electrophiles. The effortlessness of C−C bond formation, mild reaction conditions, neither catalysts nor light irradiation, and exquisite selectivity, both in terms of functional‐group tolerance and chemo‐, site‐, and stereo‐selectivity, converts this trifluorosulfonylation‐rearrangement sequence into an appealing protocol for the preparation of novel functionalized enones. The synthetic utility of this
A simple method has been developed for synthesis of γ-halo-enones. The approach employs a sequence involving initial indium-mediated allenylation reactions of phenacyl halides with propargyl bromide. This process is followed by acid-promoted rearrangement reactions of the formed homoallenic halohydrins. The new method can be incorporated into routes for the efficient synthesis of various five-membered
The room temperature radical cycloetherification/arylation cascade of allenols and diazoniumsalts has been accomplished via a combination of gold and photoredox catalysis to provide 2,3,4‐trisubstituted‐2,5‐dihydrofurans. The functionalized oxacycle formation sequence is chemo‐ and regioselective for the cycloetherification and for the position that bears the aryl moiety after the cross‐coupling.
Zinc-Catalyzed Allenylations of Aldehydes and Ketones
作者:Daniel R. Fandrick、Jaideep Saha、Keith R. Fandrick、Sanjit Sanyal、Junichi Ogikubo、Heewon Lee、Frank Roschangar、Jinhua J. Song、Chris H. Senanayake
DOI:10.1021/ol202343c
日期:2011.10.21
The general zinc-catalyzed allenylation of aldehydes and ketones with an allenyl boronate Is presented. Preliminary mechanistic studies support a kinetically controlled process wherein, after a site-selective Ban exchange to generate a propargyl zinc intermediate, the addition to the electrophile effectively competes with propargyl-allenyl zinc equilibration. The utility of the methodology was demonstrated by application to a rhodium-catalyzed [4 + 2] cycloaddition.
Synthesis of Hexahydro-1<i>H</i>-isoindole Derivatives from Arylacyl Bromides via Homoallenic Bromohydrins
A procedure has been developed for the concise synthesis of hexahydro-H-1-isoindole derivatives starting from phenacyl bromides. The approach employs a sequence involving an initial indium-mediated allenylation reaction of an arylacyl bromide with propargyl bromide. This process is followed by FeBr3-mediated S(N)2'-type substitution reaction of the formed homoallenic bromohydrin to produce a 2,5-dibromo-4-aryl-1,3-pentadiene, which then is subjected to a sequential, one-pot N-alkylation reaction with N-allyl-N-(p-tosyl)amine and a highly diastereoselective intramolecular DielsAlder reaction of the formed ene-diene to generate the target hexahydro-H-1-isoindole.