We report herein a directing group-controlled, palladium-catalyzed, regio-, stereo-, and enantiospecific anti-carboxylation of unactivated, internal allenes enabled via the synergistic interplay of a rationally designed bidentate directing group, palladium catalyst, and a multifunctional acetate ligand. The corresponding trans allyl ester was obtained in excellent yields with exclusive δ-regioselectivity and anti-carboxypalladation stereocontrol. The acetate ligand of the palladium catalyst controls the regio-, stereo- and enantioselectivity in the desired transformation. The potential of this concept has been demonstrated by the development of the chiral version of this transformation by using axial-to-central chirality transfer with good yields and enantioselectivities. Detailed investigations, including kinetic studies, order studies, and DFT studies, were performed to validate the ligand-assisted nucleopalladation process and the rationale behind the observed racemization of chiral allenes. The studies also indicated that the anti-carboxypalladation step was the rate-limiting as well as the stereo- and enantiodetermining step.

中文翻译：

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钯催化的、区域性/立体和对映体特异性未活化内部丙烯的羧化


我们在此报告了一种定向基团控制的、钯催化的、区域、立体和对映体特异性的未活化内部等位烯的抗羧化，通过合理设计的双齿定向基团、钯催化剂和多功能乙酸盐配体的协同相互作用实现的。以优异的产率获得相应的反式烯丙酯，具有独有的 δ-区域选择性和抗羧基钝化立体控制。钯催化剂的乙酸盐配体控制所需转化中的区域、立体和对映选择性。通过使用具有良好产量和对映选择性的轴向中心手性转移来开发这种转化的手性版本，证明了这一概念的潜力。进行了详细的调查，包括动力学研究、顺序研究和 DFT 研究，以验证配体辅助的核腭化过程和观察到的手性丙烯外消旋化的基本原理。研究还表明，抗羧基钝化步骤是限速以及立体和对映决定步骤。