Facile synthesis of fused polycyclic compounds via intramolecular oxidative cyclization/aromatization of ß-tetralone or ß-tetralone oximes.

A mild and efficient NBS promoted intramolecular oxidative cyclization/aromatization of ß-tetralone oximes has been explored. Under the optimized conditions, fused α-carbolines containing pentacyclic rings were obtained in moderate to good yields. Furthermore, various benzo[5,6]chromeno[2,3-b]indoles were successfully synthesized in moderate yields from ß-tetralones using slightly modified conditions. We proposed a possible reaction pathway based on the experimental results.

Synthesis of polycyclic spirooxindoles via an asymmetric catalytic one-pot stepwise Aldol/chloroetherification/aromatization procedure.

A general method for the synthesis of chiral pentacyclic spirooxindoles containing a tetrahydropyrano[2,3-b]indole scaffold through a one-pot stepwise sequence from 3-(3-indolomethyl)oxindole, paraformaldehyde and NCS is reported. Furthermore, the pentacyclic spirooxindoles could be transformed to bispirooxindole and other structurally diverse spirocyclic oxindoles.

Highly enantioselective [3+2] coupling of cyclic enamides with quinone monoimines promoted by a chiral phosphoric acid.

Enantioselective [3+2] coupling of cyclic enamides with quinone monoimines was realised using a chiral phosphoric acid as a catalyst. This transformation allowed for the synthesis of highly enantioenriched polycyclic 2,3-dihydrobenzofurans (up to 99.9% ee). The absolute configuration of one product was determined by an X-ray crystal structural analysis. We also found a possible mechanism for this reaction.