Triggering Activity of Catalytic Rod‐Like Supramolecular Polymers

Supramolecular polymers based on benzene‐1,3,5‐tricarboxamides (BTAs) functionalized with an L ‐ or D ‐proline moiety display high catalytic activity towards aldol reactions in water. High turnover frequencies (TOF) of up to 27×10^?4 s^?1 and excellent stereoselectivities (up to 96 % de, up to 99 % ee) were observed. In addition, the catalyst could be reused and remained active at catalyst loadings and substrate concentrations as low as 0.1 mol % and 50 mM , respectively. A temperature‐induced conformational change in the supramolecular polymer triggers the high activity of the catalyst. The supramolecular polymer’s helical sense in combination with the configuration of the proline (L ‐ or D ‐) is responsible for the observed selectivity.     

Bromo-Derivatives of 2′-NHR-3,4-methylenedioxychalcone and Its 4-Quinolone Isomer

Bromination reaction of 2′-NHR-3,4′-methylenedioxychalcone (1) and 2,3-dihydro-2-(3′,4′-methylenedioxyphenyl)-4(1H)-quinolone (7) with bromine and N-bromosuccinimide are discussed. Depending on the character of the R group and on the reagent used nuclear or side-chain brominated or side-chain bromo-methoxylated products were obtained.     

Depth-Based Recognition of Shape Outlying Functions

A major drawback of many established depth functionals is their ineffectiveness in identifying functions outlying merely in shape. Herein, a simple modification of functional depth is proposed to provide a remedy for this difficulty. The modification is versatile, widely applicable, and introduced without imposing any assumptions on the data, such as differentiability. It is shown that many favorable attributes of the original depths for functions, including consistency properties, remain preserved for the modified depths. The powerfulness of the new approach is demonstrated on a number of examples for which the known depths fail to identify the outlying functions. Supplementary material for this article is available online.     

CH Activation of Benzene by a Photoactivated NiII(azide): Formation of a Transient Nickel Nitrido Complex

Photochemical activation of nickel‐azido complex 2 [Ni(N₃)(PNP)] (PN^HP=2,2′‐di(isopropylphosphino)‐4,4′‐ditolylamine) in neat benzene produces diamagnetic complex 3 [Ni(Ph)(PN^PN^H)], which is crystallographically characterized. DFT calculations support photoinitiated N₂‐loss of the azido complex to generate a rare, transient Ni^IV nitrido species, which bears significant nitridyl radical character. Subsequent trapping of this nitrido through insertion into the Ni? P bond generates a coordinatively unsaturated Ni^II imidophosphorane P?N donor. This species shows unprecedented reactivity toward 1,2‐addition of a C? H bond of benzene to form 3 . The structurally characterized chlorido complex 4 [Ni(Cl)(PN^PN^H)] is generated by reaction of 3 with HCl or by direct photolysis of 2 in chlorobenzene. This is the first report of aromatic C? H bond activation by a trapped transient nitrido species of a late transition metal.     

Direct,High-Yield Transformation of Tetrahydropyranyl Ethers to Acetates

The practically quantitative transformation of steroidal tetrahydropyranyl ethers to acetates with acetyl chloride in aprotic solvents is described.     

One photon double ionization of helium: threshold behaviour

In order to study the dynamics of double photoionization of helium, we report new coincidence measurements between low energy electrons and doubly charged ions, from 78 to 95 eV photon energy. We show that the range of validity of the Wannier theory depends upon the observable. For the exponentn of the threshold law, this range amounts to some 3 eV above onset, thus confirming previous published experimental work. In contrast, the energy distribution of the two outgoing electrons is found flat, within 20%, in agreement with the theoretical predictions, but in a 15 eV energy range above threshold.