Heteroleptic Copper(I)‐Based Complexes for Photocatalysis: Combinatorial Assembly, Discovery, and Optimization

Abstract

A library of 50 copper-based complexes derived from bisphosphines and diamines was prepared and evaluated in three mechanistically distinct photocatalytic reactions. In all cases, a copper-based catalyst was identified to afford high yields, where new heteroleptic complexes derived from the bisphosphine BINAP displayed high efficiency across all reaction types. Importantly, the evaluation of the library of copper complexes revealed that even when photophysical data is available, it is not always possible to predict which catalyst structure will be efficient or inefficient in a given process, emphasizing the advantages for catalyst structures with high modularity and structural variability.

Making Copper Photocatalysis Even More Robust and Economic: Photoredox Catalysis with [CuII(dmp)2Cl]Cl

“…Indeed, subjecting the mentioned starting materials to the reaction conditions indicated, the desired product 13 was formed in good yields of 62 % employing 2.0 mol‐% of [Cu II (dmp) 2 Cl]Cl as precatalyst. The previously reported ruthenium catalyst only yielded 13 in 28 %, whereas heteroleptic [Cu I (dq)(BINAP)]BF 4 complex evaluated by Collins and co‐workers afforded 87 % of coupling product …”

“…The corresponding Cu I complex [Cu I (dmp) 2 ] + indeed shows luminescence, an even higher excited state reduction potential compared to that of [Cu I (dap) 2 ]Cl, but an excited state lifetime of 90 ns, being significantly shorter than that of [Cu(dap) 2 ]Cl (270 ns[18a]). Although these photochemical parameters of [Cu I (dmp) 2 ] + were reported,, there have been only few applications in photoredox catalysis reflected by a small number of reports using [Cu I (dmp) 2 ] + as part of screening efforts for reaction optimization , , . Therefore, we wondered, if [Cu II (dmp) 2 Cl]Cl can serve as an oxidation‐ and bench‐stable precursor for VLIH to [Cu I (dmp) 2 ] + and then the excited state lifetime of the latter is still sufficient for diffusion‐controlled photoredox catalysis.…”

Visible‐Light‐Driven, Copper‐Catalyzed Decarboxylative C(sp3)−H Alkylation of Glycine and Peptides

“…On the basis of above investigations and previous reports, a possible reaction mechanism is proposed in Scheme . Under blue LED light irradiation, the cuprous‐based complex [Cu I L] is excited to its excited state [Cu I L] * ( E 1/2 [Cu II /Cu I *]=−1.86 V versus SCE (saturated calomel electrode) in MeCN), which undergoes a SET process with 2 ( E p 0/−1 ( 2 )=−1.28 to −1.37 V versus SCE in MeCN), followed by the generation of the alkyl radical A , CO 2 , phthalimide anion, and [Cu II L]. [Cu II L] ( E 1/2 [Cu II /Cu I ]=0.38 V versus SCE in MeCN) oxidizes the glycine derivatives 1 ( E p 0/+1 ( 1 a )=0.31 V versus SCE in MeCN) to form the radical cation intermediate B , along with regeneration of [Cu I L].…”

Alkene Carboarylation through Catalyst‐Free, Visible Light‐Mediated Smiles Rearrangement

“…We were pleased to isolate product 9 a in an encouraging 42 % yield at room temperature under these conditions, using CH 2 Cl 2 as solvent. Efforts then turned towards developing the protocol to encompass more sustainable, cost effective photocatalysts such as eosin Y and a copper complex pioneered by Collins and co‐workers . Both systems returned moderate yields of product with dichloromethane as a solvent at room temperature; however, switching to a higher boiling point solvent and increasing the reaction temperature aided the reaction (Table , entry 6).…”