Introduction of Benzo[h]quinoline and 1,10-Phenanthroline Subunits by Friedländer Methodology

An improved preparation of 8-amino-7-quinolinecarbaldehyde has been developed. The methyl group of 7-methyl-8-nitroquinoline may be oxidized to an aldehyde by treatment first with dimethylformamide dimethyl acetal followed by sodium periodate. Reduction with iron provides the amino aldehyde. An analogous sequence affords 1-amino-2-naphthalenecarbaldehyde. Friedl?nder condensation of the quinoline derivative with a series of acetylaromatics provides the corresponding 2-aryl-1,10-phenanthrolines. Condensation of either amino aldehyde with 1,3-diacetylbenzene or 2,6-diacetylpyridine provides the expected Friedl?nder product. Similar chemistry is described for reactions of the amino aldehydes with 1,4-diacetylbenzene, 4,4'-diacetylbiphenyl, 1,5-diacetylanthracene, 1,2,3,4,5,6,7,8-octahydroacridine-1,8-dione, and tetracyclo[6.3.0.0.(4,11)0(5,9)]undecane-2,7-dione (TCU-2,7-dione).     

Prediction of work-related accidents according to working conditions using support vector machines

Support vector machines (SVMs), which are a kind of statistical learning methods, were applied in this research work to predict occupational accidents with success. In the first place, semi-parametric principal component analysis (SPPCA) was used in order to perform a dimensional reduction, but no satisfactory results were obtained. Next, a dimensional reduction was carried out using an innovative and intelligent computing regression algorithm known as multivariate adaptive regression splines (MARS) model with good results. The variables selected as important by the previous MARS model were taken as input variables for a SVM model. This SVM technique was able to classify, according to their working conditions, those workers that have suffered a work-related accident in the last 12 months and those that have not. SVM technique does not over-fit the experimental data and gives place to a better performance than back-propagation neural network models. Finally, the results and conclusions of this study are presented.     

A general and regioselective synthesis of cyclopentenone derivatives through nickel(0)-mediated [3 + 2] cyclization of alkenyl Fischer carbene complexes and internal alkynes

A broad range of substituted 2-cyclopentenone derivatives 3-6 are synthesized by the nickel(0)-mediated [3 + 2] cyclization reaction of chromium alkenyl(methoxy)carbene complexes 1 and internal alkynes 2. The reaction takes place with complete regioselectivity with both unactivated alkynes and activated alkynes (electron-withdrawing and electron-donating substituted alkynes). Representative cycloadducts containing boron and tin substituents are further demonstrated to be active partners in classical Pd-catalyzed C-C coupling processes to allow the production of 2-aryl- and 2-alkynyl-substituted cyclopentenones 9-13.     

Evaluation of diimine ligand exchange on Cu(I)

Four ligands have been prepared, 8,8-dimethyl-6,7,9-trihydropyrido[1,2-b]acridine and three 4,4',6,6'-tetrasubstituted derivatives of 2,2'-bipyrimidine where the substituents are methyl, phenyl, and p-tolyl. The corresponding [CuL(2)](+) salts of these ligands evidence nonequivalent NMR signals that allow an estimation of the ligand exchange barrier in both acetonitrile and chloroform solution. Lower barriers are found in the former solvent and attributed to solvent participation in the exchange process. Corresponding differences in the oxidation potentials of the complexes are explained in a similar manner. The electronic absorption properties of the complexes are also consistent with the steric and electronic properties of the ligands. [Cu(2c)(2)](PF(6)), where 2c = 4,4',6,6'-tetraphenyl-2,2'-bipyrimidine, was analyzed by X-ray diffraction and found to crystallize in the space group Pccn with a = 14.761(2) A, b = 15.007(2) A, c = 24.407(4) A, and Z = 4. The internal and external phenyl rings are disposed quite differently, with the internal rings interacting strongly with the orthogonal ligand.     

Nickel(0)-mediated [2+2+1] cyclization reaction of chromium carbene complexes and internal alkynes

Alkyl, aryl, and heteroaryl chromium Fischer carbene complexes undergo Ni(0)-mediated [2+2+1] cyclization reaction with internal unactivated and electron-poor internal alkynes to yield highly substituted cyclopentadienes with complete regioselectivity in most cases. The intramolecular version of this cyclization has been accomplished with 1,8-diphenyl-1,7-octadiyne to produce indene derivatives. This three-component [2+2+1] cyclization represents a very uncommon process in the chemistry of Fischer carbene complexes.     

Cu(I) complexes of 3,3'-polymethylene bridged derivatives of 2,2'-bi-1,10-phenanthroline

A series of 3,3'-polymethylene-2,2'-bi-1,10-phenanthrolines coordinate with Cu(I) to form dinuclear complexes [(CuL)(2)](2+). As the 3,3'-bridge is lengthened from two to four carbons, the ligand becomes more twisted about the 2,2'-bond, favoring dinuclear coordination. The distance between the two copper atoms varies from 2.92 A for the dimethylene-bridged system to 3.59 A for the tetramethylene bridge. Favorable pi-stacking interactions occur between opposing ligands and promote complex formation. Competition experiments indicate that self-recognition is important and only homoleptic complexes are observed. Under equilibrium conditions, formation of the tetramethylene-bridged complex appears to be the most favored while the dimethylene-bridged system is least favored. The intensity of the long wavelength metal-ligand charge-transfer absorption band decreases as the 3,3'-bridge is shortened. Interaction between the two copper centers is evidenced by a splitting of the oxidation wave, and this splitting increases as the Cu-Cu distance is decreased.