Alkoxides, alkali metal

Alkali metal alkoxides, r-butyl acetate neat, 45°, 30 min, 98% yield of r-butyl ester from methyl benzoate. The rate constant for the reaction increases with increasing ionic radius of the metal and with decreasing polarity of the solvent. Equilibrium for the reaction is achieved in <10 sec. Other examples eire presented. " ... 

Zinc phthalocyanine (PcZn) is prepared from phthalonitrile in solvents with a boiling point higher than 200 C, e.g. quinoline277,278 or 1-bromonaphthalene,137 or without solvent in a melt of phthalonitrile.83,116 The zinc compound normally used is zinc(ll) acetate or zinc powder. The reaction of zinc(II) acetate with phthalic acid anhydride, urea and ammonium mo-lybdate(VI) is also successful.262 The metal insertion into a metal-free phthalocyanine is carried out in an alcohol (e.g.. butan-l-ol).127,141,290 This reaction can be catalyzed by an alkali metal alkoxide.112,129... 

Overall, the alkali metal alkoxide and aryloxide systems are excellent examples in demonstrating the effects of steric influences on both molecular aggregation and also on the nature of any extended network architecture adopted. The large database of O-M complexes that have now been identified has led to a good deal of predictability regarding the coordination chemistry of these species. 

In addition to amines, alkali metal alkoxides, hydroxides, and metals themselves can be used in borylation reactions [Eq. (69)] (90IZV886). 

Access to heavier alkali metal complexes may also be achieved by metathesis between a lithium organophosphide and a heavier alkali metal alkoxide (27) ... 

The alkoxide group R is chosen so that the heavier alkali metal alkoxide MOR is soluble in ether or hydrocarbon solvents and so the by-product LiOR may easily be separated from the desired heavier alkali metal phosphide/arsenide (which is often insoluble in weakly or noncoordinating solvents such as ethers and hydrocarbons). 

Alkali metals, particularly potassium 2. Alkali metal alkoxides and amides 3. Organometallics ... 

Alkali-immobile dye-releasing quinone compounds, 19 293-294 Alkali lignins, 15 19-20 Alkali manganate(VI) salts, 15 596 Alkali manganates(V), 15 592 Alkali-metal alkoxide catalysts, 10 491 Alkali-metal alkoxides, effects of, 14 252 Alkali-metal alkylstannonates, 24 824 Alkali-metal fluoroxenates, 17 329-330 Alkali-metal hydrides, 13 608 Alkali-metal hydroxides, carbonyl sulfide reaction with, 23 622 Alkali-metal metatungstates, 25 383 Alkali-metal perchlorates, 18 211 Alkali-metal peroxides, 16 393... 

The preferential -configuration of the enol esters, derived from p-dicarbonyl compounds under phase-transfer conditions, contrasts with the formation of the Z-enol esters when the reaction is carried out by classical procedures using alkali metal alkoxides. In the latter case, the U form of the intermediate enolate anion is stabilized by chelation with the alkali metal cation, thereby promoting the exclusive formation of the Z-enol ester (9) (Scheme 3.5), whereas the formation of the ion-pair with the quaternary ammonium cation allows the carbanion to adopt the thermodynamically more stable sickle or W forms, (7) and (8), which lead to the E-enol esters (10) [54],... 

Modified MPV-type reductions carried out with chiral magnesium alkoxides and with chiral Grignard reagents have been discussed in detail (1). These reagents differ from the aluminum alkoxides since the Grignard reaction is essentially irreversible. Chiral alkali metal alkoxides have also been used to effect asymmetric reductions (1). 

Ruthenium(III) catalyses the oxidative decarboxylation of butanoic and 2-methylpropanoic acid in aqueous sulfuric acid. ° Studies of alkaline earth (Ba, Sr) metal alkoxides in amide ethanolysis and of alkali metal alkoxide clusters as highly effective transesterification catalysts were covered earlier. Kinetic studies of the ethanolysis of 5-nitroquinol-8-yl benzoate (228) in the presence of lithium, sodium, or potassium ethoxide revealed that the highest catalytic activity is observed with Na+.iio... 

