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 ...
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