Nii Shinsuke, Terao Jun, Kambe Nobuaki
Department of Molecular Chemistry & Science and Technology Center for Atoms, Molecules and Ions Control, Osaka University, Suita, Osaka 565-0871, Japan.
J Org Chem. 2004 Jan 23;69(2):573-6. doi: 10.1021/jo0354241.
A new method for regioselective carbomagnesation of alkenes and dienes has been developed by the use of a titanocene catalyst. This reaction proceeds efficiently at 0 degrees C in THF in the presence of Cp(2)TiCl(2) by the combined use of organic halides (R-X; R = alkyl, aryl and vinyl) and n-BuMgCl to afford benzyl, alpha-silylalkyl, or allyl Grignard reagents, which were trapped with various electrophiles. The present reaction involves (i) addition of carbon radicals toward alkenes or dienes in the carbon-carbon bond-forming step and (ii) transmetalation on Ti of benzyl-, alpha-silylalkyl-, or allyltitanocene with n-BuMgCl in the carbon-magnesium bond-forming step. The scope and limitations of this reaction have also been examined.
通过使用二茂钛催化剂，已开发出一种用于烯烃和二烯烃区域选择性碳镁化的新方法。该反应在Cp(2)TiCl(2)存在下，于0℃的四氢呋喃中，通过联合使用有机卤化物（R-X；R = 烷基、芳基和乙烯基）和正丁基氯化镁，高效进行，生成苄基、α-硅烷基烷基或烯丙基格氏试剂，这些试剂可被各种亲电试剂捕获。本反应涉及：(i) 在碳-碳键形成步骤中，碳自由基向烯烃或二烯烃的加成；以及(ii) 在碳-镁键形成步骤中，苄基-、α-硅烷基烷基-或烯丙基二茂钛与正丁基氯化镁在钛上的金属转移反应。还研究了该反应的适用范围和局限性。
