A facile approach to the synthesis of structurally diverse 6,8a-dihydropyrido[2,3-d]pyrimidine derivatives via a three-component domino reaction.

A concise and efficient approach to the synthesis of structurally diverse 6,8a-dihydropyrido[2,3-d]pyrimidine derivatives has been accomplished by a three-component reaction involving sulfonyl acetonitrile, an aromatic aldehyde, and 6-aminouracil. The method involves the domino Knoevenagel condensation/Michael addition/cyclization cascade in the presence of triethylamine in refluxing ethanol.

A copper-catalyzed one-pot, three-component tandem conjugative alkynylation/6-endo cyclization sequence: access to pyrano[2,3-d]-pyrimidines.

A copper catalyzed one-pot, three component reaction between barbituric acid, aldehydes and terminal alkynes has been developed for the construction of pyrano[2,3-d]pyrimidines via a tandem conjugative alkynylation/6-endo cyclization pattern. Screening of barbituric acid derived organic acceptors in conjugative alkynylation reaction and the synthetic applicability of conjugative addition products under one-pot conditions were documented for the first time.

Indium-catalyzed, novel route to ß,ß-disubstituted indanones via tandem Nakamura addition-hydroarylation-decarboxylation sequence.

A novel method for the construction of ß,ß-disubstituted indanones has been developed via tandem Nakamura addition-hydroarylation-decarboxylation process. Indium(III) triflate was demonstrated as a versatile multitasking catalyst, which catalyzes three different chemical transformations under one-pot conditions.

A highly efficient group-assisted purification method for the synthesis of poly-functionalized pyrimidin-5-yl-pyrroles via one-pot four-component domino reaction.

A highly efficient, catalyst-free group-assisted purification chemical protocol for the construction of pyrimidine containing poly-functionalized pyrroles from a four-component domino reaction of acyclic-1,3-dicarbonyls or electron deficient alkynes, aromatic amines, barbituric acid and arylglyoxal hydrates under mild reaction conditions has been developed. The prominent features of the present protocol are environmentally benign, mild reaction conditions, atom economy, no column chromatography separation, easy isolation of products and excellent yields.

Rhodium(II) catalyzed diastereoselective reactions of diazoacetamides with isatins: an efficient approach to 3-hydroxy-3,3'-bioxindoles.

The 3,3'-bioxindole derivatives were constructed in a single step via an efficient Rh(2)(OAc)(4) catalyzed reaction of diazoacetamides with isatins. This novel method provides an alternative pathway towards 3-hydroxy-3,3'-bioxindoles in good yield (up to 78%) with high diastereoselectivity (up to 95 : 5).

Indium(III) catalysed substrate selective hydrothiolation of terminal alkynes.

In(OTf)(3) is reported as the first catalyst having the ability to selectively catalyse both Markovnikov and anti-Markovnikov hydrothiolation of terminal alkynes under identical reaction conditions depending upon the nature of the thiol employed.

Microwave-promoted catalyst- and solvent-free aza-Diels-Alder reaction of aldimines with 6-[2-(dimethylamino)vinyl]-1,3-dimethyluracil.

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.

Indium catalyzed tandem hydroamination/hydroalkylation of terminal alkynes.

The first direct intermolecular hydroamination/hydroalkylation of terminal alkynes catalyzed by In(OTf)(3) under one-pot conditions leading to the formation of conjugated ketimines in good yields is described.

Unexpected deviation from diene behaviour of uracil amidine: towards synthesis of some pyrido[2,3-d]pyrimidine derivatives.

Condensation products obtained from the treatment of uracil amidine with preformed or in situ generated suitably substituted olefins unexpectedly undergo intramolecular cyclisation during silica gel chromatography to generate pyrido[2,3-d]pyrimidines. Various reaction conditions are studied and the altered nature of the uracil amidine molecule is further explored by reacting it with different suitably substituted alkenes.

Green chemistry approaches to the regioselective synthesis of spiro heterobicyclic rings using iodine as a new and efficient catalyst under solvent-free conditions.

