Hexasubstituted Benzenes with Ultrastrong Dipole Moments

Hexasubstituted benzenes have been synthesized with the highest known dipole moments, as determined by dielectric spectroscopy and DFT methods. Based on the preparation of 4,5‐diamino‐3,6‐dibromophthalonitrile, combined with a novel method to synthesize dihydrobenzimidazoles, these benzene derivatives have dipole moments in excess of 10 debye. Such dipole moments are desirable in ferroelectrics, nonlinear optics, and in organic photovoltaics. Structure determination was achieved through single‐crystal X‐ray crystallography, and the optical properties were determined by UV/Vis absorption and fluorescence spectroscopy.     

A Disilene Base Adduct with a Dative Si–Si Single Bond

An experimental and theoretical study of the base‐stabilized disilene 1 is reported, which forms at low temperatures in the disproportionation reaction of Si₂Cl₆ or neo‐Si₅Cl₁₂ with equimolar amounts of NMe₂Et. Single‐crystal X‐ray diffraction and quantum‐chemical bonding analysis disclose an unprecedented structure in silicon chemistry featuring a dative Si→Si single bond between two silylene moieties, Me₂EtN→SiCl₂→Si(SiCl₃)₂. The central ambiphilic SiCl₂ group is linked by dative bonds to the amine donor and the bis(trichlorosilyl)silylene acceptor, which leads to push–pull stabilization. Based on experimental and theoretical examinations a formation mechanism is presented that involves an autocatalytic reaction of the intermediately formed anion Si(SiCl₃)₃^? with neo‐Si₅Cl₁₂ to yield 1 .     

Total Synthesis of Cryptocaryol A by Enantioselective Iridium‐Catalyzed Alcohol C−H Allylation

The polyketide natural product cryptocaryol A is prepared in 8 steps via iridium catalyzed enantioselective diol double C?H allylation, which directly generates an acetate‐based triketide stereodiad. In 4 previously reported total syntheses, 17–28 steps were required.     

Low‐Temperature Cationic Rearrangement in a Bulk Metal Oxide

Cationic rearrangement is a compelling strategy for producing desirable physical properties by atomic‐scale manipulation. However, activating ionic diffusion typically requires high temperature, and in some cases also high pressure in bulk oxide materials. Herein, we present the cationic rearrangement in bulk Mn₂FeMoO₆ at unparalleled low temperatures of 150–300 ^oC. The irreversible ionic motion at ambient pressure, as evidenced by real‐time powder synchrotron X‐ray and neutron diffraction, and second harmonic generation, leads to a transition from a Ni₃TeO₆–type to an ordered‐ilmenite structure, and dramatic changes of the electrical and magnetic properties. This work demonstrates a remarkable cationic rearrangement, with corresponding large changes in the physical properties in a bulk oxide at unprecedented low temperatures.     

Peripheral Templation Generates an MII6L4 Guest‐Binding Capsule

Pseudo‐octahedral M^II₆L₄ capsules result from the subcomponent self‐assembly of 2‐formylphenanthroline, threefold‐symmetric triamines, and octahedral metal ions. Whereas neutral tetrahedral guests and most of the anions investigated were observed to bind within the central cavity, tetraphenylborate anions bound on the outside, with one phenyl ring pointing into the cavity. This binding configuration is promoted by the complementary arrangement of the phenyl rings of the intercalated guest between the phenanthroline units of the host. The peripherally bound, rapidly exchanging tetraphenylborate anions were found to template an otherwise inaccessible capsular structure in a manner usually associated with slow‐exchanging, centrally bound agents. Once formed, this cage was able to bind guests in its central cavity.     

Dehydrocoupling and Silazane Cleavage Routes to Organic–Inorganic Hybrid Polymers with NBN Units in the Main Chain

Despite the great potential of both π‐conjugated organoboron polymers and BN‐doped polycyclic aromatic hydrocarbons in organic optoelectronics, our knowledge of conjugated polymers with B?N bonds in their main chain is currently scarce. Herein, the first examples of a new class of organic–inorganic hybrid polymers are presented, which consist of alternating NBN and para‐phenylene units. Polycondensation with B?N bond formation provides facile access to soluble materials under mild conditions. The photophysical data for the polymer and molecular model systems of different chain lengths reveal a low extent of π‐conjugation across the NBN units, which is supported by DFT calculations. The applicability of the new polymers as macromolecular polyligands is demonstrated by a cross‐linking reaction with Zr^IV.     

Late-stage C−H Functionalization of Tryptophan-Containing Peptides with Thianthrenium Salts: Conjugation and Ligation

Bioorthogonal late-stage diversification of structurally complex peptides bears enormous potential for drug discovery and molecular imaging, among other applications. Herein, we report on a palladium-catalyzed C−H arylation of tryptophan-containing peptides with readily accessible and modular arylthianthrenium salts. Under exceedingly mild reaction conditions, the late-stage diversification of structurally complex peptides was accomplished. The tunability and ease of preparation of arylthianthrenium salts allowed the expedient stitching of tryptophan-containing peptides with drug, natural product, and peptidic scaffolds by forging sterically congested biaryl linkages. The robustness of the palladium catalysis regime was reflected by the full tolerance of a plethora of sensitive and coordinating functional groups. Hence, our manifold enabled efficient access to highly decorated, labelled, conjugated, and ligated linear and cyclic peptides.     

On the Brink of Decomposition: Controlled Oxidation of a Substituted Arsanylborane as a Way to Labile Group 13-15-16 Compounds

The reactivity of the organic-substituted arsanylborane tBuAsHBH₂NMe₃ ( 1 ) towards different elemental chalcogenes as well as organic oxidants such as O-NMe_3, Me₃Si−O−O-SiMe₃, MesCNO and cyclohexenesulfide is reported. By the reaction of 1 with grey selenium, the selenium oxidation product tBuAs(Se)HBH₂NMe₃ ( 2 ) was obtained. For the oxidation with sulfur, the two products tBuAs(S)HBH₂NMe₃ ( 3 a ) and tBuAs(S)SHBH₂NMe₃ ( 3 b ) could be isolated as oils. The structural characterization of As(tBuAs(S)SHBH₂NMe₃)₃ ( 4 ) as well as corresponding DFT computations allow insights into the decomposition behavior of 3 a and 3 b in solution. For the reaction of MesCNO with 1 , the formation of an unusual As−H activation product Mes-C(NOH)-AstBu-BH₂NMe₃ ( 5 ) is observed. In the reaction with Me₃N−O, the first isolatable oxo-arsanylboranes tBuAs(O)HBH₂NMe₃ ( 6 a ) and tBuAs(O)OHBH₂NMe₃ ( 6 b ) are obtained, with 6 b also being accessible via the controlled reaction of 1 with air.