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A new class of axially-unfixed biaryl-based pyrrolidines with C2-symmetry were designed and synthesized by using enantiopure α-proline as a chiral source. These bifunctional organocatalys provided Michael adducts in high chemical yields (up to 99 %) and with excellent stereoselectivities (up to 99:1 dr and 96 % ee) in the direct Michael addition reactions of a variety of ketones and aldehydes to nitro olefins. The transition states were proposed to clarify the stereochemical course of the examined reactions. [ABSTRACT FROM AUTHOR]

Here, we present a simulation study of temperature‐dependent electronic transitions in BiVO3 (BVO) and BiNbO3 (BNO) using density functional theory (DFT) together with generalized gradient approximation (GGA) and two‐dimensional correlation analysis (2D‐CA). The results indicate that heat accumulation can accelerate the degeneracy of V‐3d orbital in BVO and the splitting of Nb‐4d orbital in BNO at 750 K. We found changes in the type of d–p hybrid orbital as follows, for BVO: V‐dx2+y2 + dZ2‐O‐2pz → V‐dx2+y2‐O‐2pz; and for BNO: Nb‐dx2+y2‐O‐2pz → Nb‐dx2+y2 + dZ2‐O‐2pz. Furthermore, we found changes in the type of hybrid orbital leading to the following electron–electron interactions, for BVO: t2g (V‐dZ2‐O‐2pz) + eg (V‐dx2+y2‐O‐2pz) → t2g (V‐dx2+y2‐O‐2pz); and for BNO: t2g + eg (Nb‐dx2+y2 + dZ2‐O‐2pz) → t2g (Nb‐dx2+y2‐O‐2pz) + eg (Nb‐dz2‐O‐2pz). The electronic transitions are determined by a charge‐transfer from the occupied O‐2p4 orbitals to the unoccupied V‐3d3 (or Nb‐4d3) and Bi‐6p3 orbitals. Due to the temperature‐dependent electronic structure closely related to these electronic transitions, this study provides a new perspective for the design and improvement of BFO‐based temperature‐sensitive devices. [ABSTRACT FROM AUTHOR]

An abstract of the article "Diastereoselective and Enantioselective Michael Addition Reactions of Ketones and Aldehydes to Nitro Olefins Catalyzed by C2-Symmetric Axially-Unfixed Biaryl-Based Organocatalysts Derived from Enantiopure α-Proline" is presented.

The article presents chemical equations related to the article "Novel Axially Unfixed Biaryl-Based Water-Compatible Organocatalysts: Design, Synthesis and Their Asymmetric Catalysis in Direct Aldol Reactions in Water" by H. -W. Zhao and colleagues in a 2013 issue of the periodical "Synlett."

The article presents information on asymmetric direct Michael reactions of cyclohexanone with aromatic nitroolefins in water by using biaryl-based bifunctional organocatalysts.

The article presents chemical equations related to the article "Design, Synthesis and Organocatalysis of 2,2'-Biphenol-Based Prolinamide Organocatalysts in the Asymmetric Direct Aldol Reaction in Water" by H.-W. Zhao and others, published in the journal "Synlett" in 2013.