Studies on β-Enaminonitriles: A one-pot Regiospecific Synthesis of Polysubstituted 3,4-Dihydro-2(1H)-Pyridones

Reaction of α, β-unsaturated acid chlorides with primary enaminonitriles in presence of triethylamine affords, under very mild conditions, a simple and highly efficient regiospecific synthesis of polysubstituted 3,4-dihydro-2(1H)-pyridones.     

Synthesis of Spinochalcone B and Analogues

An efficient synthesis of spinochalcone B and its analogues is achieved from readily available 2H‐pyran.     

Convenient Preparation of Pyrano Benzopyranes in Aqueous Media

The three‐component reaction of aldehyde, malononitrile, and 4‐hydroxy coumarin has been efficiently performed in aqueous K₂CO₃ using a simple, clean, environmentally benign, novel procedure employing microwave irradiation. The observed yields and enhancement in reaction rates can be attributed to the uniform heating effect of microwave. The microwave‐accelerated reaction technique not only eliminates the use of external base and organic solvents but also requires only water in both the reaction step and workup, thus rendering the whole procedure into a truly ecofriendly protocol.     

A biomimetic type expedient approach to the tricyclic core of xyloketals. Application to a short, stereocontrolled synthesis of alboatrin and a remarkable epi to natural isomerisation

An expedient synthesis of the linear tetrahydrofurano benzopyran ring system of xyloketals is described involving an ortho ester Claisen rearrangement and an intramolecular cationic cyclisation. This strategy was applied for a short, stereocontrolled and high yield synthesis of the phytotoxic metabolite alboatrin.     

Microwave Promoted and Improved Thermal Synthesis of Spiro[Indole‐Pyranobenzopyrans] and Spiro[Indole‐Pyranoimidazoles]

Spiro[indole‐pyranoimidazoles] ( 5 ) and spiro[indole‐pyranobenzopyrans] ( 6 ) are readily synthesized in one step in 86–92 and 91–97% yields by the Michael condensation of 3‐dicyanomethylene‐2H‐indol‐2‐ones ( 2 ) with 1‐phenyl‐2‐thiohydantoin ( 3 ) and 4‐hydroxy‐2H‐1‐benzopyran‐2‐one ( 4 ), respectively, without using any catalyst under different reaction conditions (conventional heating and microwave irradiation using (a) polar solvents (b) neutral alumina/silica gel as inorganic solid support in solvent free conditions). 2 was synthesized in situ by the Knoevenagel condensation of indole‐2,3‐dione ( 1 ) and malononitrile in the absence of any catalyst. 100% conversion was observed in most cases on TLC which also showed the formation of a single product. The comparison between the various methods is established.