Carboxylation of C(sp2) Bromides Enabled by Metallophotoredox Dual Catalysis and Sodium Formate Open Access

Zhang, Drason (Spring 2023)

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n recent years, photoredox-mediated processes have seen a resurgence in popularity due to their ability to enable novel reactivity via pathways involving thermally inaccessible intermediates. These photoredox processes include single-electron transfer and energy transfer processes, which are attractive due to their ability to occur under mild conditions that enable high functional group tolerance. Previous work has developed formate salts as precursors to the carbon dioxide radical anion (CO2•−) via hydrogen-atom transfer (HAT) under photochemical conditions; this radical anion was shown to undergo a variety of processes, including Giese-type addition to electron-deficient olefins. Given this, our group wondered if CO2•− could instead be leveraged as a partner in C-C bond formation cross-coupling, which would enable facile access to carboxylic acids: a common organic functional group in natural products, pharmaceutical agents, and more. This report focuses on the successful development of such a method that leverages a metallophotoredox/HAT triple catalysis reaction manifold: utilizing visible light, 4CzIPN, nickel, and formate salts as a source of CO2•−, we are able to construct a wide variety of carboxylic acids bearing diverse functional groups from simple (hetero)aryl or vinyl C(sp2)-bromide starting materials. Of note, we report that catalytic amounts of N-phenyl-bis(trifluoromethanesulfonamide) play an essential role in carboxylation. Overall, we have developed a mild method enabling facile access to carboxylic acids from readily available starting materials.

Table of Contents

1 Chapter 1: Shining Light on Photoredox Methods

1.1 A Brief Discussion on the Development of Synthetic Methods

1.2 An Introduction to Visible Light Photoredox Catalysis

1.3 Shiny Acids: Photoredox-Catalyzed Carboxylation

2 Chapter 2: Development of a Novel Carboxylation Method

2.1 Initial Foray into Non-Photocatalysis Land

2.2 Hopping on the Photoredox Catalysis Train

3 Chapter 3: The Finale

4 Supporting Information

I. General Information

II. General Procedures

III. Electrochemical Measurements & 19F Spectra

III. Preparation of Starting Materials

IV. Preparation of Products from Substrate Table

V. NMR Spectra


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