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
Stereospecificannulation of hydroxyvinylethers in the presence of triflic anhydride and tertiary amines and its syntheticapplication are described. Each 1-hydroxy-2-oxabicyclo[n.4.0]alkane, 2-oxabicyclo[n.4.0]alk-1(6)-ene and 2-oxabicyclo[n.4.0]alk-1(6+n)-ene is stereoselectively synthesized from the same hydroxyvinylether depending on the choice of the reaction conditions (temperature, solvent
描述了在三氟甲磺酸酐和叔胺存在下的羟基乙烯基醚的立体定向环氧化及其合成应用。每个1-羟基-2-氧杂双环[n.4.0]烷烃,2-氧杂双环[n.4.0] alk-1(6)-烯和2-氧杂双环[n.4.0] alk-1(6 + n)-烯根据反应条件(温度,溶剂和叔胺)的选择,由相同的羟基乙烯基醚立体选择性地合成。这些化合物导致多官能化的环状化合物和一些天然产物。我们提出,这种环化反应是通过纯S N 2样机理进行的。