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meta-Selective C−H carboxylation of 1,1-diarylethylene derivatives has been achieved by using a bulky rhodium catalyst under a CO₂ atmosphere. Experimental and computational mechanistic studies indicate that tandem hydrorhodation and rhodium migrations, which include unique aryl-to-aryl 1,2-rhodium migration, are operative in the reaction conditions.

Abstract

A meta-selective C−H carboxylation reaction of 1,1-diarylethylene derivatives with CO₂ by using a rhodium catalyst with NaO ⁱ Pr as a stoichiometric reductant has been achieved. Together with hydrogenation of the ethylene moiety, a carboxyl group was introduced to the meta-position of the aryl ring with high selectivity over the ortho-positions. Experimental and computational mechanistic studies indicate that this carboxylation reaction proceeds via hydrorhodation on the ethylene moiety, followed by 1,4-rhodium migration and successive 1,2-rhodium migration on the aryl ring. The use of a bulky phosphine ligand seems to be the key to this unusual aryl-to-aryl 1,2-rhodium shift.

Nature, Published online: 13 September 2021; doi:10.1038/d41586-021-02481-y

Nature, Published online: 08 September 2021; doi:10.1038/d41586-021-02444-3

Nature, Published online: 07 September 2021; doi:10.1038/d41586-021-02394-w

Nature, Published online: 06 September 2021; doi:10.1038/d41586-021-02428-3

Nature, Published online: 01 September 2021; doi:10.1038/d41586-021-02346-4

Herein, the first decarboxylative hydroxylation reaction to synthesize phenols from benzoic acids is reported. The method overcomes the challenges associated with conventional decarboxylation of benzoic acids and can be applied even for the late-stage functionalization.

Abstract

Herein, we report the first decarboxylative hydroxylation to synthesize phenols from benzoic acids at 35 °C via photoinduced ligand-to-metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation. The aromatic decarboxylative hydroxylation is synthetically promising due to its mild conditions, broad substrate scope, and late-stage applications.

Gold catalysis: A protocol for the direct acetoxylation of C(sp³)−H bonds of saturated hydrocarbons using simple gold salts (e. g. HAuBr₄) is reported. PhI(OAc)₂ serves as the oxidant and this transformation is proposed to proceed via hydride transfer as the key step.

Abstract

In this communication we report our studies towards the development of a gold-catalyzed direct acetoxylation of C(sp³)−H bonds. We achieve this through the use of the hypervalent iodine reagent PhI(OAc)₂ in combination with a simple gold salt (HAuBr₄) as the catalyst. Through a comparison of the reactivities of cyclooctane and adamantane we judge the reaction to proceed via hydride transfer. This is further substantiated through computational studies of the relative energies for the anions, radicals and cations derived from C−H bond cleavage of cyclooctane and adamantane relevant to the C−H cleaving step.

The Cover Feature shows lignin-first fractionation in a flow-through reactor assisted by β-zeolite. More information can be found in the Full Paper by A. Kramarenko et al.