Vishnu P. Srivastava

Visible light organophotoredox catalysis: a general approach to β-keto sulfoxidation of alkenes

A mild, simple, efficient and metal-free approach to β-keto sulfoxides utilising eosin Y as an organophotoredox catalyst has been developed. This general protocol offers a direct and rapid difunctionalization of alkenes using thiophenols and atmospheric oxygen at room temperature in a one-pot procedure. The utilisation of visible light and air (O2) as inexpensive, readily available, non-toxic and eco-sustainable reagents makes this protocol compatible with the green chemistry demands.

Visible-light-mediated eosin Y catalyzed aerobic desulfurization of thioamides into amides

A novel method for the metal-free efficient synthesis of amides from thioamides using visible light and in an air atmosphere in the presence of eosin Y as an organophotoredox catalyst is reported. The protocol involves aerobic desulfurization–oxygenation of thioamides into amides in good to excellent yields at r.t. in a one-pot operation under mild conditions with the formation of nontoxic elemental sulfur as the only by-product. On the basis of several relevant experiments performed, it has been shown that the present photooxidation does not involve a singlet oxygen and accordingly a plausible organocatalytic photoredox mechanism is proposed.

Visible-light-mediated efficient conversion of aldoximes and primary amides into nitriles

A photosensitization-based approach for a convenient and efficient conversion of aldoximes and primary amides into nitriles is reported. The protocol involves eosin Y catalysed, visible-light-mediated in situ formation of the Vilsmeier–Haack reagent from CBr4 and a catalytic amount of DMF, which brings about the desired transformation to afford nitriles at r.t.

An easy access to fluoroalkanes by deoxygenative hydrofluorination of carbonyl compounds via their tosylhydrazones

An efficient and operationally simple synthesis of fluoroalkanes by deoxygenative hydrofluorination of carbonyl compounds via their tosylhydrazone surrogates is reported. The reaction can be carried out in a one-pot procedure directly from carbonyl compounds.

An easy access to unsymmetrical ureas: a photocatalytic approach to the Lossen rearrangement

An efficient and operationally simple method for the synthesis of unsymmetrical ureas from various hydroxamic acids and amines has been developed. Plausibly, the protocol involves visible-light-initiated in situ formation of Vilsmeier–Haack reagent and COBr2 with CBr4 and a catalytic amount of DMF in the presence of Ru(bpy)3Cl2 as a photocatalyst to bring about the Lossen rearrangement at room temperature.

The first example of ring expansion of N-tosylaziridines to 2-aroyl-N-tosylazetidines with nitrogen ylides in an aqueous medium

Tertiary amine catalyzed ring expansion reaction of N-tosylaziridines to 2-aroyl-N-tosylazetidines, with nitrogen ylides formed in situ from phenacyl bromide derivatives in a silica gel-water system is reported. The reaction expeditiously affords functionalized azetidines in high yields and stereoselectivities in a one-pot process. Advantageously, the protocol precludes the preparation and isolation of nitrogen ylides and their precursors in a separate step as they are formed in situ.

Visible-light-initiated photo-oxidative cyclization of phenolic amidines using CBr4 – A metal free approach to 2-aminobenzoxazoles

A mild and efficient one-pot operation for the amination of benzoxazoles has been achieved via ring opening of benzoxazoles followed by visible-light-mediated aerobic photo-oxidative cyclization of the resulting o-phenolic amidines using CBr4 as a mild oxidant. The protocol is economical and environmentally benign as it utilizes visible light and does not require any photosensitizers, additives, heating or inert conditions.

Metal-Free, One-Pot Oxidative Conversion of Aldehydes to Primary Thioamides in Aqueous Media

Abstract One-pot tandem reactions of a variety of aldehydes with aqueous ammonia, molecular iodine, and O,O-diethyl dithiophosphoric acid readily afford the corresponding primary thioamides. This is an inexpensive, practical, and metal-free way of accessing various thioamides from aldehydes in aqueous media. The pure products are obtained simply by filtration followed by successive washing with aqueous sodium thiosulfate and water. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Pd-catalysed carbonylative annulation of salicylaldehydes with benzyl chlorides using N-formylsaccharin as a CO surrogate

A convenient and highly efficient Pd-catalysed carbonylative annulation of salicylaldehydes with benzyl chlorides to afford the corresponding 3-arylcoumarins in good to excellent yields has been developed. Importantly, the protocol utilizes a commercially available, low cost, solid and easy to handle N-formylsaccharin as an alternative to the highly toxic CO gas.