Nobel Prize 2022: Organic Chemistry Click Chemistry: Retrosynthetic analysis of this small molecule chromophore, a dye with pushpull functionality across its conjugated pi system.
(CORRECTION: at 16:45, bottomleft corner of screen the reagent should be NaOH, not LiAlH4)

Discussion inspired by this reference:
Eur. J. Org. Chem.2013, 5591
https://doi.org/10.1002/ejoc.201300458

Click Chemistry is also known as BioOrthogonal Chemistry. This type of Chemistry won the Nobel Prize in 2022 for Bertozzi, Meldel and Sharpless.

This molecule is typical of a small molecule chromophore that could be investigated as part of a library of organic compounds in the development of organic electronics. For example, in organic lightemitting diodes (OLEDs) or organic solar cells (photovoltaics, OPVs). The pushpull arrangements of hetereocycles at the ends of this molecules will lead to molecular orbitals that are spatially distinct with big differences in space for the bonding and antibonding orbitals. This allows rapid charge mobility in a semiconductor device made from a crystal of a compound such as this, that could be used as part of an OLED or organic solar cell based on small molecules.

To adopt a molular retrosynthesis of this chromophore small molecule, click chemistry is used to assemble the two triazole motifs. This type of click chemistry uses copper to assist an azide alkyne cycloaddition (CuAAC) and favour the 1,4triazole product isomer.

The fluorene core is differentially halogenated using bromine and iodine to give chemoselectivity in two different Sonogashira reactions for spsp2 crosscoupling reaction. The alkynes involved are temporarily protected using silyl groups of different size by coupling on TMSacetylene and TIPSacetylene separately.

The outer heterocycles an aniline and a pyrimidine are synthesised using traditional heterocyclic and aromatic chemistry. Competing reactivity is discussed, including the fact that the pyrimidine that bears an azide functional group can isomerise to a 10 pi aromatic bicyclic heterocycle, based on a tetrazole.

#nobelprize #chemistry #physics