Recent advances in stereoselective construction of fluorinated quaternary carbon centers from fluorinated compounds

There are many fluorinated quaternary carbon structural units in pharmaceuticals and bioactive compounds. Organic chemists are interested in the stereoselective synthesis of fluorinated quaternary carbon structural units. Constructing a fluorinated quaternary carbon stereocenter can be achieved directly and efficiently by the asymmetric catalytic reaction of fluorinated compounds as substrates. This approach aims to construct fluorinated quaternary carbon stereocenters while diversifying the types of fluorinated compounds. This review introduces a series of reactions for synthesizing fluorinated quaternary carbon chiral centers through asymmetric organic catalysis and transition metal catalysis, including alkylation, arylation, Mannich, Michael addition, and allylation reactions. This work will contribute to the development of the synthesis of fluorinated quaternary carbon chiral center-containing compounds in the future.

The Enediolate Chemistry of Free Carboxylic Acids

The synthetic methodologies for the α-functionalization of free carboxylic acids through the enediolate intermediates are summarized in this review. In general, the enediolates could be generated in situ or transiently from free carboxylic acids with a stoichiometric or catalytic amount of protection reagents, including metal, boron, and silicon reagents. The in situ or transient generated enediolates were subsequently subjected to racemic or asymmetric reactions with various electrophiles, producing the α-functionalized free carboxylic acids in a single step. In addition, the enediolate could undergo an α-oxidation reaction with TEMPO through the radical process.

Benzylic Fluorination Induced by a Charge-Transfer Complex with a Solvent-Dependent Selectivity Switch

We present a divergent strategy for the fluorination of phenylacetic acid derivatives that is induced by a charge-transfer complex between Selectfluor and 4-(dimethylamino)pyridine. A comprehensive investigation of the conditions revealed a critical role of the solvent on the reaction outcome. In the presence of water, decarboxylative fluorination through a single-electron oxidation is dominant. Non-aqueous conditions result in the clean formation of α-fluoro-α-arylcarboxylic acids.