Quantitative chirality of helicenes

Heliphenes and Related Structures

“…For [n]helicenes, a plot of specific rotation versus n has two humps and has a "maximum chirality" at n = 14 [11].…”

The temperature-dependent optical activity of quartz: from Le Châtelier to chirality measures

“…It should be noted, however that for such correlations to emerge, a homologous series of structures is needed, such as the gradually changing -O(SiO 3 ) 4 -fragment used here. Indeed, other examples for correlations between the degree of chirality in a homologous series of structures or molecules and chemical/physical properties exist, 8 helicenes, 16 the deactivation of enzymes with chiral inhibitors, 17 and the enantiomeric excess of the chiral product obtained with a series of chiral catalysts. 18 The computational programs of the symmetry and chirality measures described herein can be used freely at http://www.csm.…”

Distinction between homochiral and heterochiral dimers of 1-aza[n]helicenes (n=1–7) with alkaline cations

“…The first helicene, hexahelicene or [6]helicene, was synthesized by Newman and Lednicer in 1956, and was resolved by complexation with a-(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)propionic acid (TAPA) through diastereomeric p-(or chargetransfer) complexes. 7,8 The compound has a remarkable rotation ½a 24 D ¼ À3640 (CHCl 3 ) and only starts to racemize at the melting point of 266°C. Racemization barriers of [n]helices have been calculated theoretically.…”