Recent progress in the chemistry of heavy aromatics

The aromaticity and synthetic application of “heavy benzenes”, i.e., benzenes containing a heavier Group 14 element (Si, Ge, Sn, and Pb) in place of skeletal carbon, have been the targets of many theoretical and synthetic studies. Although the introduction of a sterically demanding substituent enabled us to synthesize and isolate heavy aromatic species as a stable compound by suppressing their high reactivity and tendency to polymerize, the existence of a protection group is an obstruction to the development of functional materials based on heavy aromatics. This review will delineate the most recent topics in the chemistry of heavy aromatics, i.e., the chemistry of “metallabenzenyl anions”, which are the heavier Group 14 element analogs of phenyl anions stabilized by taking advantage of charge repulsion instead of steric protection

(E)-N-[2-(9-Fluorenyl­idene)-3a,5,7-tri­methyl-3,3a-dihydro-2H-indol-3-yl­idene]-2,4,6-trimethyl­aniline

The title compound, C33H30N2, has an E configuration at the imine double bond. The angle between the least-squares planes of the imine C=N—C group and the benzene ring of the 2,4,6-trimethylphenyl substituent is 85.38 (11)°. The crystal structure is sustained mainly by inter­molecular π–π inter­actions (3.510 Å) between the two fluorene rings and some C—H⋯π inter­actions

9,9′-Dibromo-9,9′-bifluorene

9,9′-Dibromo-9,9′-bifluorene, C26H16Br2, has a gauche conformation about the connecting C—C bond [the Br—C—C—Br torsion angle is 59.39 (16)°]. The crystal structure is sustained mainly by an inter­molecular C—Br⋯π inter­action [3.299 (2) and 3.369 (2) Å] towards the bifluorene aromatic-ring-connecting C—C bond and a weak C—H⋯π inter­action (2.86 and 2.99 Å) between the two aromatic rings

Discovery of Self‐Assembling Small Molecules as Vaccine Adjuvants

自己集合性ワクチンアジュバントの発見. 京都大学プレスリリース. 2020-10-07.Vaccine ingredients could be hiding in small molecule libraries. 京都大学プレスリリース. 2020-10-07.Immune potentiators, termed adjuvant, trigger early innate immune responses to ensure the generation of robust and long‐lasting adaptive immune responses of vaccines. Here we present study that takes advantage of a self‐assembling small molecule library for the development of a novel vaccine adjuvant. Cell‐based screening of the library and subsequent structural optimization led to the discovery of a simple, chemically tractable deoxycholate derivative (molecule 6 , also named cholicamide) whose well‐defined nano‐assembly potently elicits innate immune responses in macrophages and dendritic cells. Functional and mechanistic analyses indicate that the virus‐like assembly is engulfed inside cells and stimulates the innate immune response through toll‐like receptor 7 (TLR7), an endosomal TLR that detects single‐stranded viral RNA. As an influenza vaccine adjuvant in mice, molecule 6 was as potent as Alum, a clinically used adjuvant. The studies described here paves the way for a new approach to discovering and designing self‐assembling small‐molecule adjuvants against pathogens, including emerging viruses

Formation of Zwitterionic Fullerodendron Using a New DBN-Focal Dendron

A new poly(amidoamine) dendron having 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) at the focal point was synthesized. Interestingly, formation of zwitterionic fullerodendrons (λmax = 930 nm for C60 and 795 nm for C70) were observed by Vis-NIR spectroscopy upon the reaction of C60 or C70 with the DBN-focal dendron. In particular, the C70 anion was effectively stabilized by the site isolation effect of the dendritic wedge. The half-life of fullerodendron 12b having C70 anion at the focal point reaches 7,345 min, which is 20 times longer than that of complex between C60 and pristine DBN. Furthermore, in order to confirm the structure of the zwitterionic complex, fullerodendron 12a was reprecipitated from benzonitrile/1,2,4-trimethylbenzene, and was observed using IR spectroscopy and APPI-MS

Synthesis of a Stable Stibabismuthene; the First Compound with an Antimony-Bismuth Double Bond (BIOORGANIC CHEMISTRY-Organoelement Chemistry)

Condensation reaction of an overcrowded dihydrostibine with dibromobismuthine using 1,8- diazabicyclo[5.4.0]undec-7-ene as a base afforded the first stable stibabismuthene, the formation of which was evidenced by the UV-vis and Raman spectra and its chemical reactivity

Synthesis of rhodium–carbonyl complexes bearing a novel P,N-chelating ligand of Schiff-base type

Schiff-base type N, P-chelating ligands, phosphorus analogues of imino–anilido ligands, were designed and synthesized as a new type of ligands toward transition metals, and the rhodium–carbonyl complexes bearing the novel imino–phosphido and phosphaalkenyl-anilido ligands were synthesized as stable crystalline compounds. Their structures were definitively revealed by X-ray crystallographic analysis, showing the unique electronic features of the ligands. In addition, the effective trans-influence of the phosphorus atom was suggested on the basis of the structural parameters and spectroscopic features of the isolated complexes

Synthesis of a Dichlorodigermasilane: Double Si–Cl Activation by a Ge=Ge Unit

Halogenated oligosilanes and oligogermanes are interesting compounds in oligosilane chemistry from the viewpoint of silicon-based-materials. Herein, it was demonstrated that a 1, 2-digermacyclobutadiene derivative could work as a bis-germylene building block towards double Si–Cl activation to give a halogenated oligometallane, a bis(chlorogermyl)dichlorosilane derivative

Syntheses and structures of a stable gallole free of Lewis base coordination and its dianion

A stable Lewis base-free gallole bearing a bulky Mes[*] group (=2, 4, 6-(t-Bu)[3]C[6]H[2]) was synthesized by the treatment of Mes[*]GaCl[2] with a 3, 6-dilithio-3, 5-octadiene derivative. Reduction of the gallole with lithium metal afforded the corresponding gallole dianion species as a lithium salt. Structures of the gallole and the lithium salt of the gallole dianion have been elucidated by using X-ray crystallographic analysis, NMR spectroscopies, and density functional theory calculation

Synthesis, structure and reactivity of a 1-bromoalumole.

A stable 1-bromoalumole has been synthesized by the reaction of a 1, 4-dilithio-1, 3-butadiene derivative with AlBr[3]. The 1-bromoalumole was found to exist as a dimeric structure in the crystalline state. Reaction of the 1-bromoalumole with Mes[*]Li afforded the corresponding Mes[*]-substituted alumole (Mes[*] = 2, 4, 6-(t-Bu)[3]C[6]H[2]), demonstrating the potential of the 1-bromoalumole for the functionalization of alumoles