Enantio‐ and Diastereoselective Suzuki–Miyaura Coupling with Racemic Bicycles
作者:F. Wieland Goetzke、Mike Mortimore、Stephen P. Fletcher
DOI:10.1002/anie.201906478
日期:2019.8.26
Herein, we describe a rhodium‐catalyzed enantio‐ and diastereoselective Suzuki–Miyaura cross‐coupling between racemic fused bicyclic allylic chlorides and boronic acids. The highly stereoselective transformation allows for the coupling of aryl, heteroaryl, and alkenyl boronic acids and gives access to functionalized bicyclic cyclopentenes, which can be converted into other five‐membered‐ring scaffolds
The Asymmetric Synthesis of (3<i>S</i>,4<i>R</i>,5<i>S</i>)-3-Amino-4,5-<i>O</i>-isopropylidenedioxycyclopentene
作者:Barry M. Trost、Mark T. Sorum
DOI:10.1021/op025611l
日期:2003.5.1
The title amine, an important substructure of nucleoside Q, is available from the 3,4-epoxycyclopentene in five steps. The epoxide is directly converted to the acetonide of cis-3, 4-dihydroxycyclopentene by treatment with boron trifluoride, a ring-opening with retention of configuration, a previously unknown process since known conversions of epoxides directly to acetonides normally involve initiating by nucleophilic opening of the epoxide with inversion of configuration. Two strategies were developed for diastereoselective allylic oxidation to cis-3,4-O-isopropylidenedioxy-trans-5-hydroxycyclopentene-direct oxidation with selenium dioxide and a two-step process, epoxidation followed by base. The corresponding carbonate undergoes a palladium-catalyzed deracemization with phthalimide as nucleophile in 98% ee. Recrystallization can increase the ee to > 99%. Removal of the phthalimide group to give the title compound occurs smoothly with ethylenediamine. Thus, a most efficient five-step synthesis (six steps from cyclopentadiene) contrasts with two recent asymmetric syntheses that required 12-16 steps.