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A transition metal-catalyzed carbene insertion strategy has been developed to activate the inactivated sp2 C–H bond of medicinally important cis-stilbene acids. This approach enables the facile construction of α-pyrone and chromene-2-one skeletons on the olefinic bond of cis-stilbene acid with high atom economy, good yield, broad functional group tolerance and gram-scale synthetic feasibility. The strategy unveils the efficiency of acid functionalities as directing groups along with sulfoxonium and hypervalent iodonium ylide as carbene precursors. The constructed architectures were explored for their photophysical properties showing emission ranging from 500 to 600 nm, and the biological potential was examined through molecular docking analysis and percentage inhibition studies. Additionally, ESI-MS studies were also performed to identify the key intermediates, helping to sketch a probable mechanism. [ABSTRACT FROM AUTHOR]

A facile, metal- and additive-free C–C bond construction between imidazo[1,2-a]pyridines and coumarin-3-carboxylic acids through a decarboxylative Michael addition is reported to achieve an imidazo[1,2-a]pyridin-3-yl-chroman-2-one skeleton. In addition, heterocyclic polyaromatic dibenzoisochromenoimidazo[1,2-a]pyridin-6-ones of value for future medicinal chemistry can be obtained successfully by this procedure through a domino reaction involving Michael addition/decarboxylation/oxidation/C–H bond activation and annulation. [ABSTRACT FROM AUTHOR]

Retraction of 'Ruthenium(II) CNN Pincer Complexes as Efficient Catalysts in Oxidative Annulation of Aromatic Acids with Alkynes to Isocoumarins' by Periasamy Viswanathamurthi et al., New J. Chem., 2023, https://doi.org/10.1039/D3NJ03745B. [ABSTRACT FROM AUTHOR]

This paper reports the total synthesis of the serrulatane natural products (1R,4S,11S)-8,19-dihydroxyserrulat-14-ene (5.0% yield) and (1R,4S,11S)-8-hydroxyserrulat-14-en-19-oic acid (3.8% yield) via a silver-catalyzed 6-endo-dig benzannulation of an (-)-isopulegol derived ene-yne-ol in 17 steps. Analysis of the spectroscopic data as well as the specific rotations allowed for the confirmation of the stereochemistry at C1, C4 and C11 as (1R,4S,11S) for both natural products 8,19-dihydroxyserrulat-14-ene and 8-hydroxyserrulat-14-en-19-oic acid that were reported from the Australian desert plant, Eremophila neglecta. [ABSTRACT FROM AUTHOR]

This paper reports the development of a silver-catalyzed 6-endo-dig cyclisation of 5-alkoxy-1,5-enynes enabling benzannulation of (-)-menthone with construction of the calamenene skeleton as a single isomer. The total syntheses of (7S,10R)-2,15-dihydroxycalamenene (6 steps, 39.6%), (7S,10R)-2-hydroxy-15-calamenenal (7 steps, 10.7%) and (7S,10R)-2-Hydroxy-15-calamenenoic acid (9 steps, 33.6%) were achieved from (-)-menthone via a common intermediate. Analysis of the spectroscopic data as well as the specific rotations allowed for confirmation of the stereochemistry at C1 and C4 of the natural compounds isolated from Tarenna madagascariensis as (7R,10S)-2,15-dihydroxycalamenene and (7R,10S)-2-hydroxy-15-calamenenal, and the carboxylic acid isolated from Alpinia oxymitra was confirmed as (7S,10R)-2-hydroxy-15-calamenenoic acid. [ABSTRACT FROM AUTHOR]

The acetic acid promoted reaction of 3-hydroxy-3-(indol-3-yl)indolin-2-ones and mercapto-substituted β-enamino esters showed very interesting molecular diversity. The reaction in ethanol at room temperature in the presence of acetic acid resulted in two diastereoisomeric 3,3-disubstituted oxindoles in high yields. When the reaction was carried out in refluxing ethanol, the reaction with 3-hydroxy-3-(indol-3-yl)indolin-2-ones with N-alkyl groups gave polycyclic spirooxindoles in satisfactory yields. However, a similar reaction with 3-hydroxy-3-(indol-3-yl)indolin-2-ones with NH groups afforded functionalized dihydroindolo[3,2-c]phenothiazines with sequential ring-opening of oxindole. A plausible domino annulation mechanism was rationally proposed for the formation of different kinds of polycyclic compounds. [ABSTRACT FROM AUTHOR]

