Sodium naphthalene reductions

Sodium-naphthalene reduction of organotrineopentoxyphosphonium salts led to the instantaneous loss of phosphonium ion phosphonates and phosphites were obtained748 (reaction 224). Alkali metal amalgams are efficient reagents for the reductive cleavage of both achiral and optically active phosphonium salts configuration is retained750 (Table 23). 

In contrast, for reaction of organic halides with metallic magnesium, Whitesides ( 7) found a poor correlation with the rates of tri-n-butyltin hydride, and a reasonable correlation, especially with primary bromides, with reduction potentials, suggesting the formation of RXT. Sodium naphthalene reductions also correlate with reduction potentials for primary halides (4b). Moreover, reaction rates are faster in solvents favoring loose ion pairs over tight, further evidence for an early transition state involving election transfer and little bond dissociation. (4c)... 

Treatment with two equivalents of tert-butyl hypochlorite and subsequent reduction with sodium/naphthalene. 

Due to the commercial availability of Cp2TiCl2, its reduction and subsequent treatment with CO represents one of the most direct routes to Cp2Ti(CO)2 (1). An early example of this method was reported by Calderazzo et al. whereby Cp2TiCl2 was first reduced by sodium naphthalene at 25°C in THF for 24 hours (16). The resulting green titanocene, p.-(rf i75-fulvalene)-di-/i-hydrido-bis(cyclopentadienyltitanium) (17-22), was then treated with 1 atm of CO in toluene for 4 hours at 20°C. However, this procedure proved inefficient for the production of 1 since only 10% of the required amount of CO for complete conversion was consumed. 

Reduction is defined as acceptance of electrons. Electrons can be supplied by an electrode - cathode - or else by dissolving metals. If a metal goes into solution it forms a cation and gives away electrons. A compound to be reduced, e.g. a ketone, accepts one electron and changes to a radical anion A. Such a radical anion may exist when stabilized by resonance, as in sodium-naphthalene complexes with some ethers [122], In the absence of protons the radical anion may accept another electron and form a dianion B. Such a process is not easy since it requires an encounter of two negative species, an electron and a radical anion, and the two negative sites are close together. It takes place only with compounds which can stabilize the radical anion and the dianion by resonance. 

Reductive removal of fluorine from alkyl fluorides requires a potent reducing agent and so is not normally encountered However, hydrogenolysis of an unactivated carbon-fluorine bond in, for example, 3 p-fluorocholestane has been efficiently accomplished in 88% yield with a solution of potassium and dicyclohexyl 18 crown-6 in toluene at 25 °C [/] Similarly, sodium naphthalene in tetrahydrofuran converts 6 fluorohexene-1 and 1-fluorohexane to hydrocarbons in 50% yield at 25 °C over a 7-h period [2]... 

Reduction with sodium naphthalene of easily obtained diazadiene ruthenium ) complexes of type 65 (X = Cl) affords (rj6-arene)Ru(0) complexes 64. The latter are very reactive and undergo oxidative addition with iodine or alkyl halides to produce complexes 65 (X = I and X = CH2R, respectively) (51) [Eq. (26)]. Other ruthenium(O) complexes have been... 

Addition of acid in acetonitrile to the hexa-anion gives only traces of [Ni32H(C)6(CO)36]5 (396), although the penta-anion is stable in acetone. Reduction (sodium/naphthalene, dmf) affords the hepta- and octa-anions, which are stable for hours in solution, while oxidation (C7H7+) regenerates the hexa-anion and ultimately gives the unstable penta-anion.577 The odd-electron species do not give ESR spectra. 

Radical cations have also been trapped with the hydride ion. Irradiation of aromatic hydrocarbons such as phenanthrene, anthracene and naphthalene in aqueous acetonitrile containing sodium borohydride and an electron acceptor produces the dihydroarenes (Yasuda et ai, 1981b). With monoalkyl naphthalenes reduction in both the unsubstituted and substituted rings occurs... 

Orthometallation of triarylphosphine and triarylphosphite at mthenium has long been knovm as intramolecular C-H bond activation in ruthenium chemistry [2], but did not receive attention from organic chemists. In 1965, Chatt and Davidson documented that a Ru(0) complex, which was formed by two-electron reduction of Ru(II) by use of sodium naphthalene is capable of reversible cleavage of sp C-H bonds of naphthalene by oxidative addition/reductive elimination processes (Scheme 14.1) [3]. 

Disodium tetracarbonylferrate (Collman s reagent) is prepared by the reduction of Fe(CO)5 with sodium naphthalene in THF or sodium benzophenone ketyl in dioxane. Though it can be isolated as a white precipitate, it is usually used in THF or dioxane solution without isolation because of its highly air-sensitive and pyrophoric character. It is reported that the solubility of Na2[Fe(CO)4] is 7 x 10 M in THF and that it can be stored for moderate periods in an inert atmosphere in the dark [36]. X-ray crystallography of Na2[Fe(CO)4] (Fig. 10.2) shows that the C—Fe—C bond angle opposite to the sodium cations is significantly distorted (129.7°) [37]. However, this distortion is reduced for the potassium analogue [38]. 

Since Chatt and Davidson discovered C—H bond activation by reduction of RuCl2(dmpe)2 with a sodium/naphthalene system, the iron analogues have been widely investigated. Actually reductions of FeCl2(diphos)2 or FeH2(diphos)2 have played the central role in this area and FeCl2(diphos)2 can be prepared by the reaction of purified FeCl2 with diphosphine. 

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