Asymmetric copper-catalyzed C-N cross-couplings induced by visible light

Kainz, Quirin M.; Matier, Carson D.; Bartoszewicz, Agnieszka; Zultanski, Susan L.; Peters, Jonas C.; Fu, Gregory C.

doi:10.1126/science.aad8313

Cited by 658 publications

(349 citation statements)

References 37 publications

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“…3b–c In their recent follow-up work, the authors disclosed an elegant asymmetric variant, where efficient C–N coupling of tertiary alkyl chlorides and amines was achieved in high yields with high levels of enantioselectivity, Scheme 14. 24 Notably, in contrast to their previous report, the use of benign visible light was sufficient to promote the reaction. Also, the coupling adducts were obtained with low catalyst loading and employed commercially available chiral phosphine ligand ((S)- L *)) at low reaction temperatures.…”

Section: Visible Light-induced Cu-catalyzed Reactionscontrasting

confidence: 67%

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

2017

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Employment of simple transition metal (TM= Co, Fe, Cu, Pd, Pt, Au)-based photocatalyst (PC) led to the dramatic acceleration of known TM-catalyzed reactions, as well as to the discovery of unprecedented chemical transformations. Compared to the conventional cooperative/dual photocatalysis (type B, Figure 1), this new class of unconventional PCs operates via a single photoexcitation/catalytic cycle, where the TM complex plays a “double duty” role by harvesting light and catalyzing the chemical transformation. Also, these TM photocatalysts participate in the bond-forming/breaking event in the transformation via a substrate-TM interaction, an aspect that is uncommon for conventional photocatalysis (type A, Figure 1). This tutorial review highlights the recent advances in this emerging area.

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Section: Visible Light-induced Cu-catalyzed Reactionscontrasting

confidence: 67%

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

2017

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“…12 We hypothesized that, by linking these monodentate ligands into a tridentate ligand ( L ), we might be able to access a copper complex that would be stable to ligand substitution under cross-coupling conditions, while serving as an effective photocatalyst that could initiate new copper-catalyzed reactions upon exposure to visible light, independent of the nucleophile. …”

Section: Resultsmentioning

confidence: 99%

“…Taking into account E 00 (3.1 eV), estimated from the excitation and emission spectra (see the Supporting Information), and the ground-state redox couple, the excited state of complex 1 has a predicted reduction potential of –2.5 V versus SCE, similar to that of complex 2a (–2.6 V vs. SCE). 12a …”

Section: Resultsmentioning

confidence: 99%

Design of a Photoredox Catalyst that Enables the Direct Synthesis of Carbamate-Protected Primary Amines via Photoinduced, Copper-CatalyzedN-Alkylation Reactions of Unactivated Secondary Halides

2017

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Despite the long history of SN2 reactions between nitrogen nucleophiles and alkyl electrophiles, many such substitution reactions remain out of reach. In recent years, efforts to develop transition-metal catalysts to address this deficiency have begun to emerge. In this report, we address the challenge of coupling a carbamate nucleophile with an unactivated secondary alkyl electrophile to generate a substituted carbamate, a process that has not been achieved effectively in the absence of a catalyst; the product carbamates can serve as useful intermediates in organic synthesis as well as bioactive compounds in their own right. Through the design and synthesis of a new copper-based photoredox catalyst, bearing a tridentate carbazolide/bisphosphine ligand, that can be activated upon irradiation by blue-LED lamps, we can achieve the coupling of a range of primary carbamates with unactivated secondary alkyl bromides at room temperature. Our mechanistic observations are consistent with the new copper complex serving its intended role as a photoredox catalyst, working in conjunction with a second copper complex that mediates C–N bond formation in an out-of-cage process.

