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.     

Multiple Heterohelicenes: Synthesis,Properties and Applications**

Multiple heterohelicenes are a unique class of helical nonplanar scaffolds that have attracted great attention due to their appealing shapes, optical and electronic properties, and potential applications in chiral materials. This review describes the recent advances and challenges in the design and synthesis of representative multiple heterohelicenes with intriguing chiral properties. And the corresponding applications are also covered.