Triptycene as a scaffold in metallocene catalyzed olefin polymerization

A set of metallocene olefin polymerization catalysts bearing triptycene moieties in either position 4-5 (complexes Ty1-Ty5) or in position 5-6 (complexes Ty6-Ty8) of the basic dimethylsilyl-bridged bis(indenyl) system has been tested in propene polymerization and in ethene/1-hexene copolymerization. Comparison of the results with QSPR (quantitative structure-property relationship) predictions not parametrized for these exotic ligand variations demonstrates that trends can still be identified by extrapolation. Interestingly, Ty7, upon suitable activation, provides a highly isotactic polypropylene with an exceptional amount of 2,1 regio-errors (8%). The previously developed QSPR type models successfully predicted the low regioselectivity of this catalyst, despite the fact that the catalyst structure differs significantly from the benchmark set.

Dual gold-catalyzed regioselective synthesis of benzofulvenes via 5-endo dig cyclization

An efficient dual gold-catalyzed regioselective synthesis of benzofulvenes has been developed from substituted allyloxy 1,5-diynes via 5-endo dig cyclization. In this intramolecular organic transformation a new C-C bond formation occurs and moderate to very good yields are obtained in one pot.

Bis-benzofulvenes: Synthesis and Studies on Their Optoelectronic Properties

We report the synthesis of bis-benzofulvenes and the studies on their optical and redox properties. Bis-benzofulvenes were achieved through the Pd-catalyzed intramolecular Heck coupling followed by Ni⁰-mediated C(sp²)-Br dimerization. Low optical and electrochemical energy gaps of 2.05 and 1.68 eV were achieved by tuning the substituent on the exomethylene unit and the aromatic ring. The observed trends in the energy gaps were compared, and the frontier molecular orbitals were visualized using the density functional theory.

Regioselective Direct C-H Phosphorylation of Benzofulvenes

A practical and straightforward protocol to access site-selective C-3 phosphorylated benzofulvenes by means of cross-dehydrogenative coupling of two nucleophilic moieties, employing silver as a promoter, is described here. Remarkably, this protocol provides a broad, structurally diverse phosphorylated benzofulvene. Initial mechanistic studies shed light on its radical coupling nature, and late-stage transformations offer highly diversified benzofulvenes core.

Microwave-accelerated and benzoyl peroxide (BPO)-initiated cyclization of 1,5-enynes having cyano groups with cyclic alkanes under metal-free conditions

A novel and efficient method for preparing exocyclic indan derivatives, with this method involving benzoyl peroxide (BPO)-initiated cyclization of 1,5-enynes having cyano groups with simple cyclic alkanes under microwave irradiation, has been developed. The presented approach showed advantages of simple conditions, an environmentally friendly protocol, good functional-group tolerance, and high yields of products.

Multisubstituted C2-symmetric ansa-metallocenes bearing nitrogen heterocycles: influence of substituents on catalytic properties in propylene polymerization at higher temperatures

In this work we systematically studied the effects of modifications of substituents on the performance of the isospecific zirconocene-based catalyst family, Me2Si(2-Alk-4-(N-carbazolyl)Ind)ZrX2 (X = Cl, Me), wherein the progenitor was shown to be particularly suitable in high-temperature propylene polymerization processes. In order to obtain the required zirconocenes, we developed a novel synthetic pathway to 4-(N-carbazolyl)indenes through Pd-catalyzed cyclizations of 2,2'-dibromobiaryls with 4-aminoindenes, which were synthesized via Buchwald-Hartwig reaction or electrophilic amination of 4-indenyl Grignard reagents with trimethylsilylmethyl azide. By a number of examples, the anion-promoted rac-to-meso isomerization method was shown to work reliably well for preparation of rac-ZrMe2-complexes. Certain zirconocenes among the 21 tested in propylene polymerization at 70 and 100 °C under MAO or borate activation outperformed the parent catalyst in molecular weight capability, regio- or stereoselectivity.

Total Synthesis of Anmindenol A and Its Application to the Design, Synthesis, and Biological Evaluation of Derivatives Thereof

The first total synthesis of anmindenol A is described in four steps. A notable feature of the synthetic route includes the efficient construction of the 3,10-dialkylsubstituted benzofulvene core via a stereoselective vinylogous Stork enamine aldol condensation. The strategy provided a blueprint for the practical preparation of derivatives with modifications in the C-10 alkyl substituents. The novel derivatives inhibited nitric oxide production in stimulated RAW 264.7 macrophage cells.

Rh-Catalyzed intramolecular decarbonylative cyclization of ortho-formyl group tethered alkylidenecyclopropanes (ACPs) for the construction of 2-methylindenes

A Rh-catalyzed intramolecular cascade decarbonylative coupling reaction of ortho-formyl group-tethered alkylidenecyclopropanes has been developed, affording indene derivatives in moderate to good yields.

Gold(I)/Xiang-Phos-Catalyzed Asymmetric Intramolecular Cyclopropanation of Indenes and Trisubstituted Alkenes

The first intramolecular enantioselective cyclopropanation of indenes and trisubstituted alkenes was accomplished by using new chiral phosphine X5 derived gold(I) complexes. This reaction is a straightforward, efficient method for constructing [5-3-6] fused-ring compounds with two vicinal all-carbon quaternary stereogenic centers, a core structure shared by numerous pharmacological products, and bioactive compounds. The salient features of this transformation include high enantioselectivity (up to >98% ee), excellent yield (>97%), and nice functional group tolerance.

