Asymmetric Synthesis of Overcrowded Alkenes by Transfer of Axial Single Bond Chirality to Axial Double Bond Chirality.
Optically active overcrowded alkenes were synthesized by employing bis-beta-naphthol as a chiral template during an intramolecular coupling reaction. The major isomer 2 has a unique helical structure with twisted and folded structural moieties. Removal of the chiral template afforded overcrowded thioxanthylidene 3 with 96 % ee, which indicates that no racemization or isomerization of the enantiomers took place.
Geertsema
EM
Department of Organic and Molecular Inorganic Chemistry, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen (The Netherlands).
Meetsma
A
Feringa
BL