Pd(II)-Catalyzed oxidative alkenylation of 4-hydroxycoumarin with maleimide via a C-H bond activation strategy.

A Pd(ii)-catalyzed oxidative alkenylation of 4-hydroxycoumarins with maleimides for the synthesis of 4-hydroxy-3-maleimidecoumarins has been described. This methodology proceeds via C-H activation and C(sp2)-C(sp2) bond formation providing a series of alkenylated Heck-type products.

Recent advances in the synthesis of organophosphorus compounds via Kobayashi's aryne precursor: a review.

Organophosphorus compounds are important structural motifs that unveil enormous applications, particularly in the field of organic synthesis, agriculture, materials science and medicinal chemistry. Additionally, ortho-substituted arylphosphorus compounds have played an important role in homogeneous catalysis. Though there are several synthetic pathways for the synthesis of organophosphorus compounds, this review is particularly focused on aryne-based methodologies reported in the literature to date.

Three-Component Coupling Reactions of Aryne, DMSO, and Activated Alkyne: Stereoselective Synthesis of 2-[( o-Methylthio)aryloxy]-Substituted Dialkyl Maleates.

A transition-metal-free coupling reaction of aryne, DMSO, and activated alkyne for the synthesis of 2-[( o-methylthio)aryloxy]-substituted dialkyl maleates is reported. This cascade process is associated with several bond cleavage as well as bond formation reactions in one pot. One of our synthesized maleates has been unambiguously established by single-crystal XRD studies. This methodology allows preparation of trisubstituted vinyl ethers with excellent stereospecificity.

Aryne insertion into the P[double bond, length as m-dash]O bond: one-pot synthesis of quaternary phosphonium triflates.

A novel transition-metal free synthetic strategy has been developed for the direct synthesis of quaternary phosphonium triflates via insertion of aryne into phosphine oxide. This methodology provides good yields of quaternary phosphonium salts and one of the synthesized phosphonium salts has been unambiguously established by single crystal XRD study. Preliminary mechanistic studies suggest that the reaction proceeds via a sequential [2 + 2] cycloaddition followed by the o-arylation and protonation pathway.

Correction: A metal-free cascade reaction of ß-halo-α,ß-unsaturated aldehydes and 1,4-dithiane-2,5-diols: synthesis of polycyclic 2-formylthiophenes.

Correction for 'A metal-free cascade reaction of ß-halo-α,ß-unsaturated aldehydes and 1,4-dithiane-2,5-diols: synthesis of polycyclic 2-formylthiophenes' by Limi Goswami et al., Org. Biomol. Chem., 2017, 15, 6470-6473.

2,3-Diaroyl benzofurans from arynes: sequential synthesis of 2-aroyl benzofurans followed by benzoylation.

A cascade synthetic strategy for the direct synthesis of 2-aroyl benzofurans from aryne precursors has been developed. This reaction proceeds via C-O and C-C bond cleavage as well as C-O and C-C bond formation in a single reaction vessel. The methodology provides good yields of 2-aroyl benzofurans and tolerates a variety of functional groups. The synthesized 2-aroyl benzofurans were further benzoylated at 3-positions and one of the synthesized 2,3-diaroyl benzofuran structures was confirmed unambiguously by X-ray crystallography.

Efflux pump inhibition by 11H-pyrido[2,1-b]quinazolin-11-one analogues in mycobacteria.

Mycobacterium tuberculosis infection causes 1.8 million deaths worldwide, of which half a million has been diagnosed with resistant tuberculosis (TB). Emergence of multi drug resistant and extensive drug resistant strains has made all the existing anti-TB therapy futile. The major involvement of efflux pump in drug resistance has made it a direct approach for therapeutic exploration against resistant M. tuberculosis. This study demarcates the role of 11H-pyrido[2,1-b]quinazolin-11-one (quinazolinone) analogues as efflux pump inhibitor in Mycobacterium smegmatis. Sixteen quinazolinone analogues were synthesized by treating 2-aminopyridine and 2-fluorobenzonitrile with KtOBu. Analogues were tested, and 3a, 3b, 3c, 3g, 3j, 3l, 3m, and 3p were found to modulate EtBr MIC by >4 whereas 3a, 3g, 3i and 3o showed >4 modulation on norfloxacin MIC. 3l and 3o in addition to their very low toxicity they showed high EtBr and norfloxacin accumulation respectively. Time kill curve showed effective log reduction in colony forming unit in presence of these analogues, thus confirming their role as efflux pump inhibitor. Through docking and alignment studies, we have also shown that the LfrA amino acid residues that the analogues are interacting with are present in Rv2333c and Rv2846c of M. tuberculosis. This study have shown for the first time the possibility of developing the 11H-pyrido[2,1-b]quinazolin-11-one analogues as efflux pump inhibitors for M. smegmatis and hence unbolts the scope to advance this study against resistant M. tuberculosis as well.

A metal-free cascade reaction of ß-halo-α,ß-unsaturated aldehydes and 1,4-dithiane-2,5-diols: synthesis of polycyclic 2-formylthiophenes.

