17 ニトロオレフィンを使う新しいシクロペンテノンアヌレーションとその天然物合成への利用

概要

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Aliphatic nitroolefins (1-3), which were readily available from the corresponding nitroalcohols (G), react with trimethylsilyl enol ethers (H) in the presence of Lewis acids to give 1,4-diones directly. Several silyl enol ethers examined showed high regio-specificity and good yields in the formation of the 1,4-diones, which were then converted to conjugated cyclopentenones in high yields on alkali treatment (Table 2). Similarly, nitroolefins react with 1,3-dicarbonyl compounds in the presence of KF in hot xylene. In general, 2-alkyl-1,3-di-carbonyl compounds gave mixtures of nitroketones and triketones (Table 3), although 2-methylcyclohexane-1,3-dione (9) and 2-nitropropene (1) yielded an acetonylation product (11) quantitatively. On the other hand, 2-methylfurans were obtained in good yields on the reaction of 2-unsubstituted-1,3-dicarbonyl compounds and 1 (Table 4). The reaction mechanism of acetonylation of 9 with 1 was elucidated by means of the ^<18>o-labeled dione (22). As an application of the cyclopentenone annulation using nitroolefins, the synthesis of barbatane sesquiterpenoids (27-29) has been attempted.
天然有機化合物討論会の論文
1976-09-20