Distinct Substituents Research Articles

Enantioselective Construction of Anthracenylidene-Based Axial Chirality by Asymmetric Heck Reaction.

Anthracenylidene is an intriguing structural unit with potential in various fields. The study presents a novel approach to introducing axial chirality into this all-carbon core skeleton through a remotely controlled desymmetrization strategy. A palladium-catalyzed enantioselective Heck arylation of exocyclic double bond of anthracene with two distinct substituents at the C10 position is harnessed to realize such a transformation. The judicious identification of the P-centrally chiral ligand is pivotal to ensure the competitive competence in reactivity and stereocontrol when the heteroatom handle is absent from the anthracenylidene skeleton. Both C10 mono- and disubstituted substrates were compatible for the established catalytic system, and structurally diverse anthracenylidene-based frameworks were forged with good-to-high enantiocontrol. The subsequent derivatization of the obtained products yielded a valuable array of centrally and axially chiral molecules, thus emphasizing the practicality of this chemistry. DFT calculations shed light on the catalytic mechanism and provided insights into the origin of the experimentally observed enantioselectivity for this reaction.

Synthesis of unsymmetrical trisubstituted 1,3,5-triazines compounds

A novel approach has been reported for the synthesis of 1,3,5-triazine with three distinct substituents. The synthesis of the pivotal intermediate 2-chloro-4-R1-6-R2-1,3,5-triazine plays a critical role in achieving 1,3,5-triazine with three different substituents. This article presents two innovative one-pot processes for synthesizing various substituted 2-chloro-4-R1-6-R2-1,3,5-triazines. In the first method, substituted benzoyl isocyanates were initially synthesized by reacting different amides with oxalyl chloride. Subsequently, 21 target products of 2-chloro-4-R1-6-R2-1,3,5-triazines compounds were obtained through the cyclization of substituted benzoyl isocyanates with benzamidine hydrochloride at relatively low temperatures and a one-pot chlorination reaction. The second method involved the synthesis of the same 21 compounds of 2-chloro-4-R1-6-R2-1,3,5-triazines by reacting benzamide with oxalyl chloride followed by cyclization with different amidine hydrochloride and then a one-pot chlorination reaction. Finally, a total of 35 different unsymmetrical trisubstituted 1,3,5-triazine compounds were successfully synthesized using various reactions.

Performance of 4,5-diphenyl-1H-imidazole derived highly selective 'Turn-Off' fluorescent chemosensor for iron(III) ions detection and biological applications.

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2, were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier-transform infrared (FTIR), proton (1 H)- and carbon-13 (13 C)-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X-ray diffraction analysis. Chemosensor 1 is composed of a 1H-imidazole core with specific substituents, including a 4-(2-(4,5-c-2-yl)naphthalene-3-yloxy)butoxy)naphthalene-1-yl moiety. However, chemosensor 2 features a 1H-imidazole core with distinct substituents, such as 4-methyl-2-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)butoxy)-5-methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe3+ ) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe3+ and 2 + Fe3+ complexes were determined using the modified Benesi-Hildebrand equation, yielding values of approximately 2.2 × 103 and 1.3 × 104 M-1 , respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe3+ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe3+ , the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe3+ in live cells was demonstrated, with negligible observed cell toxicity.

Boosting organic solar cell efficiency via tailored end-group modifications of novel non-fused ring electron acceptors.

In this study, we designed and synthesized two NFREAs, 2BTh-3F and 2BTh-CN, incorporating distinct substituents to modulate their electron-withdrawing properties. We meticulously explore the distinct impacts of these substituents on NFREA performance. Our investigation revealed that the introduction of 3,5-difluoro-4-cyanophenyl in 2BTh-CN significantly enhanced electron withdrawal and intramolecular charge transfer, leading to a red-shifted absorption spectrum and optimized energy levels. Consequently, organic solar cells (OSCs) utilizing 2BTh-CN demonstrate a notable power conversion efficiency (PCE) of 15.07%, outperforming those employing 2BTh-3F (PCE of 9.34%). Moreover, by incorporating 2BTh-CN into the D18:2BTh-C2 system as a third component, we achieve a PCE exceeding 17% in a high-performing ternary OSC, ranking among the most efficient NFREA-based OSCs reported to date. Overall, our study underscores the potential of deliberate design and optimization of non-fused ring acceptor molecular structures to attain outstanding photovoltaic performance.

