Thirumanavelan Gandhi

• PhD
• Professor at Vellore Institute of Technology University

Photoinduced ruthenium‐catalyzed ortho‐benzoxylation through organophosphine ligand is unveiled. The in situ generation of the organophosphine‐ruthenium complex facilitates ligand‐to‐metal charge transfer (LMCT) under visible light, promoting the site‐selective ortho‐benzoxylation at room temperature. The broad scope of aryl, aliphatic, and heteroc...

Amidines are a vital class of bioactive compounds and often necessitate multiple components for their synthesis. Therefore, exploring efficient and sustainable methodologies for their synthesis is indispensable. Herein, we disclose an alternative and greener method for synthesizing an unexplored new class of amidines through the photochemical syner...

Organoalkali compounds have undergone a far‐reaching transformation being a coupling partner to a mediator in unusual organic conversions which finds its spot in the field of sustainable synthesis. Transition‐metal catalysis has always been the priority in C(sp³)−H bond functionalization, however alternatively, in recent times this has been serious...

Mono α‐acylation of acetone has been achieved for the first time by reacting with bench‐stable acyl azolium salts under violet‐LED light at room temperature. The intermolecular hydrogen atom transfer (HAT) from acetone to triplet state of azolium salts under violet LED irradiation resulted in thermodynamically less favourable (Z)‐α,β‐unsaturated ke...

We here report an effective NHC‐catalyzed acylation of 2‐oxindoles using aldehydes with the aid of aerobic oxidation to prepare 3‐alkylideneoxindoles ‐ a biologically active moiety. This protocol is the first report on the use of oxidized Breslow intermediate for the carbon nucleophile and applies to a wide variety of aryl aldehydes, cyclohexanal,...

An operationally simple and expeditious protocol for Ru(II)-catalyzed ortho-C(sp2)–H hydroxyalkylation of phthalazinones using commercially available ethyl glyoxalate in 2-Me-THF is reported. This greener approach involves the imine nitrogen on the phthalazinones as a directing group to effect the regioselective hydroxyalkylation. Ample examples of...

α-Branched amines are key motifs that exist in a plethora of natural products and pharmaceuticals. Herein we disclose the first convergent synthesis of α-branched amines bearing β-carbonyl in isoindolinones by employing unactivated tertiary amides and unactivated alkyl esters as benign electrophile sources. The reaction proceeds by the direct aroyl...

Herein, we developed ruthenium(II)-catalyzed oxidative dehydrogenation and hydroarylation of maleimides with phthalazinones. The product selectivity is controlled by the additives, and the hydroarylated product was obtained in water, which is an important highlight of this study. Control experiments were conducted to elucidate a plausible mechanism...

The activation and functionalization of the benzylic CH bond by transition metal catalysts have gathered much attraction owing to their occurrence in agrochemicals, pharmaceuticals, and fine chemicals. Among the various active metal catalysts, ruthenium gained upper hand, as they are comparatively economic as well as show versatile catalytic activ...

Ene‐reductases (ERs) are valuable biocatalyst that engages in stereospecific reduction of activated C=C bonds and exhibit increased prominence in the production of pharmaceutical ingredients, agrochemical synthons, and fine chemicals. In addition to traditional biocatalysis, ERs evolved in multi‐enzyme cascades, chemoenzymatic, photoenzymatic, phot...

Biocatalysis integrate microbiologists, enzymologists, and organic chemists to access the repertoire of pharmaceutical and agrochemicals with high chemoselectivity, regioselectivity, and enantioselectivity. The saturation of carbon‐carbon double bonds by biocatalysts challenges the conventional chemical methodology as it bypasses the use of preciou...

The activation and functionalization of C−F bonds in various fluoroorganics were found to be a daunting task owing to their innate inertness. Harnessing the C−F bonds will alleviate the toxicity and environmental issues posed by them, and provide new pathways to access value‐added products. Although several strategies have been employed such as met...

A new series of polycyclic aromatic hydrocarbon (PAH), pyrenoimidazole (PyFPs) having different substituents were developed as fluorescence emitters for optoelectronic applications. The compounds were synthesized by means of transition metal-free, base promoted intramolecular C-C bond formation between pyrene and phenanthridine bridged by imidazol...

