Photomediated Hydro- and Deuterodecarboxylation of Pharmaceutically Relevant and Natural Aliphatic Carboxylic Acids

Direct Hydrodecarboxylation of Carboxylic Acids via N-Hydroxyphthalimide-Mediated Hydrogen Atom Transfer

The hydrodecarboxylation of carboxylic acids is a fundamental functional group transformation in chemistry. However, current methods rely on acid preactivation, expensive photocatalysts, or transition-metal catalysts. Herein, we describe an unprecedented transition-metal- and photocatalyst-free chemoselective hydrodecarboxylation of carboxylic acids via N-hydroxyphthalimide-mediated hydrogen atom transfer. This mild method exhibits broad functional group tolerance and enables the conversion of primary, secondary, and tertiary carboxylic acids to alkanes. The versatility of this method is demonstrated through the late-stage functionalization of complex natural products and pharmaceuticals.

Enantioselective Decarboxylative Hydrogen-Atom Transfer Reaction

Direct enantioselective decarboxylative transformations of carboxylic acids have become powerful tools for constructing structurally and functionally diverse molecules. Herein, an unprecedented organocatalyzed protocol for enantioconvergent decarboxylative reduction was established by leveraging dual catalysis of photoredox-mediated radical generation and a thiol-catalyzed asymmetric hydrogen-atom transfer process. With this hydrodecarboxylation, a variety of chiral 3-substituted indolines were attained from the acids in moderate to excellent yields with high enantioselectivities.

Visible-Light Organic Photosensitizers Based on 2-(2-Aminophenyl)benzothiazoles for Photocycloaddition Reactions

We have studied 2-(2-aminophenyl)benzothiazole and related derivatives for their photophysical properties in view of employing them as new and readily tunable organic photocatalysts. Their triplet energies were estimated by DFT calculations to be in the range of 52-57 kcal mol-1, suggesting their suitability for the [2+2] photocycloaddition of unsaturated acyl imidazoles with styrene derivatives. Experimental studies have shown that 2-(2-aminophenyl)benzothiazoles comprising alkylamino groups (NHMe, NHiPr) or the native amino group provide the best photocatalytic results in these visible-light mediated [2+2] reactions without the need of any additives, yielding a range of cyclobutane derivatives. A combined experimental and theoretical approach has provided insights into the underlying triplet-triplet energy transfer process.