Reagent

About: Reagent is a research topic. Over the lifetime, 60091 publications have been published within this topic receiving 1234928 citations. The topic is also known as: reagens.

Regioregular, Head-to-Tail Coupled Poly(3-alkylthiophenes) Made Easy by the GRIM Method: Investigation of the Reaction and the Origin of Regioselectivity

Abstract: An investigation of the new synthetic method to synthesize regioregular, head-to-tail coupled poly(3-alkylthiophenes) using magnesium-halogen exchange (Grignard metathesis) called the GRIM method is described. Treatment of 2,5-dibromo-3-alkylthiophenes with a variety of alkyl and vinyl Grignard reagents resulted in two metalated, regiochemical isomers, namely, 2-bromo-3-alkyl-5-bromomagnesio- thiophene and 2-bromomagnesio-3-alkyl-5-bromothiophene in an 85:15 ratio. This ratio appears to be independent of reaction time, temperature, and Grignard reagent employed. Introduction of a catalytic amount of Ni(dppp)Cl2 to this isomeric mixture afforded poly(3-alkylthiophene) that contained greater than 95% HT-HT couplings (typically 98% HT couplings were seen). The high degree of regioregularity found in the polymer can be explained by a combination of kinetic and thermodynamic effects arising from steric and electronic effects found in the catalytic reaction. A series of reaction investigations led to a general explanation of the origin of regioregularity in polythiophene polymerization reactions. These reactions included kinetic studies and competition experiments.

Synthetic and Mechanistic Studies of Pd-Catalyzed C−H Arylation with Diaryliodonium Salts: Evidence for a Bimetallic High Oxidation State Pd Intermediate

Abstract: This contribution describes the substrate scope and mechanism of Pd-catalyzed ligand-directed C-H arylation with diaryliodonium salts. This transformation was applied to the synthesis of a variety of different biaryl products, using directing groups including pyridines, quinolines, pyrrolidinones, and oxazolidinones. Electronically and sterically diverse aryl groups (Ar) were transferred in high yield using iodine(III) reagents of general structure [Mes-I-Ar]BF(4). Mechanistic investigations have been conducted that establish the kinetic order of the catalytic reaction in each component, determine the resting state of the catalyst and the iodine(III) reagent, quantify the electronic influence of the arylating reagent on the reaction rate, and establish the intra- and intermolecular 1 degree H/D kinetic isotope effect. On the basis of these studies, this transformation is proposed to proceed via turnover-limiting oxidation of the Pd dimer [Pd(N~C)(OAc)](2) (N~C = 3-methyl-2-phenylpyridine) by [Mes-I-Ph]BF(4). This mechanism implicates a bimetallic high oxidation state Pd species as a key catalytic intermediate. The significance of this and other aspects of the proposed mechanism are discussed in detail.

Highly Efficient Copper-Catalyzed Nitro-Mannich Type Reaction: Cross-Dehydrogenative-Coupling between sp3 C−H Bond and sp3 C−H Bond

Abstract: A novel C−C bond formation method was developed via the cross-dehydrogenative-coupling (CDC) reaction catalyzed by using copper bromide in the presence of an oxidizing reagent, tert-BuOOH. The CDC reaction provides a simple and efficient catalytic method to construct β-nitroamine via the reaction between sp3 C−H and sp3 C−H bonds.

A New Reagent for Direct Difluoromethylation

Abstract: Molecular scaffolds containing alkylfluorine substituents are desired in many areas of chemical research from materials to pharmaceuticals. Herein, we report the invention of a new reagent (Zn(SO2CF2H)2, DFMS) for the innate difluoromethylation of organic substrates via a radical process. This mild, operationally simple, chemoselective, and scalable difluoromethylation method is compatible with a range of nitrogen-containing heteroarene substrates of varying complexity as well as select classes of conjugated π-systems and thiols. Regiochemical comparisons suggest that the CF2H radical generated from the new reagent possesses nucleophilic character.