Synthesis of acenaphthylene-fused heteroarenes and polyoxygenated benzo[]fluoranthenes via a Pd-catalyzed Suzuki-Miyaura/C-H arylation cascade.

Acenaphthylene-fused heteroarenes with a variety of five- and six-membered heterocycles such as thiophene, furan, benzofuran, pyrazole, pyridine and pyrimidine were synthesized via an efficient Pd-catalyzed reaction cascade in good to high yields (45-90%). This cascade involves an initial Suzuki-Miyaura cross-coupling reaction between 1,8-dihalonaphthalenes and heteroarylboronic acids or esters, followed by an intramolecular C-H arylation under the same conditions to yield the final heterocyclic fluoranthene analogues. The method was further employed to access polyoxygenated benzo[]fluoranthenes, which are all structurally relevant to benzo[]fluoranthene-based fungal natural products.

Na-Promoted Bimetallic Hydroxide Nanoparticles for Aerobic C-H Activation: Catalyst Design Principles and Insights into Reaction Mechanism.

A precious metal-free bimetallic FeMn(OH) hydroxide catalyst was developed that is capable of catalyzing aerobic C-H oxidation reactions at low temperatures, without the need for an initiator, relying sustainably on molecular oxygen. Through a systematic synthetic effort, we scanned a wide nanoparticle synthesis parameter space to lay out a detailed set of catalyst design principles unraveling how the Fe/Mn cation ratio, NaOH(aq) concentration used in the synthesis, catalyst washing procedures, extent of residual Na promoters on the catalyst surface, reaction temperature, and catalyst loading influence catalytic C-H activation performance as a function of the electronic, surface chemical, and crystal structure of FeMn(OH) bimetallic hydroxide nanostructures. Our comprehensive XRD, XPS, BET, ICP-MS, H NMR, and XANES structural/product characterization results as well as mechanistic kinetic isotope effect (KIE) studies provided the following valuable insights into the molecular level origins of the catalytic performance of the bimetallic FeMn(OH) hydroxide nanostructures: (i) catalytic reactivity is due to the coexistence and synergistic operation of Fe and Mn cationic sites (with minor contributions from Fe and Mn sites) on the catalyst surface, where in the absence of one of these synergistic sites (i.

Template-Directed Selective Photodimerization Reactions of 5-Arylpenta-2,4-dienoic Acids.

We developed an efficient method that enables selective photodimerization of 5-arylpenta-2,4-dienoic acids (i.e., vinylogous cinnamic acids).

Recent advances in the synthesis and applications of fluoranthenes.

As an important subclass of polycyclic aromatic hydrocarbons (PAHs), fluoranthenes continue to attract significant attention in synthetic organic chemistry and materials science. In this article, an overview of recent advances in the synthesis of fluoranthene derivatives along with selected applications is provided. First, methods for fluoranthene synthesis with a classification based on strategic bond disconnections are discussed.

Intramolecular through-space charge transfer between benzofuran and ynone groups on a naphthalene spacer.

We have developed a new scaffold that exhibits an efficient intramolecular through-space charge transfer (CT). In this design, electron-rich benzofuran and electron-deficient ynone groups are placed strategically in proximity a naphthalene spacer. Charge transfer is supported by distinct CT bands in the visible region (>500 nm) in their UV-vis absorption and emission spectra.

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles.

We have developed a catalytic aza-Nazarov reaction of -acyliminium salts generated in situ from the reaction of a variety of cyclic and acyclic imines with α,β-unsaturated acyl chlorides to afford substituted α-methylene-γ-lactam heterocycles. The reactions proceed effectively in the presence of catalytic (20 mol %) amounts of AgOTf as an anion exchange agent or hydrogen-bond donors such as squaramides and thioureas as anion-binding organocatalysts. The aza-Nazarov cyclization of 3,4-dihydroisoquinolines with α,β-unsaturated acyl chlorides gives tricyclic lactam products in up to 79% yield with full diastereocontrol (dr = >99:1).