Influence of substituents on the water oxidation performance for copper–bipyridine catalysts

Since it was first reported in 2012, copper-based molecular catalysts for water oxidation have gained significant attention. While investigations have endeavored to elucidate additional copper molecular catalysts for water oxidation and enhance their catalytic activities, few have systematically explored substituents' impact on their water oxidation performance. In this work, a series of copper-bipyridine catalysts, (2,2′-bipyridine)Cu(OH)2 derivatives with various substituents were synthesized by simply mixing the copper salts with 4,4′-R-2,2′-bipyridine ligands, where R represents seven distinct substituents. The UV–vis and FTIR spectra confirm the successful synthesis of the catalysts. However, only four of them are stable under the experimental conditions. The electrochemical studies show that their water oxidation potential follows the order of Cu-H < Cu-CH3 < Cu–OCH3 < Cu-CH2OH, indicating their water oxidation ability. Computation calculation indicates a linear relationship between the turnover frequency and the HOMO-LUMO energy gap. This work uncovers the influence of substituents on the catalytic properties of copper-bipyridine catalysts, offering valuable insights into the rational design of copper-based catalysts.

Enantioselective Oxidative Enolate Coupling of Oxindoles Catalyzed by Chiral Guanidinium Hypoiodite

Hypoiodite is an environmentally friendly oxidant that has been developed to drive a variety of bond-forming reactions. Recently, asymmetric oxidative bond-forming reactions using hypoiodite in the presence of chiral onium organocatalysts have been used to synthesize carbon–heteroatom bonds, but asymmetric carbon–carbon bond-forming reactions have not been reported. Herein, we present an oxidative enolate coupling reaction of oxindoles to provide optically active oxindole dimers bearing consecutive all-carbon quaternary stereogenic centers, using a chiral guanidinium hypoiodite catalyst. This reaction affords the corresponding homocoupling products with high enantioselectivity. We also describe oxidative enolate cross-coupling reactions of two oxindoles bearing electronically distinct substituents.

Mode of action of p-quinone derivatives with trypanocidal activity studied by experimental and in silico models

Quinones are attractive pharmacological scaffolds for developing new agents for the treatment of different transmissible and non-transmissible human diseases due to their capacity to alter the cell redox homeostasis.The bioactivity and potential mode of action of 19 p-quinone derivatives fused to different aromatic rings (carbo or heterocycles) and harboring distinct substituents were investigated in infective Trypanosoma brucei brucei. All the compounds, except for a furanequinone (EC50=38 μM), proved to be similarly or even more potent (EC50 = 0.5–5.5 μM) than the clinical drug nifurtimox (EC50 = 5.3 μM). Three furanequinones and one thiazolequinone displayed a higher selectivity than nifurtimox. Two of these selective hits resulted potent inhibitors of T. cruzi proliferation (EC50=0.8–1.1 μM) but proved inactive against Leishmania infantum amastigotes.Most of the p-quinones induced a rapid and marked intracellular oxidation in T. b. brucei. DFT calculations on the oxidized quinone (Q), semiquinone (Q•-) and hydroquinone (QH2) suggest that all quinones have negative ΔG for the formation of Q•-. Qualitative and quantitative structure-activity relationship analyses in two or three dimensions of different electronic and biophysical descriptors of quinones and their corresponding bioactivities (killing potency and oxidative capacity) were performed.Charge distribution over the quinone ring carbons of Q and Q.- and the frontier orbitals energies of SUMO (Q.-) and LUMO (Q) correlate with their oxidative and trypanocidal activity. QSAR analysis also highlighted that both bromine substitution in the p-quinone ring and a bulky phenyl group attached to the furane and thiazole rings (which generates a negative charge due to the π electron system polarized by the nearby heteroatoms) are favorable for activity.By combining experimental and in silico procedures, this study disclosed important information about p-quinones that may help to rationally tune their electronic properties and biological activities.