Predominantly, aggressive acid chlorides and stoichiometric coupling reagents are employed in the acylating process for synthesizing carbonyl tethered heterocycles. Herein, we report simple acyl sources, viz. methyl and phenyl esters which acylate oxindoles via mixed Claisen condensation. This straightforward protocol is mediated by LiHMDS and KOtB...

We report a direct and effective metal‐free α‐acylation of 2‐oxindoles using C‐acyl imidazolium salts as an acylating agent via C(O)−C bond cleavage. The mild reaction conditions, affordable base, additive‐free and simple substrates make this methodology very attractive for easy access to 3‐alkylidene oxindoles – privilege biologically active oxind...

DBU mediated 5-exo-dig cyclization of isothiocyanate and propargyl alcohol leading to valuable heterocyclic compounds has been accomplished. Different mode of nucleophilicity (either S-selective or N-selective) of isothiocyanates was found to depend on the substitution pattern of propargyl alcohol. The terminal propargyl alcohol and isothiocyanate...

A straight‐forward and practical metal‐free amidation and transesterification of esters have been exemplified in this protocol. This strategic reaction features mild bases and devoid of additives at a reasonable temperature (55 °C). The wide range of amines including aromatic amines, was successfully subjected to amidation that supplements the scop...

5‐exo‐dig is a versatile Baldwin tool to predict and make useful heterocyclic compounds from nucleophiles and electrophiles. In order to aid this, a novel metal‐free method is proposed to produce [1,3]‐oxathiole‐2‐thiones from a readily synthesized propargyl alcohols and easily accessible carbon disulfide, where both secondary and primary propargyl...

In the quest of new ligand system for Pd(II)/NHCs, we synthesized new dibenzofuran and dibenzothiophene based Palladium N-heterocyclic carbene catalysts D1-D6 in good yields. All the catalysts were characterized by multinuclear NMR and HRMS. X-ray crystal structure of representative dibenzothiophene based Pd(II)/NHC D4 was determined. Among the pre...

Rationally designed fluorene-based mono- and bimetallic Pd-PEPPSI complexes were synthesized and demonstrated to be effective for the one-pot sequential α-arylation/alkylation of oxindoles. This streamlined approach offers efficient access to functionalized 3,3-disubstituted oxindoles in excellent yields (up to 89%) under mild reaction conditions.

Topologically constrained naphthalimide appended Pd-NHCs were synthesized and characterized. These structurally related complexes were catalytically compared with the previously synthesized Pd-NHC in the regioselective heteroannulation of o-haloanilines and arylethynyl-trimethylsilane. The unique effect of the additive on the product selectivity ha...

Monometallic and bimetallic palladium(II)/N‐heterocyclic carbene complexes appended with naphthalimide or bisnaphthalimide moieties were designed, synthesized, and characterized. Employment of these catalysts brings about the step‐economic and regioselective heteroannulation of tertiary propargyl alcohols with o ‐haloanilines resulting in biologica...

The synthesis of π-extended 10-aryl-pyrenoimidazoles having different substituents was realised via Ru(ii)-catalyzed oxidative annulation of 10-aryl-pyrenoimidazole with diphenylacetylene. The single crystal X-ray structure of trifluoromethyl and carboxylate substituted annulated-10-aryl-pyrenoimidazoles confirms the near coplanarity of the pyrene...

An efficient, one-pot approach has been described for the synthesis of 3,5-disubstituted isoxazoles from substituted aldoximes (mixture of E and Z) and alkynes, using alkyl nitrites under conventional heating conditions. The key nitrile oxide intermediates that are required for the synthesis of isoxazoles are formed by treatment of substituted aldo...

This study presents an efficient procedure for synthesis of 3,4,5-trisubstituted 3H-oxazol-2-ones and 3,4-disubstituted (Z)-oxazolidin-2-ones from substituted propargyl alcohols and aryl/alkyl isocyanates in the presence of LiOtBu, a base, and DMF, a solvent. This one-step, low-cost and gram scale synthesis exhibits superior atom economy, good to e...

