Direct orthoruthenation of planar prochiral pyridine derivatives by C-H bond activation with [Ru(CO)2Cl2]n and its unexpected stereoselectivity

The treatment of planar prochiral pyridine derivatives with d6 [Ru(CO)2Cl2]n stereoselectively and efficiently produces new dimeric ortho-ruthenated complexes.     

Leachability and analytical speciation of antimony in coal fly ash

A new procedure was described with multiwalled carbon nanotubes as solid phase extraction packing material for the trace analysis of nicosulfuron, thifensulfuron and metsulfuron-methyl in water samples. The possible parameters influencing the enrichment were optimized and the optimal conditions were as followed: eluent, sample pH, flow rate and sample volume were acetonitrile containing 1% acetic acid, pH 3, 8 mL min⁻¹ and 500 mL, respectively. Under the optimal chromatographic separation and SPE conditions, the linear range, detection limit (S/N = 3) and precision (R.S.D., n = 6) were 0.04-40 ng mL⁻¹, 6.8 ng L⁻¹ and 2.5% for nicosulfuron, 0.04-40 ng mL⁻¹, 11.2 ng L⁻¹ and 5.4% for thifensulfuron, 0.02-20 ng mL⁻¹, 5.9 ng L⁻¹, 2.1% for metsulfuron-methyl, respectively. The established method was well employed to determine nicosulfuron, thifensulfuron and metsulfuron-methyl in tap water, seawater, reservoir water and well water samples, and satisfactory results were obtained, the spiked recoveries in the range of 87.2-100.7%, 96.5-105.6% and 83.7-111.1% for them each, respectively.     

Establishment of multivariate specifications for food commodities with discriminant partial least squares

A novel method for establishing multivariate specifications of food commodities is proposed. The specifications are established for discriminant partial least squares (DPLS) by setting limits on the predictions of the DPLS model together with Hotelling T² and square error of prediction (SPE). These limits can be tuned depending on whether type I error (i.e. a correct sample is declared out-of-specification) or type II error (i.e. an out-of-specification sample is declared within specifications) need to be minimized. The methodology is illustrated with a set of NIR spectra of Italian olive oils, corresponding to five regions and the class Liguria is the class of interest. The results demonstrate the possibility of establishing multivariate specification for olive oils from the Liguria region on the basis of spectral data obtaining type I and type II errors lower than 5%.     

Glyphosate–Exonuclease Interactions: Reduced Enzymatic Activity as a Route to Glyphosate Biosensing

N-phosphonomethyle-glycine (glyphosate) is the most widely used pesticide worldwide due to its effectiveness in killing weeds at a moderate cost, bringing significant economic benefits. However, owing to its massive use, glyphosate and its residues contaminate surface waters. On site, fast monitoring of contamination is therefore urgently needed to alert local authorities and raise population awareness. Here the hindrance of the activity of two enzymes, the exonuclease I (Exo I) and the T5 exonuclease (T5 Exo) by glyphosate, is reported. These two enzymes digest oligonucleotides into shorter sequences, down to single nucleotides. The presence of glyphosate in the reaction medium hampers the activity of both enzymes, slowing down enzymatic digestion. It is shown by fluorescence spectroscopy that the inhibition of ExoI enzymatic activity is specific to glyphosate, paving the way for the development of a biosensor to detect this pollutant in drinking water at suitable detection limits, i.e., 0.6 nm .     

Reaction of terminal phosphinidene complexes with aldimines: Synthesis of the first 1,2,3-azadiphosphetidine

Transient terminal phosphinidene complexes [RP-M(CO)₅] (M = Mo, W, R = Ph, Me), as generated from the corresponding 7-phosphanorbornadiene complexes, react with N-methyl(benzylidene)amine to afford the diazaphospholane complexes 3,4 (R = Ph) or a mixture of diazaphospholane 9 and 1,2,3-azadiphosphetidine 10 (R = Me), probably by insertion of either one molecule of imine or one molecule of phosphinidene into the weak P N bond of the unstable intermediate azaphosphiridine 11. The new complex 10 has been submitted to an X-ray crystal structure analysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9: 597–600, 1998     

Persulfuration of phosphinines: Synthesis and X-ray crystal structure analysis of a P2S3 derivative

The reaction of 4,5-dimethyl-2-phenylphosphinine with sulfur in boiling benzene in the presence of N-methylimidazole as a catalyst first yields a P-sulfide. This monosulfide further reacts with sulfur to give a diphosphinine trisulfide and a diphosphinine tetrasulfide. The X-ray crystal structure analysis of the trisulfide has been carried out. The two head-to-tail 1,6-dihydrophosphinine rings are connected by P S C and P C links, thus forming a central 1,2,4-thiadiphospholane heterocycle. The P C bridge is weak [1.881(3) Å] and sulfur can insert into it to give the symmetrical tetrasulfide with two P S C bridges.     

Reactivity of a 1,3,2‐diazaphosphinine toward propargyl‐phosphine derivatives and activated alkenes

2,5‐Diphenylphosphole and diphenylphosphino derivatives 2, 3 of 1‐phenylpropargyl were prepared by reacting the corresponding diphenylphosphinolithium and 2,5‐diphospholyl lithium salts with (3‐bromo‐prop‐1‐ynyl)‐benzene in THF at low temperature. Sulfurization of these propargyl derivatives was then carried out with elemental sulfur in toluene at 90°C to yield the corresponding phosphole 8 and phosphino 9 derivatives. Reaction of 3,5‐di‐tert‐butyl‐1,3,2‐diazaphosphinine 1 with the free phosphole derivative led to a mixture of diazaphosphinines 4 and 5 that were converted to the corresponding phosphinines 6 and 7 upon treatment with trimethylsilylacetylene in excess. Reaction of 1 with 1‐phenylpropargyl derivatives of diphenylphosphine 8 and phosphole 9 afforded 7,8‐dihydro‐1‐phospha‐2,6‐diazabarrelenes 10 and 11 having an exocyclic double bond. Formation of these compounds results from a (1,3)‐shift of a hydrogen atom from the methylene carbon atom to the bridge of the barrelene moiety. Depending on the nature of the phosphine group, the sulfur atom can also be displaced to the P atom of the barrelene moiety. The X‐ray structure of the phosphole derivative 10 was recorded. Three 6,7‐dihydro‐1‐phospha‐2,6‐diazabarrelenes bearing two ( 16 ) or one ester ( 17a,b ), or one cyano group ( 18a,b ) on the bridge were also synthesized through the reaction of 1 with ethyl acrylate, dimethyl fumarate, and acrylonitrile. The X‐ray structure of the cyano derivative 18a is also presented. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:326–333, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10152