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
DOI:10.1021/ja993976o
日期:2000.3.1
Chiral and flexible 2,4-pentanediol-tethered cyclopropanation of olefins with a carbenoid derived from a diazo ester to construct three stereogenic centers
2,4-Pentanediol-tethered cyclopropanation of an olefin with an internal carbenoid generated from a diazo ester proceeded smoothly to give a chiral adduct having three stereogenic centers under full stereocontrol. The high stereoselectivity was not affected by the structure of the olefinic portion, studied so far with six substrates. Conversion of the product cyclopropane to other optically active compounds