Alcohols alkoxides from

Synthesis. Titanium alkoxy halides are intermediates in the preparation of alkoxides from a titanium tetrahaUde (except the fluoride) and an alcohol or phenol. If TiCl is heated with excess primary alcohol, only two chlorine atoms can be replaced and the product is dialkoxydichlorotitanium alcoholate, (RO)2TiCl2 ROH. The yields are poor, and some alcohols, such as aHyl, ben2yl, and /-butyl alcohols, are converted to chlorides (46). Using excess TiCl at 0°C, the trichloride ROTiCl is obtained nearly quantitatively, even from sec- and / f/-alcohols (47,48). 

Zirconium tetrachloride is instantly hydrolyzed in water to zirconium oxide dichloride octahydrate [13520-92-8]. Zirconium tetrachloride exchanges chlorine for 0x0 bonds in the reaction with hydroxylic ligands, forming alkoxides from alcohols (see Alkoxides, METAl). Zirconium tetrachloride combines with many Lewis bases such as dimethyl sulfoxide, phosphoms oxychloride and amines including ammonia, ethers, and ketones. The zirconium organometalLic compounds ate all derived from zirconium tetrachloride. 

When the alcohol adduct from the allenylzinc reagent and diisopropyl ketone was treated with 80 mol% of allenylzinc bromide in HMPA, a mixture containing 12% of diisopropyl ketone and 88% of recovered alcohol was obtained after 7 days at ambient temperatures (equation 1). Thus, it may be deduced that the allenylzinc additions are reversible. Presumably, the propargyl adducts are intrinsically favored, but steric interactions between the R1 and R2 substituents in the propargyl product favors an increased proportion of allenyl adducts in a reversible process (see Table 1). HMPA would expectedly facilitate reversal of the addition by decreasing the ion pairing between the alkoxide anion and ZnBr cation of the adducts. This expectation was subsequently confirmed by a study of solvent effects. 

A number of contradictory views have been published concerning the structure of adsorbed alcohols and the nature of adsorption sites (for review see ref. 69). Experimental evidence from IR investigations has shown that, on alumina, alcohols form several surface complexes of very different chemical natures (e.g. refs. 31, 32, 117, 133—137) (i) alcohol molecules weakly bonded to the surface, very probably by hydrogen bonds (I) (such complexes are sometimes denoted as physically sorbed alcohols) (ii) surface alkoxides (alcoholates) (II) (iii) surface carboxy-lates (III). Less certain is the existence of species with partial double bonds or of ketone-like species. The formation of the various surface complexes is dependent on the structure of the alcohol. For examples, weakly bonded species (I) have been found with all alcohols, alkoxides (II) mostly with primary alcohols, sometimes also with secondary alcohols, but have never been reported for tertiary alcohols. 

On introducing acetochloroglucose into an alkaline solution of a monosaccharide in aqueous alcohol, apart from their condensation, partial removal of acetyl groups, in the form of ethyl acetate, occurs. This was the first indication of transesterifico-tion by alkoxide (1902), a reaction that later achieved great importance. 

Reduction then proceeds by successive transfers of hydride ion, H e, from aluminum to carbon. The first such transfer reduces the acid salt to the oxidation level of the aldehyde reduction does not stop at this point, however, but continues rapidly to the alcohol. Insufficient information is available to permit very specific structures to be written for the intermediates in the lithium aluminum hydride reduction of carboxylic acids. However, the product is a complex aluminum alkoxide, from which the alcohol is freed by hydrolysis ... 

Both reactions are used for the commercial production of alkaline and alkaline-earth alkoxides from very cheap raw materials. As far as the metal alkoxides thus formed are soluble in alcohols, both reactions are reversible. Thus, application of these methods is expedient in the case of alcohols with the boiling temperature higher than 100°C (water is distilled off). When low-boiling alcohols are used the reaction time increases greatly, water is eliminat-... 

In this case isolation of metal alkoxide from water does not require any special measures liquid TIOEt is accumulated in the bottom of the flask in a 95% mixture with EtOH, while TlOH and water comprise the upper layer [1625]. Alkaline metals react in analogous way with alcohols that do not mix with water. For instance, reaction of KOH with Et2CHOH (pentanol-3) at 120°C also results in the formation of two layers the upper (alcoholic) layer contains 40 wt% of KOR and 2 wt% of KOH while the lower (aqueous) layer contains 54 wt% of KOH [1277]. 

