Selective Halofluorination of Alkenes with Tetrabutylphosphonium Dihydrogentrifluoride in Combination with<i>N</i>-Halosuccinimide or 1,3-Dibromo-5,5-dimethylhydantoin
Alkenes and their functionalized derivatives were readily converted to the corresponding halofluorides with tetrabutylphosphonium dihydrogentrifluoride as combined with N-halosuccinimides or 1,3-dibromo-5,5-dimethylhydantoin in highly regio-, stereo-, and chemoselective manners. In particular, alkenes having a oxirane or primary hydroxyl group also underwent halofluorination selectively in good yields
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.
Hydrogenfluoride is a basic fluorinating reagent, but handling it is difficult. For this reason, some modified fluorinating reagents such as HF-pyridine, Et3N-HF, and poly(hydrogenfluoride) complex have been developed. Those reagents, however, still require aqueous work-up procedures which generate hydrogenfluoride. Recently, ionic liquids have received much attention because of the ease in handling
Halofluorination of Alkenes Using Trihaloisocyanuric Acids and HF×Pyridine
作者:Marcio de Mattos、Pierre Esteves、Lívia Crespo、Rodrigo Ribeiro
DOI:10.1055/s-0029-1220011
日期:2010.7
Halofluorination of alkenes with a new system (trihaloisocyanuric acids and HFËpyridine) results in the formation of vicinal halofluoroalkanes. The reaction is regioselective leading to Markovnikov-oriented products and the halofluorinated adducts follow anti-addition in the case of cyclohexene and 1-methylcyclohexene. Reaction yields range from 67-88%.