63 1-ニトロ-1-フェニルチオプロペンと1,3-ジカルボニル化合物の反応およびそれを用いるフラノテルペンの合成

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The 3-methylfuran structure is frequently found in terpenoids. We recently reported a one-step preparation of 2-alkylfurans by the reaction of aliphatic 2-nitroolefins and 1,3-dicarbonyl compounds, 1-nitropropene, however, gave an α-oximinodihydrofuran derivative 4 in the reaction with dimedone in place of the anticipated furan 3 under similar reaction conditions. As a reagent for this purpose, 1-nitro-1-phenylthiopropene (10) was prepared from phenylthioacetic acid and submitted to the reaction with dimedone (KF, xylene, 110°), yielding a mixture of 11a, 11b, and 12. After separation, the α-phenylthiodihydrofurans 11a and 11b were converted into 15 by oxidation followed by phenylsulfenic acid elimination, respectively. On a similar procedure, (±)-evodone (23) was synthesized from 5-methylcyclohexane-1,3-dione. The reaction of the dione 24 with 10 gave a mixture of 39 and 40. When submitted to oxidation and subsequent elimination, the mixture afforded only isoligularone (26). Although thermal isomerization of 26 to ligularone (25) is the known transformation, the direct preparation of 25 from 39 is also being studied now.
天然有機化合物討論会の論文
1978-08-22