Three-component [3 + 3] heterocyclizations have been established under microwave irradiation, providing a flexible synthetic approach toward bicyclic fused pyridines. 3,5-Dibenzylidenedihydro-2H-pyran-4(3H)-ones were subject with malononitrile and aromatic amines in cosolvent of HOAc and N,N-dimethylformamide, affording 10 examples of pyrano[4,3-b]pyridine derivatives in good to excellent yields. Similarly, seven examples of thiopyrano[4,3-b]pyridine derivatives were obtained using sulfur-tethered heterocyclones as a reaction partner.

A regioselective three-component reaction of aromatic aldehydes, 2-hydroxy-1,4-naphthoquinone and benzo[d]thiazol-5-amine in HOAc under microwave irradiation has been developed. A series of new thiazolo-fused benzo[h]acridines were synthesized with high chemical yields in this one-pot reaction. The resulting thiazolo-fused acridines were employed to further react with aldehydes and ammonium acetate to give polycyclic-fused oxazolo[5,4-a]thiazolo[5,4-j]acridines. The present synthesis shows several advantages, such as operational simplicity, fast reaction rates, which makes it a useful and attractive process of library generation for drug discovery.

Microwave-assisted three-component reaction has been established for the synthesis of benzodiazepines. This reaction promoted by HOAc was conducted by using readily available and inexpensive starting materials in water under microwave irradiation. The present green synthesis shows fascinating characteristics such as the use of water as the reaction solution, concise one-pot conditions, short reaction periods, easy purification, and reduced waste production without the use of any strong acids or metal promoters.

Concise and efficient domino [3 + 2] heterocyclization promoted by HCOOH has been established for unprecedented synthesis of 15 examples of 2-hydroxyindole-3,4-(2H,5H)-diones in good yields. The present methodology shows attractive properties such as mild reaction conditions, concise one-pot operation, short reaction periods of 15–20 min, and easy purification. The resulting 2-hydroxyindole-3,4(2H,5H)-diones are of importance for organic and medicinal research.

A new three-component approach to polyfunctionalized isochromeno[4,3-b]pyrroles has been developed with excellent regioselectivity. During these domino reactions, two ring-opening and three cyclization reactions were readily achieved through carbon–carbon bond cleavage under transition-metal-free conditions. The advantages of atom and step economy, and scope make this reaction a powerful tool for assembling tri-heterocyclic scaffolds of general chemical and biomedical interest.

A new iodonium ylide-based three-component reaction for the synthesis of highly functionalized 2-spirosubstituted dihydrofurans starting from readily available common reactants has been developed under microwave irradiation. The procedure is facile, avoiding time-consuming and costly syntheses, tedious work-up and purifications of precursors as well as protection/deprotection of functional groups. This method is very efficient because of short reaction times and easy work-up and provides an efficient strategy for the construction of the polysubstituted spiro dihydrofuran skeleton.

Concise and efficient three-component domino [4+1+1] carbocyclization to highly substituted fluoren-9-one derivatives promoted by K₂CO₃ has been developed under microwave irradiation conditions. The direct bis-cyanation and aryl amination residing in fluoren-9-one framework were achieved in a one-pot operation. The reaction proceeds at fast rates and can be finished within 30 min, which makes workup convenient to give good to excellent chemical yields.

An efficient methodology for highly diastereoselective synthesis of poly-substituted 4,5-dihydropyrrole derivatives from readily available common reactants in water has been developed. During domino processes, the formation of pyrrole skeleton and its C2-hydroxylation and C3-arylamination were readily achieved via metal-free [3+2] heterocyclization in a one-pot operation.

Brønsted acid-promoted divergent approaches for the synthesis of multi-functionalized fused pyrroles with different substituted patterns (44 examples) have been established. The divergent pathways were controlled by varying the charging sequence to give a series of new fused pyrroles selectively. The direct C(sp³)S bond formation was achieved for the two-step, one-pot reaction.