Direct Aerobic α-Hydroxylation of Arylacetates for the Synthesis of Mandelates

Cobalt Catalyzed α-Hydroxylation of Arylacetic Acid Equivalents with Dioxygen

A cobalt catalyst, under oxidative conditions, facilitates the single electron transfer process in N-pyridyl arylacetamides to form α-carbon-centered radicals that readily react with molecular oxygen, giving access to mandelic acid derivatives. In contrast to the known benzylic hydroxylation approaches, this approach enables chemo- and regioselective hydroxylation at a benzylic position adjacent to (N-pyridyl)amides. Mild conditions, broad scope, excellent selectivity, and wide synthetic practicality set up the merit of the reaction.

Construction of Bridged Benzazepines via Photo-Induced Dearomatization

Bridged benzazepine scaffolds, possessing unique structural and physicochemical activities, are widespread in various natural products and drugs. The construction of these skeletons often requires elaborate synthetic effort with low efficiency. Herein, we develop a simple and divergent approach for constructing various bridged benzazepines by a photocatalytic intermolecular dearomatization of naphthalene derivatives with readily available α-amino acids. The bridged motif is created via a cascade sequence involving photocatalytic 1,4-hydroaminoalkylation, alkene isomerization and cyclization. Interestingly, the diastereoselectivity can be regulated through different reaction modes in the cyclization step. Moreover, aminohydroxylation and its further bromination have also been demonstrated to access highly functionalized bridged benzazepines. Preliminary mechanistic studies have been performed to get insights into the mechanism. This method provides a divergent synthetic approach for construction of highly functionalized bridged benzazepines, which have been otherwise difficult to access.