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An efficient pot and time economic ‘dry-media’ synthesis of pyrimidine core containing scaffolds by application of an indium triflate catalyzed carbon–carbon bond formation procedure through Diels–Alder reaction using microwaves is described. The method is associated with some attractive characteristics such as short reaction time, high yield of products, and recyclability of recovered catalyst from the reaction mixture.

An efficient pot and step economic protocol for synthesis of pyrido[2,3-d]pyrimidine derivatives from a multicomponent aza-Diels–Alder reaction of uracil analogues, aromatic aldehydes and acetophenones in the presence of Na2CO3 in DMF was developed. The key step of the reaction is in situ generation of the reactive dienophile from aldehyde and acetophenone and their subsequent reaction with diene to give the desired product.

An one-pot, solvent-free imino Diels–Alder reaction has been developed under microwave conditions using 1-naphthylamine, aldehydes, and electron-deficient terminal alkynes in the presence of a catalytic amount of In(OTf)3 for construction of benzo[h]quinoline derivatives in short reaction times. The method is clean and operationally simple.

A solvent- and catalyst-free Diels–Alder reaction with 6-(2-morpholinovinyl)-1,3-dimethyluracil, cinnamaldehyde, and an amine has been developed for the construction of iminoquinazoline-2,4-dione derivatives within a short reaction time. The method is clean, simple, and operation friendly.

A mild and efficient protocol for the synthesis of various tetrahydroquinazolinedione and dihydropyrido[2,3-d]pyrimidine-2,4-dione templates from uracil derivatives utilizing a [4+2]-cycloaddition strategy in a one-pot reaction has been developed.

A microwave-promoted solvent- and catalyst-free aza-Diels–Alder reaction is described. 6-[2-(dimethylamino)vinyl]-1,3-dimethyluracil reacts with aldehyde and amine inside a microwave reactor to produce dihydropyrido[4,3-d]pyrimidine derivatives in excellent yield and within a very short time.

A mild and efficient protocol for the synthesis of pyrano[3,2- C]coumarins from 4-hydroxycoumarinthrough a one-pot -reaction in water under phase-transferconditions has been developed.

An efficient pot and time economic ‘dry-media’ synthesis of pyrimidine core containing scaffolds by application of an indium triflate catalyzed carbon–carbon bond formation procedure through Diels–Alder reaction using microwaves is described. The method is associated with some attractive characteristics such as short reaction time, high yield of products, and recyclability of recovered catalyst from the reaction mixture.

The reaction succeeds using aryl aldehydes as the reaction partner, but fails with alkyl aldehydes and phenyl glyoxal derivatives.

Spiroindenotetrahydropyridine derivatives are synthesized from 1,3-indanedione (I), aromatic aldehydes (II), and ammonium acetate.

Dienophiles generated in situ from aldehydes and acetophenones undergo aza-Diels—Alder reaction with uracil derivative (I) followed by oxidative aromatization to give pyridopyrimidines.

In situ generated enimines undergo Diels—Alder reactions with morpholinovinyl- or dimethylaminovinyl substituted uracil derivatives, followed by elimination of the amino group and aromatization to give the title compounds (IV) in good yields.

Uracil derivatives (I) and (IV) are employed as diene components for the reaction with aromatic nitroalkenes.

A facile synthesis of the title compounds is achieved by microwave promoted three-component aza-Diels—Alder reaction of uracil derivative (I), aldehydes, and amines.

A microwave-promoted aza-Diels–Alder reaction between 6-[2-(dimethylamino)vinyl]-1,3-dimethyluracil and aldimines has been developed for the construction of dihydropyrido[4,3-d]pyrimidines. Urea is effectively employed as an environmentally benign source of ammonia in the absence of any catalyst or solvent. The key step in the reaction is in situ generation and trapping of the reactive aldimine formed from urea and aldehyde by the diene system of the uracil. The reaction is clean, and excellent yields are obtained in a matter of a few minutes.

A microwave-promoted aza-Diels–Alder reaction between 6-[2-(dimethylamino)vinyl]-1,3-dimethyluracil and aldimines has been developed for the construction of dihydropyrido[4,3-d]pyrimidines. Urea is effectively employed as an environmentally benign source of ammonia in the absence of any catalyst or solvent. The key step in the reaction is in situ generation and trapping of the reactive aldimine formed from urea and aldehyde by the diene system of the uracil. The reaction is clean, and excellent yields are obtained in a matter of a few minutes.

The title compounds are prepared in high yields and short reaction times via phase-transfer-catalyzed reactions of 4-hydroxycoumarin (I).