Grignard compounds under Magnesium

II. Magnesium hydride is formed when magnesium dialkyls (diethyl, dibutyl, diphenyl) or the corresponding Grignard compounds are heated to 175-200°C under high vacuum for several hours. 

New 3-desoxyanthocyanidins have been prepared according to a Grignard reaction of some flavones with appropriate alkyl- and aryl-magnesium bromides. The reaction of 5,7-dihydroxyflavone (chrysin) with an excess of phenylmagnesium bromide in THF under reflux conditions, followed by hydrochloric acid hydrolysis, afforded 1 in Scheme 10.2. Flavylium salts bearing a substituent at the 4-position are important compounds since they are known to be less sensitive to nucleophiles, especially water, and they give only minor amounts of the colorless pseudobases. ... 

Metals more electronegative than magnesium, like beryllium, zinc, cadmium and mercury, form useful reagents for specific purposes, but the metals themselves are not sufficiently active to form organic derivatives under normal laboratory conditions and are unwanted in the environment since they are toxic. Aluminum compounds are useful for industrial purposes, but their use in the laboratory is insignificant in comparison with Grignard reagents. 

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