Microwave‐assisted efficient synthesis of benzo[4,5]imidazo[1,2‐a]‐pyrimidine derivatives in water under catalyst‐free conditions

Benzo[4,5]imidazo[1,2‐a]pyrimidine derivatives were synthesized via the three‐component reaction of aldehyde, β‐dicarbonyl compound and 2‐aminobenzimidazole in water under microwave irradiation and without catalyst conditions. The new protocol has the advantages of higher yield, lower cost, reduced environment impact, wider scope and convenient procedure.     

Regioselective synthesis of 4‐aryloxymethylene‐2,3,5‐trihydrothiopyrano[3,2‐b]indoles by the thio‐claisen rearrangement of 3‐(4′‐aryloxybut‐2′‐ynylthio)indoles

A number of new 4‐aryloxymethylene‐2,3,5‐trihydrothiopyrano[3,2‐b]indoles are regioselectively synthesized in 78‐84% yield by the thio‐Claisen rearrangement of 3‐(4′‐aryloxybut‐2′‐ynylthio)indoles. The endocyclic double bonded products are isolated by introducing electron withdrawing acetyl group at the indole nitrogen and also can be converted to the corresponding exocyclic isomers by deacetylation and subsequent heating.     

Synthesis of a novel class of 3‐(2′‐benzothiazolyl)‐2,3‐dihydroquinazolin‐4(1H)‐ones under solvent‐free and catalyst‐free conditions

A solvent‐ and catalyst‐free one‐pot three‐component condensation reaction approach was developed for the synthesis of a new class of 3‐(2′‐benzothiazolyl)‐2,3‐dihydroquinazolin‐4(1H)‐ones in relatively good yields.     

Synthesis of novel symmetrical bis‐schiff bases of 5,5′‐methylenebis(2‐aminothiazole)

Novel symmetrical bis‐Schiff bases have been prepared cleanly and efficiently in the presence of formic acid catalyst in methanol from the reaction of symmetrical primary bis‐amine of 5,5′‐methylenebis(2‐aminothiazole) ( 1 ) and a series of aromatic aldehyde derivatives under mild conditions. The advantages of this reaction are simplicity of the reaction procedure, simple work‐up and pure products with high yields. The structures of all the new synthesized symmetrical bis‐Schiff bases were confirmed by elemental analyses, IR, ¹H‐NMR, ¹³C‐NMR and mass spectra.     

Synthesis and herbicidal activity of 2‐(3‐(trifluoromethyl)‐5‐(alkoxy)‐1H‐pyrazol‐1‐yl)‐4‐aryloxypyrimidine derivatives

A series of 2‐(3‐(trifluoromethyl)‐5‐(alkoxy)‐1H‐pyrazol‐1‐yl)‐4‐aryloxypyrimidine derivatives were designed and synthesized. The structures of all the title compounds were confirmed by ¹H NMR and elementary analysis. These compounds were screened for herbicidal activity against rape and barnyard grass. Compound B13 exhibited moderate herbicidal activity.     

Synthesis of multi‐substituted dibenzo[b,d]furan

The synthesis of multi‐substituted dibenzo[b,d]furan derivatives 7a‐b and 11a‐b from readily available starting materials is described. These compounds are important intermediates for synthesis of molecules having wide therapeutic applications.     

A mild and highly efficient method for the synthesis of 5‐aryl‐(N‐phenyl‐)6H‐1,3,4‐thiadiazin‐2‐aminium salts using reusable heterogeneous catalysts

5‐Aryl‐6H‐1,3,4‐thiadiazin‐2‐aminium and 5‐aryl‐N‐phenyl‐6H‐1,3,4‐thiadiazin‐2‐aminium salts have efficiently been synthesized from the reaction of thiosemicarbazide and α‐haloketones in acetonitrile at room temperature using i) silica supported sodium hydrogen sulfate and ii) silica sulfuric acid as reusable heterogeneous catalysts. The experimental procedure is simple and the products are obtained in high yields.     

Synthesis of 1,3‐thiazole and 1,2,4‐oxadiazole substituted spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones

Some new derivatives of spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐dione with the heterocyclic ring such as substituted thiazole and 1,2,4‐oxadiazole attached to the indolinone ring via CH₂ linkage has been synthesized in moderate yields. The synthesis have been carried out by making use of the reactivity of the NH group of the indolinone moiety present in spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐dione.     

Microwave assisted synthesis of novel 6,7,8‐trimethoxy N‐substituted‐4‐aminoquinazoline compounds

A fast, efficient and convenient reaction of 6,7,8‐trimethoxy‐4‐chloroquinazoline and aryl (or benzyl) amines was achieved under microwave irradiation in isopropyl alcohol, providing a simple method for synthesis of novel 6,7,8‐trimethoxy N‐substituted‐4‐aminoquinazoline compounds in good yield in short time. The title compounds were evaluated for their in vitro anti‐proliferative activities against PC3 cell by MTT method.     

An efficient and green synthesis of 3,3′‐benzylidenebis (4‐hydroxy‐6‐methylpyridin‐2(1H)‐one) derivatives through multi‐component reaction in ionic liquid

A series of new 3,3′‐benzylidenebis(4‐hydroxy‐6‐methylpyridin‐2(1H)‐one) derivatives were synthesized via a three‐component reaction of an aldehyde, an aniline or ammonium acetate and 6‐methyl‐4‐hydroxypyran‐2‐one in ionic liquid. These heterocyclic compounds produced could be conveniently separated from the reaction mixture without any volatile organic solvents, and the ionic liquid could be readily reused without efficiency loss after simple treatment.     

Synthesis of alicyclic N‐substituted 1,3‐amino alcohols via 1,3‐oxazines

Alicyclic N‐substituted 1,3‐amino alcohols 13‐18 were prepared in a facile way in a one‐pot procedure from 1,3‐oxazines 5‐8 in the presence of a ketone 9‐12 . The complex reaction involves palladium‐catalyzed reduction, debenzylation and/or transimination and further reduction.