Ring-Opening Carbonyl-Olefin Metathesis of Cyclobutenes

Unveiling the Use of 1,1-Bis(triflyl)ethylene as CF3SO2CH═CH2 Source with the Assistance of (n-Bu)4NF: Synthesis of 3-[(Trifluoromethyl)sulfonyl]cyclobut-1-enes

Allylic sulfone-embedded cyclobutenes have been prepared in one pot from alkynes. The carbocycle and the alkenyl sulfone moieties were installed through consecutive bis(triflyl)cyclobutenylation of a triple bond and tetra-n-butylammonium fluoride (TBAF)-assisted hydrodesulfonylation of an allylic bis(sulfone). It is noteworthy that 1,1-bis(triflyl)ethylene acts as a CF3SO2CH═CH2 source for the first time.

Brønsted acid catalyzed Ficini [2 + 2] cycloaddition of ynamides with enones

Herein, we describe a novel metal-free Brønsted acid-catalyzed Ficini [2 + 2] cycloaddition of ynamides with enones under mild reaction conditions, leading to the formation of various cyclobutenamides in generally good to excellent yields within short reaction times. This work represents the first example of ynamides involved in a nonmetal-catalyzed [2 + 2] cycloaddition with enones.

Diazene-Catalyzed Oxidative Alkyl Halide-Olefin Metathesis

The first platform for oxidative alkyl halide-olefin metathesis is described. The procedure employs diazenes as catalysts, which effect the cyclization of alkenyl alkyl halides to generate cyclic olefins and carbonyl products. The synthesis of phenanthrene, coumarin, and quinolone derivatives is demonstrated as well as the potential to apply this strategy to other electrophiles.

Regio- and Stereoselective Intermolecular Oxysulfonylation of Alkynes with 1,3-Diketones to Access (Z)-β-Sulfonated Enethers

The first multicomponent regio- and stereoselective difunctionalization of alkynes via concomitant C-O and C-S bond formation using 1,3-diketones and sodium sulfinate has been developed for the synthesis of various sulfonated enethers. The viability of this strategy is unveiled by gram-scale, various synthetic modifications and late-stage functionalization. This transformation does not require any prefunctionalization, metal catalysts, and oxidants. The present operationally simple, efficient, and sustainable approach provides various functionalized olefins in a one-pot protocol with high Z-selectivity.

Catalytic Olefin-Imine Metathesis: Cobalt-Enabled Amidine Olefination with Enaminones

Organic metathesis reactions allow for expedient assembly of diverse molecular skeletons and appendages through the exchange of molecular fragments. The olefin-imine variant of this process, in particular, can expand the synthetic toolbox for manipulating carbon-carbon and carbon-nitrogen bonds but has thus far been achieved only on a stoichiometric metal-mediated basis. Herein, we report the development of a catalytic olefin-imine metathesis reaction, featuring cobalt-catalyzed amidine olefination with enaminones and a versatile product synthon enabling further structural diversification.

Toward Homogeneous Brønsted-Acid-Catalyzed Intramolecular Carbonyl-Olefin Metathesis Reactions

The carbonyl-olefin metathesis (COM) reaction is an attractive approach for the formation of a new carbon-carbon double bond from a carbonyl precursor. In principle, this reaction can be promoted by the activation of the carbonyl group with a Brønsted acid catalyst; however, it is often complicated as a result of unwanted side reactions under acidic conditions. Thus, there have been only a very few examples of Brønsted-acid-catalyzed COM reactions, all of which required specially designed setups. Herein, we report a new practical homogeneous Brønsted-acid-catalyzed protocol using nitromethane, a readily available solvent, to promote intramolecular ring-closing COM reactions.