Synthesis of 4-sulfonyl-1,7-diesters via K2CO3-mediated alkylative debenzoylation of α-sulfonyl o-hydroxyacetophenones with acrylates

The synthesis of 4-sulfonyl-1,7-diesters was well developed, under open-vessel conditions, by K2CO3-mediated double alkylation of α-sulfonyl o-hydroxyacetophenones with acrylates and tandem debenzoylation of the resulting α,α-disubstituted o-hydroxyacetophenones. A plausible mechanism is proposed and discussed here. This high-yielding protocol provides a highly effective intermolecular alkylation and intramolecular debenzoylation via the formation of two carbon-carbon (C-C) single bonds and the cleavage of a carbon-carbon (C-C) single bond.

A Modular Synthesis of the Rhazinilam Family of Alkaloids and Analogs Thereof

A short, modular strategy for synthesizing three representative alkaloids of the (±)-rhazinilam family and 10 non-natural analogs is described. The protocol involves a radical addition/cyclization cascade reaction that assembles the tetrahydroindolizine system decorated with appropriate groups for a subsequent Pd-mediated cyclization, which generates the nine-membered lactam.

Synthesis of [ 2 H 5 ]baricitinib via [ 2 H 5 ]ethanesulfonyl chloride

Baricitinib, typically applied as a treatment for rheumatoid arthritis, has recently attracted the attention of clinicians and researchers as a potential treatment for COVID‐19. Naturally, there has been a need for the preparation of the isotope‐labelled analogue of baricitinib to probe the pharmacokinetics of baricitinib in this new role. As such, we have developed a simple synthetic route to deuterated [²H₅]baricitinib, facilitating its formation over four steps and in a 29% overall yield based on starting [²H₅]ethanethiol (19% if we start with [²H₅]bromoethane instead). A critical component of the overall process involves the synthesis of [²H₅]ethanesulfonyl chloride, and we describe in detail the two routes that were explored to optimize this step.

Photoredox Organocatalysis for the Enantioselective Synthesis of 1,7-Dicarbonyl Compounds

We describe an asymmetric organocatalytic method to synthesize 1,7-dicarbonyl compounds containing a β-stereocenter. The chemistry relies on the formation of γ-keto radicals, generated upon oxidative ring opening of cyclobutanols mastered by an organic photoredox catalyst. These nonstabilized primary radicals are stereoselectively intercepted by an iminium ion intermediate, formed upon activation of aliphatic and aromatic enals by a chiral secondary amine catalyst. This organocatalytic photoredox method served to prepare scaffolds found in natural products and drug molecules.

Silyldienolates in Organocatalytic Enantioselective Vinylogous Mukaiyama-Type Reactions: A Review

Mukaiyama aldol, Mannich, and Michael reactions are arguably amongst the most important C-C bond formation processes and enable access to highly relevant building blocks of various natural products. Their vinylogous extensions display equally high potential in the formation of important key intermediates featuring even higher functionalization possibilities through an additional conjugated C-C double bond. Hence, it is much desired to develop highly selective vinylogous methods in order to enable unconventional, more efficient asymmetric syntheses of biologically active compounds. In this regard, silyl-dienolates were discovered to display high regioselectivities due to their tendency toward γ-additions. The control of the enantio- and diastereoinduction of these processes have been for a long time dominated by transition metal catalysis, but it received serious competition by the application of organocatalytic approaches since the beginning of this century. In this review, the organocatalytic applications of silyl-dienolates in asymmetric vinylogous C-C bond formations are summarized, focusing on their scope, characteristics, and limitations.

Sulfoxide synthesis from sulfinate esters under Pummerer-like conditions

A facile synthetic method for the preparation of allyl sulfoxides by S-allylation of sulfinate esters proceeds through sulfonium intermediates without [3,3]-sigmatropic rearrangement and further Pummerer-type reactions of the resulting allyl sulfoxides. On the basis of the plausible reaction mechanism involving sulfonium salt intermediates, S-alkynylation and S-arylation were also accomplished.

Xanthate-mediated synthesis of (E)-alkenes by semi-hydrogenation of alkynes using water as the hydrogen donor

Semi-hydrogenation of alkynes is one of the most widely used methods for obtaining alkenes in laboratory preparation and in industry. Transition metal catalysts have been extensively studied for this transformation, but the tolerance of functional groups, such as pyridine, -OH, -NH2, -Bpin, and halides, and the toxicity of the trace amount of transition metal catalysts are still highly challenging. In this study, we report a general and robust strategy to achieve the semi-hydrogenation of alkynes using inexpensive and commercially available xanthate as the mediator. Mechanism studies support a non-radical process and H2O acts as the hydrogen donor.

Thermal conversion of primary alcohols to disulfidesviaxanthate intermediates: an extension to the Chugaev elimination

Heating primaryO-alkylS-difluoro(ethoxycarbonyl)methyl xanthates yields disulfides. This extends to the Chugaev elimination.

Expeditious Synthesis of Dianionic-Headed 4-Sulfoalkanoic Acid Surfactants

4-Sulfoalkanoic acids are a class of important dianionic-headed surfactants. Various 4-sulfoalkanoic acids with straight C8, C10, C12, C14, C16, and C18 chains were synthesized expeditiously through the radical addition of methyl 2-((ethoxycarbonothioyl)thio)acetate to linear terminal olefins and subsequent oxidation with peroxyformic acid. This is a useful and convenient strategy for the synthesis of dianionic-headed surfactants with a carboxylic acid and sulfonic acid functionalities in the head group region.