Publication data for: "Tunable Endo/Exo Selectivity in Direct Catalytic Asymmetric 1,3-Dipolar Cycloadditions with Polyfunctional Lewis Acid / Azolium-Aryloxide Catalysts"

<p>This dataset contains research data for the publication "Tunable Endo/Exo Selectivity in Direct Catalytic Asymmetric 1,3-Dipolar Cycloadditions with Polyfunctional Lewis Acid / Azolium-Aryloxide Catalysts".</p>

<p>Data type and creation: The dataset comprises experimental data focused on the magnetic and electronic characterization of the paramagnetic transition metal complexes used in the study. Specifically, it includes Electron Paramagnetic Resonance (EPR) spectroscopy data, Superconducting Quantum Interference Device (SQUID) magnetometry data, and Evans method data.</p>

<p>Data structure: The dataset is organized into specific directories based on the applied analytical methods.</p>

<p>Data interpretation: The magnetic and spectroscopic measurements (EPR, SQUID, Evans) are used to elucidate the electronic structure, coordination environment, and spin states of the novel polyfunctional Lewis acid / azolium-aryloxide catalysts. These data substantiate the properties of the catalytically active metal centers, which is crucial for understanding the remarkable endo/exo-selectivity in the 1,3-dipolar cycloadditions. The included SI provides the full chemical context, interpretative details for all other findings, and complete experimental procedures.</p>

<p>Reuse potential: The magnetic characterization data can be reused by spectroscopists and computational chemists as a reference or benchmarking tool for studying, comparing, and modeling paramagnetic transition metal complexes. Furthermore, the detailed SI allows other researchers to precisely reproduce the complex catalyst syntheses and the catalytic cycloaddition protocols in their own laboratories, or to adapt the methods for new substrate classes.</p>

Abstract:<br>
Catalytic asymmetric 1,3-dipolar cycloadditions (1,3-DCA) using iminoesters as ylide precursors offer a powerful approach to accessing stereochemically complex, biologically relevant pyrrolidines. Although previous studies have already achieved impressive stereoselectivities, catalytic productivity remains a challenge, with turnover numbers (TON) typically below 20. In this article, we introduce a novel concept for catalytic 1,3-DCA that enables remarkable productivity for both endo (TON up to 4000) and the more challenging exo products (TON up to 1500). This approach, making use of modular polyfunctional Lewis acid/azolium-aryloxide catalysts, allows for precise control over endo- and exo-diastereoselectivity. The switch from endo- to exo-selectivity is accomplished by modifying the metal center, the azolium moiety, and steric factors. As detailed DFT studies reveal, both the endo- and exo-selective catalyst systems exhibit an almost perfect spatial alignment of their key functional sites, allowing for a unique interplay of Brønsted acids and bases, Lewis acids, and hydrogen bonding. The computational studies further demonstrate that these polyfunctional catalysts dramatically lower the energetic barriers of the concerted or stepwise cycloaddition key steps. However, they also precisely orchestrate and accelerate all accompanying transformations—reminiscent of enzymatic machineries.