シクロペンテンオキシドより2-アルキルシクロペンタノンの合成

概要

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2-Alkylcyclopentanones (4) were synthesized from cyclopentene oxide by the procedure described in Scheme-5. cis-1-Alkyl-2-chlorocyclopentanols (3) were produced selectively by the reaction of 2-chlorocyclopentanone (2) with various Grignard reagents. The reaction of (3) (alkyl group used ; -C6H13, -C5H11, -C4H9, -C3H7, -isoC3H, ) with aqueous alkali metal hydroxide (LiOH, NaOH, KOH, CsOH) was kinetically investigated. Rate constants (l·mol-1·h-1) for the reaction in aqueous KOH were 0.0197 (-C6H13), 0.0695 (-C5H11), 0.248 (-C4H9), 0.993 (-C3H7), and 0.398 (-isoC3H7), respectively. Apparent activation energies (2326 kcal·mol-1) varied depending an alkyl group. Compounds (4) were prepared in high yields from compounds (3). Either by the addition of dimethyl sulfoxide to aqueous alkali metal hydroxide or by the use of aqueous AgNO3 instead of alkali metal hydroxide, this reaction was accelerated remarkably without a significant change in apparent activation energies. These results suggest that the deprotonation from hydroxyl group of (3) is the first step to produce (4) from (3).
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