Transition-Metal-Free Transfer Hydrohalogenation

小分子从一个分子转移到另一个分子最近成为一个新兴领域。这样，就绕过了气体和潜在危险化学品的处理。我们的实验室引入了充分取代的环己-1,4-二烯作为氢硅烷和二氢的替代品，它们分别参与Lewis酸催化的转移硅氢化和烯烃氢化反应。实现转移氢卤化的相关矿物酸替代物是非常理想的，但化学性质不稳定，通常会迅速消除伴随芳构化的HX。我们现在设计了一种新型的转移试剂，再次基于环己-1,4-二烯平台，它具有化学稳定性，从而允许HX的可控释放以及HX转移到碳-碳多键上。该过程是质子催化的，因此，不同于早期的过渡-无金属转移反应。在这个项目中，我们将开发合成有用的低分子量代物，主要是X = I, Br， Cl甚至F，并将这些代物应用于转移氢卤化。还预计将扩大这一战略以转移硅基卤化。

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.