零价钯催化下赤霉素A_3衍生物A环的反应

Palladium Catalyzed Reactions on Ring A of Some Gibberellin A_3 Derivatives

在 ( Ph3P) 4Pd( 0 )催化下 ,赤霉素 A3( GA3)衍生物的 A环在氢供体环己烯存在时发生氢解 ,形成 1,3-二烯主产物 ;而在无氢供体时则发生 A环的芳构化反应 .通过选择适当的反应条件 ,可以得到不同主要产物 .

Ring A of some gibberellin A 3 (GA 3) derivatives was found to undergo different type of reactions under the catalysis of (Ph 3P) 4Pd(0) in different solvents. In the presence of cyclohexene as the hydrogen donor, the reaction of 3 acylated GA 3 dimethyl ester (2) afforded 1,3 dienoic acid (4) as the major product accompanying by some degree of ring A aromatization, while in the absence of cyclohexene, the reaction gave aromatized compound (5) as the predominant product. The aromatization reaction was also found to occur in ring A of GA 3 enone (6) to give aromatized product (7) in 95% yield.