Z-selective, anti-Markovnikov addition of alkoxides to terminal alkynes: an electron transfer pathway?

Potassium alkoxides undergo anti-Markovnikov addition to aryl-substituted alkynes with Z selectivity in DMF as the solvent. The yields and efficiency of the reaction was also found to be enhanced by the addition of a secondary amine ligand such as N,N′-dimethylethylenediamine. Mechanistic investigations suggest that the products, reaction rates and selectivity can be explained via a single electron transfer from the alkoxide to the alkyne. This leads to a radical anion intermediate, which then rapidly combines with the alkoxide to yield a vinyl anion whose lifetime governs the E:Z selectivity observed in the products

The chemistry of ynol and thioynol ethers

Alkynyl ethers and alkynyl thioethers (‘ynol ethers’ and ‘thioynol ethers’) are appealing building-blocks in synthetic chemistry due to their ease of manipulation and predictable reactivity. Until recently however, their potential has remained underexploited due to difficulties in preparation and isolation. Although recent advances in synthetic chemistry have highlighted various applications for ynol ethers, the equivalent thioynol examples have been rather less exploited despite a unique and fascinating reactivity profile. Although superficially the chemistry of alkynyl ethers and their sulfide counterparts are similar, close examination of their chemistry reveals important differences which can be exploited by the synthetic chemist. This review will examine the preparation of both classes of compound and examine their reactivity to highlight their powerful synthetic applications. Particular focus will be made of thiynol ethers whose chemistry exhibits some fascinating differences compared to their oxygen counterparts and have immense untapped potential for synthetic chemistry

The preparation and applications of amides using electrosynthesis

The synthesis of amides is extremely important given the ubiquitous presence of this motif in biological systems, as well as in the pharmaceutical industry, where it is estimated that amide preparation is the most common chemical reaction employed. As such, greener routes to this motif have long been a vital research goal. Amide groups are also synthetically versatile, capable of taking part in a wide range of different transformations, especially when subjected to electrochemical conditions. The current resurgence of electrosynthesis has led to new and more sustainable syntheses of (and using) amides to be published in recent times. As such, this tutorial review aims to highlight these reactions. Given the vital importance of amides and the growing interest in electrosynthesis, the combination of these two topics is an exciting and interesting field of research that holds a lot of promise in the future of synthetic chemistry

Electrochemical synthesis of copper(i) acetylides: Via simultaneous copper ion and catalytic base electrogeneration for use in click chemistry

We report an efficient and sustainable electrochemical synthesis of copper(i) acetylides using simultaneous copper oxidation and Hofmann elimination of quaternary ammonium salts. The electrochemically-generated base was also regenerated electrochemically, making it catalytic. A 'Click test' (CuAAC reaction) was performed to assess product purity and an electrochemically-promoted, one-pot CuAAC reaction was performed, which serves as a promising initial demonstration of this approach in a pharmaceutically-relevant reaction

Mechanistic studies of reactive oxygen species mediated electrochemical radical reactions of alkyl iodides

Mechanistic studies of a reactive oxygen species mediated electrochemical radical reaction of alkyl iodides are described. Hydroxyl radicals and ozone are identified to be the active species involved in the formation of alkyl radicals under mildly reducing potential (�1.0 V vs. Ag QRE) in buffered acidic conditions (pH 3.6)

An improved transition-metal-free synthesis of aryl alkynyl sulfides via substitution of a halide at an sp-centre

A simple high-yielding preparation of aryl alkynyl sulfides is presented. The reaction of a chloroacetylene with a thiolate salt in the presence of an amine mediator (dimethylamine or N,N'-dimethylethylenediamine) yields the alkynyl sulfides in excellent yields. The alkynyl chloride is easily prepared from the parent alkyne

Observations on transition metal free biaryl coupling: potassium tert-butoxide alone promotes the reaction without diamine or phenanthroline catalysts

Biaryl coupling (often labelled 'C-H activation') of aromatic systems can be achieved by potassium tert-butoxide alone in the absence of any amine or bipyridine catalyst (1,10-phenanthroline or N,N'-dimethylethylenediamine being the most common), previously reported to be essential. Various mechanistic studies and observations are presented which suggest that when 1,10-phenanthroline is employed as the catalyst, the alkoxide is destroyed almost immediately

Investigations Into the Mechanism of Copper-Mediated Glaser-Hay Couplings Using Electrochemical Techniques

The mechanism of the copper mediated C-C bond forming reaction known as Glaser-Hay coupling (alkyne dimerization) has been investigated using electrochemical techniques. Applying an oxidative potential to a copper or copper-coated graphite electrode in the presence of the organic base DABCO results in the dimerization of phenylacetylene in good yield. Further mechanistic investigation has shown that this reaction medium results in the assembly of a dinuclear Cu(I) complex which, although previously reported, has never been shown to have catalytic properties for C-C bond formation. The complex is reminiscent of that proposed in the Bohlmann model for the Glaser-Hay reaction and as such lends weight to this proposed mechanism above the alternative proposed mononuclear catalytic cycle