The bond selectivity is caused by the traceless directing nature of the hydroxyl group of propargyl alcohol.

A Ru(II)-catalyzed C-H arylation approach has been developed utilizing beta-carboline alkaloids as the directing group. Selective formations of diarylated products from moderate to excellent yields were accomplished. Broad substrate scope with excellent functional group tolerance for C1-phenyl/thienyl/PAHs-beta-carbolines was demonstrated. X-ray cr...

Ruthenium-catalyzed simple, cascade and one-pot synthesis of cinnoline-fused diones has been carried out by the C-H activation of phthalazinones/pyridazinones accomplished by the unusual deoxygenation of propargyl alcohols. The bond selectivity is accredited to the traceless directing nature of the hydroxyl group of propargyl alcohol. A sequential...

In this study, a novel series of 5-piperazinethiazole 2,2-dimethylbutanoic acid and 5-piperidinethiazole 2,2-dimethylbutanoic acid derivatives have been synthesized. Structures of the newly synthesized compounds have been elucidated using 1H-NMR, 13C-NMR, high-resolution mass spectroscopy, and high-performance liquid chromatographic analysis. The s...

A series of dihydrogen complexes trans-[Ru(eta(2)-H-2){SC(SR)H}(dppe)(2)][X][BF4] (R = CH3, X = OTf; R = C6H5CH2, X = BPh4; R = H2C=CHCH2, X = BPh4; dppe = Ph2PCH2CH2PPh2) bearing sulfur-donor ligands has been synthesized by protonation of the (alkyl dithioformate)hydrido complexes trans[Ru(H){SC(SR)H}(dppe)(2)][X] by using HBF4 center dot Et2O. Co...

Elucidation of the fundamental metal−dioxygen chemistry occurring in heme−copper enzymes requires a deep understanding of the geometric and electronic structure contributions in the enzyme active site. To assess structural and functional elements impacting the direction of heme/copper/O2 reactions, we have embarked on a systematic study of the infl...

Heme-Cu/O2 adducts are of interest in the elucidation of the fundamental metal-O2 chemistry occurring in heme-Cu enzymes which effect reductive O-O cleavage of dioxygen to water. In this report, the chemistry of four heme-peroxo-copper [FeIII-(O22-)-CuII]+ complexes (1-4), varying in their ligand architecture, copper-ligand denticity, or both and t...

Double insertion of CS2 into two Ru-H bonds of [(dppm)2Ru(H)2] (dppm = Ph2PCH2PPh2) affords the methanedithiolate complex [(dppm)2Ru(eta2-S2CH2)]. The methanedithiolate moiety has been functionalized using 2 equiv of RX resulting in bis(alkylthio)methane derivatives [(dppm)2Ru(RSCH2SR)][X]2. The bis(alkylthio)methane complex loses the bis(alkylthio...

Double insertion of CS2 into two Ru-H bonds of [(dppm) 2Ru(H)2] (dppm = Ph2PCH2PPh 2) affords the methanedithiolate complex [(dppm)2Ru(η 2-S2CH2)]. The methanedithiolate moiety has been functionalized using 2 equiv of RX resulting in bis(alkylthio)methane derivatives [(dppm)2Ru(RSCH2SR)][X]2. The bis(alkylthio)methane complex loses the bis(alkylthi...

Insertion of CS(2) into the Ru-H bond of cis-[(dppe)(2)Ru(H)(2)] takes place to afford the hydride dithioformate complex trans-[(dppe)(2)Ru(H)(SC(S)H)]. The hydride dithioformate complex reacts under very mild conditions with MeX (X = OTf, I) to give the hydride methyldithioformate derivative trans-[(dppe)(2)Ru(H)(SC(SMe)H)][X]. Three different pat...

Addition of excess carbon disulfide to cis/trans-[(dppm)(2)Ru(H)(2)] results in the methanedithiolate complex [(dppm)(2)Ru(eta(2)-S(2)CH(2))] 4 via the intermediacy of cis-[(dppm)(2)Ru(H)(SC(S)H)] 2. The X-ray crystal structure of this species has been determined.