Akula Raghunadh

A catalyst-free rapid, practical and general synthesis of 2-substituted quinazolin-4(3H)-ones leading to luotonin B and E, bouchardatine and 8-norrutaecarpine

A remarkably rapid but microwave/ultrasound/catalyst-free method has been developed for the construction of a quinazolin-4(3H)-one ring using formamide as an efficient ammonia precursor and PEG-400 as an effective solvent. The methodology afforded various 2-substituted quinazolin-4(3H)-one derivatives in good yield via a three-component reaction of isatoic anhydride, aldehydes and formamide in air. This single methodology was extended successfully to the synthesis of several alkaloids e.g. leutonin B and E, bouchardatine and 8-norrutaecarpine.

An oxidative amidation and heterocyclization approach for the synthesis of β-carbolines and dihydroeudistomin Y

Summary A novel synthetic methodology has been developed for the synthesis of dihydro-β-carboline derivatives employing oxidative amidation–Bischler–Napieralski reaction conditions using tryptamine and 2,2-dibromo-1-phenylethanone as key starting materials. A number of dihydro-β-carboline derivatives have been synthesized in moderate to good yields using this methodology. Attempts were made towards the conversion of these dihydro-β-carbolines to naturally occurring eudistomin alkaloids.

An efficient and convenient protocol for the synthesis of tetracyclic isoindolo[1,2-a]quinazoline derivatives

A convenient and one-pot synthesis of tetracyclic isoindolo [1,2-a]quinazoline derivatives via Lewis acid mediated sequential C–N bond formation reactions is reported. This protocol provides a simple and rapid strategy for the synthesis of 12-benzylidene-10,12-dihydroisoindolo[1,2-b]quinazoline derivatives. However, a variety of tetracyclo indole fused quinazoline motifs were synthesized in good yields.

Synthesis of enantiomerically pure N-(2,3-dihydroxypropyl)arylamides via oxidative esterification

Summary A highly efficient synthesis of enantiomerically pure (S) and (R)-isomers of N-(2,3-dihydroxypropyl)arylamides has been developed with good overall yields in a two step process. The key step involves the ring opening of the chiral epoxide with a nitrogen heterocyclic carbene (NHC) and further rearrangement to chiral N-(2,3-dihydroxypropyl)arylamides in high yields and enantioselectivity. During the reaction, no erosion in chiral purity was observed.

A cascade reaction for the new and direct synthesis of indolofuroquinoxalines

The 7H-indolo[3′,2′:4,5]furo[2,3-b]quinoxaline derivatives are synthesized directly from methyl 2-(2-chloro-1H-indol-3-yl)-2-oxoacetate or its N-alkyl derivatives under neutral or mildly acidic conditions. This new one-pot methodology was found to be general and greener as it avoids the use of environmentally harmful POCl3 and strong alkali required for the previously reported method. It is also amenable for scale-up.

A greener approach towards double heteroarylation of N, O and S nucleophiles: synthesis of bioactive polynuclear fused N-heteroarenes

A catalyst, ligand and solvent free method for double heteroarylation of N, O and S nucleophiles has been developed for the first time leading towards the synthesis of compounds containing an indole ring fused with pyrrolo-, furo- and thieno[2,3-b]quinoxaline moieties. This general and greener approach afforded novel compounds of medicinal importance.

De novo synthesis of 2,2-bis(dimethylamino)-3-alkyl or benzyl 2,3-dihydroquinazolin-4(1H)-one compounds

ABSTRACT A new versatile and efficient strategy for the synthesis of 2,2-bis(dimethylamino)-3-alkyl or benzyl 2,3-dihydroquinazoline-4(1H)-one compounds has been developed by one-pot multicomponent reaction with isatoic anhydride, amines followed by in situ-generated Vilsmeier reagent. The reaction has also been studied with different amines and solvents. GRAPHICAL ABSTRACT

Amberlite-15 promoted an unprecedented aza Michael rearrangement for one pot synthesis of dihydroquinazolinone compounds

A new one pot multicomponent annulation strategy for the synthesis of various dihydroquinazolinone compounds has been developed using Amberlite-15 as a catalyst, giving good to moderate yields. In this reaction the substrate scope for amines and aldehydes was also investigated. The reaction has been checked on a large scale and the possible reaction mechanism has also been proposed.

Sulfonic acid–functionalized Wang resin (Wang-OSO3H) as polymeric acidic catalyst for the ecofriendly multicomponent synthesis of polyhydroquinolines via Hantzsch condensation

ABSTRACT An efficient and green approach has been developed for the synthesis of polyhydroquinoline derivatives via Hantzsch condensation reaction directly from corresponding substituted aromatic and aliphatic aldehydes, β-keto compounds, active methylene compounds, and ammonium chloride using recyclable polymer-supported sulfonic acid catalyst under aqueous conditions. Environmental acceptability, operational simplicity, low cost, excellent functional group compatibility, and high yields are the important features of this protocol. GRAPHICAL ABSTRACT

Synthesis of 2-hydroxy-3-alkyl-2-phenyl-2,3-dihydroquinazolin-4(1H)-one via molybdenum hexacarbonyl mediated CO gas- and ligand free carbonylative reactions

Carbon monoxide gas and ligand-free conditions were developed for the synthesis of 2-hydroxy-3-alkyl-2-phenyl-2,3-dihydroquinazolin-4(1H)-one via catalytic carbonylation with molybdenum hexacarbonyl as an efficient carbonylating agent for the three-component reaction of isatoic anhydride, amine, iodobenzene. Mo(CO)6 is a solid carbon monoxide source. The quinazolinone synthesis proceeds via a sequential series of reactions such as nucleophilic attack of the amine group on the carbonyl group of isatoic anhydride followed by ring opening, subsequent decarboxylation, carbonylation and heterocyclization.