Transition-Metal-Free Transfer Hydrohalogenation

点击翻译按钮获取中文摘要

The transfer of small molecules from one molecule to another recently turned into an emerging area. By this, the handling of gaseous and potentially dangerous chemicals is bypassed. Our laboratory introduced adequately substituted cyclohexa-1,4-dienes as surrogates of hydrosilanes and dihydrogen, and these engage in Lewis acid-catalyzed transfer hydrosilylation and hydrogenation of alkenes, respectively. Related surrogates of mineral acids to achieve transfer hydrohalogenation are highly desirable but not chemically stable, usually rapidly eliminating HX concomitant with aromatization. We have now designed a new type of transfer reagent, again based on the cyclohexa-1,4-diene platform, that is chemically robust, thereby allowing for controlled release of HX as well as transfer of HX onto carbon-carbon multiple bonds. The process is proton-catalyzed and, as such, different from the earlier transition-metal-free transfer reactions. Within this project, we will develop synthetically useful low-molecular-weight surrogates, predominantly for X = I, Br, Cl and even F, and apply these to transfer hydrohalogenation. Expansion of this strategy to transfer silylhalogenation is also anticipated.