Herein, we report the rhodium-catalyzed domino arylation/cyclization reaction of unactivated internal alkynes to afford the optically active indenols in excellent yields (up to 92%) and extremely high enantioselectivities (up to 99% ee) in the presence of new amide substituted chiral diene ligands. Notably, a total of 21 new chiral diene ligands are synthesized, which are potential choices for other asymmetric reactions. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A Rh(III)‐catalyzed, transmetalation triggered C—H activation/annulation of 2‐biphenylboronic acids with diazo compounds from β‐keto esters or 1,3‐dicarboxylates has been developed, leading to the synthesis of two kinds of 9,10‐phenanthrenes. Notably, a rhodacyle was synthesized by treating the rhodium catalyst with stoichiometric amounts of 2‐biphenylboronic acids and pyridine, which was further verified to be active for the catalytic system. The reactions proceeded under redox‐neutral and air‐tolerant conditions to produce a series of all‐carbon six‐membered rings with high efficiency. [ABSTRACT FROM AUTHOR]

Bi(OTf)3‐catalyzed one‐pot tandem cyclocondensation of oxygenated arylacetic acids with salicyl alcohols provides 5‐oxadibenzo[a,d]cycloocten‐6‐ones in moderate to good yields under the refluxing MeNO2 conditions. A plausible mechanism is proposed and discussed here. In the overall reaction process, water was the only byproduct which was generated. Various metal triflates‐promoted reaction conditions are investigated for the one‐pot efficient (4+4) annulation. [ABSTRACT FROM AUTHOR]

In this article, bismuth triflate (Bi(OTf)3)‐controlled intermolecular multi‐component condensation of oxygenated arylacetic acids with electron‐withdrawing nitroarylaldehydes or electron‐donating trimethoxybenzene provide 1‐aryl isoquinolinones or o‐diaryl pyrimidines in acetonitrile at 60 °C. The uses of various metal triflates and reaction conditions are investigated in the one‐pot reaction. Only water is generated as the byproduct via (4C+1C+1N) and (2C+1N1C+1N1C) annulation routes. Plausible mechanisms have been proposed. [ABSTRACT FROM AUTHOR]

A convenient and novel 1,3‐dimethylbarbituric acid‐mediated methodology for constructing diverse benzimidazole‐fused heteroaromatics has been developed. This metal‐free cascade annulation of readily available 3‐formylchromones, 1,2‐diaminoarenes, and cyclic 1,3‐dicarbonyl compounds provides an alternative synthetic route in the green conditions. 1,3‐Dimethylbarbituric acid acts as a protecting group and accelerates intramolecular cyclization. This one‐pot protocol proceeds through cascade nucleophilic addition, ring‐opening, Michael‐type addition, intramolecular cyclization, elimination, and air oxidation reactions. [ABSTRACT FROM AUTHOR]

Rhodacarborane [(9-NMe3-7,8-C2B9H10)RhCl2]2 exhibited moderate catalytic activity in the reaction of annulation of arylcarboxylic acids with alkynes, giving naphthalenes as the major products. Effects of the substituent at the carborane ligand, as well as the nature of organic substrates, on the catalytic activity and selectivity of the reaction were estimated. In particular, it was revealed that a replacement of the NMe3 group at the carborane ligand with the SMe2 one leads to a significantly decreased activity of the catalyst. [ABSTRACT FROM AUTHOR]

A new application of hydroxylamine‐O‐sulfonic acid (HOSA) has been discovered whereby aromatic ketones react with HOSA and alkynes to form isoquinolines in the presence of a RhIII catalyst. This C–H/N–O annulation methodology gives excellent yields even without any silver additive, acid/base or metal oxidant. This is the first report wherein a directing group is simultaneously forming in situ, acting as acid additive, and also as an internal oxidant. [ABSTRACT FROM AUTHOR]

A new electrochemical decarboxylative [4+2] annulation of arylglyoxylic acids with internal alkynes involving C–H functionalization by means of a cooperative anode and ruthenium catalysis is presented. This reaction represents a mechanistically novel strategy as an ideal supplement to the decarboxylative [4+2] annulation methodology by employing an electrooxidative process to avoid the use of an additional external oxidizing reagent and utilizing H2O as the carboxyl oxygen atom source to be engaged in the synthesis of 1H-isochromen-1-ones. [ABSTRACT FROM AUTHOR]