Merging Photoredox with Nickel Catalysis: Coupling of α-Carboxyl sp3-Carbons with Aryl Halides
Science, 2014 · paper · Chemistry
Combines photoredox and nickel catalysis to couple sp3 carbons with aryl halides. It achieves decarboxylative coupling of amino acids and other carboxylic acids, and direct coupling of C–H bonds in dimethylaniline.
4 findings
Reference or label "long-lived photoexcited *IrIII state 2 (exposure time τ = 2.3 µs) (22)": τ is given as the reason the excited state is long-lived, so it is the excited-state lifetime, and it is labelled "exposure time".
- p. 2 Last paragraph, description of photocatalyst 1
long-lived photoexcited *IrIII state 2 (exposure time τ = 2.3 µs)
- p. 2 p.2, mechanism paragraph
(exposure time τ = 2.3 µs)
- p. 2 ~line 83
exposure time τ = 2.3 µs
Judge's note: Read on the page 2 image. The parenthesis supports "long-lived" and is cited to ref. 22 (Lowry et al., Chem. Mater., the photophysics of the complex). The paper describes irradiation for 48 to 72 hours (page 4), so 2.3 µs cannot be an irradiation time. The quantity is mislabelled; the value is not in question.
Second check: another model agreed
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Reference or label Page 4: the radical "should similarly intercept the putative Ni(II) intermediate 8"; in the text (pages 2-3) and in Fig. 2 the Ni(II)-aryl intermediate is 7, and 8 is the Ni(III) adduct formed when the radical is intercepted.
- p. 4 Paragraph on Csp3-H functionalization
the putative Ni(II) intermediate 8
- p. 3 First paragraph (mechanism)
forming the organometallic Ni(III) adduct 8
- p. 2 Last paragraph
would produce the Ni(II) intermediate 7
- p. 7 Fig. 2, nickel catalytic cycle
8
Judge's note: Page 2: "would produce the Ni(II) intermediate 7 … this Ni(II)-aryl species would rapidly intercept the α-amino radical 4, forming the organometallic Ni(III) adduct 8" (continued on page 3). Fig. 2 on page 7 labels 7 as LnNi(II)–Ar(I) and 8 as Alk–Ni(III)Ln(Ar)(I). The page 4 sentence refers to Fig. 2 explicitly ("corresponding to 4, Fig. 2") and says the rest of the mechanism is analogous, so no separate numbering applies. The compound number should be 7. Rated S2 because it is a wrong compound label; the mechanism as drawn is unaffected.
Second check: another model agreed
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Reference or label Fig. 3 caption defines "CFL, compact fluorescent light; Bu, butyl group; Ac, acetyl group", but Fig. 3 as printed contains no CFL or t-Bu and no reaction conditions; the general scheme with "26 W CFL light" and t-Bu is printed under Fig. 2, whose caption defines only Me, L and Alk. The Fig. 4 caption sends the reader to Fig. 3 for conditions.
- p. 9 Fig. 4 caption
Reaction conditions for (A) are the same as in Fig. 3.
- p. 9 Fig. 4A, reaction scheme
blue LEDs
- p. 7 Lower scheme under Fig. 2 (conditions for the aryl halide scope)
DMF, 26 W CFL light, 23 °C
- p. 8 Fig. 3 caption
CFL, compact fluorescent light; Bu, butyl group; Ac, acetyl group.
Judge's note: Page 8 image: Fig. 3 shows only product structures 10 to 24 with yields (labels Boc, Me, F, OMe, Cl, Ac, CO2Me, CN, CF3, Ph). Page 7 image: below the mechanism, above the Fig. 2 caption, sits the general reaction scheme ("1 mol% photocatalyst 1, 10 mol% NiCl2·glyme, 15 mol% dtbbpy, Cs2CO3, DMF, 26 W CFL light, 23 °C") and the catalyst box with t-Bu. The scheme belonging to Fig. 3 has been attached to the Fig. 2 image in this author-manuscript version. The light-source disagreement with Fig. 4A is judged separately in C011.
Second check: another model agreed
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Wording Fig. 4 caption: "Reaction conditions for (A) are the same as in Fig. 3." The Fig. 4A scheme specifies "blue LEDs" (and the caption defines LED), whereas the conditions for the aryl halide scope are "DMF, 26 W CFL light, 23 °C" (scheme on page 7; CFL defined in the Fig. 3 caption) and the text gives "white light from a 26-W compact fluorescent bulb".
- p. 8 Fig. 3 caption
CFL, compact fluorescent light; Bu, butyl group; Ac, acetyl group.
- p. 7 Fig. 2, lower panel (general reaction scheme and catalyst combination)
DMF, 26 W CFL light, 23 °C
- p. 7 Fig. 2 caption
Me, methyl group; L, ligand; Alk, alkyl group.
- p. 9 Fig. 4 caption
conditions for (A) are the same as in Fig. 3
Only the authors can say what is right here.
