New route to pyrimido[4,5‐ e][1,3,4]thiadiazine derivatives

5‐Bromo‐2‐chloro‐4‐methyl‐6‐(1‐methylhydrazino)pyrimidine is readily obtained from the recently reported 5‐bromo‐2,4‐dichloro‐6‐methylpyrimidine by treatment with methylhydrazine in chloroform. Treatment of this compound with carbon disulfide and several alkyl halides gave an intermediate which was successfully converted to its corresponding 3‐(alkylsulfanyl)‐7‐chloro‐1,5‐dimethyl‐1H‐pyrimido[4,5‐e][1,3,4]thiadiazine derivatives in basic acetonitrile. The latter compounds were reacted with secondary amines in boiling ethanol to afford the related 7‐amino derivatives.     

Synthesis of 2,4‐difuryl‐4H‐3,1‐benzothiazines via a furan ring migration reaction

A new simple synthetic approach to 2,4‐difuryl‐4H‐3,1‐benzothiazines from 2‐isothiocyanoaryldifuryl‐methanes in the presence of acidic catalyst is described. This rearrangement is a new example of furan ring migration reaction resulting from intramolecular attack with electrophilic carbon.     

Synthesis of new chromeno[4,3,2‐de]quinazolin‐2‐ones, ‐quinazolines and ‐pyrrolo[2,1‐b]quinazolines

The total synthesis of chromeno[4,3,2‐de]quinazolin‐2‐ones, ‐quinazolines and ‐pyrrolo[2,1‐b]quinazolines from easily prepared 4‐methoxy‐1‐nitro‐9H‐xanthen‐9‐one is reported. These compounds, in which a 1,3‐diazine ring is fused to the xanthene scaffold, were obtained with good overall yields in very few steps.     

An improved synthesis of 1‐acetyl‐1H‐indol‐3‐yl acetates

An efficient two steps procedure for the synthesis of 1‐acetyl‐1H‐indol‐3‐yl acetates, starting from 2‐chlorobenzoic acids, was developed and in general, moderate to good yields were obtained     

Asymmetric alkylation of N‐acylisoindolin‐1‐ones via α‐bromoimides: A novel route to 1‐substituted isoindolines

Key intermediate in the synthesis of the title compounds 9a‐c and 10a‐c was the chiral α‐bromoimide 1 which has been prepared by radical bromination of the corresponding N‐acylisoindolin‐1‐one 13. 1 was alkylated with silyl enol ethers under Lewis acid catalysis using α‐amidoalkylation methodology. N,N‐diacyliminium ion 14 is presumably the intermediate in this reaction. Further transformations of the alkylated compounds yielded 1‐substituted isoindolines as target compounds.     

Studies with 2‐arylhydrazononitriles: A novel simple,efficient route to 5‐acyl‐2‐substituted‐1,2,3‐triazol‐4‐amines

Efficient route to 5‐acyl‐2‐substituted‐1,2,3‐triazol‐4‐amines via reaction of 3‐oxo‐2‐(arylhydrazono)‐pentanenitrile with hydroxylamine hydrochloride is reported. X‐ray crystal structure has been made to confirm the structure of reaction products.     

Synthesis and antifungal activity of novel 3,6‐diaryl‐5H‐[1,2,4]triazolo[4,3‐b][1,2,4]triazepines

5‐Aryl‐3,4‐diamino‐1,2,4‐triazoles 5 on treatment with β‐chlorocinnamaldehydes 7 in the presence of catalytic amount of p‐TsOH and N,N‐dimethylformamide as an energy transfer medium under microwave irradiation and as solvent with oil‐bath heating at 80 °C affords novel 3,6‐diaryl‐5H‐[1,2,4]triazolo[4,3‐b]‐1,2,4]triazepines 8 . The structures of the synthesized compounds were established on the basis of ¹H NMR, IR, mass spectral data and elemental analysis.     

A general and versatile synthesis of 3‐phenylthio β‐lactams as lead molecules for 3‐methyl‐2‐azetidinones

Ketene‐imine cycloaddition using phosphorus oxychloride and benzenesulfonyl chloride under the described reaction conditions yielded trans 3‐phenylthio 2‐azetidinones in good yields. Desulfurization using Raney nickel and alkylation finally afforded trans 3‐methyl‐2‐azetidinones in a stereoselective manner.     

A green and efficient synthesis of furo[3,4‐e]pyrazolo[3,4‐b]‐pyridine derivatives in water under microwave irradiation without catalyst

A series of furo[3,4‐e]pyrazolo[3,4‐b]pyridine analogues of podophylloxin were synthesized via three‐component reactions of aldehydes, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐amine and tetronic acid in water under microwave irradiation without catalyst. This efficient synthesis not only offers an economical and green synthetic strategy to this class of significant compounds but also enriches the investigations on microwave‐assisted synthesis in water.     

A rapid and efficient method for synthesis of pyrimido[1,2‐a]‐benzimidazole derivatives under microwave irradiation

A rapid and efficient method for synthesis pyrimido[1,2‐a]benzimidazole derivatives from readily available starting materials is accomplished under microwave irradiation. This method has the advantages of short reaction time, operational simplicity, increased safety for small‐scale high‐speed synthesis, and minimal environment impact.     

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.     

Synthesis of substituted amino‐cycloalkyl[b]thieno‐[3,2‐e]pyridines

An efficient two respectively three steps procedure for the synthesis of cycloalkyl[b]thieno[3,2‐e]‐pyridine amines was developed and in general good to very good yields were obtained.     

Solvent‐free one‐pot approach for synthesis of substituted 2‐aminochromenes

A solvent‐free one‐pot approach for the preparation of 2‐aminochromenes in the presence of NaHCO₃ by grinding was described. Its advantages are easy work‐up, mild reaction condition, high yield and environmental compatibility.     

Green multicomponent synthesis of 1,2‐dihydro‐pyrimido[1,2‐a]‐benzimidazole‐3‐carbonitrile

1,2‐dihydro‐pyrimido[1,2‐a]benzimidazole‐3‐carbonitrile derivatives were synthesized via the three‐component reaction of aldehyde, malonodinitrile and 2‐aminobenzimidazole in water under microwave irradiation. The new protocol has the advantages of excellent yield, low cost, reduced environment impact, wide scope and convenient procedure.     

Microwave‐induced perchloric acid catalyzed novel solvent‐free synthesis of 4‐aryl‐3,4‐dihydropyrimidones via biginelli condensation

We report here domestic microwave‐induced perchloric acid‐catalyzed solvent‐free synthesis of various 4‐aryl‐3,4‐dihydropyrimidones for the first time. In all the cases the yields are excellent and the mechanism follows a simple Biginelli condensation to produce the dihydropyrimidones in a few seconds. This procedure has been successfully employed to synthesize the mitotic kinesin EG5 inhibitor Monastrol (Figure I).