Transition metal-catalyzed 1,3-acyloxy migration of propargylic esters represents one of the most straightforward routes to access allene intermediates, which could engage in various fascinating subsequent transformations. However, this process is often limited to propargylic esters with electron-donating group due to intrinsic electronic bias and the subsequent intermolecular reactions are quite limited. Herein, we disclosed an unprecedented Rh₂(II)-catalyzed 1,3-acyloxy migration of electron-deficient propargylic esters, followed by intermolecular [2+2] cycloaddition with readily available alkenes and alkynes, a large array of valuable alkylidenecyclobutane/ene scaffolds could be obtained facilely in one pot. Mechanistic studies revealed that the allene generated from Rh₂(II)-catalyzed 1,3-acyloxy migration of propargylic carboxylates is the key intermediate. Control experiments and NMR data indicated that the formyl group at the terminus of propargylic esters is crucial and the cooperative interactions between the substrate and the carboxylate ligand possibly play a signficant role in this reaction.

中文翻译：

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串联 Rh（II） 催化的 1,3-酰氧基迁移/分子间 [2+2] 烯烃和炔烃的炔丙基丙酯的分子间 [2+2] 环加成反应


炔丙酯的过渡金属催化的 1,3-酰氧基迁移代表了获得烯中间体的最直接途径之一，它可以参与各种迷人的后续转化。然而，由于本征电子偏压，这个过程通常仅限于具有供电子基团的炔丙酯，并且随后的分子间反应非常有限。在此，我们披露了前所未有的 Rh₂（II） 催化的缺电子炔丙酯的 1,3-酰氧基迁移，然后用现成的烯烃和炔烃进行分子间 [2+2] 环加成反应，在一个罐中可以很容易地获得大量有价值的烷基环丁烷/烯支架。机理研究表明，Rh₂（II） 催化的炔丙基羧酸盐的 1,3-酰氧基迁移生成的烯是关键的中间体。对照实验和 NMR 数据表明，炔丙酸酯末端的甲酰基至关重要，底物和羧酸盐配体之间的协同相互作用可能在该反应中发挥重要作用。