A direct route to conjugated enediynes from dipropargylic sulfones by a modified one-flask Ramberg–Bäcklund reaction
作者:Xiaoping Cao、Yuying Yang、Xiaolong Wang
DOI:10.1039/b207296n
日期:——
The reaction of dipropargylic sulfones with dibromodifluoromethane in the presence of alumina-supported KOH in dichloromethane solution results in facile rearrangement affording the corresponding conjugated linear and cyclic enediynes in good yields. This result shows that the direct transformation of α- and α′-hydrogen bearing sulfones assembles enediyne units without resorting to the prior preparation
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
Mechanistic Studies on Garratt–Braverman Cyclization: The Diradical–Cycloaddition Puzzle
作者:Joyee Das、Subhendu Sekhar Bag、Amit Basak
DOI:10.1021/acs.joc.6b00490
日期:2016.6.3
In this work, we present the results of extensive multiprong studies involving the fate of deuterium-labeled substrates, EPR, trapping experiments, and LA-LDI mass spectrometry to sort out the controversies relating to the mechanism of Garratt–Braverman cyclization in two systems, namely bis-propargyl sulfones and ethers. The results are in conformity with a diradical mechamism for the sulfone, while
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.