Catalytic asymmetric nucleophilic fluorination using BF3·Et2O as fluorine source and activating reagent.

Fluorination using chiral catalytic methods could result in a direct access to asymmetric fluorine chemistry. However, challenges in catalytic asymmetric fluorinations, especially the longstanding stereochemical challenges existed in BF3·Et2O-based fluorinations, have not yet been addressed. Here we report the catalytic asymmetric nucleophilic fluorination using BF3·Et2O as the fluorine reagent in the presence of chiral iodine catalyst. Various chiral fluorinated oxazine products were obtained with good to excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >20:1 dr). Control experiments (the desired fluoro-oxazines could not be obtained when Py·HF or Et3N·3HF were employed as the fluorine source) indicated that BF3·Et2O acted not only as a fluorine reagent but also as the activating reagent for activation of iodosylbenzene.

Highly efficient regio-selective ring-opening nucleophilic fluorination of aziridines and azetidines: access to ß- or γ-fluorinated amino acid derivatives.

Herein, we have presented a facile and efficient method of ring-opening nucleophilic fluorination of aziridines, affording highly regio-selective ß-fluorinated amines. Firstly, the example of ring-opening hydrofluorination of azetidines was reported. Then, the Olah's reagent also provided a promising method for the construction of enantioenriched ß-fluoro-α-amino acid derivatives, which could be used for the preparation of peptide-based bioactive molecules.