Tandem radical rearrangement/Pd-catalysed translocation of bicyclo[2.2.2]lactones. An efficient access to the oxa-triquinane core structure

The skeletal rearrangement of bicyclo[2.2.2]lactones, involving a mild and chemoselective palladium-catalysed translocation key-step, provides an efficient and diastereoselective access to synthetically useful bicyclo[3.3.0]lactones.     

Zeta-functions of renormalizable sub-Lorenz templates

We describe the Williams zeta-functions and the twist zeta-functions of sub-Lorenz templates generated by renormalizable Lorenz maps, in terms of the corresponding zeta-functions of the sub-Lorenz templates generated by the renormalized map and by the map that determines the renormalization type.     

A synthetic entry to furo[2,3-b]pyridin-4(1H)-ones and related furoquinolinones via iodocyclization

[reaction: see text] N-Methyl-4-alkoxy-3-alkynylpyridin-2(1H)-ones readily undergo iodine-promoted 5-endo-heteroannulation under mild conditions to 3-iodofuropyridinium triiodide salts in moderate to good yields. The latter may be dealkylated in situ upon exposure to an iodide anion to provide the corresponding 3-iodofuro[2,3-b]pyridin-4(1H)-ones. The same strategy applies to the formation of furo[2,3-b]quinolin-4(9H)-ones.     

Oxazaphospholidine-oxide as an efficient ortho-directing group for the diastereoselective deprotonation of ferrocene

[reaction: see text] Ortho-lithiation of (2R,4S,5R)-3,4-dimethyl-2-ferrocenyl-5-phenyl[1,3,2]oxazaphospholidine 2-oxide 2 was carried out with diastereoselectivity of >99%, affording a new and efficient way for introducing planar chirality into the ferrocene backbone. Various electrophiles were used to quench the lithiated species, showing the wide applicability of the new ortho-directing group and its potential to generate ligands for use in asymmetric catalysis.     

Objective evaluation of acute adverse events and image quality of gadolinium-based contrast agents (gadobutrol and gadobenate dimeglumine) by blinded evaluation. Pilot study

Purpose

The purpose was to objectively evaluate a recently FDA-approved gadolinium-based contrast agent (GBCA) in comparison to our standard GBCA for acute adverse events and image quality by blinded evaluation.

Methods

Evaluation was made of a recently FDA-approved GBCA, gadobutrol (Gadavist; Bayer), in comparison to our standard GBCA, gadobenate dimeglumine (MultiHance; Bracco), in an IRB- and HIPAA-compliant study. Both the imaging technologist and patient were not aware of the brand of the GBCA used. A total of 59 magnetic resonance studies were evaluated (59 patients, 31 men, 28 women, age range of 5–85 years, mean age of 52 years). Twenty-nine studies were performed with gadobutrol (22 abdominal and 7 brain studies), and 30 studies were performed with gadobenate dimeglumine (22 abdominal and 8 brain studies). Assessment was made of acute adverse events focusing on objective observations of vomiting, hives, and moderate and severe reactions. Adequacy of enhancement was rated as poor, fair and good by one of two experienced radiologists who were blinded to the type of agent evaluated.

Results

No patient experienced acute adverse events with either agent. The target minor adverse events of vomiting or hives, and moderate and severe reactions were not observed in any patient. Adequacy of enhancement was rated as good for both agents in all patients.

Conclusions

Objective, blinded evaluation is feasible and readily performable for the evaluation of GBCAs. This proof-of-concept study showed that both GBCAs evaluated exhibited consistent good image quality and no noteworthy adverse events.     

A General Acid‐Mediated Hydroaminomethylation of Unactivated Alkenes and Alkynes

In comparison to the extensively studied metal‐catalyzed hydroamination reaction, hydroaminomethylation has received significantly less attention despite its considerable potential to streamline amine synthesis. State‐of‐the‐art protocols for hydroaminomethylation of alkenes rely largely on transition‐metal catalysis, enabling this transformation only under highly designed and controlled conditions. Here we report a broadly applicable, acid‐mediated approach to the hydroaminomethylation of unactivated alkenes and alkynes. This methodology employs cheap, readily available, and bench‐stable reactants and affords the desired amines with excellent functional group tolerance and impeccable regioselectivity. The broad scope of this transformation, as well as mechanistic investigations and in situ domino functionalization reactions are reported.     

Vinyl Cation Stabilization by Silicon Enables a Formal Metal‐Free α‐Arylation of Alkyl Ketones

The ability of silicon to stabilize vinyl cationic species leads to a redox arylation of alkynes whereby the stringent limitations of reactivity and regioselectivity of alkyl‐substituted alkynes are lifted. This allows the synthesis of a range of α‐silyl‐α′‐arylketones under mild conditions in good to excellent yields and with high functional group tolerance, whereby the silicon moiety in the final products can either be removed for a formal acetone monoarylation transform, or capitalized upon for subsequent electrophilic substitutions at either side of the carbonyl group.     

A comparative study using conventional methods,ionic liquids,microwave irradiation and combinations thereof for the synthesis of 5-trifluoroacetyl-1,2,3,4-tetrahydropyridines

This study reports a comparison between conventional methods, ionic liquids, microwave (MW) irradiation, and combinations thereof for the synthesis of a series of fourteen 1-aryl-2-arylamino-5-trifluoroacetyl-1,2,3,4-tetrahydropyridines. In all of the reactions tested, the products were obtained at very good yields (87–97%), but the reaction times were very different, depending on the method used. Comparing to other methods, the time decreased to 1?min when [BMIM]BF₄ under MW irradiation was used, thus evidencing a synergic effect.