Magnesium cations alcohols

Magnesium ion-mediated nitrile oxide 1,3-DC reactions to allylic alcohols have been reviewed <02SL1371>. New examples have been recently reported, in particular, cycloadditions of aromatic and aliphatic nitrile oxides with optically active a-silylallyl alcohols in the presence of magnesium cations. The substituted isoxazolines, which were obtained with high diastereo- and enantioselectivity, were smoothly converted to [1,2]-oxazine derivatives by treatment with TBAF. For example, oxazin-3-one (S)-58 was obtained in 81% ee starting from dipolarophile (S)-55 <02T9613>. 

Q13 Magnesium is a major intracellular cation which acts as a co-factor in many intracellular enzyme reactions. Plasma concentration is normally 2 mg dl-1. This ion is abundant in the diet, and hypomagnesaemia is relatively uncommon, unless there is malabsorption or excessive loss via the kidney. However, when present, hypomagnesaemia can lead to hypoparathyroidism. Adjustment to the levels of magnesium can shift the function of the parathyroid glands back to normal. Chronic alcoholism, malnutrition, malabsorption, renal tubular dysfunction and excessive use of diuretics, such as loop and thiazide diuretics, may lead to hypomagnesaemia. Symptoms of magnesium deficiency include depression, confusion, muscle weakness and sometimes convulsions. 

Assessment of the role of the cation in MPV reduction is difficult, Conversion of alcohol to alkoxide certainly enhances the reactivity towards hydride donation, and aluminum ions aid via chelation in arranging alkoxide and carbonyl compound properly for reaction. However, alkoxides bearing cations other than aluminum may also exhibit good hydride-donating tendencies. Lithium isopropoxide reduces steroidal ketones efficiently and magnesium alkoxides derived from chiral alcohols have been used extensively in chiral syntheses. Isobomyloxy magnesium bromide (52) has been used widely for this purpose (equation 27). ... 

Magnesium indium oxide (Mglu204) is a multication oxide having two types of cation centers possessing different reductive-oxidative and acid-base properties. Also, participating in the processes of the alcohol molecule transformation causes high sensor response when alcohol detection is considered. The centers of one type can suitably participate in adsorption-desorption processes of alcohol molecules, whereas complete oxidation of intermediates proceeds effectively at the centers of another type. 

The greater effectiveness of multivalent cations as compared to monovalent cations in changing phase behavior has been recognized recently in the literature. Fleming, et al. (7), report a calcium to sodium effectiveness ratio of 14 and a magnesium to sodium effectiveness ratio of 16 for North Burbank crude oil and a surfactant system composed of 5.0 percent Petronate TRS lOB and 3.0 percent isobutyl alcohol. That paper does not indicate whether the ratios were determined at other surfactant concentrations. 

---