Free Radical Chemistry of β-Lactones. Arrhenius Parameters for the Decarboxylative Cleavage and Ring Expansion of 2-Oxetanon-4-ylcarbinyl Radicals. Facilitation of Chain Propagation by Catalytic Benzeneselenol
作者:David Crich、Xue-Sheng Mo
DOI:10.1021/ja980447w
日期:1998.8.1
loss of carbon dioxide to provide allyl radicals. When the initial radical is generated from a bromolactone with Bu3SnH and AIBN, chain propagation is poor owing to the relatively slow abstraction of hydrogen from the stannane by the allyl radical. The inclusion of catalytic Ph2Se2, reduced in situ to PhSeH, provides for much smoother cleaner reactions because of the better hydrogen donating capacity
2-Oxetanon-4-ylcarbinyl 自由基容易开环,CO 键断裂,得到 3-丁烯氧基自由基,而 3-丁烯氧基自由基又会失去二氧化碳以提供烯丙基自由基。当初始自由基由具有 Bu3SnH 和 AIBN 的溴内酯生成时,由于烯丙基自由基从锡烷中提取氢的速度相对较慢,因此链增长很差。由于硒醇具有更好的供氢能力,因此包含催化性 Ph2Se2,原位还原为 PhSeH,可提供更顺畅、更清洁的反应。衍生自 6-benzyl-1-(bromomethyl)-8-oxa-7-oxobicyclo[4.2.0] 辛烷的 oxetanon-4-ylcarbinyl 自由基是异常的,并且在与断裂过程的竞争中经历了自由基环扩张。提出了这种异常的可能原因,以及碎片和重排的 Arrhenius 函数。还介绍了简单的 2-oxetanon-4-yl 自由基断裂的 Arrhenius 函数。描述的条件是...