Absolute Configuration of 2‐(2,4,5,7‐Tetranitro‐9‐fluorenylideneaminooxy)propionic Acid (TAPA)

Abstract

were dissolved in benzene and the solution subjected to chromatographic separation on a silica-gel-60 column with benzene.Weight for weight, the ellipticities of the two enantiomer fractions were of the same magnitude but of different sign ( f 2 %).This is indicative of complete separation, for otherwise equal values with opposite signs can occur only when the precipitated enantiomers and those remaining in solution each contain the same proportion of the other enantiomerr']. The optical activity was not increased by a second resolution step.In contrast to the analogous carbon compounds ( 3 ) is not cyclized to ( 4 ) in toluene/iodine with polarized lightr*]. This is consistent with the photochemical behavior of azobenzene. A protonated form, which in the case of azobenzene can be photocy~lized[~~, is not formed-even in 70% perchloric acid.

Helicenes: Synthesis and Applications

“…Therefore, to investigate and utilize helicenes, efficient ways for optical resolution are of great significance since they are still the most practical way to obtain optically pure helicenes. Since the first reports of the resolution of 1-methyl[4]helicene 6 and hexahelicene 8 , by l -menthol and 2-(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)propionic acid (TAPA) 416 (Figure ), respectively, several new approaches for optical resolution have been discovered.…”