Palladium-Catalyzed Heck Alkynylation of Benzyl Chlorides

Catalysts

The acyl Sonogashira reaction represents an extension of Sonogashira cross-coupling to acid chlorides which replace aryl or vinyl halides, while terminal acetylenes are used as coupling partners in both reactions. The introduction of a carbonyl functional group on the alkyne backbone determines a radical change in the reactivity of the products. Indeed, α,β-alkynyl ketones can be easily converted into different heterocyclic compounds depending on the experimental conditions employed. Due to its potential, the acyl Sonogashira reaction has been deeply studied with particular attention to the nature of the catalysts and to the structures of both coupling compounds. Considering these two aspects, in this review, a detailed analysis of the literature data regarding the acyl Sonogashira reaction and its role in the synthesis of several heterocyclic derivatives is reported.

Molecules

The transition metal-catalyzed C–H bond functionalization of azoles has emerged as one of the most important strategies to decorate these biologically important scaffolds. Despite significant progress in the C–H functionalization of various heteroarenes, the regioselective alkylation and alkenylation of azoles are still arduous transformations in many cases. This review covers recent advances in the direct C–H alkenylation, alkylation and alkynylation of azoles utilizing transition metal-catalysis. Moreover, the limitations of different strategies, chemoselectivity and regioselectivity issues will be discussed in this review.

Chemistry - A European Journal, 2013

Org. Biomol. Chem., 2014

Sulfinic acids and their salts have recently emerged as versatile coupling partners to efficiently access a wide variety of hetero-and carbocyclic compounds, under relatively mild conditions. Their growing importance is attributable to their dual capacity for acting as nucleophilic or electrophilic reagents. This report summarizes recent advances in the preparation and use of sulfinates in organic synthesis.

ChemInform, 2015

A novel water soluble copper(N-heterocyclic carbene)chloride [Cu(NHC)Cl] complex of vitamin B 1 was synthesized and characterized by EDX, FT-IR and NMR spectroscopy. It was employed for three component click reaction of benzyl chlorides 1a-e, alkynes 2a-c and sodium azide 3 in water at room temperature. All the synthesized compounds 4a-o were characterized by elemental analysis, IR, and 1 HNMR spectroscopy. The catalyst was easy to prepare, very versatile, reusable and was found to be highly active at low catalyst loading for a variety of substrates with a varied nature of substituents.

RSC Adv., 2014

A novel water soluble copper(N-heterocyclic carbene)chloride [Cu(NHC)Cl] complex of vitamin B 1 was synthesized and characterized by EDX, FT-IR and NMR spectroscopy. It was employed for three component click reaction of benzyl chlorides 1a-e, alkynes 2a-c and sodium azide 3 in water at room temperature. All the synthesized compounds 4a-o were characterized by elemental analysis, IR, and 1 HNMR spectroscopy. The catalyst was easy to prepare, very versatile, reusable and was found to be highly active at low catalyst loading for a variety of substrates with a varied nature of substituents.

2012

Scytonemin and nostodione A are cyanobacteria sunscreen pigments that have interesting biological properties. The ring structures of scytonemin and nostodione A are closely related and unique among natural products. The structure is proposed to stem from the condensation of tryptophan and tyrosine-derived subunits. Gold-catalyzed cyclizations of aromatic and heteroaromatic compounds with alkynes offer new ways for the efficient construction of bioactive compounds, and have attracted much attention in the last decade. Gold-catalyzed intramolecular carbocyclization was used with the intention of constructing cyclopenta[b]indol ring systems, present in scytonemin and nostodione A, from indoles with alkynes tethered to position three. Two bond tethers gave exclusively carbazoles and one bond tethers gave a rearrangement of the alkyne. Both type of systems were explored using different gold catalysts and solvents.

2018

Pyrrole is widely known as a biologically active scaffold which possesses a diverse nature of activities. The combination of different pharmacophores in a pyrrole ring system has led to the formation of more active compounds. Pyrrole containing analogs are considered as a potential source of biologically active compounds that contains a significant set of advantageous properties and can be found in many natural products. The present review highlights the synthetic methods of representatives of nitrogen heterocycles such as pyrrole, substituted pyrroles and other related compounds. The aim of this review is to indicate and summarise the different methods for the synthesis of nitrogen containing heterocycles from the group of pyrrole and pyrrole related structures.

The decarboxylative coupling of alkynyl carboxylic acids is an attractive area of research in organic chemistry, because the structure of aryl alkyne is one of the important building blocks for the synthesis of p-conjugated compounds. The use of alkynyl carboxylic acid as an alkyne source has several advantages in handling and storage. As a catalyst, palladium, copper, nickel, and silver were employed in the decarboxylative coupling reactions. The formation of CC (sp 2-sp, sp-sp and sp 3-sp), C-N, C-P and C-S bonds has been developed. This review aims to illustrate the development of the decarboxylative coupling reaction of alkynyl carboxylic acids.

Abstract: Different cross-coupling reactions for the formation of biologically important motifs and intermediates in organic synthesis using various suitable copper catalysts are reviewed. These include C-C, C-N, C-O, C-S heteroatom bond forming, cyclization and other miscellaneous reactions catalyzed by elemental copper, copper salts, CuI, Cu (OTf)2, CuBr, Cu2O etc. The use of copper reagents instead of palladium catalysts and ligands seems to be advantageous from the commercial point of view. The methods described herein afford the products in excellent yield without using expensive and moisture/air sensitive palladium catalysts, ligands and reagents.