Browsing by Author "Rajeshwer Vanjari"

Now showing 1 - 13 of 13

A novel and simple transamidation of carboxamides in 1,4-dioxane without a catalyst
(Elsevier Ltd, 2013) Rajeshwer Vanjari; Bharat Kumar Allam; Krishna Nand Singh
An easy acylation and formylation of amines has been achieved via transamidation using 1,4-dioxane. The investigation works efficiently without an added catalyst and completes within short time under microwave irradiation. © 2013 Elsevier Ltd. All rights reserved.
AIBN-initiated metal free amidation of aldehydes using N-chloroamines
(Royal Society of Chemistry, 2014) Rajeshwer Vanjari; Tirumaleswararao Guntreddi; Krishna Nand Singh
An efficient and environmentally benign amidation of aldehydes with N-chloroamines has been developed using AIBN as an initiator. This methodology offers a metal free and base free approach and is endowed with mild reaction conditions, high yields, and good functional group tolerance. © 2014 The Royal Society of Chemistry.
Copper catalysed C-N bond formation via a sequential acylation and deacylation process: A novel strategy for the synthesis of benzanilides
(Royal Society of Chemistry, 2015) Saurabh Kumar; Rajeshwer Vanjari; Tirumaleswararao Guntreddi; Krishna Nand Singh
An efficient and mild oxidative amidation of aldehydes by means of acetanilides as amine components has been developed for the first time using copper catalysis. The approach is versatile and proceeds through sequential acylation and deacylation steps to afford benzanilides. © The Royal Society of Chemistry 2015.
Decarboxylative thioamidation of arylacetic and cinnamic acids: A new approach to thioamides
(American Chemical Society, 2014) Tirumaleswararao Guntreddi; Rajeshwer Vanjari; Krishna Nand Singh
A new decarboxylative strategy has been developed for the synthesis of thioamides via a three-component reaction involving arylacetic or cinnamic acids, amines and elemental sulfur powder, without the need of a transition metal and an external oxidant. © 2014 American Chemical Society.
Direct conversion of methylarenes into dithiocarbamates, thioamides and benzyl esters
(Elsevier Ltd, 2014) Tirumaleswararao Guntreddi; Rajeshwer Vanjari; Krishna Nand Singh
A new strategy for the synthesis of a variety of dithiocarbamates and thioamides has been developed employing inexpensive and readily available methylarenes under metal-free and solvent-free conditions. The approach offers a one-pot procedure and has also been extended to the synthesis of a diverse range of benzyl esters. © 2014 Elsevier Ltd. All rights reserved.
Elemental sulfur mediated decarboxylative redox cyclization reaction of o -chloronitroarenes and arylacetic acids
(American Chemical Society, 2015) Tirumaleswararao Guntreddi; Rajeshwer Vanjari; Krishna Nand Singh
A decarboxylative redox cyclization strategy has been developed for the synthesis of 2-substituted benzothiazoles by the reaction of o-chloronitroarenes and arylacetic acids in the presence of elemental sulfur/N-methylmorpholine under metal- and solvent-free conditions. © 2015 American Chemical Society.
Elemental sulfur mediated synthesis of benzoxazoles, benzothiazoles and quinoxalines: Via decarboxylative coupling of 2-hydroxy/mercapto/amino-anilines with cinnamic acids
(Royal Society of Chemistry, 2016) Tirumaleswararao Guntreddi; Rajeshwer Vanjari; Saurabh Kumar; Rahul Singh; Neetu Singh; Promod Kumar; Krishna Nand Singh
An easy and practical method has been developed for the synthesis of 2-benzylbenzoxazoles and 2-benzylbenzothiazoles using sulfur mediated decarboxylative coupling of cinnamic acids with 2-hydroxyanilines and 2-mercaptoanilines respectively under metal- and solvent-free conditions. However, the reaction of 2-aminoanilines with cinnamic acids leads to the formation of 2-arylquinoxalines under the same set of reaction conditions. The transformation is versatile and compatible with a number of functional groups. © 2016 The Royal Society of Chemistry.
Hypervalent iodine catalyzed transamidation of carboxamides with amines
(2013) Rajeshwer Vanjari; Bharat Kumar Allam; Krishna Nand Singh
This protocol describes the catalytic use of diacetoxyiodobenzene (DIB) for the efficient transamidation of carboxamides with amines under mild conditions. © 2012 The Royal Society of Chemistry.
MnO2 promoted sequential C-O and C-N bond formation via C-H activation of methylarenes: A new approach to amides
(2013) Rajeshwer Vanjari; Tirumaleswararao Guntreddi; Krishna Nand Singh
A novel and efficient approach for the synthesis of amides has been developed through manganese dioxide promoted nondirected C-H activation of methylarenes under mild reaction conditions employing N-chloroamines as effective coupling partners. © 2013 American Chemical Society.
Palladium-Catalyzed Site-Selective C-H Functionalization of Weakly Coordinating Sulfonamides: Synthesis of Biaryl Sulfonamides
(John Wiley and Sons Ltd, 2016) Rajeshwer Vanjari; Tirumaleswararao Guntreddi; Krishna Nand Singh
A novel and site selective C-H functionalization of unsubstituted sulfonamides has been developed for the synthesis of ortho aryl sulfonamides. The reaction involves highly regioselective ortho mono arylation of weakly coordinating SO2NH2 directing group by means of aryl iodides. Palladium acetate in the presence of silver(I) oxide is found to be the most effective catalytic system. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Sulfur promoted decarboxylative thioamidation of carboxylic acids using formamides as amine proxy
(Elsevier Ltd, 2016) Saurabh Kumar; Rajeshwer Vanjari; Tirumaleswararao Guntreddi; Krishna Nand Singh
An efficient decarboxylative thioamidation of arylacetic and cinnamic acids has been developed employing formamides as amine surrogate and sulfur as promoter. Thioamides with variant structural features are obtained under mild reaction conditions without the use of transition metal catalysts and oxidants. © 2016 Elsevier Ltd.
Sulphur promoted C(sp3)-C(sp2) cross dehydrogenative cyclisation of acetophenone hydrazones with aldehydes: Efficient synthesis of 3,4,5-trisubstituted 1H-pyrazoles
(Royal Society of Chemistry, 2015) Rajeshwer Vanjari; Tirumaleswararao Guntreddi; Saurabh Kumar; Krishna Nand Singh
A novel strategy for the cross dehydrogenative coupling (CDC) of acetophenone hydrazones and aldehydes has been developed for the synthesis of highly substituted pyrazoles. This work, for the first time, uses elemental sulfur as a promoter as well as a hydrogen acceptor in effecting the Csp3-Csp2 bond formation via C-H activation. This journal is © 2015 The Royal Society of Chemistry.
Utilization of methylarenes as versatile building blocks in organic synthesis
(Royal Society of Chemistry, 2015) Rajeshwer Vanjari; Krishna Nand Singh
The development of practical and efficient methods for C-C and C-X bond formation has attracted a great deal of current attention with the advent of C-H functionalization reactions. Hydrocarbons are perhaps the most inexpensive and readily available materials, and utilisation of such materials for the synthesis of essential chemicals is virtually and economically pragmatic. The means to utilize easily accessible hydrocarbons not only represents a useful, potent and straightforward alternative, but also constitutes an excellent opportunity to improve our chemical knowledge about a relatively unexplored domain. Early examples using alkylarenes are generally limited to their conversion to aldehydes, carboxylic acids, and nitriles. This review intends to focus on the latest developments adopting modern strategies for sp3 C-H functionalization of methylarenes to achieve a diverse range of important organic compounds. © The Royal Society of Chemistry.