Gansäuer Andreas, Lauterbach Thorsten, Narayan Sanjay
Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard Domagk Strasse 1, 53127 Bonn, Germany.
Angew Chem Int Ed Engl. 2003 Nov 24;42(45):5556-73. doi: 10.1002/anie.200300583.
Over the last few decades the use of radicals in synthesis has witnessed an explosive growth through introduction of efficient chain and electron-transfer reactions. Strained heterocycles, in particular, have emerged as a highly versatile and readily available class of radical precursors. The generation of carbinyl radicals of heterocycles has resulted in many elegant applications of heteroatom-centered radicals, such as beta fragmentations, cyclizations, and intramolecular hydrogen atom abstractions. Direct electron transfer to strained heterocycles has been realized through the use of arene radical anions. The method combines the virtues of radical and organometallic chemistry to yield useful functionalized organolithium compounds. Epoxides have been opened with high regioselectivity by titanocene(III) reagents in either stoichiometric or catalytic quantities to yield beta-titanoxy radicals. This development has resulted in many new applications in natural product synthesis.
在过去几十年里，通过引入高效的链式反应和电子转移反应，自由基在合成中的应用呈爆发式增长。特别是，张力杂环已成为一类高度通用且易于获得的自由基前体。杂环碳自由基的产生导致了许多以杂原子为中心的自由基的精妙应用，如β-断裂、环化反应和分子内氢原子夺取反应。通过使用芳烃自由基阴离子，已实现了向张力杂环的直接电子转移。该方法结合了自由基化学和有机金属化学的优点，可生成有用的官能化有机锂化合物。钛ocene(III)试剂以化学计量或催化量高区域选择性地开环环氧化合物，生成β-钛氧基自由基。这一进展在天然产物合成中带来了许多新应用。
