Samarium, pure compounds

More recently, Doris et al. have described the reductive ring-opening of a-keto epoxides [16]. In this manner, p-hydroxy ketones can be obtained in high yields. The synthesis of enantiomerically pure compounds can easily be realized. The titanocene] 111) reagents are distinctly superior to samarium diiodide, which is also known to induce this transformation. 

Samarium dichloride has been prepared by reduction of ethanolic solutions of SmCl3 with magnesium and hydrochloric acid (aqueous or anhydrous). Nevertheless, isolation of the pure compound from the reaction medium has not been achieved (Clifford et al., 1948). 

The catalysts are Tim hydrides which are generated in situ by reduction of enantio-merically pure L TiCl2 with butyllithium and PhSiH3 they are also highly effective in the asymmetric hydrogenation of imines and enamines.20 The lutetium ansa-metallocene complex (22-XVII) catalyzes the deuteration of 1-pentene (63% e.e.)21 Related samarium compounds hydrogenate imines.22... 

Samarium (II) iodide [32248-43-4] M 404.2, m 520°, b 1580. A possible impurity is Sml3 from which it is made. If present, grind the solid to a powder and heat it in a stream of pure H2. The temperature ( 500-600°) should be below the m ( 628°) of Sml3, since the molten compounds react very slowly. [WetzelmHandbookof Preparative Inorganic Chemistry (Ed. Brauer) Acadercac Press Vol II pp 1149, 1150 1965.]... 

The production of metal fullerides succeeds as well with alkaline earth metals and rare earth elements. Among others, there are mixed alkali/alkaline earth fullerides with a composition of M3, eBaxQo (0.2 < x < 2 M = K, Rb, Cs). Likewise may pure alkaline earth fullerides be obtained, for example, CasCGo that becomes a supraconductor below 8.4 K. Barium and strontium give binary fullerides too, but with stoichiometric factors of 3, 4, and 6. Ytterbium and samarium may intercalate in the C,so-crystal as well, yielding supraconductive compounds with a composition of M2.75C1S0. 

The methyl complexes dissolve in methylene chloride, toluene and benzene, but ethyl derivatives are sparingly soluble in alkanes. Reduced solubility of Sm and Gd complexes in toluene, in the authors opinion, shows some increase in the ionicity of such compounds from heavy to early lanthanoids [226]. Due to the low solubility in methylene chloride the attempts to isolate the samarium complex in analytically pure state have failed. The thermal stability of methyl complexes is rather high. Almost all compounds melt without decomposition in the temperature range 110-140°C, but the scandium and yttrium compounds may be sublimed in vacuum. The ethyl derivatives are less stable. They decompose with a notable rate even at room temperature. 

Guided by the success of the Evans and related auxiliaries, several attempts were made to use enantiomerically pure a-bromoacyl oxazolidinones for stereoselective Reformatsky reactions. Fukuzawa and coworkers developed the reaction of various bromoacetyl oxazolidinones 323 as an alternative to an asymmetric acetate aldol addition. The conversion was mediated by samarium iodide and yielded P-hydroxy carbonyl compounds 325 with high diastereoselectivity in optimal combinations of auxiliary group and aldehyde. Among the different auxiliaries, the geminal dimethyl- and diphenyl-substituted ones performed better than the original Evans oxazolidinones. The stereochemical outcome was rationalized by assuming that an O-bound samarium(III) enolate reacts via a chair-like... 

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