An efficient Cu(OTf)2-catalyzed Friedel–Crafts alkylation/cyclizaiton sequence of 3-substituted indoles with isatin-derived oxodienes was developed, and a series of structurally complex and diverse pyrrolo[1,2-a]indole spirooxindoles were first obtained in up to 99% yields. This protocol proved to be quite general and was also robust for the synthesis of 9H-pyrrolo[1,2-a]indoles.

A TfOH-catalyzed highly diastereoselective Michael addition/ketalization sequence of 3-hydroxyoxindoles and ortho-hydroxychalcones was developed, leading to biologically important bridged ketal spirooxindoles in moderate to excellent yields. Moreover, some chemical transformations were carried out to further extend the structural complexity and diversity.

The first DBU-catalyzed Michael/Pinner/isomerization cascade reaction of 3-hydrooxindoles with isatylidene malononitriles was developed, and the corresponding highly functionalized bispirooxindoles containing a fully substituted dihydrofuran motif were obtained in up to 92% yields. This protocol also provides an efficient method for the synthesis of an α-cyano-γ-butyrolactone bispirooxindole. In addition, a one-pot three-component cascade reaction was conducted. Also, the asymmetric version of the cascade reaction was achieved.

An efficient copper-catalyzed Friedel–Crafts alkylation/cyclization/isomerization sequence of 3-arylcarbonyl coumarins and 3-methyl indole was developed to afford a wide range of functionalized coumarin fused 9H-pyrrolo[1,2-a]indoles, which feature a 6-6-5-5-6 pentacyclic core, in 34–99% yields. Moreover, gram-scale experiment and chemical transformations were conducted to demonstrate the synthetic value of this protocol.

A FeCl3-catalyzed highly regioselective 1,2-addition/substitution sequence of 3-acetylcoumarins and indoles has been developed to afford highly hindered tetrasubstituted bis(indolyl)methanes bearing a biologically useful coumarin motif in 56–99% yields.

A novel and recyclable catalytic system composed of Zn[bis(2-hydroxybenzene)phthaldimine] [Zn(BHBPDI)] and tetrabutylammonium bromide (TBAB) was developed to catalyze the coupling reaction of CO2 and propylene oxide to yield the cyclic carbonate. The different parameters had been investigated. Nearly 100% selectivity and100% yield of propylene carbonate was achieved under the optimized reaction conditions. The [Zn(BHBPDI)] could be easily recovered and reused for many times. The activity of the catalytic system decreased obviously after nine recycles, but the activity was restored by adding an amount of TBAB to the reaction mixture. On the basis of the experimental results, the mechanism for the reaction was proposed.Graphical abstractA novel and recyclable catalytic system of Zn[bis(2-hydroxybenzene)phthaldimine] with tetrabutylammonium bromide was developed to catalyze the reaction of CO2 with propylene oxide under mild conditions.Highlights► The novel and recyclable catalytic system Zn(BHBPDI)/TBAB was developed. ► The reaction conditions were optimized. ► The catalyst could be easily recovered and reused. ► The reaction mechanism was proposed.

The mechanism of the cycloaddition of CO2 with propylene oxide to afford propylene carbonate catalyzed by a highly active trans-dichlorotetrapyridineruthenium [trans-Ru(py)4Cl2] complex and tetrabutylammonium chloride (TBAC) has been studied by means of electrospray ionization mass spectrometry (ESI–MS), structural characterization of trans-Ru(py)4Cl2, catalyst activity tests and so on. Further experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl chloride to re-convert the tributylamine into TBAC resulted in the inhibition of the reaction. The mechanistic study explains the reported early experimental observations well and provides a clear profile for the cycloaddition of carbon dioxide with propylene oxide using trans-Ru(py)4Cl2 as catalyst. The mechanism also fully explains the role of the TBAC by providing a role for the in situ generated tributylamine in activating the carbon dioxide.

The first DBU-catalyzed Michael/Pinner/isomerization cascade reaction of 3-hydrooxindoles with isatylidene malononitriles was developed, and the corresponding highly functionalized bispirooxindoles containing a fully substituted dihydrofuran motif were obtained in up to 92% yields. This protocol also provides an efficient method for the synthesis of an α-cyano-γ-butyrolactone bispirooxindole. In addition, a one-pot three-component cascade reaction was conducted. Also, the asymmetric version of the cascade reaction was achieved.

A FeCl3-catalyzed highly regioselective 1,2-addition/substitution sequence of 3-acetylcoumarins and indoles has been developed to afford highly hindered tetrasubstituted bis(indolyl)methanes bearing a biologically useful coumarin motif in 56–99% yields.