Electrophilic Behavior of the "Nucleophilic" Pyramidane: Reactivity of Ge-Pyramidane towards Organolithium Reagents.

The particular reactivity of the recently discovered class of the main group element polyhedral clusters, pyramidanes, remains largely unexplored. In this communication, we report the reaction of the germapyramidane with tert-butyllithium leading to the rather unusual organogermanium compound [Li(thf)]⋅2, as the product of the formal insertion of a Ge-apex into the C-Li bond. This reactivity mode exemplifies unusual electrophilic behaviour of a pyramidane, which is a priori considered as a nucleophilic reagent.

Pyramidanes: newcomers to the anti-van't Hoff-Le Bel family.

In this feature article, an overview of the chemistry of pyramidanes, as a novel class of main group element clusters, is given. A general introduction sets the scene, briefly presenting the non-classical pyramidal geometry of tetracoordinate carbon, as opposed to the classical tetrahedral configuration. Pyramidanes, as the simplest organic compounds possessing a pyramidal carbon atom, are then discussed from both computational and experimental viewpoints, to show the theoretical predictions on the stability and thus the feasibility of pyramidanes has finally culminated in the isolation of the first stable representatives of the pyramidane family featuring heavy main group elements at the apex of the square pyramid.

Organogermanium Analogues of Alkenes, Alkynes, 1,3-Dienes, Allenes, and Vinylidenes.

In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The isolable Ge-containing analogues of alkenes, alkynes, 1,3-dienes, allenes, and vinylidenes are discussed, and for each class of unsaturated organogermanium compounds, the most representative examples are given. The synthetic approaches toward homonuclear multiply bonded combinations solely consisting of germanium atoms, and their heteronuclear variants containing germanium and other group 14 elements, both acyclic and cyclic, are discussed.

From SiO to Alkoxysilanes for the Synthesis of Useful Chemicals.

The transformation of silica (SiO) to useful chemicals is difficult to explore because of the strength of the Si-O bond and thermodynamic stability of the SiO structure. The direct formation of alkoxysilanes from SiO has been explored as an alternative to the carbothermal reduction (1900 °C) of SiO to metallic silicon (Si) followed by treatment with alcohols. The base-catalyzed depolymerization of SiO with diols and monoalcohols afforded cyclic silicon alkoxides and tetraalkoxysilanes, respectively.

Probe-based confocal laser endomicroscopy in COVID-19.

Probe-based confocal laser endomicroscopy (pCLE) is a method that produces microscopic imaging of a lung tissue during bronchoscopy. We report a case ot a patient with negative nasopharyngeal swabs and suspected lung cancer who underwent pCLE. The diagnosis of COVID-19 was confirmed by PCR analyses of lavage fluid and transbrohial biopsy.

Sustainable Catalytic Synthesis of Diethyl Carbonate.

New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO and alcohols. Using tetraethyl orthosilicate (TEOS) and CO with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS.

From a (Silatrigerma)cyclobutenylium Ion to a (Silatrigerma)cyclobutenyl Radical and Back.

(Silatrigerma)cyclobutenylium ion salt was readily prepared by the reaction of cyclotrigermene with an equimolar amount of [EtSi(benzene)][B(CF)] in benzene. The homoaromatic nature of was firmly established by its crystallographic analysis, which revealed a highly folded SiGe four-membered ring (40.4°) and a remarkably short transannular Ge-Ge distance of 2.

Tuning Philicity of Dichlorosilylene: Nucleophilic Behavior of the Dichlorosilylene-NHC Complex ClSi-IPr.

Novel unsaturated four-membered ring disilene, 3,3-dichloro-1,2,4,4-tetrakis[di--butyl(methyl)silyl]-Δ-1,2,3,4-trisilagermetene, was synthesized by the ring expansion reaction of the three-membered ring 1-disilagermirene with the silylene-NHC complex ClSi-IPr. The mechanism of the unexpected formation of this compound was verified by high-level density functional theory computations, which revealed n-π as the dominant orbital interaction.

Racioethnic diversity in the dynamics of the vaginal microbiome during pregnancy.

The microbiome of the female reproductive tract has implications for women's reproductive health. We examined the vaginal microbiome in two cohorts of women who experienced normal term births: a cross-sectionally sampled cohort of 613 pregnant and 1,969 non-pregnant women, focusing on 300 pregnant and 300 non-pregnant women of African, Hispanic or European ancestry case-matched for race, gestational age and household income; and a longitudinally sampled cohort of 90 pregnant women of African or non-African ancestry. In these women, the vaginal microbiome shifted during pregnancy toward Lactobacillus-dominated profiles at the expense of taxa often associated with vaginal dysbiosis.

The vaginal microbiome and preterm birth.

The incidence of preterm birth exceeds 10% worldwide. There are significant disparities in the frequency of preterm birth among populations within countries, and women of African ancestry disproportionately bear the burden of risk in the United States. In the present study, we report a community resource that includes 'omics' data from approximately 12,000 samples as part of the integrative Human Microbiome Project.

Genomic comparison of Trypanosoma conorhini and Trypanosoma rangeli to Trypanosoma cruzi strains of high and low virulence.

Background: Trypanosoma conorhini and Trypanosoma rangeli, like Trypanosoma cruzi, are kinetoplastid protist parasites of mammals displaying divergent hosts, geographic ranges and lifestyles. Largely nonpathogenic T. rangeli and T.

Arsagermene, a compound with an -As[double bond, length as m-dash]Ge[double bond splayed right] double bond.

The first compound featuring an As[double bond, length as m-dash]Ge double bond, arsagermene Mes*As[double bond, length as m-dash]Ge(SiMetBu2)2, was synthesized, isolated and fully characterized. Crystallographic studies revealed that arsagermene has a planar Ge[double bond, length as m-dash]As bond of 2.2731(8) Å, which is notably shorter than the standard Ge-As single bond.

