Academic literature on the topic 'Alkaline earth nitride hydride'

The trends within rows and columns of the periodic table are quite well known and are not repeated here. Instead, I concentrate on a number of other chemical trends, some of which challenge the form of reductionism that attempts to provide explanations based on electronic configurations alone. In the case of one particular trend described here, the knight’s move, the chemical behavior defies any theoretical understanding whatsoever, at least at the present time. As is well known to students of inorganic chemistry, a small number of elements display what is termed diagonal behavior where, in apparent violation of group trends, two elements from adjacent groups show greater similarity than is observed between these elements and the members of their own respective groups. Of these three classic examples of diagonal behavior, let us concentrate on the first one to the left in the periodic table, that between lithium and magnesium. The similarities between these two elements are as follows:1. Whereas the alkali metals form peroxides and superoxides, lithium behaves like a typical alkaline earth in forming only a normal oxide with formula Li2O. 2.Unlike the other alkali metals, lithium forms a nitride, Li3N, as do the alkaline earths. 3.Although the salts of most alkali metals are soluble, the carbonate, sulfate, and fluorides of lithium are insoluble, as in the case of the alkaline earth elements. 4.Lithium and magnesium both form organometallic compounds that act as useful reagents in organic chemistry. Lithium typically forms such compounds as Li(CH3)3, while magnesium forms such compounds as CH3MgBr, a typical Grignard reagent that is used in nucleophilic addition reactions. Organolithium and organomagnesium compounds are very strong bases that react with water to form alkanes. 5.Lithium salts display considerable covalent character, unlike their alkali metal homologues but in common with many alkaline earth salts. 6.Whereas the carbonates of the alkali metals do not decompose on heating, that of lithium behaves like the carbonates of the alkaline earths in forming the oxide and carbon dioxide gas. 7.Lithium is a considerably harder metal than other alkali metals and similar in hardness to the alkaline earths.

The reduction of pyridines offers an attractive approach to piperidine synthesis, and now Toshimichi Ohmura and Michinori Suginome of Kyoto University have developed (J. Am. Chem. Soc. 2012, 134, 3699) a rhodium-catalyzed hydroboration of pyridines, including the reaction of 1 to produce 3. Timothy J. Donohoe at the University of Oxford has found (Org. Lett. 2011, 13, 2074) that pyridinium silanes 4 undergo intramolecular hydride transfer by treatment with TBAF to produce dihydropyridones (e.g., 5) with good diastereoselectivity. Enantioselective amination of allylic alcohols has proven challenging, but Ross A. Widenhoefer at Duke University has reported (Angew. Chem. Int. Ed. 2012, 51, 1405) that a chiral gold catalyst can effect such intramolecular cyclizations with good enantioselectivity, as in the synthesis of 7 from 6. Alternatively, Masato Kitamura at Nagoya University has developed (Org. Lett. 2012, 14, 608) a ruthenium catalyst that operates at as low as 0.05 mol% loading for the conversion of substrates such as 8 to 9. Efforts to replace transition metal catalysts with alkaline earth metal-based alternatives have been gaining increasing attention, and Kai C. Hultzsch at Rutgers University has found (Angew. Chem. Int. Ed. 2012, 51, 394) that the magnesium complex 12 is capable of catalyzing intramolecular hydroamination (e.g., 10 to 11) with high enantioselectivity. Meanwhile, a stereoselective Wacker-type oxidation of tert-butanesulfinamides such as 13 to produce pyrrolidine derivatives 14 has been disclosed (Org. Lett. 2012, 14, 1242) by Shannon S. Stahl at the University of Wisconsin at Madison. Though highly desirable, Heck reactions have rarely proven feasible with alkyl halides due to competitive β-hydride elimination of the alkyl palladium intermediates. Sherry R. Chemler at the State University of New York at Buffalo has demonstrated (J. Am. Chem. Soc. 2012, 134, 2020) a copper-catalyzed enantioselective amination Heck-type cascade (e.g., 15 and 16 to 17) that is thought to proceed via radical intermediates. David L. Van Vranken at the University of California at Irvine has reported (Org. Lett. 2012, 14, 3233) the carbenylative amination of N-tosylhydrazones, which proceeds through η3-allyl Pd intermediates constructed via carbene insertion. This chemistry was applied to the two-step synthesis of caulophyllumine B from vinyl iodide 18 and N-tosylhydrazone 19.