A Review on the Synthetic Methods towards Benzothienobenzothiophenes.

Benzothienobenzothiophenes (BTBTs) are a class of heteroacenes for which two distinct isomers have been identified depending on the locations of the fused benzothiophene motifs. Benzothienobenzothiophenes represent a class of heteroacenes demonstrating remarkable electronic properties that make them prominent in the realm of organic semiconductors. The structure of BTBTs, incorporating two sulfur atoms, contributes to their unique electronic characteristics, including narrow bandgaps and effective charge transport pathways. These compounds have gained attention for their high charge carrier mobility, making them desirable candidates for application in organic field-effect transistors (OFETs) and other electronic devices. Researchers have explored various synthetic strategies to design and tailor the properties of BTBT derivatives, leading to advancements in the development of high-performance organic semiconductors. Various synthetic techniques for benzothienobenzothiophenes have been reported in the literature including multistep synthesis, tandem transformations, electrochemical synthesis, and annulations. This review investigates the generality of each synthetic methodology by highlighting its benefits and drawbacks, and it analyses all synthetic approaches described for the creation of the two isomers. For the advantage of the readers, we have delved upon every mechanism of the reactions that are known. Finally, we have also summarized the synthetic methodologies that are used for making benzothienobenzothiophene analogues for material applications.

Re-imagining Priorities for Chemistry: A Central Science for "Freedom from Fear and Want".

Human security, defined as "freedom from want and fear and freedom to live in dignity", provides an overarching concept to address threats to human security dimensions such as health, food, economics, the environment and sustainable development, while placing the individual at the centre of attention. Chemistry is central to addressing these challenges, but surprisingly its role and contributions to human security have hitherto not been explicitly set out. This article situates chemistry in the human security framework, highlighting areas where chemistry knowledge, methods and products are vital. It underscores three complementary facets: 1) chemistry contributes to many dimensions of human security, but needs to do much more in the light of oncoming global challenges; 2) the human security framing illuminates areas where chemistry itself needs to adapt to contribute better, by intensification of current approaches and/or by building or strengthening chemistry tools, skills and competencies; and 3) repositioning as central to human security affords chemistry a powerful opportunity to refresh itself as a science for the benefit of society-and it will need to engage more directly and dynamically at the interface of science, society and policy in order to do so.

An Approach to Paracyclophane-Based Tetrathiafulvalenes: Synthesis and Characterization of a Pseudo-Geminal [2.2]Paracyclophane 1,3-Dithia-2-Thione.

The synthesis of paracyclophane-based tetrathiafulvalene precursors is described in the context of the importance of these compounds in the field of material chemistry. Pseudo-geminal bis(1,3-dithia-2-thione) was synthesized via the corresponding 1,3-dithiol-2-ylium salt. The latter was obtained by a synthetic procedure that involves 4,15-bis(acetyl)[2.2]paracyclophane, a new compound of interest for many researchers.

Blocking the Hype-Hypocrisy-Falsification-Fakery Pathway is Needed to Safeguard Science.

In chemistry and other sciences, hype has become commonplace, compounded by the hypocrisy of those who tolerate or encourage it while disapproving of the consequences. This reduces the credibility and trust upon which all science depends for support. Hype and hypocrisy are but first steps down a slippery slope towards falsification of results and dissemination of fake science. Systemic drivers in the contemporary structure of the science establishment encourage exaggeration and may lure the individual into further steps along the hype-hypocrisy-falsification-fakery continuum. Collective, concerted intervention is required to effectively discourage entry to this dangerous pathway and to restore and protect the probity and reputation of the science system. Chemists must play and active role in this effort.

Living Messages from Chemistry Icons: Legacies with Contemporary Relevance.

