Search

Herein, reactivity studies of a cyclic bis‐hydridostannylene [(ADC)SnH]2 (1‐H2) (ADC=PhC{(NDipp)C}2; Dipp=2,6‐iPr2C6H3) with various unsaturated organic substrates are reported. Reactions of terminal alkynes (RC≡CH) with 1‐H2 afford mixed acetylide‐vinyl‐functionalized bis‐stannylenes via dehydrogenation and hydrostannylation. Treatment of 1‐H2 with PhC≡CCH3 gives a unique distannabarrelene via dehydrogenative C(sp3)−H stannylation and hydrostannylation of the C≡CCH3 moiety. 1‐H2 undergoes dehydrogenative [2+2]‐cycloaddition reactions with diphenylacetylene, azobenzene, acetone, benzophenone, and benzaldehyde to form the 1,4‐distannabarrelene derivatives. The elimination of H2 in these reactions suggests the masked‐diradical property of 1‐H2. In fact, these [2+2]‐cycloaddition products are also accessible on treatments of the Sn(I) diradicaloid [(ADC)Sn]2 (1) with appropriate reagents. All compounds have been characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction. Moreover, the catalytic activity of 1‐H2 has been shown for the hydroboration of unsaturated substrates. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic behavior of the fluorene bridged verdazyl diradicals has been studied theoretically in their neutral and deprotonated states. The deprotonation of C9‐H site of the fluorene ring opens a new coupling pathway, which changes the nature of magnetic coupling. The transmission spectra analysis reveals that the transmission through fluorine has also increased due to the opening of a new coupling path after deprotonation. [ABSTRACT FROM AUTHOR]

The thermal C2-C6/ene cyclization of enyne-allenes has become an exciting venue for both mechanistic and synthetic studies. While at first most efforts were aimed at establishing the diradical nature of the thermal process and to derive therefrom efficient protocols for synthetic schemes, recent evidence has disclosed the C2-C6 cyclization as a unique reaction heavily influenced by nonstatistical dynamic effects. Depending on the substituents at the enyne-allene, one can readily identify transitions between classical and nonstatistical behaviors on the basis of experimental data. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Two novel, thioether containing benzannulated enediyne ligands, 1,2-bis(3-(quinolin-8-ylsulfanyl)prop-1-ynyl)benzene (1), and 1,2-bis(3-(pyridin-2-ylmethylsulfanyl)prop-1-ynyl)benzene (2) have been synthesized and characterized along with their corresponding Cu(I), Ag(I), Cu(II), and Pd(II) metalloenediyne complexes (3–10). Single crystal X-ray structures of the d10 and d8 N2S2 complexes show thioether coordination leading to distorted tetrahedral and trans square planar geometries about the metal centers, respectively. Based on their X-ray structures, all complexes are expected to exhibit high Bergman cyclization temperatures (>200 °C), and indeed this is the case for the Cu(I) and Ag(I) complexes (211–218 °C). In contrast, the corresponding divalent, tetragonal and trans square planar complexes of Cu(II) and Pd(II) exhibit more facile reactivity and lower solid state Bergman cyclization temperatures (186–190 °C) which more closely resemble values expected for cis-complexes. The unusual order in the thermal reactivities of these constructs can be attributed to a previously evaluated mechanism by which weak thioether coordination permits an elevated temperature trans-to-cis geometric rearrangement prior to Bergman cyclization. [Copyright &y& Elsevier]

Isomerization of soluble precursor compounds to produce fused-ring systems is an attractive approach for preparing conjugated polymers and oligomers. Cycloaromatization chemistry has previously been explored in this capacity employing reactions based on the Bergman cyclization. Using ethynyl sulfides with a terminal o-diethynylbenzene unit, an alternative strategy is demonstrated that offers selectivity advantages in the kinetically controlled radical cyclizations. The products are acene-fused thiophenes in which the diethynylsulfide acts as a relay for the diradical produced in a Bergman cyclization. [Copyright &y& Elsevier]