K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>-Mediated Selective Trifluoromethylacylation and Trifluoromethylarylation of Alkenes under Transition-Metal-Free Conditions: Synthetic Scope and Mechanistic Studies
on and -arylation of alkenes with inexpensive CF3SO2Na and K2S2O8 in aqueous media has been developed, respectively, affording the highly chemoselective synthesis of CF3-functionalized chroman-4-ones and chromanes in satisfactory yields. Control experiments and DFT calculations indicate that the CF3SO2Na/K2S2O8 system is capable of trifluoromethylating the substrate of alkenes without a transition
Alloc=allyloxycarbonyl, Boc=tert‐butyloxycarbonyl). These reactions are the first examples of the formation of medium‐sized rings by the intramolecular cyclopropanation of an alkene with a donor‐substituted rhodium carbenoid, which is not generated from a diazo compound.
new approach has been developed for the synthesis of 8-substituted 2H-chromenes, featuring a novel cascade aromatic Claisen rearrangement/o-quinone methide formation/6π-electrocyclization. This new method was demonstrated with 28 examples tolerating different substitutions at alkenes, allylic and aromatic ring and with total syntheses of three 2H-chromene natural products.
A cascade process for the synthesis of <i>ortho</i>-formyl allyl aryl ethers and 2<i>H</i>-chromen-2-ol derivatives from arynes <i>via</i> trapping of <i>o</i>-quinone methide with an activated alkene
作者:Abhilash Sharma、Pranjal Gogoi
DOI:10.1039/c8ob02507j
日期:——
A transition-metal free synthetic strategy has been developed for the direct synthesis of ortho-formyl substituted allyl aryl ethers via a cascade three-component coupling of arynes, activated alkene and N,N-dimethylformamide. The reaction proceeds via C–O and C–Cbond cleavage as well as C–C and two new C–Obond formations in a single reaction vessel. The methodology provides a good yield of ortho-formyl