Reductive elimination of naphthalene

Ru(0) active species was generated from the reductive elimination of naphthalene from a naphthylruthenium(hydrido) complex 97. 

Reaction of the electron-rich Fe(dmpe)2 [dmpe = l,2,-bis(dimethylphosphino) ethane] intermediate, generated by reductive elimination of naphthalene from Fe(dmpe)2(Np)(H), with a variety of C-H bonds leads to isolation of Fe(dmpe)(R)(H) complexes via oxidative addition ... 

Reactivity from the naphthyl hydride ruthenium complex is believed to occur via initial reductive elimination of naphthalene followed by oxidative addition of a C-H bond. These activation processes (requiring reductive elimination) occur at temperatures of 150°C in alkane or arene solvents, depending on the desired product ". This complex shows general C-H activation behavior with sp, sp, and sp hybridized C-H bonds . ... 

Usually the C-0 single bond in esters is cleaved at the acyl-0 bond, whereas examples of cleavage at the other point in esters have been reported. An electron-rich iron(O) complex produced on reductive elimination of naphthalene from a hydrido(naphthyl)iron complex undergoes oxidative addition reaction with methyl benzoate to give a methyliron benzoate complex (Eq. 22) [63]. 

Deprotection and oxidation of 12 gave 13, which was further oxidized to the sulfoxide. Elimination of the sulfoxide gave the naphthalene derivative 14, which underwent spontaneous oxidation to 15. Reductive deprotection then gave tetracycline 16. The diastereoselectivity of the air and light-mediated oxidation is remarkable. 

Conversely to their usual stability and chemical inertness, saturated perfluorocarbons can be susceptible to reductive defluorination in one-electron-transfer reactions. Thus, per-fluorodeeahydronaphthalene is converted by sodium benzenethiolate to octakisfphenylsul-fanyl)naphthalene, attacking first the weaker tertiary C — F bond (see Section 3.5.). Independent of the strong C — C bonds, in hydrocarbon-perfluorocarbon copolymers elimination of hydrogen fluoride takes place above 350 C. 

Barluenga and Yus showed that reductive lithation with naphthalene was nonetheless an effective way of making functionalised organolithiums. The (3-oxygenated species such as 11 are stable below -78 °C provided the lithium is at a primary centre (above this temperature they decompose with elimination of Li20) and can be formed by reductive lithiation of the lithium alkoxide 10.22 25 The amide 12 behaves similarly,26 and protected aldehyde 14 yields homoenolate equivalent 15.27... 

The active nickel catalyst contains one bidentate phos-phinite ligand and the overall mechanism of the reaction is believed to be similar to butadiene hydrocyanation except that the final reductive elimination step is irreversible under the conditions of the reaction. jr-Allyl intermediates (7) are believed to play an important role in the exclusive formation of the branched nitrile product observed. Formation of the C-CN bond in the final reductive ehmination from the r-allyl intermediate occurs at C(2) and not C(4), because the aromaticity of the naphthalene ring is preserved only when the bond forms with C(2). A a-alkyl complex see a-Bond) with the Ni bound to C(l), which could give the linear (anti-Markovnikov) nitrile product, does not contribute because of the much greater stability of intermediate (7), accounting for the high regioselectivity observed. 

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]. 

The cyclic phosphate and phosphoramidate derivatives of v/c-diols undergo a two-step reductive elimination on treatment with Li/NHs, Na-naphthalene, TiCl4-Mg(Hg) or TiClt-K. In acyclic systems the reaction is only moderately stereoselective. The reaction has particular value in the synthesis of tetra-substituted alkenes from highly hindered v/c-diols. Scheme 20 illustrates its use in the synthesis of [10,10]-betweenanene (49). ... 

Reductive 1,2-eIimination of chlorine and bromine from adducts of l-bromo-2-chlorocyclo-propene (see Section 5.2.2.1.2.5.) with oxygen and sulfur hetarenes has served in the synthesis of a number of cycloproparenes. This transformation is effected by low-valent titanium together with lithium aluminum hydride or an organolithium compound. Thus, reaction of the adduct 3 of l-bromo-2-chlorocyclopropene and 1,3-diphenylisobenzofuran with tita-nium(III) chloride and lithium aluminum hydride overnight in tetrahydrofuran led to elimination of both halogens together with extrusion of the oxygen and formation of 2,7-diphenyl-l/f-cyclopropa[ ]naphthalene (4) in 72% yield. 

The formation of 3 and 2 by reaction of DMPE with 1 explains the source of 2 in the preliminary reduction. More significantly, it demonstrates that 1 can reductively eliminate a C-H bond to give free naphthalene and the undetected intermediate species Fe(DMPE)2. This reaction is the first step for almost all of the following chemistry. The ruthenium and osmium analogs of 1 have been in the literature for many years (15,16) but because they are much less prone to eliminate naphthalene, they have shown little of the chemistry described below for the iron complexes. 

Aryne-nickel complexes, which were carefully studied by Bennett [6, 7], show a different reactivity, since following the insertion of a first unsaturated species, the metallacycles so formed usually undergo a second insertion and subsequent reductive elimination (Scheme 9). Thus, complex 44 undergoes the insertion of two molecules of 3-hexyne to afford 43 in good yield, and double insertion of the asymmetric alkyne t-butylacetylene into complex 44 yields naphthalene 45 with a high regioselectivity attributed to steric factors. Interestingly, the reaction of 44 with the more electron-deficient alkyne hexafluoro-... 

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