Enantiospecific Total Synthesis of (−)‐Hyacinthacine A1 and (+)‐Hyacinthacine A1 and Their Homologues Using Nitrogen Substituted Donor–Acceptor Cyclopropane

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Enantiospecific Total Synthesis of (−)-Hyacinthacine A1 and (+)-Hyacinthacine A1 and Their Homologues Using Nitrogen Substituted Donor–Acceptor Cyclopropane

Utilizing the nitrogen-substituted donor-acceptor cyclopropane, enantiospecific total syntheses of (−)-hyacinthacine A1⋅HCl and (+)-hyacinthacine A1⋅HCl were achieved. The key reactions were highly stereo- and regioselective intramolecular cyclopropanation with rhodium(II) acetate and regioselective ring opening of nitrogen-substituted D−A cyclopropanes.


Abstract

A concise and efficient enantiospecific total synthesis of (−)-hyacinthacine A1 and (+)-hyacinthacine A1 was achieved from commercially available starting material L-pyroglutamic acid and D-glutamic acid, respectively. For the synthesis of this trihydroxylated pyrrolizidine ring, we employed the nitrogen-substituted donor-acceptor cyclopropane as a key intermediate. The synthetic approach relies on two crucial steps, highly stereo- and regioselective intramolecular cyclopropanation with Rh2(OAc)4 and regioselective ring opening of a nitrogen-substituted donor-acceptor cyclopropane.

Air‐Induced Hydroxyphosphorylation of α‐Trifluoromethyl Styrenes with H‐Phosphonates and H‐Phosphine Oxides

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Air-Induced Hydroxyphosphorylation of α-Trifluoromethyl Styrenes with H-Phosphonates and H-Phosphine Oxides

Mn-mediated hydroxyphosphonylation of α-CF3-styrenes with H-phosphonates and transition-metal-free hydroxyphosphinylation of α-CF3-styrenes with H-phosphine oxides with the assistance of air were developed. A variety of β-hydroxy-β-CF3-phosphonates and β-hydroxy-β-CF3-phosphine oxides were synthesized in moderate to good yields.


Abstract

Efficient synthesis of β-hydroxy-β-CF3-phosphonates and β-hydroxy-β-CF3-phosphine oxides by Mn-mediated or transition-metal-free hydroxyphosphorylation of α-trifluoromethy)styrenes with H-phosphonates or H-phosphine oxides with the assistance of air, respectively, was described.

Trends in the Diversification of the Detergentome

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Trends in the Diversification of the Detergentome

Growing detergentome. Recent synthesis concepts and detergent building blocks, i. e., head, linker, tail, are reviewed regarding their availability and role in the expansion of the detergentome (entirety of all detergents). The development of detergents for membrane protein studies turns out to be a key driver for detergent diversity. Metric-assisted optimization strategies will facilitate the development of tailor-made and safe-to-use detergents.


Abstract

Detergents are amphiphilic molecules that serve as enabling steps for today's world applications. The increasing diversity of the detergentome is key to applications enabled by detergent science. Regardless of the application, the optimal design of detergents is determined empirically, which leads to failed preparations, and raising costs. To facilitate project planning, here we review synthesis strategies that drive the diversification of the detergentome. Synthesis strategies relevant for industrial and academic applications include linear, modular, combinatorial, bio-based, and metric-assisted detergent synthesis. Scopes and limitations of individual synthesis strategies in context with industrial product development and academic research are discussed. Furthermore, when designing detergents, the selection of molecular building blocks, i. e., head, linker, tail, is as important as the employed synthesis strategy. To facilitate the design of safe-to-use and tailor-made detergents, we provide an overview of established head, linker, and tail groups and highlight selected scopes and limitations for applications. It becomes apparent that most recent contributions to the increasing chemical diversity of detergent building blocks originate from the development of detergents for membrane protein studies. The overview of synthesis strategies and molecular blocks will bring us closer to the ability to predictably design and synthesize optimal detergents for challenging future applications.

Theoretical Understanding on the Facilitated Photoisomerization of a Carbonyl Supported Borane System

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Theoretical Understanding on the Facilitated Photoisomerization of a Carbonyl Supported Borane System

MS-CASPT2//CASSCF calculations reveal detailed mechanisms for the photoisomerization of boron compounds, showing that the steric hindrance influences their photoisomerization activity.


