environmentally-benign aqueoussolution due to the highly hydrophilic hydroxyl and amino functional groups of chitosan. The large size of the microsphere structure can greatly facilitate separation and recycling of the expensive and toxic palladiumcatalysts from the reaction mixture and the recovered Pd/PCMS catalyst can preserve the catalytic activity and selectivity for the Heck reaction without any observable
Iron-catalyzed stereospecific arylation of enol tosylates using Grignard reagents
作者:Yi-Ming Wei、Xiao-Di Ma、Lei Wang、Xin-Fang Duan
DOI:10.1039/c9cc09522e
日期:——
The stereospecific Fe-catalyzed arylation of enol tosylates was reported. Various tri- or tetrasubstituted Z or E-enol tosylates of β-keto esters were arylated using common and Knochel-type Grignard reagents with complete stereofidelity. The precursors for Z/E-zimelidine, tamoxifen and other bioactive compounds were facilely prepared without precious and toxic transition metals.
Starting from commercially available ketones, a reproducible and reliable strategy for the synthesis of tetrasubstituted nitroalkenes was successfully developed, using a two-step procedure; the HWE olefination of the ketone to form the corresponding α,β-unsaturated esters is followed by a nitration reaction to introduce the nitro group in the α position of the ester group. The enantioselective organocatalytic
(<i>Z</i>
)-Enol <i>p</i>
-Tosylate Derived from Methyl Acetoacetate: A Useful Cross-Coupling Partner for the Synthesis of Methyl (<i>Z</i>
)-3-Phenyl (or Aryl)-2-Butenoate
作者:Yuichiro Ashida、Hidefumi Nakatsuji、Yoo Tanabe
DOI:10.1002/0471264229.os094.08
日期:——
General, Robust, and Stereocomplementary Preparation of β-Ketoester Enol Tosylates as Cross-Coupling Partners Utilizing TsCl−<i>N</i>-Methylimidazole Agents
(Z)-stereocomplementary enol tosylation of beta-ketoesters using TsCl- N-methylimidazole (NMI)-Et3N or LiOH. TsCl coupled with NMI formed a highly reactive N-sulfonylammonium intermediate. Stereocongested secondary alcohols were smoothly sulfonylated using Ts(Ms)Cl-NMI-Et3N. beta-Ketoesters underwent (E)-selective tosylation using TsCl-NMI-Et3N and (Z)-selective tosylation using TsCl-NMI-LiOH (total