Visible Light Photoredox Cross-Coupling of Acyl Chlorides with Potassium Alkoxymethyltrifluoroborates: Synthesis of α-Alkoxyketones

Abstract

A visible-light, single-electron-transfer (SET), photoredox cross-coupling for the synthesis of α-alkoxyketones has been developed. In this method, various aliphatic and aromatic acyl chlorides were successfully coupled with structurally diverse potassium alkoxymethyltrifluoroborates, producing the corresponding α-alkoxyketones with high yields. In this operationally simple and mild cross-coupling protocol, the desired ketones are obtained in one step from bench stable starting materials by a bond connection that is unique to both alkylboron chemistry and photoredox/Ni catalysis.

Nickel-Catalyzed Reductive Couplings

“…2.2.1 appears to be more convincing. Noteworthy is that the photoredox/Ni dual catalysis has also been utilized to ketone synthesis under similar arylation conditions [70][71][72].…”

Photoredox Catalysis in Nickel-Catalyzed Cross-Coupling

“…Another important and unique class of organotrifluoroborate that has been utilized in the synergistic photoredox/Ni cross-coupling are alkoxymethyltrifluoroborates, which undergo cross-couplings with aryl-and heteroaryl bromides [27] as well as acyl chlorides [28], affording benzylic ethers and a-alkoxy ketones, respectively. The scope of the reaction with aryl bromides included partners with aldehyde, ketone, nitrile, methoxy, fluoride, trifluoromethyl, and amide functional groups.…”

Recent advances in dual transition metal–visible light photoredox catalysis

“…27 In a Ni transition metal merged Ir photocatalyzed coupled system, a wide variety of (hetero)aryl bromides were coupled with subtituated benzyl BF 3 K salts, 26,28 secondary alkyl trifluoroboates, 29 α-alkoxymethyltrifluoroborates, 30 Bocprotected N-trifluoroboratomethyl amino acids 31 and aryl or aralkyl acyl chlorides with α-alkoxymethyltrifluoroborates. 32 In 2016, the synthesis of 1,1-diaryl-2,2,2-trifluoroethanes (16) were investigated by Molander and his co-workers (Figure 6). 33 In their methodology excess of benzylic α-trifluoromethylated alkylboron reagents (14) were coupled with (hetero)aryl bromides (15) via Ni-Ir dual photoredox catalysis.…”

“…The developed reaction conditions enable the Narylation of aniline compounds under mild reaction conditions. Practically, 2-iodoacetanilides (31) cyclized with alkenes (32) under the irradiation of blue light, at ambient temperature. The mechanism is very similar to the previously mentioned reactions.…”