Highly Enantioselective Catalytic Lactonization at Nonactivated Primary and Secondary <i>γ</i>-C–H Bonds

Call, Arnau; Capocasa, Giorgio; Palone, Andrea; Vicens, Laia; Aparicio, Eric; Choukairi Afailal, Najoua; Siakavaras, Nikos; López Saló, Maria Eugènia; Bietti, Massimo; Costas, Miquel

doi:10.1021/jacs.3c06231

Cited by 19 publications

(2 citation statements)

References 60 publications

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“…We have recently described that these complexes effectively catalyze the intramolecular γ-lactonization of primary CÀ H bonds in carboxylic acid substrates (Scheme 1C). [36,37] On the other hand, the intermolecular oxidation of a substrate such as 2,2,3,3-tetramethylbutane was only accomplished in very low yield (< 2 %), in line with state-of-the-art oxidations with bioinspired catalysts. [38][39][40] We envisioned that the electrophilicity of the oxidizing manganese-oxo species could be enhanced by catalyst design and medium effects exerted by the solvent.…”

Section: Introductionmentioning

confidence: 67%

“…Cyclohexane derivatives 35-39 feature the same number of carbon atoms between the tertbutyl and the EWG as their acyclic C4-EWG analogues, and were all hydroxylated at the primary CÀ H bonds with high site-selectivity (� 90 %). Of notice, for substrates that contain bulky EWGs (36)(37)(38)(39), significant improvements in 1°s r were observed when compared to the corresponding C4-EWG substrates. For example, 1°sr increases substantially from 2.8 in C4-NHPiv (28) to an excellent 19.8 in 37 characterized by the presence of the same group.…”

Section: Torsional Effects On the Oxidation Of 4-tert-butylcyclohexan...mentioning

confidence: 95%

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tert‐Butyl as a Functional Group: Non‐Directed Catalytic Hydroxylation of Sterically Congested Primary C−H Bonds

Chan,

Palone,

Bietti

et al. 2024

Angewandte Chemie

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The tert‐butyl group is a common aliphatic motif extensively employed to implement steric congestion and conformational rigidity in organic and organometallic molecules. Because of the combination of a high bond dissociation energy (~ 100 kcal mol‐1) and limited accessibility, in the absence of directing groups, neither radical nor organometallic approaches are effective for the chemical modification of tert‐butyl C−H bonds. Herein we overcome these limits by employing a highly electrophilic manganese catalyst, [Mn(CF3bpeb)(OTf)2], that operates in the strong hydrogen bond donor solvent nonafluoro‐tert‐butyl alcohol (NFTBA) and catalytically activates hydrogen peroxide to generate a powerful manganese‐oxo species that effectively oxidizes tert‐butyl C−H bonds. Leveraging on the interplay of steric, electronic, medium and torsional effects, site‐selective and product chemoselective hydroxylation of the tert‐butyl group is accomplished with broad reaction scope, delivering primary alcohols as largely dominant products in preparative yields. Late‐stage hydroxylation at tert‐butyl sites is demonstrated on 6 densely functionalized molecules of pharmaceutical interest. This work uncovers a novel disconnection approach, harnessing tert‐butyl as a potential functional group in strategic synthetic planning for complex molecular architectures.

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Section: Introductionmentioning

confidence: 67%

Section: Torsional Effects On the Oxidation Of 4-tert-butylcyclohexan...mentioning

confidence: 95%

tert‐Butyl as a Functional Group: Non‐Directed Catalytic Hydroxylation of Sterically Congested Primary C−H Bonds

Chan,

Palone,

Bietti

et al. 2024

Angewandte Chemie

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Acid‐Cooperative Transition Metal‐Catalysed Oxygen‐Atom‐Transfer: Ruthenium‐Catalysed C−H Oxygenation

Doiuchi,

Shimoda,

Okazaki

et al. 2024

Adv Synth Catal

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The prospect of developing methods to control the reactivity of metal(oxo) holds appeal for both synthetic and bioinorganic chemistry. In this study, we observed that carboxylic acids enhance reactivity in C–H oxidation by forming hydrogen bonds with the oxo ligand, thereby increasing the basicity and electrophilicity of the oxo intermediate. Additionally, we discovered that H‐dicarboxylate ligands, such as oxalate, malonate, and maleate, significantly improve the catalyst turnover frequency (up to 760/h) in unactivated C(sp3)–H oxidation. Furthermore, the addition of maleic acid was also found to activate Fe and Mn(pdp)‐catalysed C–H oxygenation. Notably, Ru(bpga)(H‐maleate)2 3‐catalyzed C–H functionalization exhibited a broad functional group tolerance, including bromine, hydroxyl, benzoate, nitro, nitryl, sulfonate, imide, sulfonylamide, and carbamate, yielding up to 98% in a site‐ and chemoselective manner with only 0.1‐2.0 mmol% loading.

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Recent Advances and Prospects in Manganese‐Catalyzed C−H Activation

Anusree,

Devi,

Anilkumar

2024

Adv Synth Catal

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C–H activation represents an interesting alternative to conventional cross‐coupling methods, avoiding the requirement of additional steps to introduce activating groups. Generally, Pd‐catalyzed reactions have been extensively employed for C–H activation. The high cost and limited availability of resources of Pd have prompted us to explore alternative transition metals. In this context, researchers are turning to Earth Abundant Metals (EAMs) like manganese and iron for their potential in C–H activation.Significant progress has been made in manganese‐catalyzed C–H activation in recent years, showcasing excellent specificity, environmental compatibility, and versatility across different substrates. This review summarizes approximately 50 recent publications highlighting significant advancements in this field from 2020 to 2023.

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Highly Enantioselective Catalytic Lactonization at Nonactivated Primary and Secondary γ-C–H Bonds

Cited by 19 publications

References 60 publications

tert‐Butyl as a Functional Group: Non‐Directed Catalytic Hydroxylation of Sterically Congested Primary C−H Bonds

tert‐Butyl as a Functional Group: Non‐Directed Catalytic Hydroxylation of Sterically Congested Primary C−H Bonds

Acid‐Cooperative Transition Metal‐Catalysed Oxygen‐Atom‐Transfer: Ruthenium‐Catalysed C−H Oxygenation

Recent Advances and Prospects in Manganese‐Catalyzed C−H Activation

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