2.5. Ionic Liquids Presented in This Review 2020 3. Cyclocondensation Reactions 2020 4. Synthesis of Three-Membered Heterocycles 2022 4.1. Aziridines 2022 5. Synthesis of Five-Membered Heterocycles 2022 5.1. Pyrroles 2022 5.2. Furans 2022 5.3. Thiophenes 2023 5.4. Pyrazoles 2024 5.5. Imidazoles 2025 5.6. Isoxazoles 2027 5.7. Oxazoles, Oxazolines, and Oxazolidinones 2027 5.8. Thiazoles and Thiazolidinones 2028 6. Synthesis of Six-Membered Heterocycles 2030 6.1. Pyridines 2030 6.2. Quinolines 2031 6.3. Acridines 2033 6.4. Pyrans 2033 6.5. Flavones 2035 6.6. Pyrimidines and Pyrimidinones 2035 6.7. Quinazolines 2037 6.8. -Carbolines 2038 6.9. Dioxanes 2039 6.10. Oxazines 2039 6.11. Benzothiazines 2040 6.12. Triazines 2040 7. Synthesis of Seven-Membered Heterocycles: Diazepines 2041

Ionic liquids in heterocyclic synthesis.

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

An efficient one-pot synthesis of 4,5,6-triaryl-3,4-dihydropyrimidin-2(1H)-ones via a three-component Biginelli-type condensation of aldehyde, 2-phenylacetophenone, and urea/thiourea in the presence of a catalytic amount of t-BuOK (20 mol %) is described. The reactions proceeded efficiently at 70 °C to afford the desired products in moderate to good yields. Detailed mechanistic study shows that the Biginelli-type reaction using urea and thiourea proceeds through two totally different pathways. Enone 5 and bis-urea 8 were highly suggested as respective reaction intermediates for reactions involving thiourea and urea as substrates.

Brønsted Base-Catalyzed One-Pot Three-Component Biginelli-Type Reaction: An Efficient Synthesis of 4,5,6-Triaryl-3,4-dihydropyrimidin-2(1H)-one and Mechanistic Study

A one-pot Biginelli synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones catalyzed by triphenylphosphine as Lewis base

1-Methylimidazolium triflouroacetate ([Hmim]TFA): An efficient reusable acidic ionic liquid for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines

One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones using boric acid as catalyst

A novel sequential addition, elimination and cyclization reactions took place when aldoxime and dimedone in glycol was subjected to microwave irradiation and a new type of N-hydroxyl-acridinedione derivatives was obtainedin excellent yields (80-95%) within a short reaction time (4-8 min).

A novel cascade reaction of aryl aldoxime with dimedone under microwave irradiation: The synthesis of N-hydroxylacridine

In the reactions of α-cyanocinnamonitrile or β-cyano-β-carbothoxy styrene with 5,5-dimethyl-1,3-cyclohexanedione in the presence of ammonium acetate under microwave irradiation without solvent, the 2-amino-5,6,7,8-tetrahydro-5-oxo-4-aryl-7,7-dimethyl-4H-benzo-[b]-pyran derivatives were obtained. However, in the reactions of arylidenecyanoacetamide with 5,5-dimethyl-l,3-cyclohexanedione under the same reaction conditions, the acridine derivatives were obtained. The structures of the products were determined by single crystal X-ray diffraction analysis.

Microwave—prompted Reaction of Cinnamonitrile Derivatives with 5,5—Dimethyl—1,3—cyclohexanedione

A simple effective synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives, using boric acid as catalyst, from aromatic aldehydes, 1,3-dicarbonyl compounds and urea in glacial acetic acid is described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of excellent yields (86–97%) and short reaction time (0.5–2 h).

One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Using Boric Acid as Catalyst.

A series of 10-aryl-2,7-dimethyl-4,5-dioxo-3,6,9- trioxa-3,4,5,6,9,10-hexaanthracenes were prepared by the reaction of aromatic aldehydes with triacetic acid lactone in ethylene glycol catalysed by KF-alumina.

Youjian Feng

Papers

One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones using boric acid as catalyst

A novel cascade reaction of aryl aldoxime with dimedone under microwave irradiation: The synthesis of N-hydroxylacridine

Microwave—prompted Reaction of Cinnamonitrile Derivatives with 5,5—Dimethyl—1,3—cyclohexanedione

One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Using Boric Acid as Catalyst.

A synthesis of 10-aryl-2,7-dimethyl-4,5-dioxo-3,6,9- trioxa-3,4,5,6,9, 10-hexahydroanthracene catalysed by KF-alumina