Syntheses of 2,2′-bibenzo[7]annulenes by double Au-catalyzed sequential activation of propargylic carboxylates
作者:Young Ju Lee、Hoon Gu Heo、Chang Ho Oh
DOI:10.1016/j.tet.2016.07.060
日期:2016.10
We previously reported a novel Au-catalyzed sequential activation of two different propargyl carboxylates to 6-methylene-6H-benzo[7]annulene-5,8-diyl dicarboxylates. This reaction has been extended to syntheses of highly functionalized 2,2′-bibenzo[7]annulenes with four biphenyls bearing two sets of different propargyl carboxylates.
The first method for the preparation of isothiocyanate substituted allenes by [3,3] sigmatropic rearrangement of propargyl thiocyanates is described. These allenes undergo a variety of successive reactions such as ionic or sigmatropic isomerization, electrocyclic ring closure, cycloaddition, and electrophilic addition. Furthermore, intramolecular nucleophilic attack as well as treatment with external
The η3-allylic complex 8 was obtained from thermolysis of the neutral ruthenium furyl complex 7 with an unsaturated carbon chain on the furyl ligand. Protonation of complex 8c with HBF4 generates complex 9c with an oxygen atom and an olefin group coordinated to the ruthenium metal.
We have developed an expedient method for the synthesis of polycyclic compounds from propargyl acetates or vinylallenes involving up to three Au(I)-catalyzed elemental steps: 3,3-rearrangement, metalla-Nazarov reaction, and electrophilic cyclopropanation. The reaction proceeds under very mild conditions and in short times. The mechanism has been studied by DFT computations.