyl-1-pyrrolin-2-yl) octanoate) has been synthesized from methyl ricinoleate by two routes with an overall yield of 42 and 30%, respectively. Most of the reactions are carried out under concomitant ultrasonic irradiation (20 KHz, ca. 53 watts/cm2). Under such a reaction condition, the reaction time is considerably shortened, and product yields are high. Dehydrobromination under concomitant ultrasonic irradiation of methyl 9, 10-dibromo-12-hydroxyoctadecanoate with KOH in EtOH furnishes methyl 12-hydroxy-9-octadecynoate (66%) within 15 min. Hydration of the latter under ultrasound with mercury(II)acetate in aqueous tetrahydrofuran yields exclusively methyl 12-hydroxy-9-oxo-octadecanoate (95%) in 30 min. The hydroxy group in the latter compound is transformed to the azido function via the mesylate, and treatment of the azido-oxo intermediate (methyl 12-azido-9-oxooctadecanoate) with Ph3P under ultrasonic irradiation furnishes the requisite 1-pyrroline fatty acid ester (77%). The same azido-oxo intermediate has also been obtained by the oxidation of methyl 12-azido-9-cis-octadecenoate using benzoquinone and a catalytic amount of Pd(II)chloride in aqueous tetrahydrofuran under concomitant ultrasonic irradiation (90 min) to give the product in 45% yield. The latter reaction does not take place even under prolonged silent stirring of the reaction mixture.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP141242-A	Methyl ricinoleate		141-24-2	Price

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