Acyclic 1,4-stereocontrol via reductive 1,3-transpositions

One-pot reduction/allylic diazene rearrangement of lactic acid- and mandelic acid-derived alpha,beta-unsaturated tosyl hydrazones leads to 1,4-syn- or 1,4-anti-E-2-alkenyl arrays in high yield and diastereoselectivity. Either the syn or the anti diastereomer can be prepared by choosing the appropriate alkene stereoisomer of the hydrazone. The E-alkenes led to the 1,4-syn isomers, while the Z-alkenes led to the 1,4-anti isomers, both with > or =20:1 diastereoselectivity.     

Preparation of cyclophanes by room-temperature ring-closing alkyne metathesis with imidazolin-2-iminato tungsten alkylidyne complexes

Room-temperature ring-closing alkyne metathesis of 1,2-, 1,3-, and 1,4-bis(3-pentynyloxymethyl)benzenes has been investigated in the presence of catalytic amounts of an imidazolin-2-iminato tungsten alkylidyne complex. The m- and p-diynes selectively form the respective [10]metacyclophane or [10.10]paracyclophane, respectively, whereas a mixture of monomeric and dimeric cycloalkynes is obtained in the case of the o-diyne. DFT calculations reveal that the different selectivities can be attributed to the relative thermodynamic stability of the emerging cyclophanes.     

Gamma limit of the nonself-dual Chern-Simons-Higgs energy

We consider the Gamma limit of the Abelian Chern-Simons-Higgs energy

     

Invariant measures and maximal L2 regularity for nonautonomous Ornstein-Uhlenbeck equations

We characterize the domain of the realizations of a linear parabolicoperator defined in L² spaces with respect to a suitable measurethat is invariant for the associated evolution semigroup. Asa byproduct, we obtain optimal L² regularity results for evolutionequations with time-dependant Ornstein–Uhlenbeck operators.     

A dynamic micromixer for arbitrary control of disguised chemical selectivity

A new type of dynamic micromixer combining the concepts of parallel multi-lamination and hydrodynamic focusing was developed for arbitrary control of disguised chemical selectivity.     

The strength of the σ-, π- and δ-bonds in Re2Cl 8 2−

The geometry of Re₂Cl₈²⁻ has been optimized for the eclipsed (D _4h ) equilibrium conformation and for the staggered (D _4d ) conformation at BP86/TZ2P. The nature of the Re–Re bond which has a formal bond order four has been studied with an energy decomposition analysis (EDA). The EDA investigation indicates that the contribution of the b ₂ (δ _xy ) orbitals to the Re–Re bond in the ground state is negligibly small. The vertical excitation of one and two electrons from the bonding δ orbital into the antibonding δ* orbitals yielding the singly and doubly excited states and gives a destabilization of 17.5 and 36.1 kcal/mol, respectively, which is nearly the same as the total excitation energies. The preference for the D _4h geometry with eclipsing Re–Cl bonds is explained in terms of hyperconjugation rather than δ bonding. This is supported by the calculation of the triply bonded Re₂Cl₈ which also has an eclipsed energy minimum structure. The calculations also suggest that the Re–Re triple bond in Re₂Cl₈ is stronger than the Re–Re quadruple bond in Re₂Cl₈²⁻. A negligible contribution of the δ orbital to the metal–metal bond strength is also calculated for Os₂Cl₈ which is isoelectronic with Re₂Cl₈²⁻. Contribution of the Mark S. Gordon 65th Birthday Festschrift Issue. Theoretical Studies of Inorganic Compounds. 38. Part 37 (2006) Bessac F, Frenking G, Inorg Chem 45:6956.