Rapid Access to Hydroxyfluoranthenes via a Domino Suzuki-Miyaura/Intramolecular Diels-Alder/Ring-Opening Reactions Sequence.

In this work, we developed an efficient method for the rapid construction of fluoranthene skeleton to access a variety of substituted hydroxyfluoranthenes. The 1-iodo-8-alkynylnaphthalene derivatives, which serve as substrates for the key fluoranthene-forming step, were prepared via selective monoalkynylative Sonogashira reactions of 1,8-diiodonaphthalene. The domino reaction sequence which involves a sequential Suzuki-Miyaura coupling, an intramolecular Diels-Alder reaction, and an aromatization-driven ring-opening isomerization has been shown to give substituted hydroxyfluoranthenes in up to 92% yield.

Synthesis, anti-TB activities, and molecular docking studies of 4-(1,2,3-triazoyl)arylmethanone derivatives.

Infectious diseases such as tuberculosis (TB) are leading causes of human death. Antibiotics are effective molecules to combat bacterial infections by affecting the processes required for bacterial cell growth and proliferation. The development of new antibiotics has become an important issue as overdosed or incorrect use of antibiotic lead to the development of antibiotic resistance.

Template-Directed Photochemical Homodimerization and Heterodimerization Reactions of Cinnamic Acids.

We developed a general method for the selective photochemical homo- and heterodimerization of cinnamic acid derivatives with the use of commercially available 1,8-dihydroxynaphthalene as a covalent template. A variety of symmetrical and unsymmetrical β-truxinic acids were obtained in high yields and as single diastereomers. The use of a template not only provides the alignment of the two olefins with suitable proximity (<4.

Precious Metal-Free LaMnO Perovskite Catalyst with an Optimized Nanostructure for Aerobic C-H Bond Activation Reactions: Alkylarene Oxidation and Naphthol Dimerization.

In this article, we describe the development of a new aerobic C-H oxidation methodology catalyzed by a precious metal-free LaMnO perovskite catalyst. Molecular oxygen is used as the sole oxidant in this approach, obviating the need for other expensive and/or environmentally hazardous stoichiometric oxidants. The electronic and structural properties of the LaMnO catalysts were systematically optimized, and a reductive pretreatment protocol was proved to be essential for acquiring the observed high catalytic activities.

Aza-Nazarov Cyclization Reactions via Anion Exchange Catalysis.

A catalytic aza-Nazarov cyclization between 3,4-dihydroisoquinolines and α,β-unsaturated acyl chlorides has been developed to access α-methylene-γ-lactam products in good yields (up to 79%) as single diastereomers. The reactions proceed efficiently when AgOTf is used as an anion exchange catalyst with a 20 mol % loading at 80 °C. Computational studies were performed to investigate the reaction mechanism, and the findings support the role of the -TMS group in reducing the reaction barrier of the key cyclization step.

Enantioselective Synthesis of the Cyclopiazonic Acid Family Using Sulfur Ylides.

A convergent, nine-step (LLS), enantioselective synthesis of α-cyclopiazonic acid and related natural products is reported. The route features a) an enantioselective aziridination of an imine with a chiral sulfur ylide; b) a bioinspired (3+2)-cycloaddition of the aziridine onto an alkene; and c) installation of the acetyltetramic acid by an unprecedented tandem carbonylative lactamization/N-O cleavage of a bromoisoxazole.

Synthesis of Fluoranthene Derivatives via Tandem Suzuki-Miyaura and Intramolecular C-H Arylation Reactions under Both Homogeneous and Heterogeneous Catalytic Conditions.

A catalytic method for the synthesis of substituted fluoranthenes that operates via tandem Suzuki-Miyaura and intramolecular C-H arylation reactions is reported. The overall reaction sequence works effectively with homogeneous catalysis using Pd(dppf)Cl as well as heterogeneous catalysis using reduced graphene oxide (rGO)-CuPd nanocatalysts with low catalyst loadings. High functional group tolerance is observed under both catalytic conditions where arylboronic acids and esters having electron-withdrawing and electron-donating substituents afforded fluoranthene products in good yields (up to 78%).