Steric evaluation of Pyox ligands for asymmetric intermolecular Heck-Matsuda reaction

A structure selectivity relationship was established by systematically increasing the steric of the ligands from phenyl substituent to mesityl on the pyridine ring of Pyox and isopropyl to tert-butyl group on the oxazoline ring. The ligand 6MesPyoxsBu bearing a sterically demanding mesityl group at position 6 of the pyridine ring showed optimum catalytic activity for Heck-Matsuda desymmetrization reaction of non-activated cyclopentene using Pd(tfa)2 as the catalyst. A wide range of arenediazonium salts bearing electronically distinct substituents was evaluated in Heck-Matsuda coupling, which resulted in good to excellent isolated yields (67–92 %), excellent enantio- and diastereoselectivity (up to 96 % ee, >20:1 dr).

Synthesis, formulation, evaluation of insecticidal activity of chromen derivatives against cotton leafworm Spodoptera littoralis (Lepidoptera: Noctuidae) and their mode of action under laboratory conditions

The toxicity of benzothiazole derivatives obtained from 2-cyanomethyl benzothiazole against cotton leafworm Spodoptera littoralis 2nd and 4th instar larvae has been documented. The main objective of this research was to formulate two previously reported chromen derivatives and test their biological activity against cotton leafworm S. littoralis 2nd and 4th instar larvae under laboratory conditions. According to the standard method, two chromen derivatives with two distinct substituents (salicylaldehyde and 2-hydroxy-1-naphthaldehyde) were synthesized. Their physical and chemical properties were evaluated, and both were formulated as 10 and 9.5 percent dustable powder formulations. Both formulae were then evaluated in the laboratory on cotton leafworm S. littoralis 2nd and 4th instar larvae for mortality and developmental effect percentage. Formulation (F2) was more efficient than formulation (F3) in both cases and for both stages. Furthermore, when comparing the developmental effects on the 2nd and 4th instar larvae, the 4th instar larvae demonstrated marked tolerance. Both stages were unable to complete their life cycle. Histopathological analysis of samples from the affected stages was performed to assess the mode of action of these formulations on 4th instar larvae at their LC50 values. Experimental data showed that Formulation (F3) resulted in epidermal cells separated from the cuticular layer, necrosis, ruptured columnar cells with pyknotic nuclei, disrupted basement membrane, and weak epicuticle necrosis and separation. In comparison, formulation (F2) revealed a midgut with vacuoles, damaged columnar, muscle cell necrosis, and a ruined peritrophic matrix. Thus, the cotton leafworm S. littoralis could be combated with the newly prepared formulations (F2) and (F3).

Exploring the Reactivity of B-Connected Carboranylphosphines in Frustrated Lewis Pair Chemistry: A New Frame for a Classic System.

The primary phosphines MesPH2 and tBuPH2 react with 9‐iodo‐m‐carborane yielding B9‐connected secondary carboranylphosphines 1,7‐H2C2B10H9‐9‐PHR (R=2,4,6‐Me3C6H2 (Mes; 1 a), tBu (1 b)). Addition of tris(pentafluorophenyl)borane (BCF) to 1 a, b resulted in the zwitterionic compounds 1,7‐H2C2B10H9‐9‐PHR(p‐C6F4)BF(C6F5)2 (2 a, b) through nucleophilic para substitution of a C6F5 ring followed by fluoride transfer to boron. Further reaction with Me2SiHCl prompted a H−F exchange yielding the zwitterionic compounds 1,7‐H2C2B10H9‐9‐PHR(p‐C6F4)BH(C6F5)2 (3 a, b). The reaction of 2 a, b with one equivalent of R'MgBr (R’=Me, Ph) gave the extremely water‐sensitive frustrated Lewis pairs 1,7‐H2C2B10H9‐9‐PR(p‐C6F4)B(C6F5)2 (4 a, b). Hydrolysis of the B−C6F4 bond in 4 a, b gave the first tertiary B‐carboranyl phosphines with three distinct substituents, 1,7‐H2C2B10H9‐9‐PR(p‐C6F4H) (5 a, b). Deprotonation of the zwitterionic compounds 2 a, b and 3 a, b formed anionic phosphines [1,7‐H2C2B10H9‐9‐PR(p‐C6F4)BX(C6F5)2]−[DMSOH]+ (R=Mes, X=F (6 a), R=tBu, X=F (6 b); R=Mes, X=H (7 a), R=tBu, X=H (7 b)). Reaction of 2 a, b with an excess of Grignard reagents resulted in the addition of R’ at the boron atom yielding the anions [1,7‐H2C2B10H9‐9‐PR(p‐C6F4)BR’(C6F5)2]− (R=Mes, R’=Me (8 a), R=tBu, R’=Me (8 b); R=Mes, R’=Ph (9 a), R=tBu, R’=Ph (9 b)) with [MgBr(Et2O) n ]+ as counterion. The ability of the zwitterionic compounds 3 a, b to hydrogenate imines as well as the Brønsted acidity of 3 a were investigated.

