Synthesis of 1,3--disubstituted sterically encumbered imidazolidinone organocatalysts.

A variety of novel imidazolidinone-based organocatalysts with bulky substituents were synthesized under mild reaction conditions starting from easily accessible substrates. Different natural and unnatural amino acid methyl amides were cyclized with aromatic carbaldehydes to yield two diastereomeric MacMillan-type catalysts. Special emphasis was put on bulky residues such as mesityl and pyrene moieties.

Ring-Opening 1,3-Halochalcogenation of Cyclopropane Dicarboxylates.

Donor-acceptor cyclopropanes with two geminal carboxylic esters are reacted with chalcogenyl chlorides and bromides to afford ring-opened products bearing the halogen atoms in the 1-position, adjacent to the donor, and the chalcogenyl residue in the 3-position next to the two acceptor groups. A variety of different donors (e.g.

Ring-Opening Regio-, Diastereo-, and Enantioselective 1,3-Chlorochalcogenation of Cyclopropyl Carbaldehydes.

meso-Cyclopropyl carbaldehydes are treated in the presence of an organocatalyst with sulfenyl and selenyl chlorides to afford 1,3-chlorochalcogenated products. The transformation is achieved by a merged iminium-enamine activation. The enantioselective desymmetrization reaction, leading to three adjacent stereocenters, furnished the target products in complete regioselectivity and moderate to high diastereo- and enantioselectivities (d.

[4+3] Cycloaddition of Donor-Acceptor Cyclopropanes with Amphiphilic Benzodithioloimine as Surrogate for ortho-Bisthioquinone.

Donor-acceptor cyclopropanes were reacted with amphiphilic benzodithioloimine to give seven-membered heterocycles with two sulfur atoms. Formally, this transformation can be regarded as a [4+3] cycloaddition reaction of the three-membered ring and ortho-bisthioquinone. The benzodithioloimine serves as a surrogate for this highly reactive diene.

Reacting cyclopropenones with arynes: access to spirocyclic xanthene-cyclopropene motifs.

A formal insertion of two aryne moieties into the carbon-oxygen double bond of cyclopropenone has been realized. Spirocyclic xanthene-cyclopropene scaffolds were obtained. Mechanistically, a sequence of a formal [2 + 2]-cycloaddition followed by electrocyclic ring opening and a terminating [4 + 2]-type cycloaddition is postulated.

Carboxylate assistance for catalyzed hydroarylations of methylenecyclopropanes.

Carboxylate assistance enabled efficient and chemoselective ruthenium(II)-catalyzed hydroarylations and hydroalkenylations of highly strained methylenecyclopropanes via C-H bond activation occurring with ring conservation of the cyclopropane moieties.