Stereochemical observations on the Wittig reaction of oxido phosphonium ylides with aldehydes
作者:Bruce E. Maryanoff、Allen B. Reitz、Barbara A. Duhl-Emswiler
DOI:10.1016/s0040-4039(00)81959-0
日期:1983.1
The reaction of aldehydes with oxido ylides shows a dramatic dependence of alkene stereochemistry on the distance between oxygen and phosphorus atomsl; ylides with proximal 0 and P atoms favor production of alkenes. The high stereoselectivity with γ-oxido ylides is not mainly attributable to intramolecular proton-exchange in a Wittig intermediate.
Construction of Carbo- and Heterocycles Using Radical Relay Cyclizations Initiated by Alkoxy Radicals
作者:Hai Zhu、Jason G. Wickenden、Natalie E. Campbell、Joe C. T. Leung、Kayli M. Johnson、Glenn M. Sammis
DOI:10.1021/ol900481e
日期:2009.5.7
construction of carbo- and heterocycles has been developed using radical relay cyclizations initiated by alkoxy radicals. Linear substrates were cyclized to form a wide range of cyclopentane, pyrrolidine, tetrahydropyran, and tetrahydrofuran derivatives in excellent yields. This methodology was utilized as a key step in the synthesis of the tetrahydrofuran fragment in (−)-amphidinolide K.
Strategies to Control Alkoxy Radical-Initiated Relay Cyclizations for the Synthesis of Oxygenated Tetrahydrofuran Motifs
作者:Hai Zhu、Joe C. T. Leung、Glenn M. Sammis
DOI:10.1021/jo502499a
日期:2015.1.16
Radical relay cyclizations initiated by alkoxy radicals are a powerful tool for the rapid construction of substituted tetrahydrofurans. The scope of these relay cyclizations has been dramatically increased with the development of two strategies that utilize an oxygen atom in the substrate to accelerate the desired hydrogen atom transfer (HAT) over competing pathways. This has enabled a chemoselective 1,6-HAT over a competing 1,5-HAT. Furthermore, this allows for a chemoselective 1,5-HAT over competing direct cyclizations and beta-fragmentations. Oxygen atom incorporation leads to a general increase in cyclization diastereoselectivity over carbon analogues. This chemoselective relay cyclization strategy was utilized in the improved synthesis of the tetrahydrofuran fragment in (-)-amphidinolide K.