Leads aluminum halides

Other organometallic compounds of aluminum include the alkyl hydrides, R2A1H. Molecular association of these compounds leads to cyclic tetramers. When the dimeric and trimeric compounds are dissolved in a basic aprotic solvent, the aggregates separate as a result of formation of bonds between A1 and the unshared pair of electrons on the solvent molecule. Toward Lewis bases such as trimeth-ylamine, aluminum alkyls are strong Lewis acids (as are aluminum halides). 

Less clear is the sequence which leads to the formation of the active species in the case of catalysts prepared from zero-valent nickel complexes and aluminum halides or alkylaluminum halides (method C2). The catalytic properties of these systems, however—in particular, the influence of phosphines (76)—leaves no doubt that the active species is also of the HNiY type discussed above. In this connection, a recent electron spin resonance report that nickel(I) species are formed in the reaction of COD2Ni with AlBr3 (83 ), and the disproportionation of Ni(I) to Ni(II) and Ni(0) in the presence of Lewis acids (69) should be mentioned. 

Reaction of aluminum halides with acetonitrile solutions of terpy leads to the formation of [Al(terpy)Cl3] or [Al(terpy)2]Xj (X = Cl, Br, or I) (48). Spectroscopic and conductivity measurements suggest that these complexes are octahedral. Moore and co-workers have investigated the reaction of terpy with [A1(DMS0)6] (DMSO, dimethylsulfoxide) by NMR methods stepwise release of DMSO indicated sequential coordination of the pyridine rings, and it is noteworthy that the closure of the final ring is significantly slower than the other two, as predicted by our concepts of increasing strain in the chelated complex (78). 

Attempts to perform the cationic polymerization of vinylcyclohexane have been reported. While coordination-type polymerization of vinylcyclohexane monomer gives isotactic PCHE, polymerization under conditions that lead to the formation of carbocationic intermediates leads to polymers with a differentiated backbone structure. Instead of propagating via the vinyl carbons, the cationic polymerization proceeds via hydride shift to a tertiary carbocation, which then propagates to provide the polymer shown in Scheme 23.3 [32]. Conditions for these polymerizations typically involved the use of aluminum halide catalysts in halogenated hydrocarbon solvents at low temperatures [32,38]. For the most part, molecular weights are relatively low. 

The identification of a complex is not proof that the reaction path is by way of that particular complex, as a more unstable intermediate is likely to be involved. The reports that aluminum halides alone are not catalysts for n-butane unless a trace of olefin, oxygen, or water is present even when HX, the corresponding halogen acid, is present (Pines and Wachher, 128), lead one to suspect that both a nucleophilic and an electrophilic reagent are needed and that the role of the solvent in solvat-... 

Carbothermic reduction in the presence of an alloying element, such as copper, iron, or silicon, to decrease aluminum vapor pressures decreases volatility problems but requires a further stage to recover aluminum from the alloy product. It may be selectively dissolved from the alloy with a more volatile metal, such as mercury, lead, or zinc, and then the aluminum recovered by distillation. Or, the tendency for aluminum halides to form more volatile monohalides at high temperatures, which revert to the trihalides at lower temperatures (Eq. 12.25) may be employed. 

Substituents in the alkyl chain of alkyl aluminum compounds, such as halogens, alkoxy, alkylmercapto, or dialkylamino groups, have varying effects on the stability of the aluminum alkyls to extents which depend on the position of the group in relation to the aluminum. Interaction between the substituents and aluminum leads to activation of both the A1—C and the C-substituent bonds. If, in the case of dialkyl halomethylalanes, the substituent (Cl, Br, or I) and the aluminum are linked to the same carbon atom, the compound is especially reactive. These compounds, since their etherates are stable, may be prepared readily in ethereal solution from dialkyl aluminum halides and diazomethane 97, 98) ... 

The greater basicity of bridging CO than terminal CO leads to a strikingly richer Z —CO— chemistry for polynuclear carbonyls than for their mononuclear counterparts. For example, simple neutral carbonyls such as Fe(CO)5 and Cr(CO)6 do not form stable adducts with boron or aluminum halides, whereas neutral polynuclear carbonyls containing bridging CO ligands readily form such adducts. 

With two moles of aluminum halide, the second molecule forms a complex with thiol-ester and debenzylates the sulfur forming an ion pair and a betaine structure (IV). The zwitterion character of the betaine structure leads to a close internal approach of the reactive centers and thus to the formation of j3-thiolactone (I). 

Alkyl halides by themselves are insufficiently electrophilic to react with benzene Aluminum chloride serves as a Lewis acid catalyst to enhance the electrophihcity of the alkylating agent With tertiary and secondary alkyl halides the addition of aluminum chlonde leads to the formation of carbocations which then attack the aromatic ring... 

