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CC BY-ND-NC 4.0 · Synthesis 2019; 51(05): 1185-1195
DOI: 10.1055/s-0037-1611661
DOI: 10.1055/s-0037-1611661
feature
Oxidative Coupling of N-Methoxyamides and Related Compounds toward Aromatic Hydrocarbons by Designer μ-Oxo Hypervalent Iodine Catalyst
Further Information
Publication History
Received: 02 December 2018
Accepted: 30 December 2018
Publication Date:
05 February 2019 (online)
Published as part of the 50 Years SYNTHESIS – Golden Anniversary Issue
Abstract
Oxidative coupling strategies that can directly convert the C–H group for chemical transformations are, in theory, ideal synthetic methods to reduce the number of synthetic steps and byproduct generation. Hypervalent iodine reagents have now become one of the most promising tools in developing oxidative couplings due to their unique reactivities that are replacing metal oxidants. As part of our continuous development of oxidative coupling reactions, we describe in this report highly efficient μ-oxo hypervalent iodine catalysts for the direct oxidative coupling of N-methoxyamides and related compounds with aromatic hydrocarbons. The excellent TONs, up to over 100 times, with a best catalyst loading of 0.5 mol% were determined for the oxidative C–H/N–H coupling method, which can provide the most straightforward route to obtaining these unique arylamide compounds.
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For selected summarizations, see:
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For early studies, see:
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See ref. 9b and selected examples for introducing heteroatoms:
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For other early applications, see:
For reviews on catalytic utilizations of hypervalent iodine reagents, see:
For the first report of C–N bond-forming reaction using a catalytic amount of hypervalent iodine, see:
For early studies, see:
We have recently met the notably high reactivity of μ-oxo-bridged PIFA dimer in organic solvents as well as in water, see:
X-ray crystal structure data of PIFA:
PIDA:
The existence of strong secondary bondings between the iodine atoms and the ligand’s carbonyl oxygens appears in the structure, which was confirmed by the lower shift of carbonyl frequencies for the μ-oxo PIFA in the infrared resonance spectra compared to that of PIFA. These observations clearly account for the enhanced cationic character of the iodine center, see:
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See ref 9d and:
For the reactivities of diaryliodonium(III) salt, see:
Transition-metal-catalyzed oxidative amidations for aromatic hydrocarbons with stoichiometric hypervalent iodine reagent, see:
The combination of transition metal ([Co]) with photocatalyst:
The use of 0.5 mol% amount of iridium-based photocatalyst was reported, while the product yields was up to 52% in this case:
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Representative examples:
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Related μ-oxo-bridged chiral hypervalent iodine catalysts: