Rate Dependence on Inductive and Resonance Effects for the Organocatalyzed Enantioselective Conjugate Addition of Alkenyl and Alkynyl Boronic Acids to β-Indolyl Enones and β-Pyrrolyl Enones

Two key factors bear on reaction rates for the conjugate addition of alkenyl boronic acids to heteroaryl-appended enones: the proximity of inductively electron-withdrawing heteroatoms to the site of bond formation and the resonance contribution of available heteroatom lone pairs to stabilize the developing positive charge at the enone β-position. For the former, the closer the heteroatom is to the enone β-carbon, the faster the reaction. For the latter, greater resonance stabilization of the benzylic cationic charge accelerates the reaction. Thus, reaction rates are increased by the closer proximity of inductive electron-withdrawing elements, but if resonance effects are involved, then increased rates are observed with electron-donating ability. Evidence for these trends in isomeric substrates is presented, and the application of these insights has allowed for reaction conditions that provide improved reactivity with previously problematic substrates.

Bis-palladium(II) complex of doubly N-confused octaphyrin(1.1.1.1.1.1.1.1): Möbius aromaticity and chiroptical properties

A novel bis-palladium(II) complex of doubly N-confused octaphyrin (Pd[Formula: see text]-2) adopting a Möbius-twisted topological structure was synthesized and characterized. Due to the effective 36[Formula: see text]-electronic delocalization over the Möbius-twisted octaphyrin scaffold, characteristic Soret and Q-like absorption features were observed in the near-infrared (NIR) region. However, the complex Pd[Formula: see text]-2 exhibited weak aromatic character attributed to the distinct cross-conjugated resonance contribution as inferred from the 1H NMR chemical shifts as well as theoretical assessments ([Formula: see text] nucleus-independent chemical shift (NICS)). Since the bis-palladium(II) complexation of doubly N-confused octaphyrin 2 imparted significant conformational stability, topologically chiral enantiomers of Pd[Formula: see text]-2 were successfully separated as ([Formula: see text]- and ([Formula: see text]-twisted forms. The resulting isomers revealed relatively large circular dichroism (CD) responses with an absorption anisotropy factor of [Formula: see text] [Formula: see text] 0.009 in the NIR region ([Formula: see text] 823 nm). In addition, the cyclic voltammogram of Pd[Formula: see text]-2 revealed redox-rich properties due to its large [Formula: see text]-conjugated system.

Understanding the contribution of groove resonance to tire-road noise on different surfaces under various operating conditions

Reducing tire-road noise is now becoming more and more important during the tire development process. Tread profile randomization is used to avoid tonal components and reduce groove resonance noise. To better understand the groove resonance contribution to tire-road noise, we performed acoustic measurements on a test bench with two serial tires. We filled the grooves with acoustic foam to highlight the groove resonance’s contribution. We then varied the road surface, the tire load and the driving speed. In the end, we used a multiple linear regression to quantify the interaction between the varying parameters and the groove resonance noise. We show that groove resonance contributes an average of 1.7 dBA to the tire rolling noise of passenger car tires. Groove resonance noise also increases with the driving speed. While the tread pattern and the tire load are responsible for the spectral content of the groove resonance noise, the orientation of the road surface’s texture mainly influences the noise level of the groove resonance. The tire manufacturers should carefully consider these findings when developing noise-optimized patterns. This is especially true for tire approval tests, which take place on tracks and usually have a relatively low texture level that is oriented negatively.

Resonance contribution of scalar color octet to tt̄ production at the LHC in the minimal four-color quark–lepton symmetry model

The scalar color octet contribution to the resonance [Formula: see text]-pair production at the LHC is calculated and analyzed by taking into account the one-loop effective two-gluon vertex. It is shown that this contribution from the scalar color octet [Formula: see text] predicted by the minimal model with the four-color quark–lepton symmetry is for [Formula: see text] = 13 TeV of about a few percent for 750 [Formula: see text] 1800 GeV and can exceed 10% for 400 [Formula: see text] 750 GeV. It is also pointed out that the search for the scalar octet [Formula: see text] as the resonance in the dijet mass spectra seems to be difficult because of the smallness of its one-loop effective two-gluon interaction.