Electronic Effects in Migratory Groups. [1,4]- versus [1,2]-Rearrangement in Rhodium Carbenoid Generated Bicyclic Oxonium Ylides
作者:Navnath P. Karche、Santosh M. Jachak、Dilip D. Dhavale
DOI:10.1021/jo010431f
日期:2001.9.1
The results obtained were correlated to the mechanistic aspect of the product selectivity. The intermediacy of the intramolecular oxonium ylide formation was demonstrated by crossover experiments. The preference for the formation of 2,3 sigmatropic rearrangement product over 1,2 and 1,4 was demonstrated by performing the reaction with alpha-diazo beta-keto esters (13a, 13b) with O-allyl and O-propargyl
制备了在O-苄基的苯环上具有不同取代基(ED / EW)的各种α-重氮β-酮酯(3a-f,8a-f)。在苯回流条件下,乙酸铑(II)催化重氮化合物的分解。确定了1,4与1,2迁移产物的比率。发现迁移基团的苄基碳上的电子密度增加优选1,4个迁移产物(4、9),而电子密度的下降导致1,2个迁移产物(5、10)占优势。获得的结果与产物选择性的机械方面相关。通过交叉实验证明了分子内氧鎓叶立德形成的中间性。优先于1,2和1形成2,3σ重排产物 通过与α-重氮β-酮酯(13a,13b)与O-烯丙基和O-炔丙基在C3处的反应来证明图4。还研究了溶剂,温度和乙酸铑(II)的摩尔百分比的影响。