A two step route to indoles from haloarenes--a versatile variation on the Fischer indole synthesis

In a new variation on the Fischer indole synthesis, readily available haloarenes are converted into a wide range of indoles in just two steps by halogen-magnesium exchange, quenching with di-tert-butyl azodicarboxylate, followed by reaction with ketones under acidic conditions.     

Observation of high soft x-ray drive in large-scale hohlraums at the National Ignition Facility

The first soft x-ray radiation flux measurements from hohlraums using both a 96 and a 192 beam configuration at the National Ignition Facility have shown high x-ray conversion efficiencies of ～85%-90%. These experiments employed gold vacuum hohlraums, 6.4 mm long and 3.55 mm in diameter, heated with laser energies between 150-635 kJ. The hohlraums reached radiation temperatures of up to 340 eV. These hohlraums for the first time reached coronal plasma conditions sufficient for two-electron processes and coronal heat conduction to be important for determining the radiation drive.     

Factors affecting the quality of plutonium deposits by electrodeposition

Ultra-high resolution alpha spectrometry by microcalorimetry has demonstrated a dramatic improvement in alpha energy resolution over silicon based detectors. To characterize the optimal resolution obtained by the microcalorimeter alpha spectrometers, high quality deposits that are virtually massless are required; electrodeposition is the preferred method for the preparation of high quality deposits. In order to better understand the factors that contribute to lower alpha energy resolution and deposit yield, we have conducted a study to determine the effect of some of the parameters that are used for preparing electrodeposits. We have compared four different electrodeposition methods and four different substrate materials to determine the effect on the deposit yield and alpha energy resolution of plutonium as measured by full width at half maximum using silicon based detectors. Furthermore, we wanted to understand the effect of contaminants from environmental samples on electrodeposits. Therefore, the effect on deposit yield and alpha energy resolution with several common soil constituents (Al³⁺, Eu³⁺, Fe³⁺, K⁺, Lu³⁺, Mg²⁺, Na⁺, Zn²⁺) have been studied.     

Attaining the Optimal Gaussian Diffusion Acceleration

Sampling from probability distributions in high dimensional spaces is generally impractical. Diffusion processes with invariant equilibrium distributions can be used as a means to generate approximations. An important task in such an endeavor is to design an equilibrium-preserving drift to accelerate the convergence. Starting from a reversible diffusion, it is desirable to depart for non-reversible dynamics via a perturbed drift so that the convergence rate is maximized with the common equilibrium. In the Gaussian diffusion acceleration, this problem can be cast as perturbing the inverse of a given covariance matrix by skew-symmetric matrices so that all resulting eigenvalues have identical real part. This paper describes two approaches to obtain the optimal rate of Gaussian diffusion. The asymptotical approach works universally for arbitrary Ornstein–Uhlenbeck processes, whereas the direct approach can be implemented as a fast divide-and-conquer algorithm. A comparison with recently proposed Lelièvre–Nier–Pavliotis algorithm is made.     

Nonnegative rank factorization—a heuristic approach via rank reduction

Given any nonnegative matrix $A \in \mathbb{R}^{m \times n}$ , it is always possible to express A as the sum of a series of nonnegative rank-one matrices. Among the many possible representations of A, the number of terms that contributes the shortest nonnegative rank-one series representation is called the nonnegative rank of A. Computing the exact nonnegative rank and the corresponding factorization are known to be NP-hard. Even if the nonnegative rank is known a priori, no simple procedure exists presently that is able to perform the nonnegative factorization. Based on the Wedderburn rank reduction formula, this paper proposes a heuristic approach to tackle this difficult problem numerically. Starting with A, the idea is to recurrently extrat, whenever possible, a rank-one nonnegative portion from the previous matrix while keeping the residual nonnegative and lowering its rank by one. With a slight modification for symmetry, the method can equally be applied to another important class of completely positive matrices. No convergence can be guaranteed, but repeated restart might help alleviate the difficulty. Extensive numerical testing seems to suggest that the proposed algorithm might serve as a first-step numerical means for exploring the intriguing problem of nonnegative rank factorization.     

Potassium N‐Iodo p‐Toluenesulfonamide (TsNIK,Iodamine‐T): A New Reagent for the Oxidation of Hydrazones to Diazo Compounds

A new reagent for the oxidation of hydrazones to diazo compounds is described. N‐Iodo p‐toluenesulfonamide (TsNIK, iodamine‐T) allows the preparation of α‐diazoesters, α‐diazoamides, α‐diazoketones and α‐diazophosphonates in good yield and in high purity after a simple extractive work‐up. α‐Diazoesters were also obtained in high yield from the corresponding ketones through a one‐pot process of hydrazone formation/oxidation.     

Construction of macrocyclic thiodepsipeptides: synthesis of a nosiheptide 'southern hemisphere' model system

A 20-membered macrocyclic thiodepsipeptide has been synthesized as a model for the southern hemisphere of nosiheptide, the key steps being assembly of an acyclic precursor by amide coupling of indole and thiazole fragments followed by formation of the thiolactone in the macrocyclization step.     

Synthesis of the reported structure of the bisbenzoquinone lanciaquinone, isolated from Maesa lanceolata

Lanciaquinone, isolated from Maesa lanceolata, was originally assigned as a bisbenzoquinone with a C14-chain linking the two quinone rings. A synthesis of the reported structure, in which the key step is a double Claisen rearrangement, suggests that the structure of the natural product needs to be revised.     

Copper-catalysed approach to spirocyclic oxindoles via a direct C–H,Ar-H functionalisation

A practical and efficient entry to spirocyclic oxindoles from readily accessible anilide precursors, using only catalytic amounts of an inexpensive copper salt together with air as the sole re-oxidant, is described. In addition to providing access to a broad range of spiro-oxindole products, the utility of this method is demonstrated in a formal synthesis of the natural product, horsfiline.