Beyond individual scientific virtuosity and creativity that leading figures in chemistry have displayed, they have sometimes conveyed wider messages of significance beyond their own professional specialization. They include insights into broader aspects of science, society or the ways of the world. On the other hand, the words, attitudes and actions of eminent chemists from former times have not always presented good models for others to follow, whether judged by their own contemporary or our present standards. Both positive and negative lessons may convey to us something about humanity in general or the nature of our current predicaments and challenges. In an era when science is more necessary than ever to help meet oncoming global challenges, yet the principles and results of science are irrationally questioned, it is particularly relevant to re-connect with the broad insights and messages that can be derived from examining the thoughts and deeds of chemistry icons from the past.

Tandem α-Arylation/Cyclization of 4-Haloacetoacetates with Arynes: A Metal-Free Approach toward 4-Aryl-3-(2 H)-furanones.

An efficacious, metal-free strategy has been developed for the synthesis of 4-aryl-3-(2 H)-furanones. The reaction proceeds via the nucleophilic addition of an active methylene compound to the aryne followed by ring closing of the adduct. The reaction proceeds under mild conditions, is applicable for gram-scale synthesis of 4-aryl-3-(2 H)-furanones, and is general for a range of substituted arynes and haloacetates.

Convenient diastereoselective synthesis of annulated 3-substituted-(5S*,6S*,Z)-2-(2-(2,4-dinitrophenyl)hydrazono)-5,6-diphenyl-1,3-thiazinan-4-ones.

Racemic 2-(2,4-dinitrophenyl)hydrazono)-5,6-diphenyl-1,3-thiazinan-4-ones and (Z)-N'-(2,4-dinitrophenyl)-2,3-diphenylacrylohydrazide were formed during the diastereoselective reaction between 4-substituted 1-(2,4-dinitrophenyl)thiosemicarbazides and 2,3-diphenylcycloprop-2-enone under refluxing ethanol. The structures of the synthesized compounds were confirmed by single-crystal X-ray analyses.

The Need for Cultural Competence in Science: A Practical Approach to Enhancing Equality, Diversity, and Inclusion.

"The entire field of science needs to enhance its performance with regard to equality, diversity, and inclusion …" Read more in the Editorial by S. A. Matlin, V. W. W. Yam et al.

Existence of Two Fluorescence Bands in all- trans-Polyenes with Six and Seven Double Bonds.

From the analysis of UV/vis absorption, emission, and excitation of emission spectra of all- trans-α,ω-tetra- tert-butylpolyenes with six and seven double-bonds (3,14-di( tert-butyl)-2,2,15,15-tetramethyl-3,5,7,9,11,13-hexadecahexaene (ttbP6), and 3,16-di( tert-butyl)-2,2,17,17-tetramethyl-3,5,7,9,11,13,15-octadecaheptaene (ttbP7)) it is concluded that these hydrocarbons do not exhibit dual S1/S2 fluorescence, as could be inferred from the work of Christensen et al. [ J. Phys. Chem. A 2008 , 112 , 12629 - 12636 ]. The spectral data for ttbP6 and ttbP7 display a unique fluorescence from their S1 states.

The Chemical Sciences and Equality, Diversity, and Inclusion.

There has been mounting concern over the absence of gender equality in the sciences in recent years. This has been accompanied by a broadening of the perspective, in order to address issues of equality, diversity and inclusion, relating to a wide range of circumstances in which individuals suffer discrimination. While some progress has been made in some countries, nationally or at the level of institutions, much more needs to be done. The chemical sciences can play a leading role in addressing biases, through 1) becoming a model of good systemic practice in policies, processes, and actions; 2) developing practical skills through training in cultural competence; and 3) promoting a stronger evidence base to uncover both the extent of problems and the degree to which approaches to improve equality, diversity, and inclusion are working.

The Ethical and Social Dimensions of Chemistry: Reflections, Considerations, and Clarifications.

