Tun Soe L, Mariappan S V Santhana, Pigge F Christopher
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States.
Central NMR Facility, University of Iowa, Iowa City, Iowa 52242, United States.
J Org Chem. 2022 Jun 17;87(12):8059-8070. doi: 10.1021/acs.joc.2c00725. Epub 2022 Jun 1.
Aldehyde-derived imidazolidines participate as hydride donors in intramolecular reductive Heck-type reactions. ,'-Diphenylimidazolidines prepared from -alkynyl benzaldehydes underwent regio- and stereoselective palladium-catalyzed hydroarylation followed by formal 1,5-hydride transfer and reductive elimination to afford substituted alkenes and imidazolium moieties, the latter conveniently converted in situ to ring-opened benzanilides to simplify product isolation. Internal alkynes were converted to trisubstituted alkenes via a hydroarylation process, while a terminal alkyne was converted to a alkene via a formal hydroarylation reaction. Benzanilide products could be converted to carboxylic acid derivatives under basic conditions, resulting in the net conversion of alkynyl aldehydes to alkenyl carboxylic acids. A styrene derivative with an attached ,'-dimethylbenzimidazoline hydride donor was also found to undergo an analogous hydroarylation/benzimidazoline oxidation to give a diarylethane product.
醛衍生的咪唑烷在分子内还原型Heck反应中作为氢化物供体参与反应。由α-炔基苯甲醛制备的α,α'-二苯基咪唑烷经历区域和立体选择性钯催化的氢芳基化反应，随后进行形式上的1,5-氢化物转移和还原消除反应，得到取代烯烃和咪唑鎓部分，后者可方便地原位转化为开环苯甲酰苯胺以简化产物分离。内炔烃通过氢芳基化过程转化为三取代烯烃，而末端炔烃通过形式上的氢芳基化反应转化为反式烯烃。苯甲酰苯胺产物在碱性条件下可转化为羧酸衍生物，从而实现炔基醛向烯基羧酸的净转化。还发现带有α,α'-二甲基苯并咪唑啉氢化物供体的苯乙烯衍生物会发生类似的氢芳基化/苯并咪唑啉氧化反应，生成二芳基乙烷产物。
