Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

Abstract

Boomerang-shaped bipyrroles containing donor–acceptor units were obtained through a tandem palladium-mediated reaction consisting of a cyclization step, involving double C–H bond activation, and a double α-oxygenation. The latter reaction can be partly suppressed for the least reactive systems, providing access to α-unsubstituted boomerangs for the first time. These “α-free” systems are highly efficient fluorophores, with emission quantum yields exceeding 80% in toluene. Preliminary measurements show that helicene-like boomerangs may be usable as circularly polarized luminescent materials.

Novel Synthetic Approach to Heteroatom Doped Polycyclic Aromatic Hydrocarbons: Optimizing the Bottom-Up Approach to Atomically Precise Doped Nanographenes

“…Moving to pyrrole containing PAHs, boomerang shaped molecules based on a bipyrrole moiety have been proposed by the group of Stępień ( Scheme 14 ). These molecules are characterized by the presence of a bipyrrole unit bridged by alkyl chains of different length [ 61 ]. The bulky aromatic structures confer them a helix structure with important consequences on their chiroptical properties.…”

Acenaphthylene-fused ullazines: fluorescent π-extended monopyrroles with tunable electronic gaps

“…Here we demonstrate the synthesis of π-extended dibenzoullazines bearing acenaphthylene subunits fused to the β-β edge of the pyrrole ring (Scheme 1). This work was inspired by the chemistry of naphthalimide-fused (NMI) pyrroles, 29 which have been used as donor-acceptor units in diverse oligopyrrole motifs, [29][30][31][32][33][34][35][36][37] and their electron-rich congeners. [38][39][40][41][42][43][44][45] We show that the properties of ullazine can be controlled by introducing acenaphthylene units with variable acceptor strength.…”

Naphthalimide‐Fused Dipyrrins: Tunable Halochromic Switches and Photothermal NIR‐II Dyes

“…[38][39][40][41][42] Here we report on the halochromism and electronic structure properties of a family of dipyrrins bearing fused naphthal- imide (NMI) moieties (Figure 1). NMI pyrroles [43] have been previously shown to be versatile building blocks for the synthesis of electron-deficient porphyrins, [43][44][45] azacoronenes, [46][47][48] bipyrroles, [49][50][51] and polymers. [52] The family comprises two series of dipyrrins 1a-1f and 2a-2e, bearing respectively phenyl, and p-(dimethylamino)phenyl groups at the pyrrolic 𝛼 (or 1,9) positions (G1), and aryl substituents with variable donor/acceptor strength at the meso bridge (G2).…”