A mild synthetic route to α-nitroso diaryl pyrroles.

A new synthetic method to access α-nitroso pyrroles is presented. This method utilises the nitrosonium salt NOBF4, enabling short reaction times (<10 minutes) and avoiding the harsh acidic conditions usually associated with pyrrole nitrosation. Application of this procedure to diarylated pyrroles yielded several novel nitroso-pyrroles. Modifications to the method, through exclusion of air and inclusion of a mild base, allowed for the nitrosation of pyrroles bearing aryl groups substituted with electron-donating groups. Attempts to nitrosylate pyrroles bearing alkyl substituents resulted in the formation of a dimeric material composed of a pyrrolic unit and a 2-hydroxyimino-protected 1,5-dihydro-2H-pyrrol-2-one.

Substitution at boron in BODIPYs.

Recent synthetic achievements have led to 4,4-disubstituted-4-bora-3a,4a-diaza-s-indacenes (BODIPYs) with varying substituents at the meso, pyrrolic and/or boron sites, with each influencing photophysical properties and utility. This Feature article gives an overview of chemistry at the boron atom in BODIPYs, highlighting our contributions that evolved from synthetic curiosities and now offer this dipyrrolic skeleton potential across a wider range of applications. We first summarise preparative routes to BODIPYs through complexation of boron with the dipyrrinato ligand. The role of boron in protecting dipyrrins is then discussed, followed by strategies by which to achieve facile substitution at the boron atom.