Solvent-Minimized Synthesis of 4CzIPN and Related Organic Fluorophores via Ball Milling

Abstract

The mechanochemical synthesis of 2,4,5,6-tetra­(9H-carbazol-9-yl)­isophthalonitrile and related organic fluorophores/photocatalysts via a solvent-minimized four-fold SNAr pathway is herein described. Employing sodium tert-butoxide as base, and negating the need for any air/moisture-sensitive reaction set-ups, a selection of organic dyes was synthesized in just 1 h using this ball-milling technique. Furthermore, the transformation was then showcased on a multigram scale.

One-step hydroxylation of aryl and heteroaryl fluorides using mechanochemistry

“…It is also worth mentioning that, although many organic reactions have been already investigated with mechanochemical techniques, 14 this is not the case for S N Ar reactions, which remain underexplored with ball milling procedures. 19,20…”

Synthesis of polyfunctionalized dihydro-2-oxypyrroles catalyzed by 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a novel donor-acceptor fluorophore

“…A parallel to these discoveries is the renaissance of visible light photo-redox catalysis in organic synthesis, providing novel opportunities for the design of synthetic routes through efficient light-mediated transformations. These reasons have led to the widespread use of photo-redox catalysis in the synthesis of building blocks, pharmaceuticals, and the total synthesis of complex natural products 11 . The electron-transfer process is enabled in a significant percentage of these transformations by the use of ruthenium (II) and iridium (III) complexes as photocatalysts 12 – 14 .…”

“…1,2,3,5-Tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), which combines carbazolyl as a donor and dicyanobenzene as an electron acceptor, is a novel donor–acceptor (D–A) fluorophore (Fig. 1 shows its photocatalysis cycles 11 ). The excellent redox window, environmental and economic sustainability, as well as their broad applicability and established electronic properties, make 4CzIPN an attractive metal-free photocatalyst 6 , 14 , 16 .…”

“…The excellent redox window, environmental and economic sustainability, as well as their broad applicability and established electronic properties, make 4CzIPN an attractive metal-free photocatalyst 6 , 14 , 16 .

Figure 1 The 4CzIPN is capable of performing photocatalytic cycles 11 .

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Mechanochemical Organocatalysis: Do High Enantioselectivities Contradict What We Might Expect?

“…All of this can be largely achieved in the absence of solvent, and thus the reactor environment of a ball mill is receiving increasing interest in recent times. [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]…”