Preparation of Fluorinated Tetrahydropyrans and Piperidines Using a New Nucleophilic Fluorination Reagent DMPU/HF.

DMPU/HF (HF content 65 wt %/wt) is an ideal nucleophilic fluorination reagent for the diastereoselective synthesis of substituted 4-fluorotetrahydropyrans and 4-fluoropiperidines via a fluoro-Prins reaction. When compared to classical nucleophilic fluorination reagents like pyridine/HF, DMPU/HF gives both higher yields and better diastereoselectivity.