A metal-free cascade reaction strategy has been developed for the synthesis of novel polycyclic 2-formylthiophenes from ß-halo-α,ß-unsaturated aldehydes and 1,4-dithiane-2,5-diols. A recyclable polymer supported organic base was used to perform the reaction process. This synthetic protocol was applied to synthesize several novel polycyclic thiophenes including steroidal D-ring annelated thiophene. Our synthetic strategy provides a high yield of thiophenes, avoids a tedious work-up procedure and minimizes the formation of waste.

Palladium(II)-Catalyzed C-H Bond Activation/C-C and C-O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans.

A palladium catalyzed cascade reaction of 4-hydroxycoumarins and in situ generated arynes has been developed for the direct synthesis of coumestans. This cascade strategy proceeds via C-H bond activation/C-O and C-C bond formations in a single reaction vessel. This methodology affords moderate to good yields of coumestans and is tolerant of a variety of functional groups including halide. The methodology was applied to the synthesis of natural product flemichapparin C.

DMF Dimethyl Acetal as Carbon Source for α-Methylation of Ketones: A Hydrogenation-Hydrogenolysis Strategy of Enaminones.

A novel heterogeneous catalytic hydrogenation-hydrogenolysis strategy has been developed for the α-methylation of ketones via enaminones using DMF dimethyl acetal as carbon source. This strategy provides a very convenient route to α-methylated ketones using a variety of ketones without any base or oxidant.

Mitochondria-targeted biotin-conjugated BODIPYs for cancer imaging and therapy.

Two BODIPY-biotin conjugates KDP1 and KDP2 are designed and synthesized for targeted PDT applications. Both have good absorption with a high molar absorption coefficient and decent singlet oxygen generation quantum yields. The photosensitizers KDP1 and KDP2 were found to be localized in the mitochondria with excellent photocytotoxicity of up to 18.7 nM in MDA-MB-231 breast cancer cells. The cell death predominantly proceeded through the apoptosis pathway via ROS production.

Pd(II)-Catalyzed Oxidative Annulation via Double C-H Activations: Synthesis and Photophysical Properties of Bis-Coumarins.

A Pd(II)-catalyzed oxidative annulation reaction of 4-hydroxycoumarin and arylcarboxylic acid via double C-H bond activations has been accomplished for the synthesis of bis-coumarins. This synthetic strategy provides a wide range of structurally diversified bis-coumarins in moderate to good yields with a variety of functional group compatibility. Moreover, photophysical properties of synthesized bis-coumarins have been evaluated, which reveals their interesting fluorescent properties.

Coumarin to Isocoumarin: One-Pot Synthesis of 3-Substituted Isocoumarins from 4-Hydroxycoumarins and Benzyne Precursors.

A novel transition-metal-free direct synthesis of 3-substituted isocoumarin from 4-hydroxycoumarin and a benzyne precursor is developed. This synthetic strategy proceeds via C-O and C-C bond cleavage as well as C-O and C-C bond formations in a single reaction vessel by simple treatment with CsF in the absence of catalyst. This methodology affords moderate to good yields of 3-substituted isocoumarins and is tolerant of a variety of functional groups including halide.

Facile synthesis of 2D CuO nanoleaves for the catalytic elimination of hazardous and toxic dyes from aqueous phase: a sustainable approach.

This article reports for the first time a facile, green synthesis of 2D CuO nanoleaves (NLs) using the amino acid, namely aspartic acid, and NaOH by a microwave heating method. The amino acid acts as a complexing/capping agent in the synthesis of CuO NLs. This method resulted in the formation of self-assembled 2D CuO NLs with an average length and width of ~300-400 and ~50-82 nm, respectively. The as-synthesized 2D CuO NLs were built up from the primary CuO nanoparticles by oriented attachment growth mechanism. The CuO NLs were characterized by an X-ray diffraction (XRD) method, transmission electron microscopy (TEM), selected-area electron diffraction (SAED) pattern, and Fourier transform infrared spectroscopy (FT-IR). The optical properties were investigated using UV-visible spectroscopy. For the first time, rose bengal and eosin Y dyes were degraded photochemically by solar irradiation using CuO NLs as a photocatalyst. The synthesized CuO NLs act as an efficient photocatalyst in the degradation of rose bengal and eosin Y dye under direct sunlight. The degradation of both the dyes, namely rose bengal and eosin Y, took place within 120 and 45 min, respectively, using CuO NLs as a photocatalyst, whereas commercial CuO, SnO2 quantum dots (QDs), and commercial SnO2 took more than 120 and 45 min for the degradation of rose bengal and eosin Y, respectively. The synthesized CuO NLs showed a superior photocatalytic activity as compared to that of commercial CuO, SnO2 QDs, and commercial SnO2. The reusability of the CuO NLs as a photocatalyst in the degradation of dyes was investigated, and it was evident that the catalytic efficiency decreases to a small extent (5-6 %) after the fifth cycle of operation.