"Ethics in Chemistry" is a huge topic with various viewpoints and arguments on what it actually is and what compliance to ethical guidelines and participation in ethical discourse imply, covering principles of science and research ethics, profession ethics, and technology ethics. Overview and clarity are lost easily. The authors-members of the recently formed EuCheMS working party "Ethics in Chemistry"-present an attempt to collect and sort the ethically relevant aspects and challenges that chemists see themselves confronted with. Based on this list, strategies for ethical action are outlined. On the one hand, there are those issues that are a matter of compliance to existing guidelines and standards. On the other hand, there are those conflicts that arise at the intersection of science, technology and society and that need engaged chemists participating in the larger discourse for sustainability. This Editorial attempts to point out why this is important and what chemists can do in particular.

[2.2]Paracyclophane-Bis(triazole) Systems: Synthesis and Photochemical Behavior.

Mono-, pseudo-gem, and pseudo-para ethynylcyclophanes and bis(azides) have been employed as addition partners in CuAAC reactions to design and build complex extended molecular scaffolds. The reactivity of the resulting triazoles was investigated under photochemical conditions. A variety of newly substituted [2.2]paracyclophanes were identified; deazotization of pseudo-gem and pseudo-para adducts provided indolophane derivatives. An intramolecular stabilization effect was observed in the case of pseudo-gem derivatives. A photochemical rearrangement from a pseudo-para adduct to a pseudo-ortho product was identified.

The influence of halogen substituents on the biological properties of sulfur-containing flavonoids.

A series of halogen-substituted tricyclic flavonoids containing a 1,3-dithiol-2-ylium moiety has been synthesized from the corresponding 3-dithiocarbamic flavanones. The influence of halogen substituents on the antibacterial properties of the tricyclic flavonoids has been investigated against Staphylococcus aureus and Escherichia coli. On going from fluorine to iodine, these compounds exhibit good to excellent inhibitory properties against both Gram-positive and Gram-negative pathogens. These results suggest that size is the main factor for the change in potency rather than polarity/electronics.

Structure, NMR and Electronic Spectra of [m.n]Paracyclophanes with Varying Bridges Lengths (m, n = 2-4).

Extending our earlier studies on cyclophanes, we here report the structure, chemical shifts, spin-spin coupling constants, absorption and emission properties of [m.n]paracyclophanes, m, n = 2-4, obtained using a combination of experimental and computational techniques. Accurate values of proton chemical shifts as well as of JHH for the bridges are determined. The experimental chemical shifts, coupling constants, absorption and emission wavelengths are satisfactorily reproduced using density functional theory calculations, using both the B3LYP and ωB97X-D functionals. The geometries predicted using a functional that includes dispersion corrections (ωB97X-D) are in a better agreement with available experimental values than those obtained using the B3LYP method. Up to 8 UV-vis absorption/emission bands have been observed (or anticipated in the region below 200 nm) and assigned on the basis of quantum-chemical calculations. Optimized excited-state geometries showed that the distances between the aromatic bridgehead carbon atoms of all the [m.n]paracyclophanes in the excited state decrease compared to the ground-state geometries by ca. 0.2-0.9 Å, the largest being for [4.4]paracyclophane, though the rather large differences in the calculated emission wavelength compared to experiment cast some doubts on the accuracy of the excited-state geometries.

Antibacterial structure-activity relationship studies of several tricyclic sulfur-containing flavonoids.

A structure-activity relationship study concerning the antibacterial properties of several halogen-substituted tricyclic sulfur-containing flavonoids has been performed. The compounds have been synthesized by cyclocondensation of the corresponding 3-dithiocarbamic flavanones under acidic conditions. The influence of different halogen substituents on the antibacterial properties has been tested against Staphylococcus aureus and Escherichia coli. Amongst the N,N-dialkylamino-substituted flavonoids, those having an N,N-diethylamino moiety exhibited good to excellent antimicrobial properties against both pathogens. Fluorine-substituted flavonoids were found to be less active than those bearing other halogen atoms.

Attempts to prepare an all-carbon indigoid system.

