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537 results on '"Daugulis, Olafs"'

51. Copper-catalyzed arylation of heterocycle C-H bonds

Author

Hien-Quang Do and Daugulis, Olafs

Subjects
Arylation -- Research, Copper -- Chemical properties, Heterocyclic aromatic compounds -- Chemical properties, Chemistry
Abstract

The article explains the development and efficiency of a new approach for direct arylation of heterocycle C-H bonds by aryl halides, using copper as a catalyst. The technique can be widely used for organic synthesis due to its readily available starting materials.

Published
2007

52. Palladium-catalyzed anilide ortho-arylation and subsequent one-pot cyclization to phenanthridines

Author

Shabashov, Dmitry and Daugulis, Olafs

Subjects
Aniline -- Structure, Aniline -- Chemical properties, Arylation -- Analysis, Palladium -- Structure, Palladium -- Chemical properties, Palladium -- Electric properties, Biological sciences, Chemistry
Abstract

A study conducted demonstrates that anilides possessing a number of different acyl groups could be arylated by aryl iodides by using palladium catalysis. The arylation products could be converted to phenanthridines by the reaction with trifluoroacetic anhydride.

Published
2007

53. Two methods for direct ortho-arylation of benzoic acids

Author

Chiong, Hendrich A., Quynh-Nhu Pham, and Daugulis, Olafs

Subjects
Benzoic acid -- Structure, Benzoic acid -- Chemical properties, Arylation -- Analysis, Palladium -- Structure, Palladium -- Chemical properties, Spin coupling -- Research, Chemistry
Abstract

Two new palladium-catalyzed methods are developed for the direct ortho-arylation of free benzoic acids. Inter- and intramolecular isotope effects for the benzoic acid arylation by aryl chlorides are determined and are found to be the same with a magnitude of 4.4 pointing toward heterolytic C-H cleavage as the turnover-limiting step.

Published
2007

54. Catalytic coupling of haloolefins with anilides

Author

Zaitsev, Vladmir G. and Daugulis, Olafs

Subjects
Palladium -- Chemical properties, Aniline -- Chemical properties, Olefins -- Chemical properties, Chemistry
Abstract

A strategy in which C-H activation reactions promoted by Pd(II) are combined with beta-heteroatom elimination to create a catalytic cycle and achieve the arylation of haloolefins is described. The catalytic cycle can be subdivided into four parts, which includes C-H activation.

Published
2005

65. Ethylene Polymerization with Ni(II) Diimine Complexes Generated from 8-Halo-1-naphthylamines: The Role of Equilibrating Syn/AntiDiastereomers in Determining Polymer Properties

Author

Wang, Bin, Daugulis, Olafs, and Brookhart, Maurice

Abstract

A series of 8-halonapthalen-1-amines (6a–d, X = F, Cl, Br, I) were prepared and converted to the α-diimines of 2,3-butanedione (7a–d). The nickel dibromide and zinc dibromide complexes of these diimines (3a–dand 8a–d, respectively) were obtained in good yields from standard precursors. NMR spectroscopic analysis of the zinc diimine complexes show the existence of synand antidiastereomers with syn/antiratios of ca. 2:1 (F), 2:1 (Cl), 1:1.5 (Br), and ca. 1:22 (I). Variable temperature NMR spectroscopy was used to calculate barriers to interconversion of these diastereomers which fall in the range 17–18.5 kcal/mol. Activation of nickel dibromide complexes 3a–dwith modified methyl alumoxane (MMAO) yields cationic diimine complexes in which the 8-halo substituents lie over the axial coordination sites. Ethylene polymerization using these activated complexes is reported. The antidiastereomer of the diiodo catalyst (10d) in which both axial sites are blocked yields high molecular weight PE (ca. 106g/mol) as the major fraction with a high turnover frequency at 40 °C. The minor syndiastereomer of 10din which only one axial site is blocked produces low molecular weight PE as a minor fraction. PE formed from the dichloro catalyst 10balso exhibits a bimodal polymer distribution, but the high molecular weight fraction from the antidiastereomer is minor, while the syndiastereomer produces low molecular weight PE. The dibromo complex (10c) is unique in that interchange of diastereomers is on a time scale such that the PE produced shows a very broad molecular weight distribution (MWD ca. 14), spanning the range from the low to high molecular weight regimes. Catalyst 10a, bearing the small fluoro substituents, yields very low molecular weight PE (ca. 600 g/mol).