Solubility of LiCl in MeOH, EtOH, and"BuOH is 30.4, 19.6, and 13.9%, respectively. That is why after refluxing of the reaction mixture and washing off the precipitate with alcohol, alkoxides free from LiCl are obtained. However, this reaction in many cases is also complicated by formation of bimetallic complexes. Formation of stable intermediate complexes is especially characteristic when LiOR is applied for alkoxylation. Thus Li4Y40(0Bu )12Cl2 was isolated in reaction of YC13 with 2 mols of LiOBu (i.e., on lack of OR-ligands) [553]. 

Mann, G. Hartwig, J. F. Palladium alkoxides potential intermediacy in catalytic animation, reductive elimination of ethers, and catalytic etheration. Comments on alcohol elimination from Ir(III)./. Am. Chem. Soc. 1996, 118, 13109-13110. 

Diethyl ether is prepared commercially by intermolecular dehydration of ethanol with sulfuric acid. The Williamson ether synthesis, another route to ethers, involves preparation of an alkoxide from an alcohol and a reactive metal, followed by an SN2 displacement between the alkoxide and an alkyl halide. 

Iminodithiazoles 108 prepared from Appel salt 20 and o-aminobenzyl- and o-aminophenethyl-alcohols can be converted into 3,1-benzoxazine 109a and 3,1-benzoxazepine 109b by treatment with sodium hydride in THF (Equation 22) <1997SL704>. The oxygen-containing heterocycles 109 are apparently formed by cyclization of the alkoxide from dithiazole 108 onto the imine bond, followed by loss of S2 with generation of the cyano group. 

Both the structural features of the alcohol and the reaction conditions used are important in determining which of the decomposition pathways is followed. If the lead alkoxide from a primary or secondary alcohol is formed in the presence of a donor solvent, such as pyridine, oxidation to an aldehyde or ketone is the primary mode of decomposition (63) (Reaction XXXVIII). 

In the 2,3-dihydro-5-oxo-5Ff-oxazolo[3,2-c]pyrimidinium salt (207) there are three sites for reactions with nucleophilic reagents, viz. C-2, C-8a and C-7. Products resulting from attack at C-2 are observed with DMSO, water, alcohols, benzoate, chloride, diethylamine and pyridine. Products resulting from attack at C-8a are observed with water, hydroxide, alcohols, alkoxide and isopropylamine. Diethylamine also causes attack at C-7 of the cation, which results in cleavage of the pyrimidine ring (75JOC1713). 

In addition to catalyzing hydroformylation, the platinum SPO complexes are excellent hydrogenation catalysts for aldehydes (as already demonstrated by the side products of hydroformylation), in particular, in the absence of carbon monoxide. Further, in ibis process, the facile heterolytic splitting of dihydrogen may play a role. The hydrogenation of aldehydes requires the presence of carboxylic acids, and perhaps the release of alkoxides from platinum requires a more reactive proton donor than that available on the nearby SPO. For example, 4 hydrogenates 2-methylpropanal at 95 °C and 40 bar of H2 to give the alcohol, with a TOF of 9000 mol moN h (71). 

Intermolecular Nucleophilic Substitution with Heteroatom Nucleophiles. A patent issued in 1965 claims substitution for fluoride on fluorobenzene-Cr(CO)3 in dimethyl sulfoxide (DMSO) by a long list of nucleophiles including alkoxides (from simple alcohols, cholesterol, ethylene glycol, pinacol, and dihydroxyacetone), carboxylates, amines, and carbanions (from triphenyhnethane, indene, cyclohexanone, acetone, cyclopentadiene, phenylacetylene, acetic acid, and propiolic acid). In the reaction of methoxide with halobenzene-Cr(CO)3, the fluorobenzene complex is ca. 2000 times more reactive than the chlorobenzene complex. The difference is taken as evidence for a rate-limiting attack on the arene ligand followed by fast loss of halide the concentration of the cyclohexadienyl anion complex does not build up. In the reaction of fluorobenzene-Cr(CO)3 with amine nucleophiles, the coordinated aniline product appears rapidly at 25 °C, and a carefiil mechanistic study suggests that the loss of halide is now rate limiting. 

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