Silver mediated direct C–H arylation of 3-bromoisothiazole-5-carbonitrile

Palladium catalyzed direct C–H arylation of 3-bromoisothiazole-5-carbonitrile with aryl/hetaryl iodides in the presence of AgF gave 13 4-aryl/hetaryl-3-bromoisothiazole-5-carbonitriles. The scope of this arylation was investigated and explanations for the limitations proposed. 3-Bromoisothiazole-5-carboxamide was isolated as a side-product, and its formation was attributed to Ag⁺-catalyzed hydration of the C-5 nitrile. The analogous phenylation of 3-chloroisothiazole-5-carbonitrile and 3-bromoisothiazole-4-carboxamide gave 3-chloro-4-phenylisothiazole-5-carbonitrile and 3-bromo-5-phenylisothiazole-4-carboxamide in 83 and 64% yields, respectively.     

Synthesis of asymmetric 3,5-diaryl-4H-1,2,6-thiadiazin-4-ones via Suzuki–Miyaura and Stille coupling reactions

Asymmetric 3,5-diaryl substituted 4H-1,2,6-thiadiazin-4-ones can be prepared from 3,5-dichloro-4H-1,2,6-thiadiazin-4-one (1) via a multi-step protocol: selective nucleophilic mono-chloro substitution gives either the mono-methoxy or benzyloxy substituted mono-chlorothiadiazinones that can be phenylated via Suzuki–Miyaura coupling. Subsequent BBr₃ mediated dealkylation gives 3-hydroxy-5-phenyl-4H-1,2,6-thiadiazin-4-one (9) that can be activated by a modified Finkelstein halodehydroxylation via the triflate, enabling further arylation reactions using Suzuki–Miyaura or Stille coupling chemistry.     

Ascorbic Acid/Iodine and Triphenylphosphine/Iodine as Reducing Agents for the As(V)[dbnd]O Group

The scope of ascorbic acid/iodine and triphenylphosphine/iodine in methanol for the direct reduction of arsenic(V) compounds having the As[dbnd]O group has been investigated. Ascorbic acid/iodine reduces arsonic acids, diphenylarsinic acid (but not dimethylarsinic acid), and triphenylarsine oxide. The rates of reduction depend on the electronic effects of the ligands bound to arsenic and on the hydrogen-bonding strength of the species, when present. When the As(V) compound has an [sbnd]NH ₂ or an [sbnd]NH ₃ ⁺ group, the reduction product reacts with a ketonic form of dehydroascorbic acid, giving condensation product(s). Triphenylphosphine/iodine reduced slowly the zwitterionic o-aminophenylarsonic acid but reduced faster the hydrochloric acid salt of the same acid. It reduced dimethylarsinic acid as well because the powerful electron-withdrawing Ph ₃ P ⁺coordinated to As[dbnd]O seems to outweigh the electronic and hydrogen bonding effects.     

On the mathematical formulation of the problem of reassembling fragmented objects: two new theorems

In this paper two new theorems are proved in association with the problem of matching three dimensional solid bodies. Rigorous mathematical criteria are given in order to test if two such bodies actually match in a certain position. Since this problem finds important application to the actual problem of reassembling fragmented objects e.g. archaeological, special care is taken to account for small gaps between matching fragments and fuzziness of the matching parameters.     

New SPE loading material for affinity‐based separation of cyclodextrins from drug:CD complexes in order to overcome Beer's law deviations

Molecular inclusion of guest molecules within CDs is known to alter guest molecule spectrophotometric absorptivity, making their determination, based on spectrophotometric data, inaccurate. Therefore specific analytical methods capable of quantifying the drugs as free molecules must be developed and validated. SPE was selected to simplify sample and avoid more time‐consuming alternatives. A new solid phase was synthesized and characterized by infrared spectrometry, differential scanning calorimetry and elemental analysis. The competitive complexation of adamantane groups immobilized on the silica substrate facilitates drug:CD complex dissociation and elimination of CD from samples. The drug molecules, now free from CD, can be easily analysed by an already available HPLC method. This new SPE loading material was employed in the determination of ketoprofen in its CD complex as a representative example of the utility of this novel material. The calculated analytical errors were reduced from a maximum of 20.79% (without SPE) to a minimum of 3.99%.     

Primes of the form <Emphasis Type="Italic">x</Emphasis><Superscript>2</Superscript> + (<Emphasis Type="Italic">x</Emphasis> + 1)<Superscript>2</Superscript>. Proper divisors of composites of the same form

The aim of the present paper is to characterize prime numbers of the form n = x ² + (x + 1)² and to obtain certain proper divisors of composite numbers of the same form, i.e. divisors d of n such that 1 < d < n.      

On the relation of the vacancy formation parameters and the Gruneisen constant in metals

By using the Swenson formula, for the pressure derivative of the bulk modulus, and the Slater formulation for the Gruneisen constant a simple useful relation between the vacancy-formation entropy and the Gruneisen constant is derived in the case of metals. This relation also indicates that actually a close correlation between the vacancy-formation enthalpy, the coefficient of the volume expansivity and the corresponding melting point exists.