Inhibition of Shiga toxin-converting bacteriophage development by novel antioxidant compounds

Oxidative stress may be the major cause of induction of Shiga toxin-converting (Stx) prophages from chromosomes of Shiga toxin-producing Escherichia coli (STEC) in human intestine. Thus, we aimed to test a series of novel antioxidant compounds for their activities against prophage induction, thus, preventing pathogenicity of STEC. Forty-six compounds (derivatives of carbazole, indazole, triazole, quinolone, ninhydrine, and indenoindole) were tested. Fifteen of them gave promising results and were further characterized. Eleven compounds had acceptable profiles in cytotoxicity tests with human HEK-293 and HDFa cell lines. Three of them (selected for molecular studies) prevent the prophage induction at the level of expression of specific phage genes. In bacterial cells treated with hydrogen peroxide, expression of genes involved in the oxidative stress response was significantly less efficient in the presence of the tested compounds. Therefore, they apparently reduce the oxidative stress, which prevents induction of Stx prophage in E. coli.

Cascade Dehydrogenative Hydroboration for the Synthesis of Azaborabenzofulvenes

Tandem dehydrogenative hydroboration has been established to be highly effective in the synthesis of BN isosteres of benzofulvene and derivatives. The scope of this synthetic method is applicable to a variety of substrates. Spectroscopic and computational studies indicate that the new azaborabenzofulvenes have similar electronic properties as their carbonaceous analogues.

Central-axial-central chirality transfer: asymmetric synthesis of highly substituted indenes bearing a stereogenic quaternary carbon center from optically active propargyl alcohols

An asymmetric synthesis of highly substituted indenes 3, bearing a quaternary stereogenic carbon center, has been developed via the central-axial-central chirality transfer from optically active propargyl alcohols 1. This transformation involves the addition/rearrangement of 1 and ynamides 2 to give tetra-substituted allenes 4 and further cyclization of 4.

Cyclooxygenase-1-selective inhibitors based on the (E)-2'-des-methyl-sulindac sulfide scaffold

Prostaglandins (PGs) are powerful lipid mediators in many physiological and pathophysiological responses. They are produced by oxidation of arachidonic acid (AA) by cyclooxygenases (COX-1 and COX-2) followed by metabolism of endoperoxide intermediates by terminal PG synthases. PG biosynthesis is inhibited by nonsteroidal anti-inflammatory drugs (NSAIDs). Specific inhibition of COX-2 has been extensively investigated, but relatively few COX-1-selective inhibitors have been described. Recent reports of a possible contribution of COX-1 in analgesia, neuroinflammation, or carcinogenesis suggest that COX-1 is a potential therapeutic target. We designed, synthesized, and evaluated a series of (E)-2'-des-methyl-sulindac sulfide (E-DMSS) analogues for inhibition of COX-1. Several potent and selective inhibitors were discovered, and the most promising compounds were active against COX-1 in intact ovarian carcinoma cells (OVCAR-3). The compounds inhibited tumor cell proliferation but only at concentrations >100-fold higher than the concentrations that inhibit COX-1 activity. E-DMSS analogues may be useful probes of COX-1 biology in vivo and promising leads for COX-1-targeted therapeutic agents.

Synthetic approaches to multifunctional indenes

The synthesis of multifunctional indenes with at least two different functional groups has not yet been extensively explored. Among the plausible synthetic routes to 3,5-disubstituted indenes bearing two different functional groups, such as the [3-(aminoethyl)inden-5-yl)]amines, a reasonable pathway involves the (5-nitro-3-indenyl)acetamides as key intermediates. Although several multistep synthetic approaches can be applied to obtain these advanced intermediates, we describe herein their preparation by an aldol-type reaction between 5-nitroindan-1-ones and the lithium salt of N,N-disubstituted acetamides, followed immediately by dehydration with acid. This classical condensation process, which is neither simple nor trivial despite its apparent directness, permits an efficient entry to a variety of indene-based molecular modules, which could be adapted to a range of functionalized indanones.

Identification of novel indanylsulfonamide guanylhydrazones as potent 5-HT6 serotonin receptor antagonists

Changing the N,N-(dimethylamino)ethyl side chain in the N-[3-(aminoethyl)inden-5-yl]sulfonamide 5-HT(6) serotonin receptor agonists 1 by a conformationally rigid guanylhydrazone moiety at the indene 3-position led to the identification of the title indanylguanylhydrazones 6, which exhibited excellent binding affinities and an antagonistic response at the 5-HT(6) receptor, with K(i) and IC(50) values in the nanomolar range (K(i) >or= 1.2 nM, IC(50) >or= 47 nM, and I(max) <or= 173%).

Indene-based frameworks targeting the 5-HT6 serotonin receptor: ring constraint in indenylsulfonamides using cyclic amines and structurally abbreviated counterparts

Further studies in quest of 5-HT(6) serotonin receptor ligands led to the design and synthesis of a few selected examples of N-(inden-5-yl)sulfonamides with a ring-constrained aminoethyl side chain at the indene 3-position, some of which exhibited a high binding affinity, such as the pyrrolidine analogue 28 (K(i)=3nM). Moreover, the structurally abbreviated N-(inden-5-yl)sulfonamides showed K(i) values > or = 43 nM, which indicates that neither the N,N-aminoethyl nor the conformationally restricted aminoethyl side arm at the indene 3-position are required for binding. Selected compounds were then tested in a functional cAMP stimulation assay and found to act as 5-HT(6) antagonists, although with moderate potency at the micromolar level.