Directed <i>ortho</i> Metalation Reaction of Aryl <i>O</i>-Carbamates on Solid Support

Milburn, Claire; Rr, Milburn; Snieckus,

doi:10.1021/ol0476220

Cited by 13 publications

(5 citation statements)

References 21 publications

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“…We note that this palladium catalyzed ortho -bromination is complementary to the widely used directed ortho -metalation method, which uses highly reactive organolithium reagents stoichiometrically to produce ortho -brominated aryl- O -carbamates. , A plausible mechanism for the present ortho -bromination reaction could involve Pd(II)/Pd(IV) catalysis. Initial C–H activation of the carbamate substrate would generate the palladacycle, which can then oxidatively add the NBS to furnish the corresponding Pd(IV) intermediate.…”

Section: Resultsmentioning

confidence: 95%

Palladium Catalyzed C–H Functionalization of O-Arylcarbamates: Selective ortho-Bromination Using NBS

John

Nicholas

2012

J. Org. Chem.

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A series of cyclometalated palladium complexes derived from O-phenylcarbamates has been synthesized by the reaction of the respective carbamates with Pd(OAc)(2) in the presence of acids, CF(3)CO(2)H, CF(3)SO(3)H, and p-TsOH. The palladacycles were observed to coordinate amines and electron rich anilines but not sulfonamides or carboxamides. Analysis of the (t)Bu-NH(2) adduct of the palladacycle 2b (2b·(t)Bu-NH(2)) by NMR spectroscopy (NOE) revealed a cis-coordination of the amine. However, the amine adducts failed to undergo ortho-amination (C-N bond formation) under varied reaction conditions. Notably, the palladacycle 1d was found to react efficiently with N-iodosuccinimide (NIS) to yield the ortho-iodinated carbamate, 1e. More significantly, this reaction can be extended to a palladium-catalyzed ortho C-H bromination of aryl-O-carbamates even at 5 mol % loading of Pd(OAc)(2) using N-bromosuccinimide (NBS).

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Section: Resultsmentioning

confidence: 95%

Palladium Catalyzed C–H Functionalization of O-Arylcarbamates: Selective ortho-Bromination Using NBS

John

Nicholas

2012

J. Org. Chem.

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“…Finally, because dithianes are well established for the Umpolung reaction of the carbonylic C-atom, this reaction was also successfully investigated on the linker system . Such transformations on the solid support are quite difficult to achieve and are only reported in a few examples . In our case, the desired product 37 was isolated in a modest yield of 16% over four steps (Scheme ).…”

Section: Resultsmentioning

confidence: 95%

Solid-Phase Organic Synthesis of Difluoroalkyl Entities using a Novel Fluorinating Cleavage Strategy: Part 1. Linker Development: Scope and Limitations

2009

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An efficient method to synthesize gem-difluorinated compounds on solid supports is described. The strategy is based on the design of a novel sulfur linker system that enables, to the best of our knowledge for the first time, the release of target structures from the resin under simultaneous fluorination. Starting from an immobilized dithiol, coupling with an excess of aldehyde or ketone furnished dithianes. These can be further functionalized prior to release from the resin using our newly developed fluorinating cleavage conditions. Amide forming reactions, palladium-catalyzed reactions (Heck, Suzuki, and Sonogashira couplings), reductions, alkylations, and olefinations were successfully explored on the linker. The difluorinated target substances were obtained in modest to excellent yields and in high purities.

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“…Other arenes brominated with this reagent include a triptycene, 49 a different N-Boc-aniline, 50 a phenol 51 and a tethered carbamate. 52 Bromination of 2-lithio-1,3-dimethoxybenzene was much more efficient using this reagent ( (Table 4, entries 2 and 6, respectively). Examples of lithiated hetarenes similarly brominated are two separate indoles, 28,53 a pyridine 54 and a thiazole.…”

Section: Methodsmentioning

confidence: 97%

Processing Aryllithium and Hetaryllithium Intermediates: Formation of Halogen and Chalcogen Derivatives

Slocum¹,

Shelton²,

Moran³

2005

Synthesis

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Introduction of a halogen (F, Cl, Br, I) or a chalcogen (O, S, Se, Te) via the intermediacy of an aryllithium or hetaryllithium is reviewed. Representative examples are presented to demonstrate the range of substituted aromatic compounds accessible via formation of the lithio-intermediate followed by treatment with an appropriate derivatizing agent. Where possible, the merits and the limitations of the various reagents utilized for introduction of a specific halogen or chalcogen are discussed.

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Directed ortho Metalation Reaction of Aryl O-Carbamates on Solid Support

Cited by 13 publications

References 21 publications

Palladium Catalyzed C–H Functionalization of O-Arylcarbamates: Selective ortho-Bromination Using NBS

Palladium Catalyzed C–H Functionalization of O-Arylcarbamates: Selective ortho-Bromination Using NBS

Solid-Phase Organic Synthesis of Difluoroalkyl Entities using a Novel Fluorinating Cleavage Strategy: Part 1. Linker Development: Scope and Limitations

Processing Aryllithium and Hetaryllithium Intermediates: Formation of Halogen and Chalcogen Derivatives

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