Synthesis of Fluorenones from Benzaldehydes and Aryl Iodides: Dual C–H Functionalizations Using a Transient Directing Group

The first synthesis of substituted fluorenones directly from benzaldehydes and aryl iodides via a Pd­(II)-catalyzed C­(sp²)–H functionalization cascade is reported. Featuring anthranilic acid as an inexpensive transient directing group, the process is compatible with a variety of benzaldehydes and aryl iodides. A three-step synthesis of the antiviral drug Tilorone was completed in an excellent overall yield (40%), demonstrating the utility of this method

Pd-Catalyzed <i>Ortho</i> C–H Hydroxylation of Benzaldehydes Using a Transient Directing Group

The direct Pd-catalyzed <i>ortho</i> C–H hydroxylation of benzaldehydes was achieved using 4-chloroanthranilic acid as the transient directing group, 1-fluoro-2,4,6-trimethylpyridnium triflate as the bystanding oxidant, and <i>p</i>-toluenesulfonic acid as the putative oxygen nucleophile. The unusual C–H chlorination and polyfluoroalkoxylation reactions signaled the importance of external nucleophiles to the outcome of Pd­(IV) reductive eliminations

Expanded Bodipy Dyes: Anion Sensing Using a Bodipy Analog with an Additional Difluoroboron Bridge

Oxalyl-tethered pyrroles can be doubly bridged with two difluoroboron chelating units to yield bright orange dyes. Interestingly, in polar organic solvents, the addition of fluoride and cyanide result in reversible detachment of the otherwise stable difluoroboron bridges, resulting in sharp changes in color. Thus, this novel compound behaves as a highly selective chromogenic sensor for fluoride and cyanide ions

Expanded Bodipy Dyes: Anion Sensing Using a Bodipy Analog with an Additional Difluoroboron Bridge

Oxalyl-tethered pyrroles can be doubly bridged with two difluoroboron chelating units to yield bright orange dyes. Interestingly, in polar organic solvents, the addition of fluoride and cyanide result in reversible detachment of the otherwise stable difluoroboron bridges, resulting in sharp changes in color. Thus, this novel compound behaves as a highly selective chromogenic sensor for fluoride and cyanide ions

Modulating OxyB-Catalyzed Cross-Coupling Reactions in Vancomycin Biosynthesis by Incorporation of Diverse d‑Tyr Analogues

We report a general method for synthesizing diverse d-Tyr analogues, one of the constituents of the antibiotic vancomycin, using a Negishi cross-coupling protocol. Several analogues were incorporated into the vancomycin substrate–peptide and reacted with the biosynthetic enzymes OxyB and OxyA, which install the characteristic aromatic cross-links. We find that even small structural perturbations are not accepted by OxyA. The same modifications, however, enhance the catalytic capabilities of OxyB leading to the formation of a new macrocycle within the vancomycin framework