In this addition to OBC‘s online Organocatalysis collection, Shu-Li You and co-workers from Shanghai Institute of Organic Chemistry report a highly efficient tandem double Friedel–Crafts reaction between indoles and 2-formylbiphenyl derivatives catalysed by chiral N-triflyl phosphoramide which produces various fluorene derivatives in excellent yields and ee.
Notably, the fluorene products obtained with the chiral N-triflyl phosphoramide have the opposite absolute configuration compared to that obtained with the corresponding chiral phosphoric acid. This allows access to both enantiomers of the products by utilizing different catalysts derived from one enantiomer of binaphthol.
This paper is FREE to access for 4 weeks, and while you’re there why not have a look at the rest of the Organoncatalysis collection.
Enantioselective synthesis of fluorene derivatives by chiral N-triflyl phosphoramide catalyzed double Friedel–Crafts alkylation reaction
Shou-Guo Wang, Long Han, Mi Zeng, Feng-Lai Sun, Wei Zhang and Shu-Li You
Org. Biomol. Chem., 2012,
DOI: 10.1039/C2OB07168A
