Diene-titanium complexes as synthetic intermediates for the construction of three- or five-membered carbocycles

It has been shown that diene-titanium complexes exhibit substrate-dependent 1,2- or 1,4-dicarbanion reactivity. On this basis, 3-cyclopentenylamines and spiro-vinylcyclopropane lactams were easily prepared by using homoallylic Grignard reagents, Ti(O-i-Pr)4, and nitriles or cyanoesters, respectively.     

Remainder Pade Approximants for the Exponential Function

Following our earlier research, we propose a new method for obtaining the complete Pade table of the exponential function. It is based on an explicit construction of certain Pade approximants, not for the usual power series for exp at 0 but for a formal power series related in a simple way to the remainder term of the power series for exp. This surprising and nontrivial coincidence is proved more generally for type II simultaneous Pade approximants for a family with distinct complex a's and we recover Hermite's classical formulas. The proof uses certain discrete multiple orthogonal polynomials recently introduced by Arvesu, Coussement, and van Assche, which generalize the classical Charlier orthogonal polynomials.     

Photocatalytic C−H Functionalization of Nitrogen Heterocycles Mediated by a Redox Active Protecting Group

Herein, we report a photocatalytic strategy for the C−H functionalization of saturated azaheterocycles under mild conditions with only one equivalent of starting material. Our strategy is based on a redox active benzamide protecting group that is activated via a halogen-atom transfer (XAT) process to trigger the formation of an α-amino radical. This nucleophilic radical intermediate was then engaged in Giese additions and radical cross couplings to afford C−H alkylated and arylated products.     

Rhodium(II)-Catalyzed Selective C(sp3)−H Amination of Alkanes

The development of an efficient catalytic system enabling the conversion of alkanes to valuable nitrogen-containing building blocks is reported. Light alkanes can be selectively functionalized by an intermolecular C(sp³)−H amination reaction that proceeds at room temperature in the presence of only 1 mol % of a dirhodium(II) complex. Selective amination of tertiary C(sp³)−H within acyclic or cyclic alkanes used as limiting components leads to the corresponding amides isolated with yields in the 51–96 % range. The reaction, that can be performed on a gram-scale, applies with equal levels of efficiency and selectivity to more complex hydrocarbons.     

Two-state model of a general Heun class with periodic level-crossings

A specific constant-amplitude periodic level-crossing model of the semi-classical quantum time-dependent two-state problem that belongs to a general Heun class of field configurations is presented. The exact analytic solution for the probability amplitude, generally written for this class in terms of the general Heun functions, in this specific case admits series expansion in terms of the incomplete Beta functions. Terminating this series results in an infinite hierarchy of finite-sum closedform solutions each standing for a particular two-state model, which generally is only conditionally integrable in the sense that for these field configurations the amplitude and phase modulation functions are not varied independently. However, there exists at least one exception when the model is unconditionally integrable, that is the Rabi frequency and the detuning of the driving optical field are controlled independently. This is a constant-amplitude periodic level-crossing model, for which the detuning in a limit becomes a Dirac delta-comb configuration with variable frequency of the levelcrossings. The exact solution for this model is derived, the Floquet exponents are determined and study of the population dynamics in the system for various regions of the input parameters is done.     

Protein NMR Resonance Assignment without Spectral Analysis: 5D SOlid‐State Automated Projection SpectroscopY (SO‐APSY)

Narrow proton signals, high sensitivity, and efficient coherence transfers provided by fast magic‐angle spinning at high magnetic fields make automated projection spectroscopy feasible for the solid‐state NMR analysis of proteins. We present the first ultrahigh dimensional implementation of this approach, where 5D peak lists are reconstructed from a number of 2D projections for protein samples of different molecular sizes and aggregation states, which show limited dispersion of chemical shifts or inhomogeneous broadenings. The resulting datasets are particularly suitable to automated analysis and yield rapid and unbiased assignments of backbone resonances.     

Synthesis and Properties of Benzo‐Fused Indeno[2,1‐c]fluorenes

A set of fully‐conjugated indenofluorenes has been synthesized and confirmed by solid‐state structure analysis. The indeno[2,1‐c]fluorenes and their benzo‐fused analogues all contain the antiaromatic as‐indacene core. The molecules possess high electron affinities and show a broad absorption that reaches into the near‐IR region of the electromagnetic spectrum. All of the featured compounds reversibly accept up to two electrons as revealed by cyclic voltammetry. Analysis of molecule tropicity using NICS‐XY scan calculations shows that, while the as‐indacene core is less paratropic than s‐indacene, benz[a]‐annulation further reduces the antiaromaticity of the core. Antiaromatic strength of the as‐indacene core can also be tuned by the position of fusion of additional arenes on the outer rings.     

Synthesis,Aromaticity, and Application of peri-Pentacenopentacene: Localized Representation of Benzenoid Aromatic Compounds

We report the synthesis and optoelectronic properties of TIPS-peri-pentacenopentacene ( TIPS-PPP ), a vertical extension of TIPS-pentacene ( TIPS-PEN ) and a low-band-gap material with remarkable stability. We found the synthetic conditions to avoid the competition between 1,2- and 1,4-addition of lithium acetylide on the large aromatic dione. The high stability of TIPS-PPP is due to the peri-fusion which increases the aromaticity by generating two localized aromatic sextets that are flanked with 2 diene fragments, similar to two fused-anthracenes. Like TIPS-PEN , TIPS-PPP shows the archetypal 2D brickwall motif in crystals with a larger transfer integral and smaller reorganization energy. The high mobility of up to 1 cm² V^?1 s^?1 was obtained in an organic field-effect transistor fabricated by a wet process. Also, TIPS-PPP was used as a near-infrared (NIR) emitter for NIR organic-light-emitting-diode devices resulting in a high external quantum efficiency at 800 nm.     

Enantioselective palladium(0)-catalyzed intramolecular cyclopropane functionalization: access to dihydroquinolones,dihydroisoquinolones and the BMS-791325 ring system

Taddol-based phosphoramidite ligands enable enantioselective palladium(0)-catalyzed C–H arylation of cyclopropanes. The cyclized products are obtained in high yields and enantioselectivities. The reported method provides efficient access to a broad range of synthetically attractive cyclopropyl containing dihydroquinolones and dihydroisoquinolones as well as allows for an efficient enantioselective construction of the 7-membered ring of the cyclopropyl indolobenzazepine core of BMS-791325.