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. The structure of the products was confirmed by X-ray crystallography. Broad signals in (13) C NMR studies suggest that several conformers, slowly interconverting on the NMR timescale, are present at room temperature.

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., aryl, N, and O) are used. The stereospecificity of the reaction is demonstrated by using a chiral starting material.

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 achievedb yamergedi minium-enamine activation.T he enantioselective desymmetrization reaction, leadingt ot hree adjacent stereocenters, furnished the target products in complete regioselectivity and moderate to high diastereo-and enantioselectivities (d.r.u pt o15:1a nd e.r.upt o9 3:7).Because of their high strain energy (about 27.5 kcal mol À1

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. The use of an electron-rich aryne precursor led to ring cleavage of the cyclopropene to afford an unprecedented xanthylium salt.

Owing to their special electronic properties cross-conjugated systems have experienced a renaissance in recent years, [1] and also pentafulvalene and its substituted analogues have come back into focus. [2,3] Originally regarded as laboratory curiosities displaying nonplanar structures and unusual bond lengths and angles, [4] they have attracted attention as ligands [5] for transition metals and as two-electron acceptors affording aromatic dianions. [6] Whereas the parent fulvalene is unstable at temperatures above À78 8C, [7] the perchloro derivative shows completely reversible redox behavior. [6b] Further investigations with fulvalene vinylogues [6b] indicate properties conducive to tuning the performance of organic-based batteries on a molecular level.The preparation of symmetrical pentafulvalenes has been realized for the most part by the coupling of two cyclopentadienyl rings, involving strong lithium bases and often molecular oxygen as the oxidant or CuCl 2 as the coupling promoter. [7,8] Other couplings have been performed by the Grignard addition to ketones [9] and homo couplings employing halogenated species and transition metals. [10] Also diazo compounds, which readily release nitrogen, have served as starting materials. [11] An alternative synthetic pathway investigated in the last decade accesses dibenzopentafulvalenes 1 by reductive Bergman-type cyclizations of cross-conjugated enediynes 2 (Scheme 1, top). [12] Highly substituted unsaturated oligocyclic systems can also be prepared by carbopalladation reactions. In the last two decades a number of domino carbopalladation sequences have been developed, yielding homo-and heterocyclic systems such as lactones, chromanes, molecular switches, and further complex systems in one single step from relatively simple starting materials. [13][14][15] Herein we disclose a novel dibenzopentafulvalene synthesis which affords the pentafulvalene framework in only one step through a quadruple carbopalladation process. Our retrosynthetic strategy relied on a readily available biphenylacetylene and two tethered alkyne moieties 4 (Scheme 1, bottom). We envisioned that a sequence starting with the oxidative addition of Pd into the CÀBr bond followed by three carbopalladation steps to the CÀC triple bonds and finishing with a final carbopalladation to the newly formed alkene would provide the dibenzopentafulvalene skeleton 3.To test our approach, we chose the biphenyl derivative 7 which was coupled with various diynes (Scheme 2). Biphenyl 7 was synthesized in two steps by the Suzuki-Miyaura coupling of the trisubstituted arene 5 and boronic acid 6 followed by removal of the silyl protecting groups in 75 % overall yield. Various diynes were obtained by Sonogashira cross-coupling of terminal diyne 8; the respective alcohols were transformed by Appel reaction into propargylic iodides 9. Final nucleophilic substitution of 9 by the phenolic hydroxy group in 7 afforded the domino substrates 4 in good to excellent yields.We initially chose substrate 4 a to optimize the rea...