First attempts are described to prepare a precursor for an all-carbon analog of indigo, the tetracyclic triene 4. Starting from indan-2-one (9) the α-methylene ketone 13 was prepared. Upon subjecting this compound to a McMurry coupling reaction, it dimerized to the bis-indene derivative 17, rather than providing the tetramethyl derivative of 4, the hydrocarbon 14. In a second approach, indan-1-one (18) was dimerized to the conjugated enedione 21 through the bis-1-indene dimer 19. All attempts to methylenate 21 failed, however. When 19 was treated with the Tebbe reagent, the dimer 23 was produced, presumably through a Cope reaction of the intermediately generated isomer 22. The bis-indene derivative 23 can be alkylated with 1,2-dibromoethane to produce a 1:1 mixture of the spiro compounds 24 and 25. Although 9 could be reductively dimerized to 30, the conversion of this olefin to 14 failed.

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups.

The two isomeric bis(isocyanates) 4,12- and 4,16-di-isocyanato[2.2]paracyclophane, 16 and 28, have been prepared from their corresponding diacids by simple routes. The two isomers are versatile intermediates for the preparation of various cyclophanes bearing substituents with nitrogen-containing functional groups, e.g., the pseudo-ortho diamine 8, the bis secondary amine 23, and the crownophanes 18 and 19. Several of these new cyclophane derivatives (18, 19, 22, 26, 28) have been characterized by X-ray structural analysis.

The chemical behavior of terminally tert-butylated polyolefins.

The chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition to 3 and 7 yielded the dibromides 17 and 18, respectively, i.e., the oligoene system has been attacked at its terminal olefinic carbon atoms. Analogously, the higher vinylogs 19 and 20 yielded the 1,8- and 1,10-bromine adduts 23 and 24, respectively, when less than 1 equivalent of bromine was employed. Treatment of tetraene 19 with excess bromine provided tetrabromide 25. In epoxidation reactions, both with meta-chloroperbenzoic acid (MCPBA) and dimethyldioxirane (DMDO) two model oligoenes were studied: triene 7 and tetraene 19. Whereas 7 furnished the rearrangement product 31 with MCPBA, it yielded the symmetrical epoxide 32 with DMDO. Analogously, 19 was converted to mono-epoxide 33 with MCPBA and to 34 with DMDO. Diels-Alder addition of 7 with N-phenyltriazolinedione (PTAD) did not take place. Extension of the conjugated π-system to the next higher vinylog, 19, caused NPTD-addition to the symmetrical adduct 37 in good yield. Comparable results were observed on adding NPTD (equivalent amount) to pentaene 20 and hexaene 21. Using 36 in excess provided the 2:1-adduct 40 from 21 and led to a complex mixture of adducts from heptaene 22. With tetracyanoethylene (TCNE) as the dienophile, tetraolefin 19 yielded the symmetrical adduct 43, although the reaction temperature had to be increased. Pentaene 20 and hexaene 21 led to corresponding results, adducts 44 and 45 being produced in acceptable yields. With nonaene 42 and TCNE the 2:1-adduct 48 was generated according to its spectroscopic data. Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52.

[2.2]Paracyclophane derivatives containing tetrathiafulvalene moieties.

The synthesis of [2.2]paracyclophane derivatives containing tetrathiafulvalene units has been accomplished by the coupling reaction of 4-([2.2]paracyclophan-4-yl)-1,3-dithiol-2-thione in the presence of trimethylphosphite. The 1,3-dithiol-2-thione derivative was in turn synthesized by the regioselective bromination of 4-acetyl[2.2]paracyclophane, then through the corresponding dithiocarbamates and 1,3-dithiolium salts.

A facile synthesis of Pechmann dyes.

A facile synthesis of Pechmann dyes has been accomplished by the reaction of substituted N-phenacyl-4-dimethylaminopyridinium halides with dimethyl maleate in the presence of DBU. Based on a related 4-DMAP elimination product and an isolated monolactone intermediate a reaction mechanism has been proposed. The scope of this synthetic method is determined by the availability of α-haloaroyl or heteroaroyl derivatives. DBU=1,8-diazabicycloundec-7-ene, DMAP=4-dimethylaminopyridine.