Search results for "Halogenation"

The influence of fluorine position on the properties of fluorobenzoxaboroles

2015

5-Fluoro-2,1-benzoxaborol-1(3H)-ol, a potent antifungal drug also known as Tavaborole or AN2690, has been compared with its three isomers in terms of its activity against several fungi as well as pKa and multinuclear NMR characterization. The molecular and crystal structure of 6-fluoro-2,1-benzoxaborol-1(3H)-ol was determined and compared with that of AN2690.

Designed Synthesis of New ortho-Carborane Derivatives: from Mono- to Polysubstituted Frameworks

2008

The use of nucleophilic and electrophilic processes allow the designed synthesis of several B-iodinated derivatives of o-carborane. Because of the straightforward Pd-catalyzed conversion of B-I to B-C bond with Grignard reagents, such as methylMgBr and biPhenylMgBr, both, symmetrical 3,6-R 2-1,2- closo-C 2B 10H 10 and asymmetrical 3-I-6-Me-1,2- closo-C 2B 10H 10 could be obtained. Not only conventional reactions in solution have been studied but also a highly efficient, clean and fast solvent-free procedure has provided successful results to regioselectively produce B-iodinated o-carborane derivatives by a careful control of the reaction conditions. The high number of nonequivalent leaving …

5-Alkenyl-1,2,3-thiadiazole

1986

Es wird die Herstellung der Titelverbindungen 5 durch Bromierung-Dehydrobromierung entsprechender 5-Alkyl-1,2,3-thiadiazole 3, ihre spektroskopische Charakterisierung und ihre Umsetzung mit 4-Phenyl-4H-1,2,4-triazol-3,5-dion (6) zu 7, 8 beschrieben. 5-Alkenyl-1,2,3-thiadiazoles A method of preparation for the title compounds 5, by bromination-dehydrobromination of the corresponding 5-alkyl-1,2,3-thiadiazoles 3, their spectroscopical characterization, and the reaction of 5 with 4-phenyl-4H-1,2,4-triazole-3,5-dione (6) with formation of 7, 8 is described.

C–H Halogenation of Pyridyl Sulfides Avoiding the Sulfur Oxidation: A Direct Catalytic Access to Sulfanyl Polyhalides and Polyaromatics

2019

Palladium-catalyzed oxidative C–H halogenation and acetoxylation reactions of S-unprotected sulfides, selectively directed by pyridinyl groups, allows the formation of C–X bonds (X = I, Br, Cl, OAc) by using simple halosuccinimide or phenyliodine diacetate (PIDA) oxidants. The undesired formation of sulfoxides and/or sulfones, which are usually observed under oxidative conditions, is fully obviated. Under the solvent-dependent conditions that we proposed, sulfide C–H functionalization is achieved in less than 1 h without any direct electrophilic halogenation at the pyridine moiety. N-Directed ortho-C–H activation of aryl also facilitates dibromination reactions which are hardly accessible w…

Cross-Metathesis Reactions as an Efficient Tool in the Synthesis of Fluorinated Cyclic β-Amino Acids

2009

The synthesis of enantiomerically pure, cyclic, gamma,gamma-difluorinated beta-amino acids with various ring sizes has been carried out with a cross-metathesis (CM) reaction being one of the key steps, followed by a Dieckmann-type condensation to bring about the cyclization. Subsequent catalytic hydrogenation under microwave irradiation with (-)-8-phenylmenthol as a chiral auxiliary led to the successful chemo- and diastereoselective chemical reduction of the resulting cyclic beta-enamino esters. The efficiency and scope of the CM reaction with different types of fluorinated imidoyl chlorides and unsaturated esters has also been studied in order to determine the optimal reaction conditions …

ChemInform Abstract: Enantioselective Palladium-Catalyzed Oxidative β,β-Fluoroarylation of α,β-Unsaturated Carbonyl Derivatives.

2016

The site-selective palladium-catalyzed three-component coupling of deactivated alkenes, arylboronic acids, and N-fluorobenzenesulfonimide is disclosed herein. The developed methodology establishes a general, modular, and step-economical approach to the stereoselective β-fluorination of α,β-unsaturated systems.

Olefin metathesis reactions with fluorinated substrates, catalysts, and solvents.

2014

Synthesis of quadruped-shaped polyfunctionalized o-carborane synthons

2011

[EN] o-Carborane derivatives with precisely defined patterns of substitution have been prepared from 8,9,10,12-I-4-1,2-closo-C2B10H8 by replacing the iodine atoms, bonded to four adjacent boron vertices in the cluster, with allyl, and subsequently 3-hydroxypropyl groups. The resulting structures, comprising four pendant arms and two reactive vertices located on opposite sides of a central o-carborane core, can be envisaged as versatile precursors for dendritic growth

Palladium C–N bond formation catalysed by air-stable robust polydentate ferrocenylphosphines: a comparative study for the efficient and selective cou…

2014

The arylation of aniline derivatives with dichloroarenes under a low palladium content (below the currently used 5 to 10 mol%) was studied using nine different ferrocenylphosphine ligands, including the easily accessible 1,1′-bis(diphenylphosphino)ferrocene, DPPF. The electron-enriched air-stable tridentate ferrocenylpolyphosphine 1,2-bis(diphenylphosphino)-1′-(diisopropylphosphino)-4-tert-butylferrocene, L5, employed in 2 mol% in combination with 1 mol% [PdCl(η3-C3H5)]2 allows an efficient and selective coupling, while such demanding substrates currently induce chloroarene homocoupling and/or dehalogenation processes. The scope and limitation of the optimized system are explored, with a fo…

Selective and Scalable Dehydrogenative Electrochemical Synthesis of 3,3′,5,5′-Tetramethyl-2,2′-biphenol

2019

3,3′,5,5′-Tetramethyl-2,2′-biphenol is a compound of high technical significance, as it exhibits superior properties as building block for ligands in the transition-metal catalysis. However, side reactions and overoxidation are challenging issues in the conventional synthesis of this particular biphenol. Here, an electrochemical method is presented as powerful and sustainable alternative to conventional chemical strategies, which gives good yields up to 51%. Despite using inexpensive and well-available bromide-containing supporting electrolytes, the issue of bromination and general byproduct formation is effectively suppressed by adding water to the electrolyte. Additionally, the scalabilit…