Sequential Staudinger ketene-imine cycloaddition, RCM approach to highly rigid macrocrocyclic bisazetidinones.
An efficient approach to highly rigid macrocyclic bisazetidinones with interesting structural feature was achieved via sequential Staudinger ketene-imine cycloaddition of o-allyloxyphenoxyketene and bis-arylidenediamines followed by RCM. The ketene-imine cycloaddition afforded the corresponding bis-o-allyloxyphenoxyazetidinones as the cis-cis diastereomers, exclusively obtained as a mixture of cis-syn-cis and cis-anti-cis. RCM of the latter using Grubbs' catalysts afforded good yields of the corresponding novel macrocyclic bisazetidinones. The cis-anti-cis bisazetidinones are readily identified by (1)H NMR using Eu(hfc)(3) chiral shift reagent. (1)H NMR indicated the high shielding effect of the aryl substituents on one of the ortho-H's of the condensed phenylene ring, and VT (1)H NMR indicates the highly restricted rotation of the aryl groups, thus offering a highly rigid system.
Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait. yehiaai@kuc01.kuniv.edu.kw
Yehia A
YA
Ibrahim
Talal F
TF
Al-Azemi
Mohamed D
MD
Abd El-Halim