Photochemical Nickel-Catalyzed Reductive Migratory Cross-Coupling of Alkyl Bromides with Aryl Bromides

Abstract

A novel method to access 1,1-diarylalkanes from readily available, nonactivated alkyl bromides and aryl bromides via visible-light-driven nickel and iridium dual catalysis, wherein diisopropylamine ( PrNH) is used as the terminal stoichiometric reductant, is reported. Both primary and secondary alkyl bromides can be successfully transformed into the migratory benzylic arylation products with good selectivity. Additionally, this method showcases tolerance toward a wide array of functional groups and the presence of bases.

Migratory Arylboration of Unactivated Alkenes Enabled by Nickel Catalysis

“…Notably,t he 1,1difunctionalized product 6a was selectively formed when 1,10-phenanthroline-4,7-diol (L7)was used (entry 7). Furthermore,o ther commonly used diboron reagents were also examined in this three-component reaction (entries [11][12][13], and B 2 neo 2 (3b), B 2 hex 2 (3c), and B 2 cat 2 (3d)p roved to be suitable for the migratory difunctionalization reaction. Furthermore,o ther commonly used diboron reagents were also examined in this three-component reaction (entries [11][12][13], and B 2 neo 2 (3b), B 2 hex 2 (3c), and B 2 cat 2 (3d)p roved to be suitable for the migratory difunctionalization reaction.…”

“…[8] Herein, we report the first nickel-catalyzed, regioselective arylboration of unactivated terminal alkenes,d elivering 1,ndifunctionalized (n > 2) products ( Figure 1b). [10] Stimulated by the pioneering studies on 1,2-arylboration of styrenes [3a-e] and our previous work in the nickel-catalyzed migratory cross-couplings, [11,12] we hypothesized that if areaction could be initiated by insertion of olefins into aN i ÀB bond, and an ickel migration occurred before the CÀCb ond formation, a1 , n-arylboration (n > 2) reaction of unactivated alkenes would be achieved ( Figure 1c). [10] Stimulated by the pioneering studies on 1,2-arylboration of styrenes [3a-e] and our previous work in the nickel-catalyzed migratory cross-couplings, [11,12] we hypothesized that if areaction could be initiated by insertion of olefins into aN i ÀB bond, and an ickel migration occurred before the CÀCb ond formation, a1 , n-arylboration (n > 2) reaction of unactivated alkenes would be achieved ( Figure 1c).…”

Migratory Arylboration of Unactivated Alkenes Enabled by Nickel Catalysis

“…[9] Accordingly, an array of diarylsubstituted alkylboronic esters are prepared, and they are valuable synthons and an important pharmacophores in many drugs and other biologically relevant molecules (see Table S1 in the Supporting Information). [10] Stimulated by the pioneering studies on 1,2-arylboration of styrenes [3a-e] and our previous work in the nickel-catalyzed migratory cross-couplings, [11,12] we hypothesized that if areaction could be initiated by insertion of olefins into aN i ÀB bond, and an ickel migration occurred before the CÀCb ond formation, a1 , n-arylboration (n > 2) reaction of unactivated alkenes would be achieved ( Figure 1c). Remarkably,t he incorporation of ab oron group will provide substantial opportunities for further transformations.…”

“…[8] Phosphine ligands,s uch as tricyclohexylphosphine (L8;e ntry 8) were also examined in this three-component transformation, but proved to be ineffective.I nterestingly,t he 1,3-arylboration product could also be generated when the reaction was conducted under an oxygen atmosphere (entry 10). Furthermore,o ther commonly used diboron reagents were also examined in this three-component reaction (entries [11][12][13], and B 2 neo 2 (3b), B 2 hex 2 (3c), and B 2 cat 2 (3d)p roved to be suitable for the migratory difunctionalization reaction. Among them, B 2 hex 2 (3c)a fforded the desired products with the best regioselectivity,a lbeit in as lightly lower yield, presumably benefiting from an appropriate steric effect.…”

Alkyl‐C‐C‐Bindungsbildung durch Nickel/Photoredox‐Kreuzkupplung

“…Im ersten Beispiel diente die Oxidation von Tr is(trimethylsilyl)silan als Elektronenquelle fürdie reduktive Erzeugung von Radikalen aus Alkylbromiden. [68] Neben Alkyl-Aryl-Kreuzkupplungen wurden reduktive Ni/Photoredox-Bedingungen fürd ie Homokupplung von Arylhalogeniden [69] und Alkylhalogeni-den [67a] sowie die Carboxylierung von Aryl-und Alkylbromiden entwickelt. Insgesamt führen beide Reaktionswege zu einem insgesamt reduktiven Katalysezyklus.Diese Methode wurde erfolgreich zur Kupplung von Heteroarylbromiden mit verschiedenen funktionalisierten primären, sekundären und sogar tertiären Alkylbromiden durchgeführt.…”