Selenium has attracted great interest as an essential element, and certain diseases have been eradicated by dietary supplementation of this element. Selenium is essential for cell metabolism as a component of glutathione peroxidase and other enzyme systems. Current interest lies in the prevention of certain cancers by supplementation with selenium [1–4]. One proposed mechanism for this activity is the cytotoxic effect of selenium on tumor cells [5, 6]. Organoselenium compounds continue to attract the attention of many investigators owing to a series of unique properties. There are data showing that organoselenium compounds are capable of sensitizing processes in the living organism, and there are four known naturally occurring proteins containing the selenium atom. Therefore, despite the high toxicity of selenium compounds [7–9], many of them have been prepared as and anticancer agents [10–15] and for other medicinal effects like antiviral [16–18], antimicrobial [19–22], and fungicidal [23–25] activities. Heterocyclic annelated pyridazines also attract considerable attention, which arises mainly from the large variety of interesting pharmacological, herbicidal, insecticidal, and fungicidal activities [26–30]. In the last two decades we have been involved in a program aimed at developing new synthesis of heterocyclic systems of anticipated biological and/or pharmacological effects [31–37]. In continuation of this program, some selenium-containing heterocyclic compounds were required for evaluation as biodegradable agrochemicals. The starting compound 4-cyano- 5,6-diphenylpyridazine-3(2H)- selenone 1, which was prepared as previously described [38] seemed suitable to fulfill this objective.

This paper presents U–Pb ID-TIMS geochronological data from granitoids in the Hafafit area in the Central and South Eastern Desert, Egypt. It dates several Neoproterozoic magmatic pulses and metamorphic events, and constrains one episode of U, Nb and Ta mineralisation along the Nugrus Shear Zone, part of the Eastern Desert Shear Zone, to 608±1 Ma. The data testify to the localized nature of deformation in the Eastern Desert, illustrating that previous subdivisions of granitoids into “Older” and “Younger” based on field criteria are inadequate. With robust ages fromgranitoids in theMeatiq, El Sibai and El Shalul areas the newages indicate 6 pulses of magmatism and/or metamorphism at (1) 705–680, (2) c. 660, (3) 635–630, (4) 610–604, (5) 600–590 and (6) c. 540 Ma. Most pulses are defined by ages from granitoids in both gneiss windows/domes and in the overlying eugeoclinal allochthon; the two tiers represent different crustal levels of related rocks. We propose that pulses 1–3 are syn-orogenic, pulses 4 and 5 reflect exhumation of mid-crustal gneisses along the Eastern Desert Shear Zone, whereas the final pulse post-dates the East African orogeny. Based on available data we propose that the tectono-magmatic evolution above applies to the entire Eastern Desert.

This paper presents U–Pb ID-TIMS geochronological data from granitoids in the Hafafit area in the Central and South Eastern Desert, Egypt. It dates several Neoproterozoic magmatic pulses and metamorphic events, and constrains one episode of U, Nb and Ta mineralisation along the Nugrus Shear Zone, part of the Eastern Desert Shear Zone, to 608±1 Ma. The data testify to the localized nature of deformation in the Eastern Desert, illustrating that previous subdivisions of granitoids into “Older” and “Younger” based on field criteria are inadequate. With robust ages fromgranitoids in theMeatiq, El Sibai and El Shalul areas the newages indicate 6 pulses of magmatism and/or metamorphism at (1) 705–680, (2) c. 660, (3) 635–630, (4) 610–604, (5) 600–590 and (6) c. 540 Ma. Most pulses are defined by ages from granitoids in both gneiss windows/domes and in the overlying eugeoclinal allochthon; the two tiers represent different crustal levels of related rocks. We propose that pulses 1–3 are syn-orogenic, pulses 4 and 5 reflect exhumation of mid-crustal gneisses along the Eastern Desert Shear Zone, whereas the final pulse post-dates the East African orogeny. Based on available data we propose that the tectono-magmatic evolution above applies to the entire Eastern Desert.

The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm3 have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that MnIII is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed.

The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm3 have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that MnIII is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed.

The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm3 have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that MnIII is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed.

Tetra-n-butyl ammonium bromide (TBAB) was found to be an efficient phase-transfer catalyst for the synthesis of pyrido[2,3-d]pyrimidines by one-pot reaction of 6-aminouracils, aromatic aldehydes, and malononitrile or ethyl cyanoacetate in water under ultrasonic irradiation. The advantages of this method are the use of an inexpensive and readily available catalyst, short reaction time, easy work-up, improved yields, and the use of water as a solvent that is environmentally benign.