Iodine catalyzes the pseudo four-component reaction of an aldehyde, a urea or thiourea, and cyclic 1,3-dicarbonyl compounds under microwave irradiation in a solvent-free condition to yield various σ symmetric spiro heterobicyclic rings in excellent yields.

A strategy to synthesize taxol side chain and (-)-epi cytoxazone via chiral Brønsted acid-Rh(2)(OAc)(4) co-catalyzed enantioselective three-component reactions.

A new approach to synthesize optically active ß-amino-α-hydroxyl acid derivatives via chiral Brønsted acid-Rh(2)(OAc)(4) cocatalyzed three-component reactions of diazo acetates with alcohols and imines is reported. A matched reaction system was identified to give the products in moderate diastereoselectivity and good enantioselectivity. Application of this methodology is demonstrated in the efficient synthesis of a taxol side chain and (-)-epi-cytoxazone.

Zinc triflate: a highly efficient reusable catalyst in the synthesis of functionalized quinolines via Friedlander annulation.

An environmentally friendly and highly efficient procedure for the preparation of quinolines and fused polycyclic quinolines has been developed by a simple Friedlander annulation reaction of 2-aminoaryl ketone with carbonyl compounds in presence of zinc triflate under microwave irradiation and solvent-free conditions. The reaction also proceeds effectively when In(OTf)(3) was used in lieu of Zn(OTf)(2) as the catalyst. The catalyst can be recovered after the reaction and reused efficiently in subsequent runs.

The tert-amino effect in heterocyclic chemistry: synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives.

The synthesis of novel fused heterocycles is based on reactions proceeding by the mechanism of the tert-amino effect, which generalizes cyclization of certain derivatives of 3-methyl-1-phenyl-2-pyrazolin-5-ones. Using this strategy a variety of fused heterocycles is obtained by the Knoevenagel condensation of 5-tert-amino-3-methyl-1-phenylpyrazolone-4-carboxal-dehyde 3 with active methylene compounds such as malononitrile and cyanoacetamide followed by cyclisation using anhydrous zinc chloride.

An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium-catalyzed multi-component domino reaction.

Various novel pyrano [2,3-d]pyrimidines 5 and furopyrano [2,3-d]pyrimidines 7 were synthesized in 80-99% yields via a multicomponent domino Knoevenagel/hetero-Diels-Alder reaction of 1,3-dimethyl barbituric acid with an aromatic aldehyde and ethyl vinyl ether/2,3-dihydrofuran in presence of 1 mol% of indium(III) chloride. The reaction also proceeds in aqueous media without using any catalyst, but the yield is comparatively less (65-70%).

Regiospecific one-pot synthesis of pyrimido[4,5-d]pyrimidine derivatives in the solid state under microwave irradiations.

Electron rich 6-[(dimethylamino)methylene]amino uracil 1, undergoes [4+2] cycloaddition reactions with various in situ generated glyoxylate imine and imine oxides 6 to provide novel pyrimido[4,5-d]pyrimidine derivatives of biological significance, after elimination of dimethylamine from the (1:1) cycloadducts and oxidative aromatisation. This procedure provides a convenient method for the direct synthesis of pyrimido[4,5-d]pyrimidines in excellent yields when carried out in the solid state and under microwave irradiations.

One-pot synthesis of novel 1H-pyrimido[4,5-c][1,2]diazepines and pyrazolo[3,4-d]pyrimidines.

Novel 1H-pyrimido [4,5-c][1,2]diazepines 3 & 4 and pyrazolo [3,4-d]pyrimidines 6 were regioselectively synthesised by the reaction of 1,3-dimethyl-6-hydrazinouracils 1 with various alpha,beta-unsaturated compounds 2 and alpha-ketoalkynes 8 in excellent yields.

Microwave-induced enzyme-catalyzed chemoselective reduction of organic azides.

A lipase enzyme, suspended in organic media along with organic azides and irradiated under microwaves, enhances the reaction rate over thermal heating and affords the corresponding amines in high yields. The present biocatalytic method employing lipase is a significant development with remarkable regio- and chemoselectivity under microwave irradiation in organic media with excellent yields for the reduction of azide functionality.