Catalytic asymmetric nucleophilic fluorination using BF<sub>3</sub>·Et<sub>2</sub>O as fluorine source and activating reagent.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34172752.
- Also identified by DOI 10.1038/s41467-021-24278-3 and PMC identifier 8233348.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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 BF<sub>3</sub>·Et<sub>2</sub>O-based fluorinations, have not yet been addressed. Here we report the catalytic asymmetric nucleophilic fluorination using BF<sub>3</sub>·Et<sub>2</sub>O 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 Et<sub>3</sub>N·3HF were employed as the fluorine source) indicated that BF<sub>3</sub>·Et<sub>2</sub>O acted not only as a fluorine reagent but also as the activating reagent for activation of iodosylbenzene.