Non‐Innocent Methylene Linker in Bridged Lewis Pair Initiators

Deprotonation usually occurs as an unwanted side reaction in the Lewis pair polymerization of Michael acceptors, for which the conjugated addition of the Lewis base to the acid‐activated monomer is the commonly accepted initiation mechanism. This has also been reported for B?P‐based bridged Lewis pairs (BLPs) that form macrocyclic addition products. We now show that the formerly unwanted deprotonation is the likely initiation pathway in the case of Al?P‐based BLPs. In a detailed study of a series of Al?P‐based BLPs, using a combination of single‐crystal diffraction experiments (X‐ray and neutron) and mechanistic investigations (experimental and computational), an active role of the methylene bridge was revealed, acting as a base towards the α‐acidic monomers. Additionally, the polymerization studies proved a living behavior combined with significantly high activities, narrow molecular mass distributions, and the possibility of copolymerization.     

Synthesis,Characterization, and Theoretical Investigation of Two‐Coordinate Palladium(0) and Platinum(0) Complexes Utilizing π‐Accepting Carbenes

An elegant general synthesis route for the preparation of two coordinate palladium(0) and platinum(0) complexes was developed by reacting commercially available tetrakis(triphenylphosphine)palladium/platinum with π‐accepting cyclic alkyl(amino) carbenes (cAACs). The complexes are characterized by NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction. The palladium complexes exhibit sharp color changes (crystallochromism) from dark maroon to bright green if the C‐Pd‐C bond angle is sharpened by approximately 6°, which is chemically feasible by elimination of one lattice THF solvent molecule. The analogous dark orange‐colored platinum complexes are more rigid and thus do not show this phenomenon. Additionally, [(cAAC)₂Pd/Pt] complexes can be quasi‐reversibly oxidized to their corresponding [(cAAC)₂Pd/Pt]⁺ cations, as evidenced by cyclic voltammetry measurements. The bonding and stability are studied by theoretical calculations.     

Sex-dependent gene expression in early brain development of chicken embryos

Background  

Differentiation of the brain during development leads to sexually dimorphic adult reproductive behavior and other neural sex dimorphisms. Genetic mechanisms independent of steroid hormones produced by the gonads have recently been suggested to partly explain these dimorphisms.     

First enantioselective total synthesis of (+)-(R)-Pinnatolide using an asymmetric domino allylation reaction

An efficient total synthesis of (+)-(R)-Pinnatolide is described. As a key step an asymmetric multicomponent domino allylation reaction of methyl levulinate is used to form the quaternary stereogenic center in a highly selective way.