Ruthenium(IV) complexes were identified as key intermediates of C−H/O−H activations by weak O‐coordination. Thus, the annulations of sulfoxonium ylides by benzoic acids provided expedient access to diversely‐decorated isocoumarins with ample scope. Detailed experimental and computational studies provided strong support for a facile BIES‐C−Hactivation, along with cyclometalated ruthenium(IV) intermediates
for the preparation of 3-substituted isocoumarins via palladium-catalyzed nucleophilic addition/oxidative annulation of bromoalkynes with benzoic acids has been developed. Remarkably, preliminary mechanistic studies indicated that the transformation might proceed via a stereo- and regioselective nucleophilic addition and C–H functionalization procedure.
The Rh(III)-catalyzed C–H activation initiated cyclization of benzoicacids with electron-rich geminal-substituted vinyl acetates was described. The reaction was employed to prepare a range of 3-aryl and 3-alkyl substituted isocoumarins selectively.
Sulfoxonium Ylides as Carbene Precursors: Rhodium(III)‐Catalyzed Sequential C−H Functionalization, Selective Enol Oxygen‐Atom Nucleophilic Addition, and Hydrolysis
作者:Yuanqiong Huang、Xueli Lyu、Hongjian Song、Qingmin Wang
DOI:10.1002/adsc.201900861
日期:2019.11.19
Herein, we report a protocol for Rh(III)‐catalyzed annulation reactions between oxazolines and sulfoxonium ylides via a sequence involving C−H activation, selective enol oxygen‐atom nucleophilic addition, and hydrolysis. This practical, operationally simple protocol has a wide substrate range, excellent regioselectivity, and moderate to good yields.
Pd-Catalyzed/Iodide-Promoted α-Arylation of Ketones for the Regioselective Synthesis of Isocoumarins
作者:Alessandra Casnati、Raimondo Maggi、Giovanni Maestri、Nicola Della Ca’、Elena Motti
DOI:10.1021/acs.joc.7b01355
日期:2017.8.4
synthesized directly from 2-halobenzoates and ketones through a palladium-catalyzed α-arylation step followed by an intramolecular cyclization process. The addition of iodide anions to the reaction mixture increased yields and selectivities especially when 2-bromobenzoates were employed. This phosphine-free one-potsynthesis features a high functional group tolerance and gives access to richly decorated