Search results for "coupling"

Synthesis of Highly Substituted Unsymmetrical 1,2-Diamines, 1,2-Diimines, Imidazolium Salts and Imidazolylidenes by Aldimine Cross-Coupling

2007

α-Aminonitriles derived from aromatic aldehydes and primary amines can be deprotonated quantitatively without the use of protecting groups. The 1,2-addition of the resulting stabilized α-aminocarbanions to imines yields α-aminoimines and the tautomeric enediamines. These unstable compounds can directly be oxidized to 1,2-diimines or reduced to 1,2-diamines in a one-pot reaction. 1,2-Diamines can be obtained in high diastereoselectivity by reduction of the 1,2-diimines. In this case, the relative configuration of the products can be chosen depending on the reduction conditions. Cyclization of the unsymmetrical diimines with halomethyl ethers or esters leads to 1,3,4,5-tetrasubstituted imidaz…

Palladium-Catalyzed C—C Coupling Reactions in the Enantioselective Synthesis of 2,4-Disubstituted 4,5-Dehydropiperidines Using Galactosylamine as a S…

2005

Abstract Stereoselective synthesis of enantiomerically pure 2,4-disubstituted piperidine derivatives, which are considered interesting pharmacophoric structures, was achieved starting with a tandem Mannich–Michael reaction sequence on O -pivaloylated N -galactosyl aldimines. Subsequent conversion of the thus formed 2-substituted dehydropiperidinones into the corresponding enol triflates was carried out by conjugate hydride addition and trapping the enolate with N , N -bis(trifluoromethanesulfonyl)aniline. Their Suzuki–Miyaura coupling with aryl and heteroaryl boronic acids was performed under conditions compatible with the carbohydrate structure, in particular, with the sensitive N -glycosi…

Bis(N-substituted oxamate)palladate(ii) complexes as effective catalysts for sustainable Heck carbon–carbon coupling reactions in n-Bu4NBr as the sol…

2015

Five bis(oxamato)palladate(II) complexes of the formulae (n-Bu4N)2[Pd(4-Fpma)2] (1), (n-Bu4N)2[Pd(4-Clpma)2] (2), (n-Bu4N)2[Pd(4-Brpma)2] (3), (n-Bu4N)2[Pd(4-Brpma)2]·H2O (3a), (n-Bu4N)2[Pd(4-MeOpma)2] (4) and (n-Bu4N)2[Pd(4-Isopma)2] (5) (n-Bu4N+ = tetra-n-butylammonium, 4-Fpma = N-4-fluorophenyloxamate, 4-Clpma = N-4-chlorophenyloxamate, 4-Brpma = N-4-bromophenyloxamate, 4-MeOpma = N-4-methoxyphenyloxamate and 4-isopma = N-4-isopropylphenyloxamate) have been easily prepared and characterized by spectroscopic methods and the crystal structures of two of them (3a and 4) have been determined by single crystal X-ray diffraction. Each palladium(II) ion in 3a and 4 is four-coordinate with two o…

Cobalt−NHC Catalyzed C(sp 2 )−C(sp 3 ) and C(sp 2 )−C(sp 2 ) Kumada Cross‐Coupling of Aryl Tosylates with Alkyl and Aryl Grignard Reagents

2020

ChemInform Abstract: Rhodium Catalyzed Oxidative Coupling of Salicylaldehydes with Diazabicyclic Olefins: A One-Pot Strategy Involving Aldehyde C-H C…

2013

The title reaction involves the first example of ring opening and ring closing of bicyclic hydrazines (I) via metal catalyzed oxidative coupling reaction.

A Versatile Grafting-to Approach for the Bioconjugation of Polymers to Collagen-like Peptides Using an Activated Ester Chain Transfer Agent

2009

DepartmentofMaterials Science and Engineering, University of Delaware, 201DuPont Hall, Newark, Delaware 19716,Received February 24, 2009Revised Manuscript Received April 24, 2009Biohybrid materials consisting of synthetic polymers andbiological moieties have gained more and more interest in therecent years.

Nickel‐Catalyzed C(sp2)−C(sp3) Kumada Cross‐Coupling of Aryl Tosylates with Alkyl Grignard Reagents

2019

Aryl tosylates are an attractive class of electrophiles for cross‐coupling reactions due to ease of synthesis, low price, and the employment of C−O electrophiles, however, the reactivity of aryl tosylates is low. Herein, we report the Ni‐catalyzed C(sp2)−C(sp3) Kumada cross‐coupling of aryl tosylates with primary and secondary alkyl Grignard reagents. The method delivers valuable alkyl arenes by cross‐coupling with challenging alkyl organometallics possessing β‐hydrogens that are prone to β‐hydride elimination and homo‐coupling. The reaction is catalyzed by an air‐ and moisture stable‐Ni(II) precatalyst. A broad range of electronically‐varied aryl tosylates, including bis‐tosylates, underwe…

Outstandingly robust anodic dehydrogenative aniline coupling reaction

2020

Abstract Oxidative treatment of anilines usually leads to the formation of black polymers, often referred to as “aniline black”. This over-oxidation is hardly controllable and also a challenging task in the anodic conversion of anilines. Here, a quick and efficient access to valuable building blocks by anodic cross- and homo-coupling of aniline and benzidine derivatives is reported. This electrosynthesis is easily performed in a simple undivided cell using constant current conditions. The key to the observed outstanding performance and robustness of this system is attributed to the used solvent 1,1,1,3,3,3-hexafluoroisopropanol. The extraordinary performance over a broad range of current de…

Modular Access to 9,9-Spirobifluorenes by Oxidative Coupling Using Molybdenum Pentachloride

2013

The strong oxidizing agent molybdenum pentachloride was used for an efficient direct C–C bond formation of 9,9-diarylfluorenes to the corresponding 9,9-spirobifluorenes. Thus, a versatile method that is compatible with labile groups, such as iodo moieties, was established. By this approach important building blocks for light emitting polymers were synthesized in high yields.

1H,13C and17O NMR study of chlorovanillins and some related compounds

1992

1H, 13C and 17O NMR chemical shifts and nJ(H,H), 1J(C,H) and 3J(C-6, H-formyl) spin—spin coupling constants of chlorinated vanillins (3-methoxy-4-hydroxybenzaldehydes) were determined. The variation in the long-range 4J(H,H) value between the formyl proton and an ortho-proton suggests that the ortho-substituent strongly forces the formyl group out of the aromatic plane. This can also be observed by considering the 3J(C-6,H-formyl) values and the 13C and 17O NMR chemical shifts. The 17O NMR chemical shifts show a linear correlation with the torsion angle of the formyl group calculated by molecular mechanics. The 13C and 17O NMR chemical shifts of the methoxyl group also possess strong predic…