Non-Uniformity and Generalised Sacks Splitting

We show that there do not exist computable functions f ₁(e, i), f ₂(e, i), g ₁(e, i), g ₂(e, i) such that for all e, i ∈ ω, (1) $ {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)} \leqslant _{{\rm T}} {\left( {W_{e} - W_{i} } \right)}; $ (2) $ {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)} \leqslant _{{\rm T}} {\left( {W_{e} - W_{i} } \right)}; $ (3) $ {\left( {W_{e} - W_{i} } \right)} \not\leqslant _{{\rm T}} {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)} \oplus {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)}; $ (4) $ {\left( {W_{e} - W_{i} } \right)} \not\leqslant _{{\rm T}} {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)}{\text{unless}}{\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\emptyset};{\text{and}} $ (5) $ {\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)}{\text{unless}}{\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\emptyset}. $ It follows that the splitting theorems of Sacks and Cooper cannot be combined uniformly.     

Pd asymmetric allylic alkylation (AAA). A powerful synthetic tool

Palladium catalyzed asymmetric allylic alkylations represent a challenging problem because the mechanism of the reaction places the chiral environment distal to the bond breaking or making events responsible for the asymmetric induction. Furthermore, unlike virtually every other asymmetric process, many strategies can be employed for introduction of asymmetry and many different types of bonds can be formed. While over 100 different ligands have been designed, a family of ligands derived from 2-diphenylphosphinobenzoic or 1-naphthoic acid and chiral scalemic diamines have been successful in inducing excellent enantioselectivity by five different enantiodiscriminating events. These methods have already provided practical strategies towards numerous biological targets--some of which are adenosine and its enantiomer, aflatoxin B, aristeromycin, calanolide A and B, carbovir, cyclophellitol, ethambutol, galanthamine, mannostatin, neplanocin, phyllanthocin, sphingofungins E and F, tetraponaines, vigabatrin, and valienamine.     

US Environmental Protection Agency Method 326.0, a new method for monitoring inorganic oxyhalides and optimization of the postcolumn derivatization for the selective determination of trace levels of bromate

The development of US Environmental Protection Agency (EPA) Method 317.0 provided a more sensitive, acceptable alternative to EPA Method 300.1 to be proposed as one of the recommended compliance monitoring methods for Stage II of the Disinfectants/Disinfection By-Products (DBP) Rule. This work was initiated to evaluate other postcolumn reagents (PCRs) that might be utilized to provide an additional, alternative method in order to augment compliance monitoring flexibility for inorganic oxyhalide DBP anions. Modifications of the method reported by Salhi and von Gunten, which included adjustment and optimization of flow-rates, reaction temperature, and delivery of the PCR, improved the method performance. Method 326.0 incorporates an acidic solution of potassium iodide containing catalytic amounts of molybdenum(VI) as the PCR and provides acceptable precision and accuracy for all analytes and a postcolumn bromate detection limit in reagent water of 0.17 microg/l.     

Chemo-, regio-, and enantioselective Pd-catalyzed allylic alkylation of indolocarbazole pro-aglycons

[reaction: see text] Monosubstituted isomerically pure indolopyrrolocarbazole precursors have been prepared via palladium-catalyzed asymmetric allylic alkylation methodology, employing both achiral cyclopentenyl electrophiles and chiral glycal derivatives. Chemoselective allylation of (bis)indole lactam pro-aglycon 3 allows access to N-distally substituted indolopyrrolocarbazole derivatives; glyoxamide precursor 14 provides entry into N-proximally substituted derivatives.     

Mechanisms of tetrazole formation by addition of azide to nitriles

It is well-known that azide salts can engage nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.     

Enolstannanes as electrofugal groups in allylic alkylation

Enolstannanes serve as nucleophiles towards allylic acetates under the influence of palladium(O) catalyst.