Metal-Mediated/Catalyzed Oligomerisation of Arynes: Towards the Synthesis of Tailor-made Oligo(ortho-)arylenes

• Applicant: Professor Dr. Daniel B. Werz
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 560180456

The aim of this project is to investigate oligomerization reactions of arynes that lead to ortho,ortho-linked oligoarylenes. Previous work in the group had shown that such oligomerizations (with distributions up to the octamer) are possible. The reaction design used so far, which was based on using sterically encumbered, relatively unreactive electrophiles that allowed a competitive reaction leading to oligomerization with the aryne as the electrophile, is, however, only of limited use with regard to possible functional groups as termini. For this reason, based on our own preliminary work and literature precedence on the copper-catalyzed polymerization of arynes, defined oligomerization reactions that lead to biaryls, triaryls, etc. are now to be investigated. In a first work package, we will investigate which functional groups as termini are able to be attached to such oligoarylenes. Nucleophiles such as halides, but also alkyl/aryl chalcogenides, are intended to initiate a copper-mediated oligomerization. The resulting oligoarylene-copper species are then intended to terminate the sequence by reaction with electrophiles such as alkyl/allyl halides, Michael systems, epoxides or activated carbonyl compounds. Possibly, conversion into more reactive cuprates might be required to allow access to a wide range of terminal substituents. Major attention will be paid to optimizing the conditions so that the oligomer distribution is as narrow as possible. In addition to copper-mediated processes, copper-catalyzed variants of aryne oligomerization are also to be investigated, with the two termini arising from a heterolytic bond cleavage of strongly polarized compounds (e.g. NIS, RSCN or benzyl halides). In a second work package, the findings will be extended to both unsymmetrically substituted arynes and hetarines. The focus here is on questions of regioselectivity; in the case of hetarines, the possibility of coordination with the copper-containing species needs to be considered, which might force selective attacks. In addition, strained cycloalkynes such as in situ generated cyclopentynes and cyclohexynes should also be subjected to corresponding oligomerization reactions. Intramolecular terminations with cyanides or strained heterocycles should allow access to bridged biaryl systems. In a third work package, oligomerization reactions with structurally different arynes are to be carried out in such a way that oligomers with different arene units in the same molecule are accessible. For this purpose, a suitable activation mode is to be established that enables the precise activation of the aryne precursors added one after the other. One possibility for this is temperature-controlled aryne releases, which will be realized via different aryne precursors. Effective ways to stabilize the intermediately formed anionic species under the reaction conditions will be investigated, which will pave the way for this difficult transformation.

• DFG Programme: Research Grants