Abstract

Boron compound BOMes2 containing an internal B−O bond undergoes highly efficient photoisomerization, followed by sequential structural transformations, resulting in a rare eight-membered B, O-heterocycle (S. Wang, et al. Org. Lett. 2019, 21, 5285–5289). In this work, the detailed reaction mechanisms of such a unique carbonyl-supported tetracoordinate boron system in the first excited singlet (S1) state and the ground (S0) state were investigated by using the complete active space self-consistent field and its second-order perturbation (MS-CASPT2//CASSCF) method combined with time-dependent density functional theory (TD-DFT). Moreover, an imine-substituted tetracoordinated organic boron system (BNMes2) was selected for comparative study to explore the intrinsic reasons for the difference in reactivity between the two types of compounds. Steric factor was found to influence the photoisomerization activity of BNMes2 and BOMes2. These results rationalize the experimental observations and can provide helpful insights into understanding the excited-state dynamics of heteroatom-doped tetracoordinate organoboron compounds, which facilitates the rational design of boron-based materials with superior photoresponsive performances.

An Unexpected Synthesis of Crowded Triphenylenes

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An Unexpected Synthesis of Crowded Triphenylenes

Reaction of 2,5-dibromothiophene dioxide with two equivalents of tetracyclone yields a heptaphenyl triphenylene, presumably by double Diels-Alder addition followed by fragmentation and rearrangement of the resulting radicals.


Abstract

In attempts to make octaphenyldibenzofuran (7) and octaphenyldibenzothiophene (8), 2,5-dibromofuran (4) and 2,5-dibromothiophene (5), respectively, were heated with tetracyclone (2) under forcing conditions, but only single addition products, such as 2-bromo-4,5,6,7-tetraphenylbenzofuran (10) and 2-bromo-4,5,6,7-tetraphenylbenzothiophene (12) were observed. However, when 2,5-dibromothiophene-1,1-dioxide (6) was heated with tetracyclone, the chief product was 1,2,3,4,6,7,8-heptaphenyltriphenylene (14). Similarly, when compound 6 was heated with acecyclone (15), the product was 11,18,20-triphenyldiacenaphtho[a,h]triphenylene (16). Both 14 and 16 have been characterized by X-ray crystallography. They are proposed to form from double Diels-Alder addition products of the cyclopentadienones by extrusion of sulfur dioxide and rearrangement of the resulting radicals.

Second‐Generation Total Synthesis of the Pigment Aurantricholone

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Second-Generation Total Synthesis of the Pigment Aurantricholone

Previously, 6,6-dimethoxy-6,7-dihydrobenzocyclohepten-5-ones (“ketoketals”) gained by ring-closing metatheses (“RCMs”) gave 6-hydroxybenzocyclohepten-5-ones (“benzotropolones”) by hydrolyses with 10 equiv. of hot TsOH. Now, an RCM-based ketoketal allowed to reach the benzotropolone aurantricholone by total synthesis for the second time and to avoid a forcing hydrolysis. Another key to success was establishing the pulvinone(−like) motifs by our recently developed Suzuki strategy.


Abstract

Our first total synthesis of aurantricholone established its benzotropolone core by the ring-enlargement of a tetralone. Here we describe another total synthesis of aurantricholone. It reaches the benzotropolone core from a known olefin metathesis product via an equally known dibromide, both of which contain a ketoketal moiety. The next transformation - step 9 overall - engaged this motif in a β-elimination of ROH rather than in a hydrolysis under the forcing acidic conditions indispensable in all prior benzotropolone preparations from such an intermediate. In step 10, the C sp2−Br bonds of the elimination product underwent two doubly Z-selective Suzuki couplings with a boronylated O-methyl 4-methylidenetetronate. This gave penta(O-methyl)aurantricholone. Its NMR shifts matched essentially those of a derivative of natural aurantricholone by Steglich et al. Three O−Me bonds were cleaved with BBr3/CH2Cl2 (step 11) and two O−Me bonds with LiBr/DMF (step 12). A 1 : 3 co-crystal of aurantricholone and DMSO allowed for an X-ray structure analysis.

Organic Molecule Bifunctionalized Polymeric Carbon Nitride for Enhanced Photocatalytic Hydrogen Peroxide Production

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Organic Molecule Bifunctionalized Polymeric Carbon Nitride for Enhanced Photocatalytic Hydrogen Peroxide Production

Organic molecule bifunctionalized polymeric carbon nitride (MBCN) with edge-grafted and interchain-embedded benzene rings as the respective electron-donating group and charge-transfer channel exhibits significantly enhanced photocatalytic H2O2 production activity due to the promoted separation/transfer of photogenerated charge carriers and visible light absorbance. Based on density functional theory calculation and experimental results, we propose the transfer path of photogenerated electrons.