Lead dioxide Aluminum carbide, hydrogen peroxide, hydrogen sulfide, hydroxylamine, ni-troalkanes, nitrogen compounds, nonmetal halides, peroxoformic acid, phosphorus, phosphorus trichloride, potassium, sulfur, sulfur dioxide, sulfides, tungsten, zirconium... 

An alternative route to a furanosyl halide of 2-deoxy-D-nbo-hexose was envisaged, involving the lithium aluminum hydride reduction of ethyl 2,3-anhydro-/ -D-allofuranoside which could, presumably, lead to ethyl... 

A thio-substituted, quaternary ammonium salt can be synthesized by the Michael addition of an alkyl thiol to acrylamide in the presence of benzyl trimethyl ammonium hydroxide as a catalyst [793-795]. The reaction leads to the crystallization of the adducts in essentially quantitative yield. Reduction of the amides by lithium aluminum hydride in tetrahydrofuran solution produces the desired amines, which are converted to desired halide by reaction of the methyl iodide with the amines. The inhibitor is useful in controlling corrosion such as that caused by CO2 and H2S. 

The nucleophilic addition of alcohols [130, 204-207], phenols [130], carboxylates [208], ammonia [130, 209], primary and secondary amines [41, 130, 205, 210, 211] and thiols [211-213] was used very early to convert several acceptor-substituted allenes 155 to products of type 158 and 159 (Scheme 7.25, Nu = OR, OAr, 02CR, NH2, NHR, NRR and SR). While the addition of alcohols, phenols and thiols is generally carried out in the presence of an auxiliary base, the reaction of allenyl ketones to give vinyl ethers of type 159 (Nu = OMe) is successful also by irradiation in pure methanol [214], Using widely varying reaction conditions, the addition of hydrogen halides (Nu= Cl, Br, I) to the allenes 155 leads to reaction products of type 158 [130, 215-220], Therefore, this transformation was also classified as a nucleophilic addition. Finally, the nucleophiles hydride (such as lithium aluminum hydride-aluminum trichloride) [211] and azide [221] could also be added to allenic esters to yield products of type 159. 

Looking for a more efficient catalyst to carry out this reaction thus became the most important issue. To achieve this, a large number of common Lewis acids were screened, including the halides of aluminum, iron, zinc, titanium, zirconium, nickel, copper, tin and lead. A number of these compounds did show activities as ether cleavage catalysts. The most effective catalysts were the halides... 

Reduction of the halides 2,6-Ar2H3C6AlX2(OEt2) (Ar = Mes or Trip X = Cl or Br) with alkali metals with the objective of synthesizing Al-Al bonded species leads to decomposition with deposition of aluminum met-... 

A compound that includes an aminopyrimidine ring as well as the quaternary salt present in thiamine shows preferential inhibition of absorption of that co-factor by coccidia parasites over uptake by vertebrates. The compound is thus used in poultry where coccidiosis is an economically important disease. Condensation of ethoxymethylenemalononitrile (42-1) with the amidine (42-2) leads to the aminopyrimidine (42-4), probably via the intermediate addition-elimination intermediate (42-3). The nitrile group is then reduced to the methylamino derivative (42-5) by means of hthium aluminum hydride. Exhaustive methylation, for example by reaction with formaldehyde and formic acid, followed by methyl iodide leads to the quaternary methiodide (42-6). The quaternary salt is then displaced by bromine, and the resulting benzyhc-like cylic halide (42-7) is displaced by 2-picoline (42-8). There is thus obtained amprolium (42-9) [43]. 

While metallocenes are usually acetylated with acid halides, acid anhydrides, or carboxylic acids, a number of other acylating agents have been reported. The reaction of ferrocene with various isocyanates and aluminum chlorides leads to N-substituted ferrocenecarboxamides (IX) (89). Use of ruthenocene in place of ferrocene leads to analogous results (88). The preparation of V-phenyl-ferrocenecarboxamide from phenyl isocyanate in this manner has been used as a proof of structure for the product obtained from the Beckmann rearrangement of benzoylferrocene oxime (124). 

The 3-oxo-2//-furans (260) obtained from the reaction of a-halogenoacyl halides with /3-ketonic esters at -20 °C show no tendency to enolize to the hydroxyfurans (261) but rather behave as unsaturated ketones (Scheme 71) (73RTC731). 2,4-Dialkylfurans (262) are obtained by condensation of acyl halides with allyl halides catalyzed by aluminum chloride (73KGS1434). The acid catalyzed condensation of 2-chlorocyclopentanone with dimethyl /3-oxoglutarate leads to the furan ester (263) (77JHC711). 

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