Lithium naphthalide

Reaction between sulfides and lithium or lithium naphthalide... 

The first examples of mononuclear disulfur and diselenium complexes of platinum have been described.330 Reduction of the sterically hindered complex trans- PtC 2( P M e2A r)2] (Ar = 2,4, 6-tris[bis(trimethylsilyl)methyl]phenyl, 2,6-bis[bis(trimethylsilyl)-methyl]-4-[tris(trimethylsilyl) methyl]-phenyl) with lithium naphthalide in THF solution affords the platinum(0) species [Pt(PMe2Ar)2]. Oxidative addition of elemental sulfur or selenium yields the dichalcogenatoplatinum(II) complexes of the type [PtE2(PMe2Ar)2] (E = S, Se) containing a unique PtE2 ring system. The complexes are stable to air in the solid state, but slowly decompose in solution after several days at room temperature. 

A third approach is to use a stoichiometric amount of preformed lithium naphthalide. This approach allows for very rapid generation of the metal powders as reductions are diffusion controlled. Very low to ambient temperatures can be used for the reduction. In some cases the reductions are slower at low temperatures due to low solubility of the metal salts. 

This approach frequently leads to the most active metals as the relatively short reduction times at low temperatures leads to reduced sintering of the metal particles and hence higher reactivity. Fujita, et aL(62) have recently shown that lithium naphthalide in tqluepe can be prepared by sonicating lithium, naphthalene, and N, N, N, N-tetramethylethylene-diamine (TMEDA) in toluene. This allows reductions of metal salts in hydrocarbon solvents. This proved to be especially beneficial with cadmium(49). An extension of this approach is to use the solid dilithium salt of the dianion of naphthalene. Use of this reducing agent in a hydrocarbon solvent is essential in the preparation of highly reactive uranium(54). This will be discussed in detail below. 

However, when the reductions were carried out with lithium and a catalytic amount of naphthalene as an electron carrier, far different results were obtained(36-39, 43-48). Using this approach a highly reactive form of finely divided nickel resulted. It should be pointed out that with the electron carrier approach the reductions can be conveniently monitored, for when the reductions are complete the solutions turn green from the buildup of lithium naphthalide. It was determined that 2.2 to 2.3 equivalents of lithium were required to reach complete reduction of Ni(+2) salts. It is also significant to point out that ESCA studies on the nickel powders produced from reductions using 2.0 equivalents of potassium showed considerable amounts of Ni(+2) on the metal surface. In contrast, little Ni(+2) was observed on the surface of the nickel powders generated by reductions using 2.3 equivalents of lithium. While it is only speculation, our interpretation of these results is that the absorption of the Ni(+2) ions on the nickel surface in effect raised the work function of the nickel and rendered it ineffective towards oxidative addition reactions. An alternative explanation is that the Ni(+2) ions were simply adsorbed on the active sites of the nickel surface. 

The highly reactive cadmium can be prepared by two different methods. One approach is a room temperature reduction of CdC with lithium naphthalide in THF or DME. The second approach allows the preparation of the reactive metal in a hydrocarbon solvent. First, lithium naphthalide is prepared in benzene addition of this solution to CdC produces a highly reactive cadmium powder. 

The reduction of a solution of a trialkylphosphine copper(I) iodide complex (CuIPR ) with preformed lithium naphthalide (LiNp) in THF or DME under argon was found to give a more reactive copper species, which will undergo oxidative addition with a variety of organic substrates at room... 

A fast equilibrium between these two compounds is established at room temperature or above188. An analogous reaction189 between di-9-phenanthryltin dichloride, Phen2SnCl2 and lithium naphthalide at —78°C yields hexa-9-phenanthryltristannacyclopropane via a... 

Procedure B. Finely cut (0.15 g, 22.0 mmol) and a stoichiometrical amount of naphthalene (2.80 g, 22.0 mmol) were weighed into a 100-ml flask, and ZnCl2 (1.5 g, 11.0 mmol) was weighed into a 50-ml flask. The Lithium and naphthalene were dissolved in THF (20 ml) in ca. 2h. ZnCl2 was dissolved in THF (20 ml) and the solution was transferred into the flask with lithium naphthalide via cannula over 10 min. The reaction mixture was further stirred for 1 h, and the resulting black suspension of active zinc thus prepared was ready for use. 

The reduction of di(neopentyl)gallium chloride with lithium naphthalide was reported to afford the gallium clusters (Ga-CH2CMe3) , but their structures are hitherto unknown. It was assumed that different species with up to 12 gallium... 

An early effort to generate a 3-lithiated propionic acid derivative and react it with (external) electrophiles was reported in 1978 [42]. Since simple 3-lithioesters failed to undergo the required reaction, the alkyl carboxylate portion was protected by preceding conversion to the carboxylate anion. Treatment of lithium 3-bromo-propionate with lithium naphthalide generated the desired dilithiated propionic acid, which gave moderate yields of y-hydroxy acid addition products with carbonyl compounds, Eq. (45). 

In the reduction of conjugated dienes cis 1,4-addition of trimethyl-chlorosilane to give c -l,4-bis(trimethylsilyl)-2-butene is favored with sodium in THF, lithium naphthalide in THF, and with lithium in diethylether. It appears that the anion radical, which in nonionizing solvents should exist in a cis configuration, leads to the cis 1,4-addition of the silyl groups, whereas the dianions produced by further reduction lead to trans products (140). 

Cadmium(0). A reactive cadmium powder can be prepared by reaction of CdCl2 with lithium naphthalide in glyme or THF. A more reactive cadmium powder is obtained by reaction of CdCl2 with lithium naphthalide prepared by sonication in TMEDA and toluene. A third form is prepared by treatment of Cd3Li with 1 equiv. of I2 to leach the lithium. 

Lithium (8.46 mmol) and naphthalene (10.1 mmol) were mixed with 15 ml THF, stirred 2 hours, and then cooled to — 100°C. In a separate reaction vessel, CuCN (8.0 mmol) and LiBr (17.27 mmol) in 5 ml THF were stirred until the Cu(I) salt dissolved. The solution was cooled to —40°C and transferred into lithium naphthalide using a cannula and the mixture stirred 5 minutes. The catalytic agent was ready for immediate use. 

In the application of this methodology to the preparation of C-glycosides, Beau and Sinay [183] utilized dimethyl carbonate as an electrophile. As shown in Scheme 7.65, the resulting product mixture favored the (3 oriented ester group in a ratio of 20 1. Subsequent reductive cleavage of the phenylsulfone was accomplished on treatment with lithium naphthalide giving the a-C-glycoside in 72% overall yield. Similar results were observed when phenyl benzoate was used as an electrophile. 

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