Solvent-free synthesis and properties of functionalized hydrazines and bishydrazines as energetic ingredients for propulsion applications

International audienc

Synthesis of Triangular Tripalladium Cations as Noble-Metal Analogues of the Cyclopropenyl Cation

The first C-3-symmetric 44-core-valence-electron triangular palladium clusters, [{(SAr)(PAr3)Pd}(3)](+), have been synthesized by activation of the CS bond of isothioureas. Owing to delocalized metal-metal bonding, these stable complexes are the first noble-metal analogues of the -aromatic cyclopropenyl cation [C3H3](+), with their all-metal aromaticity involving d-type atomic orbital

Rearrangements of N-Acyl Isothioureas. Alternate Access to Acylguanidines from Cyanamides

We report a tin-free one-pot radical approach to the synthesis of N-acyl isothioureas and acylguanidines from N-acyl cyanamides. Photoactivated reduction of aromatic disulfides in the presence of Hünig’s base results in hydrothiolation of the cyanamide moiety, followed by spontaneous 1,3-migration of the acyl group. Onward reaction of the isothioureas obtained with amines led to the corresponding N-acylguanidines, where the acyl group is attached to the nitrogen atom formerly at the cyano-end of the starting materia

The Cyanamide Moiety, Synthesis and Reactivity

The cyanamide moiety provides many opportunities as a building block for the synthesis of nitrogen-containing heterocycles. This review discusses the reported methods for the preparation of alkyl- and N-acylcyanamides and illustrates their reactivity vis-à-vis nucleophilic additions, cycloadditions, radical chemistry and coordination chemistr

Expeditious Synthesis of Phenanthridines from Benzylamines via Dual Palladium Catalysis

A method for the synthesis of phenanthridines from benzylamines and aryl iodides which uses a dual palladium-catalyzed process is developed. The domino sequence ends via an intramolecular amination and an oxidative dehydrogenation. No protecting group or prefunctionalization of the amine is required, and the process uses dioxygen as the terminal oxidan

Influence of microvascular obstruction on regional myocardial deformation in the acute phase of myocardial infarction: a speckle-tracking echocardiography study

International audienceBACKGROUND: In the acute phase of myocardial infarction (MI), infarct size and microvascular obstruction (MVO) are important prognostic factors for cardiovascular outcome. MI size is a major determinant of myocardial function, but the specific effect of MVO is less documented. The aim of this study was to evaluate the impact of MVO on longitudinal myocardial strain assessed by speckle-tracking echocardiography. METHOD: Speckle-tracking echocardiography and contrast-enhanced cardiac magnetic resonance studies were performed in 69 patients 72 hours after first acute MI. Segmental and global longitudinal systolic strain (epsilonL) was measured using speckle-tracking echocardiography. Transmural extent of MI, MI size, and the presence or absence of MVO were assessed using contrast-enhanced cardiac magnetic resonance. Left ventricular (LV) ejection fraction was assessed at 6 months using echocardiography. RESULTS: The mean infarct size was 23 +/- 13% of LV mass. MVO was present in 64% of patients. MVO was significantly associated with epsilonL impairment (-7.8 +/- 4.9% vs -16.3 +/- 6.4%, P \textless .001), and epsilonL remained significantly worse in MVO-positive segments after adjustment for transmural extent of MI. A epsilonL value \textgreater -12.5% predicted the presence of MVO with 83% sensitivity and 75% specificity. On multivariate analysis, global epsilonL and MI size, but not MVO, were identified as independent predictors of LV ejection fraction at follow-up (beta = -0.9, P = .023, and beta = -0.2, P = .034, respectively). CONCLUSION: In the acute phase of MI, segmental and global epsilonL is significantly altered by the presence of MVO, in addition to MI size. However, MI size but not MVO independently predicts LV ejection fraction at follow-up

Intramolecular homolytic substitution of sulfinates and sulfinamides : a computational study

Ab initio and density functional theory (DFT) calculations predict that intramolecular homolytic substitution by alkyl radicals at the sulfur atom in sulfinates proceeds through a smooth transition state in which the attacking and leaving radicals adopt a near collinear arrangement. When forming a five-membered ring and the leaving radical is methyl, G3(MP2)-RAD//ROBHandHLYP/6-311++G(d,p) calculations predict that this reaction proceeds with an activation energy (ΔE1‡) of 43.2 kJ mol−1. ROBHandHLYP/6-311++G(d,p) calculations suggest that the formation of five-membered rings through intramolecular homolytic substitution by aryl radicals at the sulfur atom in sulfinates and sulfinamides, with expulsion of phenyl radicals, proceeds with the involvement of hypervalent intermediates. These intermediates further dissociate to the observed products, with overall energy barriers of 45–68 kJ mol−1, depending on the system of interest. In each case, homolytic addition to the phenyl group competes with substitution, with calculated barriers of 51–78 kJ mol−1. This computational study complements and provides insight into previous experimental observations

Intramolecular homolytic substitution of seleninates: a computational study

Ab initio and density functional theory (DFT) calculations predict that intramolecular homolytic substitution by alkyl radicals at the selenium atom in seleninates proceeds through smooth transition states in which the attacking and leaving radicals adopt a near collinear arrangement. When forming a five-membered ring and the leaving radical is methyl, G3(MP2)-RAD calculations predict that this reaction proceeds with an activation energy (DE 1) of 30.4 kJ mol-1. ROBHandHLYP/6-311++G(d,p) calculations suggest that the formation of five-membered rings through similar intramolecular homolytic substitution by aryl radicals, with expulsion of phenyl radicals, proceeds with the involvement of a hypervalent intermediate. This intermediate further dissociates to the observed products, with overall energy barriers of about 40 kJ mol-1. Homolytic addition to the phenyl group was found not to be competitive with substitution, with a calculated barrier of 57.6 kJ mol-1. This computational study provides insight into homolytic substitution chemistry involving seleninates

La reconversion de la main-d'oeuvre : bilan des problematiques (1950-1988)

INIST AR 13620 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc