TY - JOUR
T1 - Mechanistic study of the thermal acid-catalysed rearrangement of trans-methyl chrysanthemate to lavandulyl derivatives
AU - Goldschmidt, Zeev
AU - Crammer, Bernard
AU - Ikan, Raphael
PY - 1984
Y1 - 1984
N2 - 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 cyclopropylcarbinylhomoallyl 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 gave 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-ylidenehexanoate (25) possibly the result of a hydride transfer from the solvent. Deuterium exchange was observed in the isobutenyl sidechain 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.
AB - 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 cyclopropylcarbinylhomoallyl 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 gave 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-ylidenehexanoate (25) possibly the result of a hydride transfer from the solvent. Deuterium exchange was observed in the isobutenyl sidechain 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.
UR - http://www.scopus.com/inward/record.url?scp=37049105243&partnerID=8YFLogxK
U2 - 10.1039/p19840002697
DO - 10.1039/p19840002697
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AN - SCOPUS:37049105243
SN - 1472-7781
SP - 2697
EP - 2705
JO - Journal of the Chemical Society, Perkin Transactions 1
JF - Journal of the Chemical Society, Perkin Transactions 1
ER -