Transmission of substituent effects through unsaturated systems. Part 6. Kinetics of reduction of β-substituted α,β-unsaturated ketones with sodium borohydride
作者:Serge Geribaldi、Michèle Decouzon、Bernard Boyer、Claude Moreau
DOI:10.1039/p29860001327
日期:——
regioselectivity of reduction is discussed. The linear free energy relationships obtained between the rate constants and σp or σp+ confirm that these 3-substituted cyclohexenone structures are good models for the investigation of the substituent effects on the reactivity of ethylenic systems. Comparison of reaction constants for the three series leads to the conclusion that, as for borohydride reductions of acetophenone
已在碱性溶液中确定了将硼氢化钠加至3取代的5,5-二甲基环己-2-烯酮(1),对位取代的3-苯基环己烯酮(2)和对位取代的苯乙酮(3)的速率常数。(NaOH,0.025 mol l –1)的水-二恶烷(1:1 v / v)在298 K下。在这些条件下,共轭环己烯酮体系(1)和(2)进行排他的1,2-还原,生成相应的烯丙醇。讨论了还原的区域选择性。速率常数与σp或σp +之间获得的线性自由能关系证实这些3-取代的环己烯酮结构是研究取代基对烯键体系反应性影响的良好模型。对这三个系列的反应常数进行比较得出的结论是,就苯乙酮的硼氢化物还原而言,环己烯酮还原必须在反应坐标的最后四分之一处具有较晚的过渡态。