Imidodiphosphoric Acids Catalysed Asymmetric Functionaliza‐tion with Thiols: Access to Oxindole Derived ɑ‐Chiral Thioethers

AbstractChiral imidodiphosphoric acid‐catalysed asymmetric functionalization of 3‐hydroxy bisindoles was established. Sulfur‐containing groups could be successfully introduced into isatin frameworks using commercially available thiols. The transformation was compatible with substrates bearing distinct substituents, both aromatic and aliphatic thiols were amenable to afford the desired products. A total of 41 reactions furnished various chiral 3‐thiooxindoles in 23%–99% yield, with 72%–99% enantioselectivity.magnified image

Total syntheses and antiproliferative activities of prenostodione and its analogues.

A high-yielding total synthesis of the indole alkaloid prenostodione was completed in 4 steps and 44% overall yield from 1H-indole-3-carboxylic acid. The expedient syntheses of prenostodiones containing distinct substituents at the para position of the phenyl frame underscored the scope of this methodology. The cytotoxic activities of the tert-butyl esters of prenostodione analogues were tested using six tumor cell lines. Preliminary structure-activity studies revealed the importance of the identity of the aromatic substituent at the C-4 position for cytotoxic activity. The IC50 values of these compounds were found to compare satisfactorily with those of the commercially available drugs etoposide and cisplatin. Furthermore, the compounds with, respectively, -OMe (14d) and -NO2 (14f) groups at C-4 were more selective than these control compounds in PC-3, K-562, and MCF-7 cells. Also, computational studies were carried out to determine the ADMET profiles and passive membrane permeabilities of the compounds. The results suggested the promise of 14d and 14f as hit compounds for the development of new anticancer agents.

Recovery of acetophenones from acetophenone hydrazones using ultraviolet radiation and chlorinated solvents. An experimental and theoretical investigation

Abstract We report the complete recover of ketones from their corresponding hydrazones under UV-radiation. A series of - CH 3 , –H and - NO 2 p-substituted acetophenone hydrazones was prepared and subjected to irradiation experiments using UV light (254 nm) in CCl 4 , CHCl 3 and CH 2 Cl 2 . The process was monitored by UV-VIS and 1D/2D NMR spectra. The recovery time was found to be profoundly affected by the halogenation degree of the solvent with the shortest times observed for CCl 4 . Small fluctuations in recovery times were observed for the distinct substituents, but no clear trend could be stablished. In CCl 4 , the recovery time is essentially independent of the substituent. Additionally, NMR spectra showed that the process goes to completion. Density functional theory (DFT) calculations showed that the recovery time is closely related to the bond dissociation enthalpy for the C–Cl bond. Based on these observations, a mechanism was proposed and analyzed by DFT calculations. Al the reactions involved presented activation energies much bellow the energy required to break the C–Cl bond. Therefore, the C–Cl bond breaking is identified as the rate determining step.

Pressure-induced remarkable luminescence-changing behaviours of 9, 10-distyrylanthracene and its derivatives with distinct substituents

Piezochromic luminescence behaviours of 9, 10-distyrylanthracene (DSA) derivatives with different substituents based on their single crystal structures were investigated under hydrostatic pressure via a diamond anvil cell (DAC), compared with the anisotropic force produced from grinding. Upon grinding, three single crystals show identifiable blue-shifts in fluorescent spectra because of the disturbance for ordered crystal structure to amorphous state, but nearly sightless color changes. The high-pressure fluorescent experiments applied by DAC reveal three DSA crystals all show large red-shifts. High pressure absorption spectra display that a new charge transfer state appears when -CH3 or -2CN is introduced to DSA and all of them show obvious red-shifts. Once the pressure was relieved gradually to the ambient pressure, the fluorescence and absorption spectra both entirely recovered, indicating this geometric change is reversible in a certain pressure region, which is further confirmed by Raman spectra. The relationships between molecular structures and spectroscopic behaviours were further discussed by their single crystal data. This work provides deep insights into the relationship between molecular structure and photo-physical properties of practical mechanochromic luminescent materials, and is significant in the potential applications of pressure transducers.

