Structural Aspects of 5‐methylthio‐1‐oxa‐6,6a δIV‐dithia‐2‐azapentalenes

Alkylation of 5‐[1‐hydroxyiminoalkyl]‐1,2‐dithiole‐3‐thiones using methyl iodide in the presence of sodium hydroxide gives derivatives which may be considered as being 5‐methylthio‐1‐oxa‐6,6a δ^IV‐dithia‐2‐azapentalenes with quantitative yields. The structure of oxadithiazapentalene attributed to the alkylation products is founded on X‐ray analysis and NMR and IR data.     

Validation of a new method using the reactivity of electrogenerated superoxide radical in the antioxidant capacity determination of flavonoids

This article lays out a new method to measure the antioxidant capacity of some flavonoids. The methodology developed is based on the kinetics of the reaction of the antioxidant substrate with the superoxide radical (O(2)(*-)). A cyclic voltammetric technique was used to generate O(2)(*-) by reduction of molecular oxygen in aprotic media. In the same experiment the consumption of the radical was directly measured by the anodic current decay of the superoxide radical oxidation in the presence of increasing concentrations of antioxidant substrate. The method was statistically validated on flavonoid monomers and on the standard antioxidants: trolox, ascorbic acid and phloroglucinol. The linear correlations between the anodic current of O(2)(*-) and the substrate concentration allowed the determination of antioxidant index values expressed by the substrate concentration needed to consume 30% (AI(30)) and 50% (AI(50)) of O(2)(*-) in given conditions of oxygen concentration and scanning rate. The fidelity of the method was examined intraday and interlaboratories.     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.     

Electroorganic synthesis. Reductive alkylation of functionalized 1,2-dithiole-3-thiones

Two-electron reduction of some substituted 1,2-dithiole-3-thiones 1 followed by alkylation of the dianionic intermediates leads through electrosynthesis to mixture of Z and E isomers of the corresponding substituted alkyl-(3-thioalkyl)-2-propenedithioates 2, 3 in satisfactory yield. The structure of those products was established by ¹³C and ¹H nmr and mass spectroscopy. The isomers ratios were determined by nmr spectroscopy.     

Additions of enantiopure alpha-sulfinyl carbanions to (S)-N-sulfinimines: asymmetric synthesis of beta-amino sulfoxides and beta-alphamino alcohols

The addition of the lithium anions derived from (R)- and (S)-methyl and -ethyl p-tolyl sulfoxides to (S)-N-benzylidene-p-toluenesulfinamide provides an easy access route to enantiomerically pure beta-(N-sulfinyl)amino sulfoxides. Stereoselectivity can be achieved when the configurations at the sulfur atoms of the two reagents are opposite (matched pair), thus resulting in only one diastereoisomer, even for the case in which two new chiral centers are created. The N-sulfinyl group primarily controls the configuration of the carbon bonded to the nitrogen, whereas the configuration of the alpha-sulfinyl carbanion seems to be responsible for the level of asymmetric induction, as well as for the configuration of the new stereogenic C-SO carbon in the reactions with ethyl p-tolyl sulfoxides. An efficient method for transforming the obtained beta-(N-sulfinyl)amino sulfoxides into optically pure beta-amino alcohols, based on the stereoselective non-oxidative Pummerer reaction, is also reported.     

Spin-singlet clusters in the ladder compound NaV2O5

The space group of alpha(')-NaV2O5 turns below T(c) = 34 K from Pmmn with all V sites equivalent, into Fmm2 with three independent vanadium sites per layer. This is incompatible with models of charge ordering into V4+ and V5+. Our structure determination indicates that the phase transition consists of a charge ordering with three distinct valence states, formally V4+, V4.5+, and V5+. The singlet formation is not associated with dimerization on the spin ladder, but with the formation of spin clusters. Finally, we ascribe the quadrupling of the c axis to the large polarizability of the V2O5 skeleton.     

Dependence of pulser driving responses on electrical and motional characteristics of NDE ultrasonic probes

Acoustic performance in ultrasonic transmitters can be improved by means of a suitable electrical driving response and matching/tuning networks. It is important to predict this electrical response, but doing so is not easy because it departs notably from the nominal pattern with the loading probes. In practice, the analysis of HV pulser spikes in NDE applications requires fairly complex models in the transient regime and, in addition, non-linear problems could arise, especially in the case of tuned transmitters. In this paper, the most relevant influences of loading characteristics of NDT ultrasonic probes on the pulser electrical driving responses are evaluated in time and frequency domains. Conventional pulse generators and typical NDE pulsers are considered. Driving responses are analysed across commercial ultrasonic probes and, alternatively, across similar purely electrical loads. Distinct influences on pulser responses from electrical and motional sections of the probes are identified. All these aspects are studied on the basis of experimental and computer results.     

Isolation and structural data of the opened ring derivative of a 1,2,4‐triazolothieno‐1,4‐diazepine

The preparation of the trihydrochloride form of 2‐[3‐(aminomethyl)‐5‐methyl‐1,2,4‐triazol‐4‐yl]‐3‐(2‐chlorobenzoyl) thieno[2,3‐c]‐4,5,6,7‐tetrahydropyridine ( 2 ) the ring opened derivative of a 1,2,4‐triazolo‐thieno‐1,4‐diazepine is described. Its structural properties are given, and are compared with those of the corresponding closed form 4H‐6‐(2‐chlorophenyl)‐1‐methyl‐7,8,9,10‐tetrahydropyrido[4′,3′:4,5]thieno[3,2‐f]‐[1,2,4]triazolo[4,3‐a][1,4]diazepine ( 1 ).