α-Aroylidineketene dithioacetal chemistry: CuI catalyzed synthesis of 2-styryl benzimidazoles enroute to regioselective hydrothiolation

Dhanalakshmi, Pandi; Shanmugam, Sivakumar

doi:10.1016/j.tet.2015.06.008

Cited by 12 publications

(9 citation statements)

References 40 publications

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“…The identity of the leaving portion (Scheme ) S,S‐dimethyl carbonodithioate (IV) and urea (V) was not found in the reaction mixture which could be left through workup or volatile nature of the substance. To support the reaction mechanism and to confirm the removal of methanethiol group,, a model reaction was performed by involving 3,3‐bis(benzylthio)‐1‐(4‐bromophenyl)prop‐2‐en‐1‐one 6 (prepared separately) with 2.1 equivalent of CAN under optimized reaction conditions. The crude reaction mixture (after workup with water) was analyzed by GC‐MS and confirmed the formation of corresponding 4‐bromo‐benzoic acid 2a along with phenylmethanethiol 7 as a eliminated product (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

CAN‐Supported Chemoselective Oxidative Conversion of α‐Aroylketene‐(S,S)‐acetals to Aryl Carboxylic Acids

Babu

Shanmugam

2017

ChemistrySelect

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Chemoselective oxidative conversion of α‐aroylketene‐(S,S)‐acetals to aryl carboxylic acids in the presence of Ceric ammonium nitrate (CAN) has been achieved under mild reaction condition. The internal nitrate ligand present in CAN acted as an oxidant and favored selective conversion of α‐aroylketene‐(S,S)‐acetals to aryl acid. α‐Hydrogen is necessary to initiate radical by Ce(IV) via α‐C‐H bond cleavage. The current synthetic strategy is compatible for various aromatic groups under mild conditions. The method is appropriate for electron rich as well as deficient α,β‐unsaturated system.

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Section: Resultsmentioning

confidence: 99%

CAN‐Supported Chemoselective Oxidative Conversion of α‐Aroylketene‐(S,S)‐acetals to Aryl Carboxylic Acids

Babu

Shanmugam

2017

ChemistrySelect

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“…The synthesis of 2‐styryl benzimidazoles from condensation of 4 with various α ‐ aroylidineketene dithioacetals ( 123 ) was reported by Dhanalakshmi et al . They selectively synthesized 2‐styryl benzimidazoles ( 124 ) over the regioselective hydrothiolation product under acetic acid and CuI (10 mol %) catalyst conditions (Scheme ) .…”

Section: Other Important Coupling Reactionsmentioning

confidence: 99%

“…In another green approach involving Er (OTf) 3 catalyst, by Cano et al, 1,2-disubstituted benzimidazole derivatives (109) were selectively synthesized in 78-98% yield. The reaction between o-phenylenediamine and aldehydes (108) under reflux conditions at 80°C for 2-5 min gave 1,2-disubstituted product (109), while a similar reaction in water at low temperature of 1-2°C in 2-5 min gave 2-substituted product (110) only (Scheme 39) [105]. The catalyst was found to be superior over Yb and Ce triflates with respect to time and yield of reaction.…”

Section: Aldehydesmentioning

confidence: 99%

Recent Trends in the Synthesis of Benzimidazoles From o‐Phenylenediamine via Nanoparticles and Green Strategies Using Transition Metal Catalysts

Singhal

Khanna

Panda

et al. 2019

Journal of Heterocyclic Chem

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Benzimidazole is a heterocyclic moiety of immense importance as it acts as a primary “biolinker” in diverse synthetic routes to obtain bioactive compounds. Substituted benzimidazoles are known to possess a varied range of pharmacological applications, namely, anti‐cancer, anti‐diabetic, anti‐inflammatory, and antiviral like anti‐HIV and anti‐fungal. A number of reviews covering the important aspects of benzimidazoles such as pharmacological activities, SAR studies, and well‐known methods of synthesis have appeared in the literature. However, green synthetic methods particularly using transition metal (TM) catalysts and their nanoparticles, although being more viable and extensively applied by researchers in the present scenario, have not been exclusively and expansively reviewed. Besides this, the vital precursors required for knitting the skeleton of benzimidazole are mainly o‐aryldiamines. The conventional synthesis generally involved the condensation of these diamines with carbonyl/carboxylic acid derivatives either via high temperature heating or via adding strong acids, mostly resulting in poor yields or mixtures. However, recent trends are replacing these conditions by mild and green conditions through TM catalysts. Therefore, the current review emphasizes on the recent trends adopted in the synthesis of benzimidazoles using condensation reaction of o‐phenylenediamines and various aldehydes/ester/amide/alcohols with TM in a catalytic role in nanoform and under environmentally benign green conditions.

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“…In the case of 2a, in the CSD there were three similar structures, i.e. refcodes HESBIR (Yan et al, 2006), KUDYAL01 (Dhanalakshmi & Shanmugam, 2015) and QULMAN (Dhanalakshmi & Shanmugam, 2015) (see Scheme 2). The molecule of HESBIR is planar, like the molecules of 2a and 2b.…”

Section: Moleculementioning

confidence: 99%

The structures of benzimidazole derivatives and their potential as tuberculostatics

et al. 2018

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Tuberculosis still remains a very important problem, especially its multidrug resistant varieties (MDR-TB). Among the potential tuberculostatics, there are two benzimidazole derivatives, namely 5,6-dimethyl-2-phenylethylbenzo[d]imidazole (1) and (E)-5,6-dimethyl-2-styryl-1H-benzo[d]imidazole (2) which showed significant tuberculostatic activities, better than those of Pyrazinamide and Isoniazyd. Also, the cytotoxicity of 1 appeared promising. The compounds were studied (with the use of X-ray diffraction) in the form of the hemihydrate of 1, C17H18N2·0.5H2O (1a), the methanol hemisolvate of 2, C17H16N2·0.5CH3OH (2a), and the acid oxalate salt of 2, namely (E)-5,6-dimethyl-2-styryl-1H-benzo[d]imidazolium hydrogen oxalate, C17H17N2 +·C2HO4 − (2b). All three structures reveal a similar extended conformation, despite the flexible linker between the two aromatic systems and the different types of strong intermolecular hydrogen bonds. The molecules of 2a are practically planar due to the double bond in the linker, which enables conjugation along the whole molecule, while the molecules of 1a exhibit the possibility of parallel orientations of their aromatic systems, despite the aliphatic (ethyl) linker.

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α-Aroylidineketene dithioacetal chemistry: CuI catalyzed synthesis of 2-styryl benzimidazoles enroute to regioselective hydrothiolation

Cited by 12 publications

References 40 publications

CAN‐Supported Chemoselective Oxidative Conversion of α‐Aroylketene‐(S,S)‐acetals to Aryl Carboxylic Acids

CAN‐Supported Chemoselective Oxidative Conversion of α‐Aroylketene‐(S,S)‐acetals to Aryl Carboxylic Acids

Recent Trends in the Synthesis of Benzimidazoles From o‐Phenylenediamine via Nanoparticles and Green Strategies Using Transition Metal Catalysts

The structures of benzimidazole derivatives and their potential as tuberculostatics

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