Versatile Synthetic Route for Β-Functionalized Chlorins and Porphyrins By Varying the Size of Michael Donors: Syntheses, Photophysical and Electrochemical Redox Properties

The β-functionalization of meso-tetraphenylporphyrins is of great interest since the electronic properties of the macrocycle can be altered by small changes in the substituents.1 β-nitroporphyrins exhibited interesting catalytic, photophysical and nonlinear optical properties2 and are important precursor for further functionalization to attain a wide variety of chlorins.3 The electronic properties of chlorins allow to capture of more light of longer wavelength region for light harvesting, PDT, and singlet oxygen generation.4 To better understand the effects of distinct substituents, Herein we have developed rational methods for the synthesis of stable tailorable chlorins and porhyrins, wherein each chlorin bears vicinal groups at the reduced pyrrole ring whereas each porphyrin bears mono-substituent at β-position. The size dependent approach has been applied for the fine tuning of product formation from porphyrins to chlorins. The regioselectivity displayed in these reactions highlight the importance of method that facilitates the direct and predictable introduction of cyclic Michael donors at β-pyrrolic position.5 A hypsochromic shift (~ 8-10 nm) in the longest wavelength (Qy) absorption band was observed upon substitution of electron withdrawing groups (IND and BENAC) at 2,3-postion of meso-tetraphenylchlorin. Single crystal X-ray diffraction analysis revealed the quasi planar to moderate nonplanar conformation of chlorins due to trans orientation of β-substituents, whereas porphyrin exhibited higher mean plane deviation from 24-atom core (Δ24) as compared to chlorins. Electronic nature of synthesized macrocyclic skeletons was authenticated by electrochemical and protonation/deprotonation studies which revealed that the porphyrin core was more susceptible towards protonation, whereas deprotonation of chlorin macrocycle was more facile. References : (a) Senge, M. O.; Medforth, C. J.; Sparks, L. D.; Shelnutt, J. A.; Smith, K. M. Inorg. Chem. 1993, 32, 1716-1723 (b) Kumar, R.; Sankar, M. Inorg. Chem. 2014, 53, 12706-12719; (c) Grover, N.; Sankar, M; Song, Y.; Kadish, K.M. Inorg. Chem. 2016, 55, 584-597.(a) Bartoli, J. F.; Mansuy, O.; Le, B.-O.; Ozette, K. L. B.; Palacio, M.; Mansuy, D. J. Chem. Soc., Chem. Commun. 2000, 827−828. (b) Chirvony, V. S.; van Hoek, A.; Schaafsma, T. J.; Pershukevich, P. P.; Filatov, I. V.; Avilov, I. V.; Shishporenok, S. I.; Terekhov, S. N.; Malinovskii, V. L. J. Phys. Chem. B 1998, 102, 9714-9724.Shea, K. M.; Jaquinod, L.; Smith, K. M. Dihydroporphyrin Synthesis: New Methodology. J. Org. Chem. 1998, 63, 7013-7021.(a) Chlorophylls and Bacteriochlorophylls; Grimm, B.; Porra, R. J.; Rüdiger, W.; Scheer, H. Eds.; Springer: Dordrecht, NL, 2006; Vol. 25. (b) The Purple Phototrophic Bacteria; Hunter, C. N.; Daldal, F.; Thurnauer, M. C.; Beatty, J. T.; Eds.; Springer: Dordrecht, NL, 2009; Vol. 28.Chaudhri, N.; Grover, N.; Sankar, M. Inorg. Chem. 2017, 56, 11532-11545. Figure 1

Diving into the Water: Inducible Binding Conformations for BRD4, TAF1(2), BRD9, and CECR2 Bromodomains.

