Indium–Arsenic Molecules with an InAs Triple Bond: A Theoretical Approach

The effect of substitution on the potential energy surfaces of RInAsR (R = F, OH, H, CH₃, and SiH₃ and R′ = SiMe­(Si<i>t</i>Bu₃)₂, Si<i>i</i>PrDis₂, and <i>N</i>-heterocyclic carbene (NHC)) is determined using density functional theory calculations (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). The computational studies demonstrate that all of the triply bonded RInAsR species prefer to adopt a bent geometry, which is consistent with the valence electron model. The theoretical studies show that RInAsR molecules that have smaller substituents are kinetically unstable with respect to their intramolecular rearrangements. However, triply bonded R′InAsR′ species that have bulkier substituents (R′ = SiMe­(Si<i>t</i>Bu₃)₂, Si<i>i</i>PrDis₂, and NHC) occupy minima on the singlet potential energy surface, and they are both kinetically and thermodynamically stable. That is, the electronic and steric effects of bulky substituents play an important role in making molecules that feature an InAs triple bond viable as a synthetic target. Moreover, two valence bond models are used to interpret the bonding character of the InAs triple bond. One is model [A], which is best represented as . This interprets the bonding conditions for RInAsR molecules that feature small ligands. The other is model [B], which is best represented as . This explains the bonding character of RInPAsR molecules that feature large substituents

Triply Bonded GalliumPhosphorus Molecules: Theoretical Designs and Characterization

The effect of substitution on the potential energy surfaces of triple-bonded RGaPR (R = F, OH, H, CH₃, SiH₃, SiMe­(Si<i>t</i>Bu₃)₂, Si<i>i</i>PrDis₂, Tbt (C₆H₂-2,4,6-{CH­(SiMe₃)₂}₃), and Ar* (C₆H₃-2,6-(C₆H₂-2,4,6-<i>i</i>-Pr₃)₂)) compounds was theoretically examined by using density functional theory (i.e., M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). The theoretical evidence strongly suggests that all of the triple-bonded RGaPR species prefer to select a bent form with an angle (∠Ga–P–R) of about 90°. Moreover, the theoretical observations indicate that only the bulkier substituents, in particular, for the strong donating groups (e.g., SiMe­(Si<i>t</i>Bu₃)₂ and Si<i>i</i>PrDis₂) can efficiently stabilize the GaP triple bond. In addition, the bonding analyses (based on the natural bond orbital, the natural resonance theory, and the charge decomposition analysis) reveal that the bonding characters of such triple-bonded RGaPR molecules should be regarded as R′Ga←PR′. In other words, the GaP triple bond involves one traditional σ bond, one traditional π bond, and one donor–acceptor π bond. Accordingly, the theoretical conclusions strongly suggest that the GaP triple bond in such acetylene analogues (RGaPR) should be very weak

Triple-Bonded BoronPhosphorus Molecule: Is That Possible?

The effect of substitution on the potential energy surfaces of RBPR (R = H, F, OH, SiH₃, and CH₃) is studied using density functional theories (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). There is significant theoretical evidence that RBPR compounds with smaller substituents are fleeting intermediates, so they would be difficult to be detected experimentally. These theoretical studies using the M06-2X/Def2-TZVP method demonstrate that only the triply bonded R′BPR′ molecules bearing sterically bulky groups (R′ = Tbt (=C₆H₂-2,4,6-{CH­(SiMe₃)₂}₃), SiMe­(Si<i>t</i>Bu₃)₂, Ar* (=C₆H₃-2,6-(C₆H₂-2,4,6-<i>i</i>-Pr₃)₂), and Si<i>i</i>PrDis₂) are significantly stabilized and can be isolated experimentally. Using the simple valence-electron bonding model and some sophisticated theories, the bonding character of R′BPR′ should be viewed as R′BI PR′. The present theoretical observations indicate that both the electronic and the steric effect of bulkier substituent ligands play a key role in making triply bonded R′BPR′ species synthetically accessible and isolable in a stable form

Substituent Effects on Boron–Bismuth Triple Bond: A New Target for Synthesis

The substituent effects on the potential energy surfaces of RBBiR (R = F, OH, H, CH₃, SiH₃, Tbt, Ar*, SiMe­(Si<i>t</i>Bu₃)₂, and Si<i>i</i>PrDis₂) are determined using density functional theories (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). The theoretical results show that all of the triply bonded RBBiR molecules prefer to adopt a bent geometry (i.e., ∠RBBi ≈ 180° and ∠BBiR ≈ 90°), which agrees well with the valence-electron bonding model. It is also demonstrated that the smaller groups, such as R = H, F, OH, CH₃, and SiH₃, neither kinetically nor thermodynamically stabilize the triply bonded RBBiR compounds, except for H₃SiBBiSiH₃. However, triply bonded R′BBiR′ molecules that feature bulkier substituents (R′ = Si<i>i</i>PrDis₂, SiMe­(Si<i>t</i>Bu₃)₂, Tbt, and Ar*) are predicted to have a thermodynamic and kinetic global minimum. This theoretical study finds that both the steric and the electronic effects of bulkier substituent groups play a significant role in forming triply bonded RBBiR species that are experimentally obtainable and isolable in a stable form

Total Synthesis of (+)-Antrocin and Its Diastereomer and Clarification of the Absolute Stereochemistry of (−)-Antrocin

Using 2,2-dimethyl cyclohexanone as the starting compound, (+)-antrocin and its diastereomer have been synthesized. The absolute stereochemistry of (−)-antrocin, a natural sesqui-terpenoid and an antagonist in some types of cancer cells, was clarified using the character data of (+)-antrocin. The synthetic procedure involved two key steps: (1) the reaction of vinyl magnesium bromide with 2,2-dimethyl-6-<i>t</i>-butyl-dimethyl-silyoxy-methyl-1-cyclo-hexanone to give a vinyl cyclohexanol derivative and (2) a highly stereoselective intramolecular Diels–Alder (IMDA) reaction of the camphanate-containing triene intermediate. The relative energy levels of the possible transition states of the IMDA reaction of the camphanate-containing triene were obtained from density functional theory calculations, proving the stereospecific formation of the target molecule