19957-75-6Relevant articles and documents
Preparation of 5-hydroxy-4-methyl-2(5H)-furanone
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, (2008/06/13)
5-Hydroxy-4-methyl-2(5H)-furanone is prepared by cyclization of alkyl β-formylcrotonates by heating with dilute aqueous hydrochloric acid or, advantageously, in the presence of dilute aqueous hydrochloric acid and catalytic amounts of methanol as solubilizer, subsequent workup of the reaction mixture by distillation and, where appropriate, isomerization of the 5-methoxy- or 5-ethoxy-4-methyl-2(5H)-furanone, which is formed as byproduct, by heating with dilute hydrochloric acid.
Asymmetric 1,3-dipolar cycloadditions to 5-(R)-menthyloxy-2(5H)-furanone
Rispens,Keller,De Lange,Zijlstra,Feringa
, p. 607 - 624 (2007/10/02)
Various diazo compounds, nitrile oxides, nitrones and azomethine ylides were examined in 1,3-dipolar cycloadditions to enantiomerically pure 5-(R)-menthyloxy-2(5H)-furanone 1a. Pyrazoline 9 was obtained in 100% c.y. as a mixture of 2 diastereoisomers in ratios up to 72:28, whereas pyrazoline 16 was obtained in 100% c.y. as a single enantiomer. Photochemically pyrazolines 9 and 10 have been converted to cyclopropanes 11 and 13. Under thermal conditions pyrazoline 9 is converted to 4-methyl-5-menthyloxy-2(5H)-furanone. Isoxazoles 21a-24a were obtained enantiomerically pure via nitrile oxide addition to 1a in 64-67% yield. Nitrone addition afforded isoxazolidines 27, 28 and 34 with complete anti-facial- and regiochemistry, but with endo-exo-selectivities up to 76%. Enantiomerically pure isoxazolidines were obtained in 25-75% yield. Pyrrolidine 36 was obtained diastereomerically pure in 81% c.y. Pyrrolidines 42 and 45, however, were obtained as diastereomeric mixtures in 37% resp. 6% yield.
