An (4 + 1) annulation of donor-acceptor 2-aryolcyclopropanes with selenium or sulfur powder has been developed. One-step conversion of donor-acceptor 2-aryolcyclopropanes provided direct access to multisubstituted selenophenes and thiophenes. A variety of functional groups could be tolerated under the reaction conditions.

An [3 + 3] annulation of 2-aminochromen-4-ones with substituted benzylidene Meldrum's acids has been developed. This reaction included a sequential intermolecular Michael addition/intramolecular nucleophilic addition/ring opening of Meldrum's acid/ removal of acetone/decarboxylation sequence, which possessed excellent step in a single operation for direct generating to substituted chromeno[2,3-b]pyridinones from readily available substrates.

The Cs2CO3-mediated formal (4 + 2) cascade annulation strategy for the synthesis of 2-aminoquinoxalines has been developed using D-A cyclopropanes and o-benzenediamines as the substrates. The protocol provides an efficient method of accessing a broad range of 2-aminoquinoxaline derivatives in good to excellent yields with good functional-group tolerance.

A DBU-promoted (4 + 1)-annulation reaction between donor-acceptor (D-A) cyclopropanes and 3-phenylisoxazolone has been developed. Using this method, some valuable spiroisoxazol-5(4H)-one derivatives can be obtained easily in good yields. This protocol features producing highly stereospecific products, atomic economy, mild reaction conditions, and good efficiency, constituting an array of spiroisoxazol-5(4H)-ones.

Efficient synthesis of highly functionalized cyclopentenols with an exocyclic Z double bond was investigated via a (3 + 2) annulation reaction of 2-aroyl-D-A (donor-acceptor) cyclopropanes with alkynoates in the presence of DABCO. This synthetic approach featured a wide range of readily available 2-aroyl-substituted D-A cyclopropanes with diverse functional groups, densely substituted cyclopentenols with two stereogenic centers and an exocyclic double bond in a highly stereocontrolled manner and had operationally simple and mild reaction conditions.

An effective DABCO-promoted (4+1) annulation reaction for the synthesis of ethyl (2-amino-1H-pyrrol-1-yl)acetate derivatives from 2-aroyl-3-arylcyclopropane-1,1-dicarbonitriles and ethyl glycinate was developed. This strategy is characterized by the readily accessible starting materials, mild conditions, and simplicity of operation.

A novel one-pot pseudo-three-component reaction of 2-amino-4H-chromen-4-ones with 4-benzylidene-5-alkyl-2-aryl-2,4-dihydro-3H-pyrazol-3-ones was investigated for the synthesis of the spiro[chromeno[2,3-b]pyridine-3,4 '-pyrazole] derivatives. This procedure involved Michael addition, elimination, and hetero-Diels-Alder sequences, affording a series of spiropyrazolone-chromeno[2,3-b]pyridines in good yields that possessed cis relationships between two aryl groups and the carbonyl of the pyrazolone unit.

The efficient synthesis of 4-hydroxy-3-arylindolin-2-ones via phosphoric acid-mediated annulation of various β-nitrostyrenes and 1,3-cyclohexanedione is described. This annulation reaction gives a practical method for affording a diverse set of oxindoles, having simple experimentation, readily available starting materials, and very good yields. Additionally, substituted 1,3-cyclohexanediones under the same conditions afforded tetrahydrobenzofuran oxime compounds.

This innovative reaction involved the [3+3] annulation of 2-amino-4H-chromen-4-ones and 4-benzylideneoxazol-5(4H)-ones. The process provided quick and easy access to a broad range of structurally diverse and highly functionalized 1,3,4,5-tetrahydro-2H-chromeno[2,3-b]pyridines in moderate to good yields, which possess trans-form C3 and C4 substituents.

The efficient synthesis of fully substituted pyrazoles with a dicyanomethyl group was developed via an annulation reaction of 2-aroyl D-A cyclopropanes with arylhydrazines in the presence of DBU/AlCl3 reaction systems. This synthetic approach featured a wide range of readily available aroyl-substituted D-A cyclopropanes with diverse functional groups and a diversity of substituents on pyrazole products and had operationally simple and mild reaction conditions.

