Unexpected Substituent Effects in Spiro-Compound Formation: Steering N-Aryl Propynamides and DMSO toward Site-Specific Sulfination in Quinolin-2-ones or Spiro[4,5]trienones

DMSO/SOCl2-Enabled Synthesis of 3-Chloroindoles via Desulfonylative Chlorocyclization of N,N-Disubstituted 2-Alkynylanilines

The application of the DMSO/SOCl2 system enabled the intramolecular cyclization/chlorination of N,N-disubstituted 2-alkynylanilines, leading to the synthesis of a series of 3-chloroindoles with moderate to good yields. Differing from the previously reported interrupted Pummerer reaction featuring the introduction of SMe moiety, the current approach adopted an alternative pathway that realized the incorporation of chlorine atom to the indole skeleton via a desulfonylative chlorocyclization process.

Cis-Selective Double Spirocyclization via Dearomatization and Isomerization under Thermodynamic Control

Spiro compounds have been considered key scaffolds for pharmaceutical applications. Although many synthetic methods exist for monospirocycles, fewer approaches are known for dispirocycles. Here, we report a highly cis-selective method for constructing a 5/6/5-dispirocyclic structure containing pyrrolidine and γ-lactam rings with various substituents from a series of N-arylpropiolamides. The high cis-selectivity would result from isomerization under thermodynamic control. Cis- and trans-diastereomers can be in equilibrium, favoring cis-adducts.

Synthesis of Spiro[5.5]trienones- and Spiro[4.5]trienones-Fused Selenocyanates via Electrophilic Selenocyanogen Cyclization and Dearomative Spirocyclization

A practical strategy for the synthesis of spiro[5.5]trienones-fused selenocyanates and spiro[4.5]trienones-fused selenocyanates through electrophilic selenocyanogen cyclization and dearomative spirocyclization is reported. This approach was conducted under mild conditions with broad substrate scope and good functional group tolerance. The utility of this procedure is exhibited in the late-stage functionalization of nature product and drug molecules.

Application of DMSO as a methylthiolating reagent in organic synthesis

In the past decades, DMSO has been widely used not only as a common solvent but also as an environmentally benign oxidant in various organic transformations. Most strikingly, DMSO can be used as a sulfur source to construct methylthiolated building blocks of potential biologically active molecules, which is a remarkable achievement in the field of organic sulfur chemistry. The purpose of this review article is to summarize and discuss the main developments in the application of DMSO as a methylthiolating reagent to introduce the -SMe functionality in organic synthesis.

Divergent Synthesis of Chalcogenylated Quinolin-2-ones and Spiro[4,5]trienones via Intramolecular Cyclization of N-Aryl­propynamides Mediated by Diselenides/Disulfides and PhICl2

The reaction of N-arylpropynamides with (dichloroiodo)benzene (PhICl2) and diselenides/disulfides resulted in a divergent synthesis of chalcogenylated quinolinones and spiro[4.5]trienes through intramolecular electrophilic cyclization and chalcogenylation. The chalcogenyl functional group was introduced by an electrophilic reactive organosulfenyl chloride or selenenyl chloride species, generated in situ from the reaction of disulfides/diselenides and PhICl2. Notably, the divergent cyclization pathways were determined by the substituent type on the aniline ring in N-arylpropynamide substrates. Substrates bearing a fluoro, methoxy or trifluoromethoxy group at the para-position of the aniline underwent an alternative spiralization pathway to give the 3-chalcogenylated spiro[4,5]trienones.