Reactivity and derivatization of five-coordinate, chelated aluminum.

The convenient five-coordinate starting materials, Salen((t)Bu)AlCl (Salen((t)Bu) = N,N'-alkylene (or arylene) bis (3,5-di-tert-butyl-2-hydroxybenzylideneamine) (1-4) can be used in a wide range of reactions to form five-coordinate aluminum compounds. Herein, these reagents were used to produce new five-coordinate azides, LAlN(3) (L = Salen((t)Bu) (5), Salpen((t)Bu) (6), and Salomphen((t)Bu) (7)) through trimethylsilylhalide elimination. The decomposition of the azides produce first hydroxide (LAlOH (L = Salen((t)Bu) (8)) and, subsequently in the presence of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe(3) (L = Salen((t)Bu) (9), Salpen((t)Bu) (10), and Salomphen((t)Bu) (11)). Alkane elimination reactions may also be used to access this type of compound as evidenced by the formation of Salomphen((t)Bu)AlOSiPh(3) (12). Additionally, the first structurally characterized five-coordinate monomeric amide, Salcen((t)Bu)AlN(SiMe(3))(2) (13), can prepared by a salt elimination utilizing Salcen((t)Bu)AlCl (4). The compounds were characterized by spectroscopic methods ((1)H and (27)Al NMR, MS, and IR) and, in the case of 2 (Salpen((t)Bu)AlCl), 3 (Salomphen((t)Bu)AlCl) 9, 11, 12, and 13, by X-ray analysis. Several of the compounds were explored as potential catalysts for the living polymerization of propylene oxide.

[Asthma risk factors]. / Factores de riesgo para asma.

OBJECTIVE: To study the magnitude of risk factors known for asthma in 6-10 year-old children. MATERIAL AND METHODS: This is a case- and control-study with 6-10 year-old children; 58 were asthmatic and 117 were control, with a relation 2:1. Asthmatic patients were recruited from consult of immuno-allergies department and control patients, from familial medicine consult of Hospital de Especialidades 71, IMSS. Indirect (mother) and directed surveys were applied, they were of multiple option for exploring the most known in literature-risk factors. Statistical management was performed by odds ratio with confidence interval of 95%. RESULTS: The following variables were considered risk factors: ingestion of artificial colorants before having 1 year old (OR = 13.2), living in an urban area (OR = 7.74), maternal smoking during pregnancy (OR = 2.4), wool contact before having 1 year old (OR = 2.11), passive smoking exposure during pregnancy (OR = 1.486) and feeding with industrialized milk (OR = 1.2). CONCLUSIONS: Environmental risk factors are very important in our population, as well as early ablactation; however, ingestion before having 1 year old of allergens as egg, chocolate, orange and mango was not considered risk factor.