An annulation reaction of 2-aroyl D-A cyclopropanes with o-benzenediamines via selective cleavage of C-C bonds of cyclopropane in the presence of DBU/Sc(OTf)3 reaction systems was developed for the direct preparation of 2-aryl-3-benzylquinoxalines. This synthetic approach tolerated a wide range of readily available aroyl-substituted D-A cyclopropanes with diverse functional groups and had operationally simple and mild reaction conditions.

Acetic acid-catalyzed (3 + 2) cyclization reaction of substituted 2-aroyl-3-aryl-1,1-dicyanocyclopropanes with arylhydrazines was investigated for the efficient synthesis of 4-dicyanomethyl-1,3,5-triaryl-4,5-dihydropyrazoles in good yields, in which 4,5-double substituents are predominantly trans selective. This approach included the consecutive condensation, ring opening, and double nucleophilic cyclization reaction.

An efficient process to access chromeno-fused azafluorenones (chromeno[2,3-b]indeno[2,1-e]pyridine) via the three-component reaction between 2-amino-4H-chromen-4-ones, aromatic aldehydes and 1H-indene-1,3(2H)-dione is described. This approach includes successive the Aldol condensation, the Michael addition, intramolecular nucleophilic addition and aromatization. The structure of a product obtained was determined based on X-ray diffraction studies.

A three-component reaction of 2-amino-4H-chromen-4-ones, aromatic aldehydes, and 4,4-dialkoxycyclohexa-2,5-dien-1-ones for the concise synthesis of chromeno[2,3-c]dihydroisoquinoline derivatives has been investigated. This reaction involved consecutive ZnCl2-promoted Micheal addition and intramolecular Friedel-Crafts alkylation. This synthetic protocol offered several advantages, including the readily accessible starting materials, good functional group tolerance, and simplicity of operation. Additionally, the structures of products obtained were determined based on X-ray diffraction studies.

An efficient protocol for the synthesis of 2-aryl-5-benzyl-pyrimidine-4,6-diamines from readily available substituted 2-benzyl-idenemalononitriles and substituted benzamidines was developed. This practical protocol provides high value pyrimidine-4,6-diamines in moderate to good yields under simple reaction conditions. This approach also enables some modifications of structurally complex bioactive molecules and exhibits potential applications in medicinal chemistry.

A novel ZnCl2‐promoted three‐component reaction strategy for the synthesis of hexahydrochromeno[2,3‐b]quinoline derivatives via the Aldol condensation/Michael addition/cycloaddition/dehydration cascade reaction of 2‐amino‐4H‐chromen‐4‐ones, aromatic aldehydes, and cyclohexane‐1,3‐dione was investigated. This procedure is environmentally friendly, highly efficient, and has a broad scope. The structures of the products obtained were determined based on x‐ray diffraction studies.

A pseudo-three-component annulation reaction of substituted 2-amino-4H-chromen-4-ones with aromatic aldehydes promoted by DBU was investigated to access polysubstituted 5H-chromeno[2,3-b]pyridines. This reaction included a sequential intermolecular nucleophilic addition/Michael cyclization/intramolecular epoxidation/ring opening/aromatization sequence, which possessed excellent step and atom economy in a single operation for generating 3-hydroxy-5H-chromeno[2,3-b]pyridines from readily available substrates.

An acetic acid mediated regioselective [3 + 3] cycloaddition of substituted cyclopropane-1,1-dicarbonitriles with in situ generated mercaptoacetaldehyde was developed for the synthesis of highly stereoselective tetrahydrothiopyranols. This transformation created two new bonds in a single operation for generating complexity in tetrahydrothiopyrans. This method is characterized by cheap and readily available starting materials, simple operation, and mild reaction conditions.

A formal [3+3] cascade annulation strategy for the synthesis of 2-arylchromeno[2,3-b]pyridinones has been developed using 2-aminochromones and substituted cinnamaldehydes or aromatic aldehydes and ethanal as the substrates. The strategy supplies a novel and atom-economical method of accessing a broad range of chromeno[2,3-b]pyridine derivatives in good yields with good functional-group tolerance. The method highlights the inherent practicality of this synthetic transformation.

DABCO-promoted cyclization reaction of substituted 2-amino-4H-chromen-4-ones with substituted 2,6-dibenzylidenecyclohexan-1-ones was investigated under mild conditions. This reaction provided a novel and efficient access to the 7,8,9,10-tetrahydro-12H-chromeno[2,3-b]quinolin-12-ones in good yields, the exocyclic double bond of which is predominantly E-selective.