Synthesis of Dihydrobenzofurans with Quaternary Carbon Center under Mild and Neutral Conditions
摘要:
A new method has been developed for the construction of dihydrobenzofurans from O-aryloxime ethers bearing an alpha-cyano group using a sequential regioselective isomerization/[3,3]-sigmatropic rearrangement/cyclization reaction in MeOH without any catalysts under neutral conditions at ambient temperature. The current transformation provides environmentally benign and atom-economical access to a variety of dihydrobenzofurans containing a quaternary carbon from readily available cyclic and acyclic oxime ethers.
A new method has been developed for the construction of dihydrobenzofurans from O-aryloxime ethers bearing an alpha-cyano group using a sequential regioselective isomerization/[3,3]-sigmatropic rearrangement/cyclization reaction in MeOH without any catalysts under neutral conditions at ambient temperature. The current transformation provides environmentally benign and atom-economical access to a variety of dihydrobenzofurans containing a quaternary carbon from readily available cyclic and acyclic oxime ethers.
Reagent-Controlled Regioselective [3,3]-Sigmatropic Rearrangement of <i>N</i>-Trifluoroacetyl Enehydroxylamine and Its Synthetic Application
Regioselective [3,3]-sigmatropic rearrangement provides a novel method for the construction of hexahydrodibenzofuran with a quaternary carbon in the ring juncture. Upon treatment with TFAA, oxime ethers carrying an electron-withdrawing group smoothly underwent regioselective rearrangement to give the hexahydrodibenzofuran with a quaternary carbon. On the other hand, the reaction of oxime ethers with TFAT-DMAP gave tetrahydrodibenzofurans carrying a substituent at the 4-position. The hexahydrodibenzofuran with a quaternary carbon was effectively converted into a key intermediate for lunarine synthesis.