Judge's note: Page 9 image: the panel A scheme reads "1 mol% photocatalyst 1, 10 mol% NiCl2·glyme, 15 mol% dtbbpy, Cs2CO3, DMF, 23 °C, blue LEDs". Page 7 image: the general scheme reads "DMF, 26 W CFL light, 23 °C". Catalyst loadings, base, solvent and temperature match; the light source does not. The main text never mentions LEDs; the supplementary text is not among the files and might say which light source was used for which substrates. Only the light-source point is judged here; the misplaced scheme is C012. The formatting differences ("26 W" vs "26-W", "23 °C" vs "23°C") in one reviewer note are house style and not counted.
Second check: another model agreed
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8 minor (typos and the like; most checked by the judge only)
Wording Boc and Cbz are expanded as "tert-butyl carbamoyl (Boc)" (page 2) and "N-benzyl carbamoyl (N-Cbz)" (page 4); the groups drawn in the figures are carbamates (tert-butoxycarbonyl, benzyloxycarbonyl), which these names do not describe.
- p. 2 Last paragraph
tert-butyl carbamoyl (Boc)
- p. 4 Second paragraph
N-benzyl carbamoyl (N-Cbz)
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that Boc stands for tert-butoxycarbonyl and Cbz for benzyloxycarbonyl, and that a carbamoyl group is R2N-C(O)-. Both phrases are printed as quoted (page 2 and page 4 images). Figs. 2 to 4 draw N-Boc and N-Cbz protected amines. The intent (a tert-butyl or benzyl carbamate) is clear, so this is a naming point only.
Second check: another model agreed
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Typo Mismatched brackets: "[tert-butyl carbamoyl (Boc)–Pro-OCs, E1/2red = +0.95 V versus SCE in CH3CN) (17)" opens with a square bracket and closes with a round one.
- p. 2 Last paragraph
[tert-butyl carbamoyl (Boc)–Pro-OCs, E1/2red = +0.95 V versus SCE in CH3CN)
- p. 2 mechanism paragraph
[tert-butyl carbamoyl (Boc)–Pro-OCs, E1/2red = +0.95 V versus SCE in CH3CN) (17)
- p. 2 last paragraph, ~line 89
[tert-butyl carbamoyl (Boc)–Pro-OCs, E1/2red = +0.95 V
Judge's note: Seen on the page 2 image: the aside opens with "[" before "tert-butyl" and closes with ")" after CH3CN. The neighbouring potentials use matched braces.
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Typo DMF is expanded as "N,N´-dimethylformamide (DMF)"; the compound has one nitrogen, so the locants should be N,N.
- p. 3 First paragraph
N,N´-dimethylformamide (DMF)
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that dimethylformamide has a single nitrogen carrying both methyl groups, so the primed locant is wrong. The prime is printed on the page 3 image ("N,N´-dimethylformamide"), so it is not an extraction artefact.
Second check: none (judge only)
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Typo Stray space in the catalyst formula: "Ir[dF (CF3)ppy]2(dtbbpy)PF6" on page 3; pages 2 and 4 print "Ir[dF(CF3)ppy]2(dtbbpy)PF6".
- p. 3 ~line 112
Ir[dF (CF3)ppy]2(dtbbpy)PF6
Judge's note: The gap between "dF" and "(CF3)" is visible on the page 3 image and is wider than in the same formula on page 2 and page 4. Cosmetic.
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Typo Missing space: "(28 to 32, 72 to 91%yield)".
- p. 4 carboxylic acid scope paragraph
72 to 91%yield
Judge's note: Seen on the page 4 image: "91%yield" is printed without a space; the other yield ranges on the page read "% yield".
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Typo Stray space before the hyphen: "the general use of Csp3 -bearing carboxylic acids".
- p. 4 first lines
the general use of Csp3 -bearing carboxylic acids
Judge's note: The page 4 image shows a visible gap between the superscript 3 and "-bearing"; other compounds on the page ("Csp3–H") have none. Purely cosmetic.
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Typo Inconsistent spacing in the Fig. 4 caption: "[1 mole % (mol %)]; NiCl2·glyme (10 mol %), dtbbpy (15 mol%)".
- p. 9 Fig. 4 legend
dtbbpy (15 mol%)
Judge's note: Seen on the page 9 image: "mol %" with a space twice, then "15 mol%" without. Cosmetic only.
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Typo The Fig. 4 caption defines "*Iodoarenes used as aryl halide, X = I." but no asterisk appears in Fig. 4; only the dagger is used ("37 60% yield†").
- p. 10 Fig. 4 caption, continued
*Iodoarenes used as aryl halide, X = I.
- p. 9 Fig. 4B, products 34-37
34 84% yield
- p. 9 Fig. 4B products 34-36
84% yield
Judge's note: Page 9 image: products 34 (84%), 35 (72%) and 36 (93%) carry no mark, 37 carries a dagger, and no asterisk is visible elsewhere in panels A or B. The caption text on page 10 was read from the text layer. The dagger is legible at this resolution, so an asterisk of the same size would be too, though a mark lost in the low-resolution figure cannot be fully excluded. The text on page 4 says 34 to 36 come from iodoarenes, so the meaning is recoverable.
Second check: none (judge only)