Studies Directed toward the Synthesis of Aspidophytine: Construction of Its Perhydroquinoline Core.

We have developed an efficient route for the synthesis of the perhydroquinoline core of the indole alkaloid aspidophytine (2), starting from commercially available and inexpensive 3-acetylpyridine. This densely functionalized perhydroquinoline core displays four contiguous stereocenters including an all-carbon quaternary center. The synthetic sequence features a highly effective Diels-Alder reaction using a carbamate-substituted siloxy diene accompanied by a spontaneous intramolecular substitution of the newly formed 3°-alkyl bromide with a carbamate group.

Non-precious metals catalyze formal [4 + 2] cycloaddition reactions of 1,2-diazines and siloxyalkynes under ambient conditions.

Copper(I) and nickel(0) complexes catalyze the formal [4 + 2] cycloaddition reactions of 1,2-diazines and siloxyalkynes, a reaction hitherto best catalyzed by silver salts. These catalysts based on earth abundant metals are not only competent, but the copper catalyst, in particular, promotes cycloadditions of pyrido[2,3-d]pyridazine and pyrido[3,4-d]pyridazine, enabling a new synthesis of quinoline and isoquinoline derivatives, as well as the formal [2 + 2] cycloaddition reaction of cyclohexenone with a siloxyalkyne.

Stacks and clips: Uncanny similarities in the modes of self-assembly in tenary Ag(I) complexes with 1,2-diazines and chelating heteroarenes.

The first synthesis and structural elucidation of Ag(I) ternary complexes with 1,2-diazines and chelating heteroarenes have been described. Conserved modes of inter-cation Ag⋯ and ⋯ stacking interactions result in near identical patterns of cation self-assembly in these ternary complexes.

[2+2+2] Cycloadditions of siloxy alkynes with 1,2-diazines: from reaction discovery to identification of an antiglycolytic chemotype.

Cycloaddition uncovered: The title reaction produces novel polycyclic compounds with high efficiency and excellent diastereoselectivity under mild reaction conditions. A small-molecule library, synthesized using this reaction, yielded a novel chemotype which inhibited glycolytic ATP production by blocking glucose uptake in CHO-K1 cells. DMF=N,N-dimethylformamide, Tf=trifluoromethanesulfonyl, TIPS=triisopropylsilyl.

Squaramide-catalyzed enantioselective Michael addition of masked acyl cyanides to substituted enones.

Masked acyl cyanide (MAC) reagents are shown to be effective umpolung synthons for enantioselective Michael addition to substituted enones. The reactions are catalyzed by chiral squaramides and afford adducts in high yields (90-99%) and with excellent enantioselectivities (85-98%). The addition products are unmasked to produce dicyanohydrins that, upon treatment with a variety of nucleophiles, provide γ-keto acids, esters, and amides.

Exploring the potential of diarylacetylenediols as hydrogen bonding catalysts.

In the course of a search for new classes of hydrogen bonding catalysts, we have examined diarylacetylenediols as potential catalysts for the Diels-Alder reaction. General and efficient methods have been developed for the preparation of these diols. Their structures were systematically modified, and increased activity was observed for those possessing an electron-withdrawing group on the aryl groups.

Salen promoted enantioselective Nazarov cyclizations of activated and unactivated dienones.

A novel class of chiral 5,5'-di(2,4,6-trialkyl)aryl salen-metal complexes have been developed and shown to catalyze highly enantioselective Nazarov cyclization reactions, giving rise to cyclopentenoids in 90:10-98:2 er. Significantly, the catalysts also promote, for the first time, highly enantioselective Nazarov reactions of "unactivated" dienones, producing hydrindenone products having in place three contiguous chiral centers.

Silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes.

A highly effective silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes has been developed. The reactions provide ready access to a wide range of siloxy naphthalenes and anthracenes, which are formed in good to high yields, under mild reaction conditions, using low catalyst loadings.