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“…A notable exception is the light-induced, copper-catalysed C-N coupling of alkyl halides recently developed [16][17][18] . Nevertheless, the scope of amine nucleophiles is limited to carbazoles 16,18 and amides 17,19 . Alternative, formal C-N coupling of alkyl electrophiles via the addition of alkyl radicals to nitroarenes has been reported 20,21 .…”

mentioning

confidence: 99%

“…Moreover, the product-yielding C(sp 3 )-N reductive elimination step is rarely demonstrated 15 . A notable exception is the light-induced, copper-catalysed C-N coupling of alkyl halides recently developed [16][17][18] . Nevertheless, the scope of amine nucleophiles is limited to carbazoles 16,18 and amides 17,19 .…”

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confidence: 99%

Decarboxylative C(sp3)–N cross-coupling via synergetic photoredox and copper catalysis

et al. 2018

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A mines are one of the most important structural motifs in pharmaceuticals, agrochemicals and organic materials 1,2 . Alkylation and reductive amination reactions are still commonly used to prepare and modify amines, and new methods derived from reductive amination, such as the borrowing hydrogen 3 strategy, have been reported [4][5][6][7] . Nevertheless, the most significant development in amine synthesis has been transition-metal-catalysed C-N coupling of aryl electrophiles (halides and pseudo halides) with amine nucleophiles [8][9][10][11] (Fig. 1a). The C-N coupling of alkyl electrophiles, however, is largely under-developed (Fig. 1a). A perceived difficulty is β -hydrogen elimination from a metal alkyl intermediate originated from oxidative addition of the alkyl electrophile, which has posed considerable challenges in analogous C-C crosscoupling of alkyl electrophiles [12][13][14] . Moreover, the product-yielding C(sp 3 )-N reductive elimination step is rarely demonstrated 15 . A notable exception is the light-induced, copper-catalysed C-N coupling of alkyl halides recently developed [16][17][18] . Nevertheless, the scope of amine nucleophiles is limited to carbazoles 16,18 and amides 17,19 . Alternative, formal C-N coupling of alkyl electrophiles via the addition of alkyl radicals to nitroarenes has been reported 20,21 .The group of Baran has recently trailblazed the use of redox-active esters derived from alkyl carboxylic acids as superior surrogates of alkyl halides in decarboxylative C-C cross-coupling reactions [22][23][24] . Extension to a decarboxylative carbon-heteroatom, particularly C-B bond formation has also been reported 19,[25][26][27][28][29] . The key attributes of alkyl carboxylic acids 30,31 are their unparalleled availability, stability and non-toxic nature, which are in stark contrast with alkyl halides, ketones and aldehydes. While several precedents of decarboxylative imidation 32 and amination 19,33 are known, they are limited to a narrow scope of very special substrates or intramolecular reactions. A general metal-catalysed decarboxylative C-N coupling of redox-active esters with anilines will provide valuable methodology for the synthesis of alkylated anilines (Fig. 1b), which requires alkyl halides and carbonyl compounds 6 as starting reagents using the currently standard methods of alkylation and reductive amination, respectively. Further foreseen advantages of such a decarboxylative amination include applicability to bulky primary and secondary alkyl groups and immunity to over-alkylation, both of which are major limitations of direct alkylation (Fig. 1b). Despite its conceptual simplicity and resemblance to decarboxylative C-C coupling, the intermolecular decarboxylative C-N coupling of redoxactive esters poses significant hurdles. The activation principle of redox-active esters originates from amide-bond synthesis; thus, amide formation can compete when amine nucleophiles are used. Moreover, decarboxylative C-C coupling reactions of redox-active esters were, until now, all init...

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Asymmetric copper-catalyzed C-N cross-couplings induced by visible light

Cited by 658 publications

References 37 publications

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

Design of a Photoredox Catalyst that Enables the Direct Synthesis of Carbamate-Protected Primary Amines via Photoinduced, Copper-CatalyzedN-Alkylation Reactions of Unactivated Secondary Halides

Decarboxylative C(sp3)–N cross-coupling via synergetic photoredox and copper catalysis

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