The biological role played by non-BET bromodomains remains poorly understood, and it is therefore imperative to identify potent and highly selective inhibitors to effectively explore the biology of individual bromodomain proteins. A ligand-efficient nonselective bromodomain inhibitor was identified from a 6-methyl pyrrolopyridone fragment. Small hydrophobic substituents replacing the N-methyl group were designed directing toward the conserved bromodomain water pocket, and two distinct binding conformations were then observed. The substituents either directly displaced and rearranged the conserved solvent network, as in BRD4(1) and TAF1(2), or induced a narrow hydrophobic channel adjacent to the lipophilic shelf, as in BRD9 and CECR2. The preference of distinct substituents for individual bromodomains provided selectivity handles useful for future lead optimization efforts for selective BRD9, CECR2, and TAF1(2) inhibitors.

ChemInform Abstract: A Concise Synthesis of 3‐Aroylflavones via Lewis Base 9‐Azajulolidine‐Catalyzed Tandem Acyl Transfer—Cyclization.

Lewis base-catalyzed tandem acyl transfer–cyclization of acylated o-alkynoylphenols leading to 3-aroylflavones was developed. 9-Azajulolidine smoothly promoted the reaction of the aroyl derivatives at ambient temperature, and the structure-diversed synthesis of 3-aroylflavones with distinct substituents was achieved in moderate to excellent yields.

Serendipitous synthetic entrée to tetradehydro analogues of cobalamins

Tetradehydrocorrin macrocycles occupy a saturation level halfway between that of octadehydrocorrins and corrins (e.g., cyanocobalamin). While octadehydrocorrin chemistry is relatively well understood, few studies have been done on more reduced macrocycles owing to synthetic limitations. The reaction of a 2,3-dihydro-1,3,3-trimethyldipyrrin (Western half) bearing a 7-(4-iodophenyl) group and a 1-(dimethoxymethyl)-9-bromo-2,3-dihydro-3,3-dimethyldipyrrin (Eastern half) bearing a 7-p-tolyl group in the presence of Ga(OTf)3 afforded the corresponding B,D-tetradehydrocorrin (1) in 24% yield. Use of a Western half bearing a 7-(4-ethylphenyl) group afforded the B,D-tetradehydrocorrin (2) in 29% yield. Each tetradehydrocorrin bears a 1-methyl group at the A–D ring junction (and hence is enantiomeric), a geminal dimethyl group in each pyrroline ring, and distinct substituents at the 7- and 17-positions; characterization included 1H and 13C NMR spectroscopies, absorption spectroscopy, mass spectrometry, and X-ray crystallography (2 only). Treatment of 1 or 2 with CoCl2 afforded the cobalt chelate as a mixture of stereoisomers containing an apical methoxide or hydroxide ligand. The cobalt-tetradehydrocorrin was characterized by absorption spectroscopy, mass spectrometry, infrared spectroscopy and electrochemistry. The cobalt chelate was smoothly titrated with THF, pyridine, and KCN or Bu4NCN. While the assignment of the oxidation state of the cobalt remains provisional, the use of natural abundance versus isotopically substituted solvents or titrants (CD3OD, K13CN) enabled clear identification of the apical ligands. The facile access to stable, synthetically tailored B,D-tetradehydrocorrins should open the door to fundamental studies of simple surrogates of cyanocobalamin.

N-Heterocyclic Carbene-Catalyzed Annulation of α-Cyano-1,4-diketones with Ynals

In this paper, the first stereoselective annulation reaction between α-cyano-1,4-diketones and ynals, mediated by catalytic amounts of a triazolium salt precatalyst and cocatalytic amounts of a weak carboxylate base, is disclosed. The title transformation proceeds smoothly under mild reaction conditions and generates three contiguous stereogenic centers, one of which is a quaternary acetal carbon. This reaction tolerates a wide variety of electronically distinct substituents on both reaction partners and affords privileged bicyclic scaffolds in 61-90% isolated yields and with up to 20:1 diastereomeric preference.

A concise synthesis of 3-aroylflavones via Lewis base 9-azajulolidine-catalyzed tandem acyl transfer–cyclization

Lewis base-catalyzed tandem acyl transfer-cyclization of acylated o-alkynoylphenols leading to 3-aroylflavones was developed. 9-Azajulolidine smoothly promoted the reaction of the aroyl derivatives at ambient temperature, and the structure-diversed synthesis of 3-aroylflavones with distinct substituents was achieved in moderate to excellent yields.