Poly-4-vinylpyridinium Poly(Hydrogen Fluoride): A Solid Hydrogen Fluoride Equivalent Reagent
作者:George A. Olah、Xing-Ya Li、Qi Wang、G. K. Surya Prakash
DOI:10.1055/s-1993-25924
日期:——
Poly-4-vinylpyridinium poly(hydrogen fluoride) (PVPHF), containing 35-60% hydrogen fluoride by weight, was prepared as a solid hydrogen fluoride equivalent reagent. PVPHF with 60% hydrogen fluoride by weight was found to be a versatile fluorinating agent for the hydrofluorination and bromofluorination of alkenes and alkynes, fluorination of alcohols as well as other fluorination reactions. Low hydrogen fluoride content PVPHF (3 equivalents of hydrogen fluoride to 1 equivalent of 4-vinylpyridine unit) was also found to be an efficient reagent for bromofluorination of alkenes in the presence of 1,3-dibromo-5,5-dimethylhydantoin. Fluorosulfonic acid-modified PVPHF showed enhanced reactivities for the fluorination of secondary alcohols.
The reaction of alkenes with N-bromosuccinimide and triethylamine tris(hydrofluoride) produces vic-bromofluoroalkanes (1) with high yields. As long as the addition to the double bond is sterically unhindered, bromine and fluorine get attached with very high regioselectivity, the latter halogen occupying the more substituted, carbocation stabilizing position. 2-Fluoro-1-alkenes give 1-bromo-2,2-di-fluoroalkanes