1,1′-Bi(trishomobarrelenyl) - Synthesis and Chiroptic Properties

1,1′‐Bi(endo,exo,syn‐pentacyclo[3.3.3.02,4.06,8.09,11]undecyl)[1,1′‐bi(trishomobarrelenyl)] (4) has been prepared as a 1:1 mixture of its meso‐ and d,l‐diastereomers in six steps from trishomobarrelene 1 via the amine 5, the N,N′‐bis(trishomobarrelenyl)sulfamide 6 and the 1,2‐(trishomobarrelenyl)diazene 7 in 16 % overall yield. Crystals of meso‐4 were grown from a pentane solution of the mixture and subjected to an X‐ray structure analysis. The (+)‐ and the (–)‐enantiomer were isolated by HPLC on a chiral‐phase column. They exhibited significantly enhanced molar optical rotations which are consistent with the presence of three helically arranged 1,2‐dicyclopropylethane units in their skeletons. The absolute configuration of the (+)‐enantiomer was assigned on the basis of DFT computed optical rotations of both enantiomers to be all‐(S).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) (+)‐ And (–)‐1,1′‐bi(endo,exo,syn‐pentacyclo[3.3.02,4.06,8.09,11]undecyl) [1,1′‐bi(trishomobarrelenyl)], prepared along with the meso‐diastereomer, exhibit significantly enhanced molar optical rotations due to the presence of three helically arranged 1,2‐dicyclopropylethane units in their skeletons.