Ring-Expansion Induced 1,2-Metalate Rearrangements: Highly Diastereoselective Synthesis of Cyclobutyl Boronic Esters
作者:Durga Prasad Hari、Joseph C. Abell、Valerio Fasano、Varinder K. Aggarwal
DOI:10.1021/jacs.0c00813
日期:2020.3.25
2-migrations. Normally, such shifts are induced by α-leaving groups or by reactions of alkenyl boro-nates with electrophiles. Herein, we present a new strategy to in-duce 1,2-metallate rearrangement, via ring expansion of vinylcyclo-propyl boronate complexes activated by electrophiles. This leads to a cyclopropane-stabilized carbocation which triggers ring expansion and concomitant 1,2-metallate rearrangement
有机硼化合物的广泛合成用途源于它们易于进行 1,2-迁移的能力。通常,这种转变是由α-离去基团或由烯基硼酸酯与亲电子试剂的反应引起的。在此,我们提出了一种新策略,通过亲电子试剂激活的乙烯基环丙基硼酸酯络合物的环扩张来诱导 1,2-金属化物重排。这导致环丙烷稳定的碳正离子引发环膨胀和伴随的 1,2-金属盐重排。这种新工艺提供了具有高水平非对映选择性的药用相关 1,2-取代环丁基硼酸酯。可以使用范围广泛的有机锂和格氏试剂、亲电子试剂和乙烯基环丙基硼酸酯。该方法被应用于 (±)-格兰地醇的短期立体选择性合成。