Abstract

Modifying the polymeric carbon nitride (CN) with organic molecules is a promising strategy to enhance the photocatalytic activity. However, most previously reported works show that interchain embedding and edge grafting of the organic molecule can hardly be achieved simultaneously. Herein, we successfully synthesized organic molecule bifunctionalized CN (MBCN) through copolymerization of melon and sulfanilamide at a purposely elevated temperature of 550 °C. In MBCN, the edge grafted and interchain embedded benzene rings act as the electron-donating group and charge-transfer channel, respectively, rendering efficient photocatalytic H2O2 production. The optimal MBCN exhibits a significantly improved non-sacrificial photocatalytic H2O2 generation rate (54.0 μmol g−1 h−1) from pure water, which is 10.4 times that of pristine CN. Experimental and density functional theory (DFT) calculation results reveal that the enhanced H2O2 production activity of MBCN is mainly attributed to the improved photogenerated charge separation/transfer and decreased formation energy barrier (▵G) from O2− to the intermediate 1,4-endoperoxide (⋅OOH). This work suggests that simultaneous formation of electron donating group and charge transfer channel via organic molecule bifunctionalization is a feasible strategy for boosting the photocatalytic activity of CN.

Enantioselective Construction of Axially Iodobenzocarbazole Derivatives by Stereogenic‐at‐Cobalt(III)‐Complex‐Catalyzed Iodoarylation of Alkynes

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Enantioselective Construction of Axially Iodobenzocarbazole Derivatives by Stereogenic-at-Cobalt(III)-Complex-Catalyzed Iodoarylation of Alkynes

A direct protocol for the facile construction of axially chiral iodobenzocarbazole derivatives via the catalytic asymmetric iodocyclization of indole moiety linked alkynes, using stereogenic-at-cobalt(III)-complex as the catalyst, has been developed. A range of versatile axially chiral iodobenzocarbazoles were obtained with up to 98 % ee under mild conditions.


Abstract

A new synthetic approach to novel axially chiral iodobenzocarbazole derivatives based on the highly enantioselective intramolecular iodoarylation of linked alkyne-indole systems was developed by using the versatile chiral catalyst, stereogenic-at-cobalt(III)-complex, through an axially chiral iodinated vinylidene o-quinone methide (IVQM) intermediate. This protocol provides 21 examples in excellent yields with good to high enantioselectivities (up to 96 % yield, 98 % ee). Furthermore, the introduced iodine atoms can easily be converted into other functional groups.

Quantifying the Resistive Losses of the Catalytic Layers in Anion‐Exchange Membrane Fuel Cells

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Quantifying the Resistive Losses of the Catalytic Layers in Anion-Exchange Membrane Fuel Cells

An operando anion-exchange membrane fuel cell (AEMFC) was analyzed via artificial intelligence. Using impedance spectroscopy genetic programming (ISGP), we quantified the resistances of the various physical processes occurring in the system for the first time providing valuable information to the AEMFC community with wider applicability to other electrochemical process.


Abstract

The existing gap in the ability to quantify the impacts of resistive losses on the performance of anion-exchange membrane fuel cells (AEMFCs) during the lifetime of their operation is a serious concern for the technology. In this paper, we analyzed the ohmic region of an operating AEMFC fed with pure oxygen followed by CO2-free air at various operating currents, using a combination of electrochemical impedance spectroscopy (EIS) and a novel technique called impedance spectroscopy genetic programming (ISGP). Presented here for the first time in this work, we isolated and quantified the individual effective resistance (Reff) values occurring in the AEMFC and their influence on performance as operating conditions change. We believe that this first work is vital to help distinguish the influence of the individual catalytic and mass-transfer processes in this technology thereby providing valuable data to the AEMFC community, with potentially wider applicability to other electrochemical devices where individual physical processes occur simultaneously and need to be sequestered for deeper understanding.

Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air‐Water Interface

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Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface

Surfactants significantly influence the air-water interfacial properties, yet their connection with the surfactant molecular structure remains unclear. Combining simulations and experiments to explore the molecular arrangement of SDS and DTAB surfactants at the air-water interface reveals noteworthy findings, which offer valuable insights into the influence of surfactants on the macroscopic behaviour of aqueous foams and foaming solutions, particularly the foamability and foam stability.


Abstract

Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br− counterions compared to smaller Na+ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H+ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H+ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.