BN-naphthalene (2) and BN-tetralin (7) have been prepared by a short synthesis from allyltributylstannane (3). The reaction of 3 with BCl3 followed by diallylamine and Et3N afforded ...(diallylamino)diallylborane (5), which gave 1,4,5,8-tetrahydro1,2azaborino1,2-a1,2azaborine (6), on treatment with Grubbs (I) catalyst. The reaction of 6 with Pd gave 2 and 7. The reaction of 7 with Cr(CO)6 gave the corresponding Cr(CO)3 adduct 8, for which a crystal structure has been obtained. The isomerization of 6 to 7 has been examined using DFT calculations.
The reaction of 2,5-dihydro-2-diisopropylamino-1,2-thiaborole (5) with 2 equiv of LDA followed by CH2Cl2 gives 2-(diisopropylamino)-2H-1,2-thiaborin (2c), which has been spectroscopically and ...structurally characterized. DFT calculations indicate that formally aromatic 2c has a limited π-delocalized bonding in its heterocyclic ring.
Allylic CH bond activation and addition across the CC double bond are both observed in the reactions of alkenes with a stannylene/phenyl iodide reagent. The relative amounts of each of these ...products are sensitive to the steric bulk of the alkene and of the aryl halide.
Two polymorphic structures of Cp*GeCl were determined by single-crystal X-ray diffraction analysis: (I) a dimer in the form of a parallelogram in solid state (yellow crystals, P21/n) and (II) an ...infinite ladder of alternating parallelograms (colorless crystals, C2/c). Melting experiments in X-ray capillary tubes revealed that the C2/c polymorph converts to the P21/n polymorphic structure. Variable-temperature and concentration-dependent 1H NMR spectroscopy suggest an equilibrium between a monomer and either a dimer or higher oligomer species. Variable-temperature 1H NMR (from 25 to −80 °C) of Cp*GeCl (P21/n) dissolved in toluene-d 8 indicates that lower temperature favors the dimers and/or oligomers. Increasing concentration (from 0.05 to 0.65 M) also favors the dimer or oligomer structure. The addition of chloride ions (from 0.1 to 1.0 equiv) via the addition of tetrabutylammonium chloride to solutions prepared from Cp*GeCl resulted in the formation of Cp*2Ge. Addition of increasing amounts (from 5 to 42 mg) of Cp*GeCl to a sample of Cp*2Ge gave no evidence of exchange by 1H NMR spectroscopy. Similarly, the addition of one equivalent of methyl mesylate to various concentrations of Cp*GeCl (0.06, 0.09, and 1.8 M) did not result in the formation of methyl chloride, indicating that an equilibrium involving chloride ions is not operative.
The coronavirus disease 2019 (COVID-19) Exposure Assessment Tool (CEAT) allows users to compare respiratory relative risk to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for various ...scenarios, providing understanding of how combinations of protective measures affect risk. CEAT incorporates mechanistic, stochastic, and epidemiological factors including the (i) emission rate of virus, (ii) viral aerosol degradation and removal, (iii) duration of activity/exposure, (iv) inhalation rates, (v) ventilation rates (indoors/outdoors), (vi) volume of indoor space, (vii) filtration, (viii) mask use and effectiveness, (ix) distance between people (taking into account both near-field and far-field effects of proximity), (x) group size, (xi) current infection rates by variant, (xii) prevalence of infection and immunity in the community, (xiii) vaccination rates, and (xiv) implementation of COVID-19 testing procedures. CEAT applied to published studies of COVID-19 transmission events demonstrates the model’s accuracy. We also show how health and safety professionals at NASA Ames Research Center used CEAT to manage potential risks posed by SARS-CoV-2 exposures.
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Photolysis of vinylazide 1, which has a built-in acetophenone triplet sensitizer, in argon-saturated toluene results in azirine 2, whereas irradiation in oxygen-saturated toluene yields cyanide ...derivatives 3 and 4. Laser flash photolysis of azide 1 in argon-saturated acetonitrile shows formation of vinylnitrene 1c, which has a λmax at ∼300 nm and a lifetime of ∼1 ms. Vinylnitrene 1c is formed with a rate constant of 4.25 × 105 s–1 from triplet 1,2-biradical 1b. Laser flash photolysis of 1 in oxygen-saturated acetonitrile results in 1c-O (λmax = 430 nm, τ ≈ 420 μs acetonitrile). Density functional theory (DFT) calculations were used to aid in the characterization of the intermediates formed upon irradiation of azide 1 and to validate the proposed mechanism for its photoreactivity.
![Syntheses of [6,6]-Fused-Ri...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0276-7333/small "Syntheses of [6,6]-Fused-Ring 1,2-Azaborines")
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