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Abstract: A base-promoted cascade reaction of α-ketoester with benzylidene-malononitrile was developed under mild reaction conditions, which enabled the synthesis of polyfunctionalized 2-amino- 3-cyano-4H-pyrans containing ester motifs at 6-position with good to excellent yields. These transformations not only construct various polyfunctionalized 4H-pyrans, which add a new member to the family of 4H-pyrans, but also provide an efficient approach for the synthesis of fully substituted 4Hpyran derivatives.

The regioselective [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones with functional olefins was established with DABCO as a base under mild conditions.

The methodology for the synthesis of fluorene-based atropisomers was developed via the strategy of aromatic ring formation. By this strategy, an efficient benzannulation of indene-based diene with benzoylacetonitrile divergently promoted by DABCO and a chiral organocatalyst was established, and various atropisomeric fluorene-based skeletons were generated in good yields, which not only provide a new strategy for the construction of atropisomeric biaryls but also offer a new member to the atropisomeric family.

An efficient cascade reaction of 1-indanylidenemalononitrile with 3-benzylidenebenzofuran-2(3H)-one divergently promoted by DABCO or chiral organocatalyst was developed under mild reaction conditions, and various spiro-dihydrofluorene-benzofuranones were produced in gratifying results, respectively. It is worth noting that both the spiro and axially chiral products can be obtained by tuning the reaction conditions. The mechanism of the transformation was also studied by quantum chemical calculations.

Coumarin-3-thioformates acting as a new type of 3-carbon partner were firstly prepared and engaged in reacting with 3-hydroxyoxindoles and 3-aminooxindoles by using DABCO or Et3N as the catalyst. A wide scope of structurally diverse spiro-fused pentaheterocyclic compounds including spiro-butyrolactoneoxindole[3,4-c]coumarins and spiro-butyrolactamoxindole[3,4-c]coumarins, which combined oxindole, dihydrofuranone or pyrrolidone, and coumarin in one molecule, could be smoothly obtained in high yields via a tandem Michael addition–lactonization/lactamization process under mild conditions.

Coumarin-3-formylpyrazoles have been synthesized and applied as 3-carbon synthons in reaction with 3-hydroxyoxindoles by using DABCO as the catalyst. A range of structurally diverse spiro-fused pentacyclic spirooxindoles, bearing a spirooxindole-γ-lactone and a 3,4-dihydrocoumarin substructure, could be smoothly obtained in good to excellent yields (up to 99%) with excellent diastereoselectivities (all cases >20 : 1 dr). The asymmetric version of this tandem reaction was preliminarily investigated by using chiral organocatalysts.

An efficient [3+3] benzannulation of Morita–Baylis–Hillman carbonates with 1-indanylidenemalononitrile was achieved under metal-free reaction conditions selectively delivering a wide range of functional multi-substituted fluorene or fluorenone compounds in high yields, respectively (up to 86% yield). Moreover, experiments and quantum chemical calculations were also performed to study the mechanism of the transformation.

We have successfully established an efficient catalytic system, which was effective for construction of both spiro[pyrrolidine-benzofuran-3-one] and spiro[pyrrolidine-benzofuran-2-one] compounds. The first 1,3-dipolar cycloaddition of 2-alkylidene-benzofuran-3-one with azomethine ylides with simple functional ionic liquids as catalysts was developed, affording a variety of spiro[pyrrolidine-benzofuran-3-one] compounds containing highly substituted pyrrolidine motifs with a spiro quaternary stereogenic center in excellent yields (73-99 %). The highly efficient catalytic system exhibited broad substrate scopes under mild conditions. Meanwhile, this catalytic system was also extended to the cycloaddition of 3-alkylidene-benzofuran-2-one with azomethine ylides and gave spiro[pyrrolidine-benzofuran-2-one] compounds in high yields (82-99 %) and 1,3-dipolar cycloaddition of 2-alkylidene-benzofuran-3-one with pyrazolidinone-based dipoles giving the desired products in 25–85 % yields.

A highly regioselective addition–elimination of Morita–Baylis–Hillman adducts promoted by base ionic liquids (0.5 mol%) was reported to afford a variety of functional alkenes in excellent yields (up to 99%). This protocol provides a new method to access functional alkenes directly. Recycled base ionic liquids could be reused at least five times and the isolated yield of the product was almost consistent after five runs.

The first diastereo- and enantioselective cascade Mannich/cyclization reaction of 3-isothiocyanato oxindoles with cyclic ketimines has been successfully developed. By using chiral bifunctional organocatalysts, a range of structurally diverse chiral polycyclic spiro-thioimidazolidine-oxindoles, bearing two contiguous tetrasubstituted stereocenters, could be obtained in excellent yields (up to 99%) with good diastereo- and enantioselectivities (up to >20:1 dr and 94.5:5.5 er) under mild reaction conditions.

The 1,3-dipolar cycloaddition of 2-alkylidene-1-indanone with azomethine ylides has been developed successfully promoted by simple imidazolium salts to construct a variety of spirocycles containing highly substituted pyrrolidines efficiently, affording the corresponding compounds in excellent yields (up to 99%). The highly efficient catalytic system exhibited broad substrate scopes under mild conditions.

An efficient asymmetric [3 + 2]-cycloaddition reaction of 3-isothiocyanato oxindoles and formaldimines in-situ generated from 1,3,5-trisubstituted-hexahydro-1,3,5-triazines with a cinchona alkaloid-derived thiourea as the catalyst has been developed. A range of biologically important spiro-imidazolidinethione-oxindoles were obtained in excellent yields with good enantioselectivities (up to 99% yield and 93% ee).