Ring-Opening of Indoles: An Unconventional Route for the Transformation of Indoles to 1<i>H</i>-Pyrazoles Using Lewis Acid
作者:Subhankar Panda、Nirmalya Pradhan、Debasis Manna
DOI:10.1021/acscombsci.8b00071
日期:2018.10.8
unusual transformation of indoles to pyrazoles via an aromatic ring-opening strategy has been developed. The salient feature of this strategy involves the C2–N1 bond opening and concomitant cyclization reaction of the C2═C3 bond of the indole moiety with the tosylhydrazone, which proceeds under transition-metal and ligand free conditions. This ring-opening functionalization of indoles provides a wide scope
coupling partners can be employed for the synthesis of conjugated dienes by palladium-catalyzed cross-coupling with tosylhydrazones: α,β-unsaturated ketone and aryl halide or alkenyl halide and non-conjugated tosylhydrazone. Depending on the substrate, a vinylogous hydride elimination is responsible for the formation of the final dienes.
Wittig Ylide Mediated Decomposition of <i>N</i>-Sulfonylhydrazones to Sulfinates
作者:Deepika Choudhary、Vineeta Khatri、Ashok K. Basak
DOI:10.1021/acs.orglett.7b03953
日期:2018.4.6
N-Sulfonylhydrazones generate sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes
A Transition-Metal-Free and Base-Mediated Carbene Insertion into Sulfur-Sulfur and Selenium-Selenium Bonds: An Easy Access to Thio- and Selenoacetals
作者:Dhanarajan Arunprasath、Govindasamy Sekar
DOI:10.1002/adsc.201600855
日期:2017.2.20
A transition‐metal‐free and base‐mediated carbene insertion across sulfur‐sulfur and selenium‐selenium bonds has been developed by employing N‐tosylhydrazone as a stable and safe carbene precursor. The ylide formation from carbene followed by Stevens rearrangement are considered to be the key steps. This thiol and selenol‐free protocol delivers thioacetals and selenoacetals in good to excellent yields
be transformed into alkyl azides through a reductivecoupling of the corresponding tosylhydrazones in a process that takes place simply in the presence of K2CO3, tetrabutylammonium bromide (TBAB), and NaN3 (top of scheme). The application of this methodology followed by the Cu‐catalyzed azide–alkyne cycloaddition allows the direct transformation of carbonylcompounds into triazoles (bottom of scheme)
简单而直接:可以通过在相应的甲苯磺酰nes的还原偶联反应中,简单地在K 2 CO 3,四丁基溴化铵(TBAB)和NaN 3的存在下,将醛和酮转化为烷基叠氮化物。 )。这种方法的应用,再加上铜催化的叠氮化物-炔烃环加成反应,可以使羰基化合物直接转化为三唑(方案底部)。