The use of N‐(p‐chlorophenyl)methylbenzoxazole‐2‐thione as a sulfur‐atom donor enables the catalytic [2+2+1] cycloaddition of diynes in wet DMF at 80 °C when open to air, thus affording diverse fused thiophenes with good yields and wide functional‐group compatibility. A plausible mechanism, involving a cationic ruthenacycle intermediate, was also proposed on the basis of several control experiments
Base catalyzed rearrangement of π-conjugated sulfur and selenium bridged propargylic systems
作者:Samuel Braverman、Yossi Zafrani、Hugo E Gottlieb
DOI:10.1016/s0040-4020(01)00923-1
日期:2001.10
A series of novel π-conjugated bis-propargylic sulfides, selenides, sulfoxides and sulfones have been prepared. In the presence of amine bases these compounds underwent facile isomerization to the corresponding allenes, followed by a tandem cyclization and aromatization of the latter via a diradical intermediate. While the reactions of sulfones and sulfoxides were almost spontaneous and proceeded in
Sequential Intermediates in the Base-Catalyzed Conversion of Bis(π-conjugated propargyl) Sulfones to 1,3-Dihydrobenzo- and Naphtho[<i>c</i>]thiophene-2,2-dioxides
作者:Yossi Zafrani、Hugo E. Gottlieb、Milon Sprecher、Samuel Braverman
DOI:10.1021/jo051692i
日期:2005.11.1
In a recent article, we reported on the base-catalyzed rearrangements of dipropargyl selenides, -sulfides, -sulfoxides, and -sulfones that eventually lead to polycyclic aromatic products. In the present work, we report on the first isolation and characterization of the thiophene dioxide intermediates 5b,c from a mild tandem isomerization/cyclization/aromatization of bis(π-conjugated propargyl) sulfones
The synthesis and base catalyzed rearrangement of bis-γ-phenylpropargyl sulfone, sulfoxide and sulfonium salts are described. In contrast to the first two compounds which undergo a fast acetylene to allene isomerization followed by a tandem cyclization and aromatization via a diradical mechanism, the latter compound undergoes a [2,3]-sigmatropic shift via the corresponding ylide intermediate.