Published
2019
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66. N-Aminopyridinium Ylide-Directed, Copper-Promoted Amination of sp2C–H Bonds

Author

Kwak, Se Hun and Daugulis, Olafs

Abstract

N-Aminopyridinium ylides are used as monodentate directing groups for copper-promoted C–H/N–H coupling of sp2C–H bonds with pyrazoles, imidazoles, and sulfonamides. Reactions proceed in fluorinated alcohol solvents at elevated temperatures and require use of 1.3–3 equiv of copper(II) acetate. This appears to be the first method for copper-promoted C–H/N–H coupling directed by a removable monodentate auxiliary in absence of added ligands.

Published
2019
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67. 1-Aminopyridinium Ylides as Monodentate Directing Groups for sp3C–H Bond Functionalization

Author

Le, Ky Khac Anh, Nguyen, Hanh, and Daugulis, Olafs

Abstract

1-Aminopyridinium ylides are efficient directing groups for palladium-catalyzed β-arylation and alkylation of sp3C–H bonds in carboxylic acid derivatives. The efficiency of these directing groups depends on the substitution at the pyridine moiety. The unsubstituted pyridine-derived ylides allow functionalization of primary C–H bonds, while methylene groups are unreactive in the absence of external ligands. 4-Pyrrolidinopyridine-containing ylides are capable of C–H functionalization in acyclic methylene groups in the absence of external ligands, thus rivaling the efficiency of the aminoquinoline directing group. Preliminary mechanistic studies have been performed. A cyclopalladated intermediate has been isolated and characterized by X-ray crystallography, and its reactivity was studied.

Published
2019
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78. Copper-catalyzed arylation and alkenylation of polyfluoroarene C-H bonds

Author

Daugulis, Olafs and Hien-Quang Do

Subjects
Chemical bonds -- Research, Chemical bonds -- Observations, Benzene -- Research, Benzene -- Chemical properties, Ligands -- Research, Ligands -- Chemical properties, Chemistry
Abstract

A general method is described for the copper-catalyzed arylation and alkenylation of polyfluorobenzene C-H bonds. The results are obtained by using a combination of copper iodide catalyst, phenanthroline ligand, aryl bromide or aryl iodide coupling partner, and DMF or DMF/xylene mixed solvent.

Published
2008

92. Highly regioselective arylation of sp(super 3) C-H bonds catalyzed by palladium acetate

Author

Zaitsev, Vladimir G., Shabashov, Dmitry, and Daugulis, Olafs

Subjects
Palladium -- Electric properties, Palladium -- Chemical properties, Carbon compounds -- Electric properties, Carbon compounds -- Chemical properties, Arylation -- Research, Chemistry
Abstract

A new arylation process based on C-H is developed and it allows for the beta-arylation of carboxylic acid derivatives and gamma-arylation of amine derivatives. Efforts are underway to extend this methodology to arylation of esters and alkenylation of amides and esters.

Published
2005

93. Palladium-Catalyzed Pyrazole-Directed sp3 C−H Bond Arylation for the Synthesis of β-Phenethylamines.

Author

Gulia, Nurbey and Daugulis, Olafs

Subjects
*PYRAZOLES, *ARYLATION, *ARYL iodides, *HALIDES, *OZONOLYSIS
Abstract

We have developed a method for palladium-catalyzed, pyrazole-directed sp3 C−H bond arylation by aryl iodides. The reaction employs a Pd(OAc)2 catalyst at 5-10 mol % loading and silver(I) oxide as a halide-removal agent, and it proceeds in acetic acid or acetic acid/hexafluoroisopropanol solvent. Ozonolysis of the pyrazole moiety affords pharmaceutically important β-phenethylamines. [ABSTRACT FROM AUTHOR]

Published
2017
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