130602-12-9Relevant academic research and scientific papers
Computationally Guided Catalyst Design in the Type i Dynamic Kinetic Asymmetric Pauson-Khand Reaction of Allenyl Acetates
Burrows, Lauren C.,Jesikiewicz, Luke T.,Lu, Gang,Geib, Steven J.,Liu, Peng,Brummond, Kay M.
, p. 15022 - 15032 (2017/10/31)
The Rh(I)-catalyzed allenic Pauson-Khand reaction (APKR) is an efficient, redox-neutral method of synthesizing α-acyloxy cyclopentenones. An enantioselective APKR could provide access to chiral, nonracemic α-acyloxy and α-hydroxy cyclopentenones and their corresponding redox derivatives, such as thapsigargin, a cytotoxic natural product with potent antitumor activity. Rapid scrambling of axial chirality of allenyl acetates in the presence of Rh(I) catalysts enables the conversion of racemic allene to enantiopure cyclopentenone product in a dynamic kinetic asymmetric transformation (DyKAT). A combined experimental and computational approach was taken to develop an effective catalytic system to achieve the asymmetric transformation. The optimization of the denticity, and steric and electronic properties of the ancillary ligand (initially (S)-MonoPhos, 58:42 er), afforded a hemilabile bidentate (S)-MonoPhos-alkene-Rh(I) catalyst that provided α-acyloxy cyclopentenone product in up to 14:86 er. Enantioselectivity of the Rh(I)-(S)-MonoPhos-alkene catalyst was rationalized using ligand-substrate steric interactions and distortion energies in the computed transition states. This asymmetric APKR of allenyl acetates is a rare example of a Type I DyKAT reaction of an allene, the first example of DyKAT in a cyclocarbonylation reaction, and the first catalyst-controlled enantioselective APKR.
Indirect electroreductive sequential radical reaction catalyzed by a Ni(II) complex. One-step preparation of functionalized (methylene)cyclopentanes
Ozaki,Mitoh,Ohmori
, p. 1435 - 1440 (2007/10/03)
Substituted (methylene)cyclopentanes were prepared by one-step reaction at room temperature from butynyl iodides and activated olefins by sequencing of free radical addition and cyclization reactions. The reactions, which were conducted by indirect electroreduction catalyzed by a nickel(II) complex, proceeded with modest selectivity for formation of the Z(methylene)cyclopentanes.
