Cesium (Z)-2-Carbomethoxyethenethiolate: A Reagent for the Preparation of (Z)-2-Carbomethoxyethenyl Thioethers Including Selected Cysteine and Homocysteine Derivatives

Click Nucleophilic Conjugate Additions to Activated Alkynes: Exploring Thiol-yne, Amino-yne, and Hydroxyl-yne Reactions from (Bio)Organic to Polymer Chemistry

The 1,4-conjugate addition reaction between activated alkynes or acetylenic Michael acceptors and nucleophiles (i.e., the nucleophilic Michael reaction) is a historically useful organic transformation. Despite its general utility, the efficiency and outcomes can vary widely and are often closely dependent upon specific reaction conditions. Nevertheless, with improvements in reaction design, including catalyst development and an expansion of the substrate scope to feature more electrophilic alkynes, many examples now present with features that are congruent with Click chemistry. Although several nucleophilic species can participate in these conjugate additions, ubiquitous nucleophiles such as thiols, amines, and alcohols are commonly employed and, consequently, among the most well developed. For many years, these conjugate additions were largely relegated to organic chemistry, but in the last few decades their use has expanded into other spheres such as bioorganic chemistry and polymer chemistry. Within these fields, they have been particularly useful for bioconjugation reactions and step-growth polymerizations, respectively, due to their excellent efficiency, orthogonality, and ambient reactivity. The reaction is expected to feature in increasingly divergent application settings as it continues to emerge as a Click reaction.

Synthesis of l-indospicine, [5,5,6-2H3]-l-indospicine and l-norindospicine

Indospicine is a non-proteogenic amino acid that accumulates as the free amino acid in livestock grazing Indigofera plant species and causes both reproductive losses and hepatotoxic effects.

Stereoselective synthesis and reaction of gold(i) (Z)-enethiolates

Bench-top-storable (Z)-enethiol reagents: gold (Z)-1-decenylthiolates were synthesized stereoselectively in high yields.

Nucleophilic attack of 2-sulfinyl acrylates: a mild and general approach to sulfenic acid anions

An increasing number of reactions of sulfenic acid anions are being demonstrated in the literature. As such, mild, general and reliable means for the generation of sulfenates are due. In the current paper, an addition/elimination of 2-sulfinyl acrylates using various nucleophiles is demonstrated and evaluated as a protocol for alkane- and arenesulfenate generation. Cyclohexanethiolate, methoxide and n-butyllithum each exhibit some merit for the reaction, and the thiolate is established as a mild, selective and effective reagent to release sulfenates from 2-sulfinyl acrylates. The stereospecificity of the addition/elimination of each nucleophile is recognized, and an explanation for the specificity is offered for thiolate and methoxide.

Diastereoselective alkylations of a protected cysteinesulfenate

To further understand stereoselection in the alkylation of sulfenate anions, a protected cysteinesulfenate was generated in THF solution at low temperature. Introduction of a reactive alkylating agent brings about a cysteinyl sulfoxide in 51-75% yield, with diastereomeric ratios at the sulfinyl group ranging from 83:17 to 95:5. An internally complexed lithium counterion is proposed to account for the stereoselectivity.