Barium room-temperature synthesis

Samson,)., Manning, E.P., Yang, N.-I. and Matsui, H. (2006) Room temperature synthesis of ferroelectric barium titanate nanoparticles using peptide nanorings... 

The four-membered azetidine ring remains unaffected by sodium in liquid ammonia, 94 methanolic ammonia, 95 5M barium hydroxide at 100 °C for 24 hours, 87 sodium hydroxide under ester saponification conditions, 87 HC1 at room temperature, 96,97 catalytic hydrogenation under normal conditions, 87,95 and ozonolysisJ87 Correspondingly, as observed for proline, the azetidine-2-carboxylic acid (2) raises no particular difficulties in the synthesis of related peptides. 

The most frequently used method of this type is the reaction of hydrazones (247) with diazonium compounds to afford formazans (248). These can be cyclized with carbonyl compounds in the presence of acid to yield verdazylium cations (252) which are reduced under basic conditions to give the verdazyls (253) which can be further reduced to the tetrahydro-l,2,4,5-tetrazines (254). The formazans (248) can be alkylated and the alkylfor-mazans (249) cyclized by heating or treatment with a base to form the tetrahydrotetrazines (250). It is not necessary to isolate the alkylated compounds (249) the complete reaction (248-250) can be carried out at room temperature in the presence of barium oxide or hydroxide in DMF. Oxidation of (250) provides a synthesis of verdazyls (251) (see Section 2.21.3.4.2). 

For the synthesis, as shown in Scheme 13.2, when acetophenone was treated with phosphorus pentachloride, first with cooling and then warming to 40°C to complete the reaction, the corresponding benzylic dichloride (1,1-dichloro-l-phenylethane) was obtained in good yield. Dissolution of the dichloride in ethanol followed by addition of ethanolic potassium cyanide (KCN) and standing for 48 h at room temperature resulted in a solution from which potassium chloride (KCl) precipitated and which had a strong odor of hydrogen cyanide (HCN).The ethanol was removed by distillation, and the residue was treated at room temperature for 8h with barium hydroxide [Ba(OH)2]. Acidification resulted in the isolation of tropic acid in low yield. 

The reaction is facile at room temperature and in the absence of catalysts only for alkali metals (M = Li, Na, K) and barium [59]. To obtain the derivatives of alkaline earth metals with aliphatic alcohols, it is necessary to apply heat (reflux) and add a catalyst, usually elementary iodine, to clean the surface of the metal applied [110]. The same is true for aluminum alkoxides that can be produced in high yields by reaction of aluminum metal with dry alcohols on addition of l2(s) [2]. For drying the alcohols, one can apply aluminum alkoxides produced even from household aluminum foil, but it is necessary to remember that the latter is doped by some few percent of iron and is not a suitable material for the synthesis of aluminum alkoxides for preparation of high-purity ceramics. 

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