Resolution of a Configurationally Stable Hetero[4]helicene

We have developed an efficient chemical resolution of racemic hydroxy substituted dithia-aza[4]helicenes (DTA[4]H) 1(OH) using enantiopure acids as resolving agents. The better diastereomeric separation was achieved on esters prepared with (1S)-(-)-camphanic acid. Subsequent simple manipulations produced highly optically pure (>= 99% enantiomeric excess) (P) and (M)-1(OH) in good yields. The role of the position where the chiral auxiliary is inserted (cape- vs. bay-zone) and the structure of the enantiopure acid used on successful resolution are discussed.

Automated summary

In this study, an efficient chemical resolution method was developed for the separation of racemic hydroxy substituted dithia-aza[4]helicenes. Enantiopure acids were used as resolving agents, leading to better diastereomeric separation. Highly optically pure products were obtained through subsequent manipulations.