Dipartimento di Chimica Organica A. Mangini, Università di Bologna, Viale Risorgimento 4, I-40136, Bologna, Italy.
Org Biomol Chem. 2010 Aug 7;8(15):3444-50. doi: 10.1039/c001848a. Epub 2010 Jun 1.
Allylindium dichloride is an effective reagent for carrying out photolytically initiated radical allylation reactions, as also proved by EPR experiments. In the presence of suitable azides that can give rise to electrophilic radicals, a homolytic chain reaction occurs with formation of allylated compounds. With delta-azido esters and chlorides generation of primary indiumaminyl radicals is followed by a very efficient 1,5-H shift process that gives rise to electrophilic carbon-centred radicals, whose subsequent allylation by the starting indium reagent, followed by aqueous workup, eventually affords allylated nitrogen heterocycles in good yields. Some comparative theoretical calculations accounted for the observation that analogous reactions with an organoallyltin reagent did not work at all. The results show that the reaction with allylindium dichloride seems strongly favoured by both a lower BDE of the allyl-metal bond and a considerably faster, exothermic 1,5-H migration step.
烯丙基二氯化铝是一种有效的试剂，可用于进行光引发的自由基烯丙基化反应，这也被 EPR 实验所证明。在合适的叠氮化物存在下，这些叠氮化物可以产生亲电自由基，会发生均裂链反应，形成烯丙基化合物。对于 delta-叠氮酯和氯化物，会生成初级的铟氨基自由基，然后是非常有效的 1,5-H 迁移过程，生成亲电的碳中心自由基，随后由起始铟试剂进行烯丙基化，再经过水相处理，最终以良好的收率得到烯丙基化的氮杂环。一些比较理论计算解释了观察到的现象，即类似的与有机烯丙基锡试剂的反应根本不起作用。结果表明，与烯丙基二氯化铝的反应似乎强烈受到较低的烯丙基-金属键的 BDE 和更快、放热的 1,5-H 迁移步骤的影响。
