Issue 0, 1984

Mechanistic study of the thermal acid-catalysed rearrangement of trans-methyl chrysanthemate to lavandulyl derivatives

Abstract

trans-Methyl chrysanthemate (17) under acid conditions at room temperature rearranged to the lavandulyl esters: methyl trans-5-methyl-2-propen-2-ylhex-3-enoate (18) and methyl trans-5-methyl-2-(2-hydroxypropan-2-yl)hex-3-enoate (19) which was formed by a cyclopropylcarbinyl–homoallyl rearrangement. Both (18) and (19) further isomerise and dehydrate to the stable methyl trans-5-methyl-2-propan-2-ylidenehex-3-enoate (20). Under similar acidic conditions, (18) and (19) each give a mixture of lavandulyl esters and (17); minor amounts of side products, methyl trans-5-methylhex-3-enoate (21), methyl trans-5-methyl-2-(2-methoxypropan-2-yl)hex-3-enoate (22), methyl cis-5-methyl-2-propen-2-ylhex-2-enoate (23) were detected after some time. Acid methanolysis of (17) gave a substantial amount of (22) and its isomer, methyl 2,2-dimethyl-3-(2-methoxypropan-2-yl)cyclopropanecarboxylate (26). There was also found in low concentration, methyl trans-5-methyl-2-propan-2-ylhex-3-enoate (24) and methyl 5-methyl-2-propan-2-ylidenehexanpate (25) possibly the result of a hydride transfer from the solvent. Deuterium exchange was observed in the isobutenyl side-chain of (17) and the isobutenyl moiety of (18) and (19). At 130°C under similar acidic conditions a mixture of unsaturated γ- and δ-lactones was obtained from (17). The principal lactone was dihydro-5-propan-2-yl-3-propan-2-ylidenefuran-2(3H)-one (29). Mechanisms for the formation of these products are discussed. The fact that lavandulyl derivatives were obtained may shed new light on the biogenesis of chrysanthemic acid in plants.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1984, 2697-2705

Mechanistic study of the thermal acid-catalysed rearrangement of trans-methyl chrysanthemate to lavandulyl derivatives

Z. Goldschmidt, B. Crammer and R. Ikan, J. Chem. Soc., Perkin Trans. 1, 1984, 2697 DOI: 10.1039/P19840002697

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