Diastereo-differentiating intramolecular cyclopropanations of prochiral olefins and a diazo ester linked by optically active 2,4-pentanediol
作者:Atsushi Mori、Takashi Sugimura、Akira Tai
DOI:10.1016/s0957-4166(97)00040-2
日期:1997.3
Intramolecular cyclopropanation of 3, the substrate having a chiral auxiliary as a linking bridge between a diazo ester and cyclohexene, was found to give the cyclopropane 4 having over 99% diastereomeric excess (d.e.) in 91.5% yield. The reaction was also carried out at 138°C (p-xylene reflux) to give 4 of 88.2% d.e.
Temperature-Independent Stereoselectivity in Intramolecular Cycloaddition of Ketene Generated from Diazoester in Solution and in Vapor Phase: How Entropy Term Governs the Selectivity
The intramolecular [2 + 2] cycloaddition between alkene and ketene linked with 2,4-pentanediol tether was performed in a wide range of temperature, −60 to +400 °C. When the ketene was generated by ...
The first vaporphase asymmetric synthesis was successfully carried out by FVP of a 2,4-pentanediol (PD)-tethered substrate carrying cyclohexene and diazo ester moieties at high temperature up to 400°C. The intramolecular [2+2] cycloaddition of the ketene was strictly stereocontrolled by the entropy term.
Temperature-Independent Stereocontrolled [2+2] Cycloaddition. Potential of the 2,4-Pentanediol Tether in Asymmetric Reactions as a Differential Activation Entropy Promoter
作者:Takashi Sugimura、Takahiro Tei、Atsushi Mori、Tadashi Okuyama、Akira Tai