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Synthetic investigations towards spiroconjugated ketones and derivatives thereof are presented. These studies led to the development of a short procedure for the synthesis of spiroconjugated tetraketone 1 in two steps with 10 % overall yield and the first-time synthesis of spirocyclic trindone 2. The optoelectronic properties of these compounds based on spectroscopic and electrochemical measurements in combination with DFT calculations as well as their molecular structures in the solid state are presented and discussed.

Nine title compounds are prepared (extended synthetic approaches described) and subjected to optimized conditions A.

Stimuli-responsive capsules are of interest in drug delivery, fragrance release, food preservation, and self-healing materials. Many methods are used to trigger the release of encapsulated contents. Here we highlight mechanisms for the controlled release of encapsulated cargo that utilize chemical reactions occurring in solid polymeric shell walls. Triggering mechanisms responsible for covalent bond cleavage that result in the release of capsule contents include chemical, biological, light, thermal, magnetic, and electrical stimuli. We present methods for encapsulation and release, triggering methods, and mechanisms and conclude with our opinions on interesting obstacles for chemically induced activation with relevance for controlled release.

To find out whether the 1,4-addition to 1,2:3,4-diepoxides, which so far has been observed only once, is of a more general character, we investigated the reaction of a variety of O-, C-, N-, and S-nucleophiles with the model compound 1,2:3,4-diepoxy-2,3-dimethylbutane (Scheme 4). In several cases, 1,4-addition products could, indeed, be observed besides the expected 1,2-adducts (Table).

trans-3,4:5,6-Diepoxycyclohex-1-ene (anti-benzene dioxide) (5) was brought into reaction with several S, O, and C nucleophiles. S and O nucleophiles gave the bis-adducts stemming from independent reaction of the two epoxy functions. C nucleophiles, on the other hand, led to 1,4-addition products. A deuterium labelling experiment showed that BuLi added to the vinyloxirane part of 5 rather than to the conjugated diepoxide function, yielding the cis-adduct. Cuprates gave - as expected - predominatly the trans-products.

In the preceding communication we described a fully synthetic pathway to the structure proposed for ( )-diazonamide A (1, Scheme 1).[1] This material is not identical to the natural product, which raises the obvious question: What is the true structure of diazonamide A? Herein we provide an answer. In addition, we report that defined synthetic entity 8 induces, with equal potency, a toxic phenotype in cell culture indistinguishable from that produced by natural ( )-diazonamide A. Spectroscopic data for the heterocyclic cores of diazonamides A and B are nearly identical.[2] So when the crystal structure of a p-bromobenzamide derivative of diazonamide B was reported as 3,[2a] the diazonamide A assignment Scheme 1. Initial diazonamide structure assignments.

Representative procedure for the preparation of 7: A solution of lithium hexamethyldisilazide in THF (1, 0.20 mL, 0.20 mmol) was added dropwise to a solution of 1 (0.038 g; 0.20 mmol) in THF (0.5 mL) at 78C. The resulting pale yellow solution was stirred for 10 min at the same temperature, and then a solution of coumarin 2b (0.032 g; 0.22 mmol) in THF (0.5 mL) was added dropwise at 78C. After 30 min, a solution of trans chalcone 5c (0.045 g, 0.22 mmol) was added dropwise. The reaction mixture was stirred for a further 30 min at the same temperature, and then a solution of trimethylsilyl chloride (0.31 mL) in methanol (5 mL) was added at 78C. The reaction mixture was warmed to room temperature overnight. The solvents were removed in vacuo to give the crude product, which was purified by column chromatography (1:1 petroleum ether/ethyl

Immunotoxicology concerns actions of chemicals which lead to adverse immune reactions. Current research challenges are the prediction of the immunotoxicologic risk potential of a chemical and a deeper mechanistic understanding of chemical-induced adverse immune reactions, to develop therapeutic or avoidance strategies. Small chemicals (SCs) can interfere with any cell type or function of the immune system. SCs are ubiquitous as food components, life-style products, or environmental pollutants. Besides their possible unspecific toxicity, they might form protein adducts, become part of recognized antigens, or they could be disruptors of immune signalling pathways. The incidence of autoimmune and allergic diseases has been rising over the last years, and evidence increases that SCs are important in this. Also, immunopharmacologists actively search for immunomodulating chemicals as urgently needed drugs. The aryl hydrocarbon receptor (AhR) is a SC-triggered transcription factor, and thus could link environmental signals to cellular responses. Recent research has shown a defined role for AhR in immunotoxicology. Here, we discuss concepts of SC immunotoxicity, and how AhR might be involved in adverse immune responses.

A carbon nanotube, if it could be cut sideways at the end like a pipe, would yield beltlike structures. These subunits of carbon nanotubes, in their simplest manifestation as the [6]ncyclacenes, are composed of conjugated six-membered rings that are annelated, that is, made of a series of consecutively fused ring structures. These seemingly simple “one-benzene-thick” slices are of considerable interest as models—for electronic structure and spectroscopic properties, for example—for carbon nanotubes. In the late 1980s Stoddart and co-workers, soon to be followed by other groups, embarked on the synthesis of [6]ncyclacenes. The necessary curved shape of the belt was achieved with boat-shaped precursors for Diels−Alder reactions, namely, 7-oxanorbornene derivatives. The preferred endo-addition in Diels−Alder reactions assured an efficient synthesis of beltlike systems containing 12 to 18 six-membered rings. However, the removal of the auxiliary oxygen centers to achieve [6]ncyclacenes as fully conjugated sys...

In this article we show synthetic pathways to [6.8](n)cyclacenes demonstrated by the de novo synthesis of [6.8](3)cyclacene as the first purely hydrocarbon cyclacene and of precursors for [6.8](4)cyclacene. The design of the de novo synthesis by exploring alternative pathways is discussed and various precursors are shown. Crucial to the synthesis of [6.8](3)cyclacene were two cyclization steps. The first is a Wittig trimerization reaction which yielded the hexamethyl substituted all-cis-[2(3)]metacyclophanetriene. For the second cyclization step the methyl groups were converted to aldehyde functionalities by two subsequent oxidation steps of N-bromosuccinimide (NBS) bromination and oxidation with 2-iodoxybenzoic acid (IBX). The final cyclization of the second set of double bonds was achieved by a McMurry-coupling reaction. Towards the synthesis of [6.8](4)cyclacene different synthetic pathways to methyl substituted all-cis-[2(4)]metacyclophanetetraenes were explored. Insights into the structures of [2(3)]metacyclophanetri- and [2(4)]metacyclophanetetraenes were gained by X-ray crystallographic investigations on various intermediates. A crystallographic analysis of [6.8](3)cyclacene revealed a D(3h) symmetrical structure with planar benzene rings and a formation of tubular structures in the solid state.

Two different types of cyclacenes, utilizing eight-membered and six-/four-membered rings as building blocks ([6.8]n and CpCo-capped [4.8]ncyclacenes), have been theoretically investigated with respect to their geometries, relative energies, and magnetic properties (aromaticity).

A series of fused isoquinoline–pyridazinooxazine chimera were prepared in good overall yield from phenethylamide 1 and 4,5-dichloropyridazin-3-one 2 via Smiles rearrangement and Pictet–Spengler cyclization.