Hydroxy-, Methoxymercuration and Lewis Acid Catalyzed Formyloxylation of Methyl Linoleate

Methyl linoleate (1) reacts by hydroxymercuration-demercuration to methyl hydroxyoctadecenoates (2) of the ricinolic acid type and tetrahydrofurans 4, 5. Good yields of 4,5 are favored by high concentrations of 1 and reagents and reflux temperature. Methyl ricinolate cyclizes in an analogous reaction nearly quantitatively to 4 with a high diastereoselectivity in favor of the syn-isomer. The methoxymercuration-demercuration leads to mono- and dimethoxy adducts. Mercury(II) acetate can be substituted for nontoxic electrophiles. 1 affords in formic acid with BF₃-etherate or HBF₄ as Lewis acids the mono- and diformiates in a ratio of 1:1 and 77% yield. In contrast to the oxymercuration, however, this addition is fairly regiounselective.