Transition-metal-catalyzed homogeneous dehydrogenation and isomerization are common organic molecular activation reactions. Palladium hydrides are good olefin isomerization catalysts but are usually short-lived species under redox-active dehydrogenation conditions. Here, we show that Pd-H in the presence of an N-heterocyclic carbene ligand and an alkene regulator enables transfer-dehydroaromatization, avoiding the homo-disproportionation pathway. The desired product is obtained with up to 99:1 selectivity, and the exo-to-endo olefin isomerization can be carried out in one pot. In contrast to previously reported methods that rely on the efficient removal of Pd-H, the approach reported herein benefits from the steric effects of the N-heterocyclic carbene and the choice of alkene to regulate the competing reactivity of allylic C‒H activation and hydropalladation. This method circumvents the challenges associated with tedious olefin separation and a low exo-to-endo olefin isomerization ratio and expands the scope to include challenging endo- and exo-cyclic olefins under mild, neutral, and oxidant-free conditions. Overall, herein, we provide a strategy to synthesize (hetero)aromatic compounds via chemoselective dehydrogenation of cyclic alkenes over ketones and the dehydrogenative Diels-Alder reaction of a cyclic enamine.

过渡金属催化的均相脱氢和异构化是常见的有机分子活化反应。氢化钯是良好的烯烃异构化催化剂，但在氧化还原活性脱氢条件下通常是短寿命的物质。在这里，我们展示了在 N-杂环卡宾配体和烯烃调节剂存在下的 Pd-H 能够实现转移-脱氢芳构化，避免了均歧化途径。以高达 99:1 的选择性获得所需的产品，并且可以在一锅中进行外-内烯烃异构化。与先前报道的依赖于有效去除 Pd-H 的方法相比，本文报道的方法受益于 N-杂环卡宾的空间效应和烯烃的选择，以调节烯丙基 C-H 活化和加氢反应的竞争反应性。该方法避免了与繁琐的烯烃分离和低外-内烯烃异构化率相关的挑战，并将范围扩大到包括在温和、中性和无氧化剂条件下具有挑战性的内环和外环烯烃。总体而言，本文提供了一种通过环烯烃对酮的化学选择性脱氢和环烯胺的脱氢 Diels-Alder 反应来合成（杂）芳族化合物的策略。该方法避免了与繁琐的烯烃分离和低外-内烯烃异构化率相关的挑战，并将范围扩大到包括在温和、中性和无氧化剂条件下具有挑战性的内环和外环烯烃。总体而言，本文提供了一种通过环烯烃对酮的化学选择性脱氢和环烯胺的脱氢 Diels-Alder 反应来合成（杂）芳族化合物的策略。该方法避免了与繁琐的烯烃分离和低外-内烯烃异构化率相关的挑战，并将范围扩大到包括在温和、中性和无氧化剂条件下具有挑战性的内环和外环烯烃。总体而言，本文提供了一种通过环烯烃对酮的化学选择性脱氢和环烯胺的脱氢 Diels-Alder 反应来合成（杂）芳族化合物的策略。