From Borapyramidane to Borole Dianion.

Nonclassical pyramidanes with their inverted tetrahedral configuration of the apical atom are among the most challenging synthetic targets in cluster chemistry. In this Communication, we report on the synthesis and structure of the first representative of pyramidal compounds with the group 13 element at the apex, namely, chloroborapyramidane 2. Reduction of 2 with excess of lithium metal unexpectedly produced the cage-opening product, borole dianion derivative {3·[Li(thf)]}, a 6π-electron aromatic system.

Bis(stibahousene).

Strained hydrocarbons constitute one of the most prominent classes of organic compounds. Among them, bicyclo[2.1.

The Evolutionary Loss of RNAi Key Determinants in Kinetoplastids as a Multiple Sporadic Phenomenon.

We screened the genomes of a broad panel of kinetoplastid protists for genes encoding proteins associated with the RNA interference (RNAi) system using probes from the Argonaute (AGO1), Dicer1 (DCL1), and Dicer2 (DCL2) genes of Leishmania brasiliensis and Crithidia fasciculata. We identified homologs for all the three of these genes in the genomes of a subset of these organisms. However, several of these organisms lacked evidence for any of these genes, while others lacked only DCL2.

A Cationic Phosphapyramidane.

Pyramidanes C[C R ] constitute a novel class of highly strained and reactive polyhedral clusters that attracted a great deal of attention of both theoreticians and experimentalists. Although well-studied from the theoretical viewpoint, pyramidanes were synthetically inaccessible, and only very recently their very first isolable representatives have been described. In this Communication, we report on the synthesis and structural studies of the cationic pyramidane with the Group 15 element at the apex, namely, phosphapyramidane, an isoelectronic analogue of the neutral pyramidanes of the Group 14 elements.

From a Si3-Cyclopropene to a Si3S-Bicyclo[1.1.0]butane to a Si3S-Cyclopropene to a Si3S2-Bicyclo[1.1.0]butane: Back-and-Forth, and In-Between.

Compact and highly reactive bicyclo[1.1.0]butanes constitute one of the most fascinating classes of organic compounds.

Pentagermapyramidane: crystallizing the "transition-state" structure.

The first example of the homonuclear pyramidanes, pentagermapyramidane, was synthesized, fully characterized, and computationally studied to reveal its peculiar structural features and the nature of its apex-to-base bonding interactions. Both solid-state and solution structures of pentagermapyramidane are discussed based on the computed stabilities of its square-pyramidal and distorted forms.

Whole exome sequencing to estimate alloreactivity potential between donors and recipients in stem cell transplantation.

Whole exome sequencing (WES) was performed on stem cell transplant donor-recipient (D-R) pairs to determine the extent of potential antigenic variation at a molecular level. In a small cohort of D-R pairs, a high frequency of sequence variation was observed between the donor and recipient exomes independent of human leucocyte antigen (HLA) matching. Nonsynonymous, nonconservative single nucleotide polymorphisms were approximately twice as frequent in HLA-matched unrelated, compared with related D-R pairs.

Stibasilene Sb═Si and its lighter homologues: a comparative study.

The multiply bonded derivatives of the heavier main group elements are among the most challenging targets for synthetic pursuits. Those of them featuring a double bond between the silicon and group 15 element are represented mostly by the silaimines -N═Si< and phosphasilenes -P═Si< with a very few examples of arsasilenes -As═Si<. In this contribution, we report on the synthesis and structural elucidation of the first stable stibasilene and novel phosphasilene and arsasilene derivatives, featuring an identical substitution pattern.

Pyramidanes.

Pyramidane is an elusive but highly desirable target for synthetic chemists that has attracted a great deal of attention because of its nonclassical structure and unusual bonding features. Although well studied on theoretical grounds, neither the parent all-carbon pyramidane nor its derivatives containing heavier group 14 elements have ever been isolated and characterized. In this Communication, we report on the synthesis and structural elucidation of the first stable representatives of this class of highly strained polyhedral compounds: germa- and stannapyramidanes Ge[C4(SiMe3)4] and Sn[C4(SiMe3)4].

Spirobis(pentagerma[1.1.1]propellane): a stable tetraradicaloid.

In this contribution, we report a spirobis(pentagerma[1.1.1]propellane) derivative as a novel type of molecular architecture in cluster chemistry that features two spiro-fused [1.

Toward a silicon version of metathesis: from Schrock-type titanium silylidenes to silatitanacyclobutenes.

Olefin metathesis is one of the most important industrial processes for the production of alkenes. In contrast, silicon versions of metathesis are unknown given the lack of available silylene transition-metal complexes suitable for [2 + 2] cycloaddition with unsaturated substrates. Here, we report the synthesis of 18-electron titanium silylene complexes featuring different Lewis base ligands and classified on the basis of structural, computational, and reactivity studies as Schrock-type silylene complexes.

Novel organometallic reagents: geminal dianionic derivatives of the heavy group 14 elements.

This Forum review describes the most recent achievements in the novel prospective field of highly reactive main-group organometallics, namely, geminal dianionic derivatives of the heavy group 14 elements (Si, Ge, Sn). A brief historical introduction to the topic is followed by discussion of the current state of affairs in the field of stable derivatives and prospects for future efforts, highlighting our own synthetic approach and recent results. The most important experimental contributions, including synthesis of 1,1-dilithiosilane, -germane, and -stannane derivatives; dilithio(halo)silanes (lithiosilylenoids); metallole 1,1-dianions; and heavy analogues of the cyclobutadiene dianion derivatives, are presented, along with a discussion of the synthetic applications of the above-mentioned organometallic compounds.