6.1 Thiol–Ene/Yne Click Reactions: A Powerful Tool Toward Diversity-Oriented Synthesis

The clickable addition reaction between thiols and unsaturated compounds leading to the generation of (branched/linear) thioethers or (branched/linear) vinyl sulfides is known as the hydrothiolation reaction. Based upon the nature of unsaturation, i.e. double bond or triple bond, hydrothiolation reactions are classified as thiol–ene and thiol–yne click reactions, respectively. These reactions have emerged as a powerful and widely used strategy for the generation of carbon–sulfur bonds due to several associated benefits including versatile synthetic procedures, wide functional-group tolerance, high atom economy with few to no byproducts, and simple purification. The hydrothiolation reactions have numerous trapping applications in the fields of polymer chemistry, nanoengineering, pharmaceuticals, natural products, and perhaps most importantly in medicinal chemistry for the synthesis of many drugs and bioactive molecules.

Modular and stereoselective synthesis of tetrasubstituted vinyl sulfides leading to a library of AIEgens

Tetraarylethylenes exhibit intriguing photophysical properties and sulfur atom frequently play a vital role in organic photoelectric materials and biologically active compounds. Tetrasubstituted vinyl sulfides, which include both sulfur atom and tetrasubstituted alkenes motifs, might be a suitable skeleton for the discovery of the new material molecules and drug with unique functions and properties. However, how to modular synthesis these kinds of compounds is still challenging. Herein, a chemo- and stereo-selective Rh(II)-catalyzed [1,4]-acyl rearrangements of α-diazo carbonyl compounds and thioesters has been developed, providing a modular strategy to a library of 63 tetrasubstituted vinyl sulfides. In this transformation, the yield is up to 95% and the turnover number is up to 3650. The mechanism of this reaction is investigated by combining experiments and density functional theory calculation. Moreover, the “aggregation-induced emission” effect of tetrasubstituted vinyl sulfides were also investigated, which might useful in functional material, biological imaging and chemicalnsing via structural modification.

Computational Design of Radical Recognition Assay with the Possible Application of Cyclopropyl Vinyl Sulfides as Tunable Sensors

The processes involving the capture of free radicals were explored by performing DFT molecular dynamics simulations and modeling of reaction energy profiles. We describe the idea of a radical recognition assay, where not only the presence of a radical but also the nature/reactivity of a radical may be assessed. The idea is to utilize a set of radical-sensitive molecules as tunable sensors, followed by insight into the studied radical species based on the observed reactivity/selectivity. We utilize this approach for selective recognition of common radicals—alkyl, phenyl, and iodine. By matching quantum chemical calculations with experimental data, we show that components of a system react differently with the studied radicals. Possible radical generation processes were studied involving model reactions under UV light and metal-catalyzed conditions.

ESI-MS Analysis of Thiol-yne Click Reaction in Petroleum Medium

Petroleum contains a large number of heteroatomic compounds, but today, most of them are not efficiently utilized. The constant development of the sustainability concept recalls for rethinking the usage of fossil resources with improved chemical utility. In order to initiate research aimed at involving active petroleum compounds in chemical transformations, a new analytical method for product detection is needed. Here, we study the click reaction of thiols with alkynes, leading to the formation of α-vinyl sulfides directly in the petroleum environment. The reaction was carried out using an (IMes)Pd(acac)Cl catalyst, which demonstrated tolerance to petroleum components. In this study, the concentration of thiols ranged from 1 M to 0.01 M (from 8% to 0.1%). To detect products at low concentrations, a special alkyne labeled with an imidazole moiety was used. This approach made it possible to observe the formation of vinyl sulfides by electrospray ionization mass spectrometry (ESI-MS), which provides an opportunity for further optimization of the reaction conditions and future developments for the direct involvement of oil components in chemical reactions.

Catalytic conversion of alkynes to α-vinyl sulfides mediated by carbene-linker-carbene (CXC) rhodium and iridium complexes

The performance of a set of mono- and bimetallic Rh(i) and Ir(i) complexes bearing carbene-linker-carbene (CXC) bis-triazolylidene ligands (with X = O, N) coordinated in a bridging or chelating fashion was evaluated in the hydrothiolation of alkynes.

Synthesis of vinyl sulfides and thioethers via hydrothiolation reaction of 4-hydroxydithiocoumarin and arylacetylenes/styrenes†

Synthesis of vinyl sulfides (3a-m) and thioethers (7a-k), exclusive Markovnikov products, are reported by using copper(I) iodide catalyzed regioselective hydrothiolation reaction of terminal alkynes/alkenes and 4-hydroxydithiocoumarin. However, anti-Markovnikov hydrothiolation products...

Sodium iodide-mediated synthesis of vinyl sulfides and vinyl sulfones with solvent-controlled chemical selectivity

Solvent-controlled selectivity of the elimination/coupling reaction was realized for divergent synthesis of vinyl sulfides and vinyl sulfones. The described protocol is more convenient for the preparation of vinyl sulfide and vinyl sulfone related skeletons.