Based on our previous studies, the scope of the transformation of 2-furylcarbinols into spirofurooxindoles, and also the skeletal rearrangements of spiro[furo-oxindoles] and spiro[thieno-oxindoles] were studied. The spiro[furo-oxindoles] thermally rearranged into spiro[pentenone-oxindoles] by a mechanism involving the conrotatory electrocyclization of the 4π-electron system. The free energy of the electrocyclization step was calculated to interpret the stereochemical outcomes. In contrast, the spiro[thieno-oxindoles] were rearranged under acidic conditions into thieno[2,3-c]quinolin-4-ones, involving an interesting dienone–phenol-like mechanism. The transformation of 2-furylcarbinols into spiro[pentenone-oxindoles] seems to be the first stepwise C-Piancatelli rearrangement. The spirooxindole products were biologically evaluated, and some of them showed promising cytotoxic activities against DU145 and LNCaP tumor cell lines.

A palladium nanoparticle catalyst (PdNPs@[Bmim]Lac) has been prepared by a simple, mild and efficient chemical approach using 1-butyl-3-methylimidazolium lactate ([Bmim]Lac) ionic liquid) as a stabilizer. This catalyst exhibits excellent activity, stability, recyclability and simple manipulation in Suzuki-Miyaura reactions at room temperature in air.

Spirofurooxindoles derived from α-furylcarbinols were rearranged into spirocyclopentenoneoxindoles exclusively or as a mixture of spirocyclopentenoneoxindoles and indoles under different reaction conditions. Along with our previous studies, the stepwise C-Piancatelli rearrangement has been presented for the first time.

The regioslective reduction of electron-rich dienes to monoolefins and the reductive cleavage of allyl esters were fulfilled by employing a sodium borohydride-nickel chloride-methanol catalytic system with exceedingly simple manipulations and high functional group tolerability. Both of the reductive reactions may involve π-allylnickel intermediates generated from fresh nickel boride.

A copper sulfate pentahydrate-catalyzed intramolecular Friedel–Crafts reaction using an oxocarbenium species derived from a furan ring as the alkylating agent was developed for the first time. By using this protocol, spirofurooxindoles 9 with multi-reactive sites were synthesized simply and concisely. In addition, selective hydrogenation of the endo-cyclic double bond and full hydrogenation of the endo and exo-cyclic double bonds of spirofurooxindoles 9 provided spirofurooxindoles 11 and 12, respectively.

Two methods including NBS/AgNO₃ system and MCPBA oxidation have been developed for the selective oxidations of the exo-cyclic double bond of spiroacetal enol ethers 2 with multi reactive sites into spiro-pyanones 3 and 4. In addition, possible mechanisms for these conversions are proposed.

Two acid-catalyzed conversions of furandiols 8 and its dehydration spiroacetalized products 9 into oxabicyclic cyclopentenones 10 in good to excellent yields are reported. To disclose the mechanism of these conversions, the fact that H₂O catalyzes the conversion of 9 into 10 is presented and intermediates 9k and 20i have been structurally verified. In addition, two other related conversions of spiroacetal enol ethers 11 and 14 derived from 8 into cyclopentenones are presented, for which an intramolecular aldol reaction is the key step. On the basis of these results, we propose that these conversions occur through an aldol condensation step instead of electrocyclization of the 4π-electron system, which was previously reported.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

For the first time, an unusal cleavage of N-tert-butyloxycarbonyl (N-Boc) protection from N-Boc-protected benzamide under basic conditions in excellent yields is reported. The deprotection involves the N-Boc emigration from the benzamide to form 2-O-Boc group followed by O-Boc deprotection on the phenyl ring.