In the conventional extension 24) of this synthesis to S-alkyhsothio-ureas, low yields of the expected biguanides were obtained. Curd, Rose et al. 128, 131) have improved this synthesis by performing the condensation under conditions which first convert the S-alkylisothiourea into the corresponding cyanamide (i.e. in non-hydroxylic organic media boiling above 100°, and in the presence of an alkali metal alkoxide). 

Alkaline nitration with alkoxide bases and nitrate esters was first explored by Endres and Wislicenus who synthesized phenylnitromethane by treating ethyl phenylacetate with potassium ethoxide in ethanol, followed by addition of ethyl nitrate and hydrolysis-decarboxylation of the resulting a-nitroester with aqueous acid. Phenylnitromethane is synthesized in a similar way via alkaline nitration of benzyl cyanide, followed by treatment of the resulting a -nitronitrile with aqueous base. ° Wieland and co-workers used alkali metal alkoxides and nitrate esters for the nitration of cyclic ketones but the yields and purity of product are often poor. ° ... 

Hanawalt and Richey observed that additions of alkali-metal alkoxides to diaUtylmag-nesium led in some reactions to behavior resembling that of trialkylmagnesates. This includes enhanced reactivities in addition to pyridine leading to 4- or 2-aIkyl-substituted... 

The generation of dichlorocarbene for addition to olefins has been realized by the use of chloroform and alkali metal alk-oxides4 6 (preferably potassium feri-butoxide), sodium trichloro-acetate,6 butyllithium and bromotrichloromethane,7 and the reaction of an ester of trichloracetic acid with an alkali metal alkoxide.2,8 The latter method, which is here illustrated by the preparation of 2-oxa-7,7-dichloronorcarane, generally gives higher yields of adducts. 

In organic solvents the acidity functions H corresponding to hydrogen dissociation from neutral indicator acids were reported for solutions of alkali metal alkoxides in various alcohols (2), using nitroanilines (21), aminobenzenecarboxylic acids (22), or indols (23) as indicators. For addition reactions of methoxide and ethoxide ions to neutral indicator acids, acidity functions J (also denoted as Hr) based on use of nitrobenzenes (21) and a-cyanostilbenes (18) as indicators in methanol and dimethylsulfoxide-methanol and -ethanol mixtures were reported. Recently (24) the acidity function J- (denoted as Jm) was derived for methoxide ion solutions in methanol using substituted benzaldehydes as indicators. These scales involve arbitrary choice of water as the solvent for determination of the dissociation constant of the anchoring acid. 

Double alkoxides with alkali metals A[M(OR)6] (Table 8) were formed from the reaction of the pentaalkoxides with alkali metal alkoxides. The double alkoxides of Mg, Ca, Sr and Ba with Nb and Ta have been synthesized in the presence of MgCl2 as a catalyst.169 Refluxing M(OPri)5 and A(OPri)3 (A = A1 or Ga) in isopropyl alcohol afforded double isopropoxides of the type [MA(OPr )8J and [MA2(OPr1)n]170. [NbTa(OMe)10] appears to be the first mixed transition metal alkoxide isolated.171 NMR showed it to be in dynamic equilibrium with the symmetrical M2(OMe)i0 dimers in solution, with close to random distribution of the three species. 

In anionic polymerization the reaction is initiated by a strong base, eg, a metal hydride, alkali metal alkoxide, oiganometaUic compounds, or... 

There have been few investigations of the reactions of polyhydroxy compounds with alkali metal alkoxides in nonaqueous media at room temperature.. Percival" reported the preparation of D-glucose-NaOEt and D-glucose NaOMe by treating d-glucose with sodium ethoxide, and penta-O-acetyl-D-glucopyranose with sodium methoxide, respectively. The adducts were dried under vacuum at 60° for 24 hours, a treatment which would make the presence of any significant proportion of alcohol of solvation unlikely. Any traces of moisture in the preparative medium preclude the formation of an aJkoxide adduct. 

In summary, the reaction between an alkali metal alkoxide and a poly-hydroxy compound in hot alcoholic media produces an alcoholate and, possibly, a small proportion of alkoxide adduct however, the conditions governing the ratio of alcoholate to adduct have not yet been well defined. Reactions with alkali metal hydroxides and cyanides produce mixtures (of alcoholate and adduct) that consist mainly of alcoholate. Occurrence of reactions between alkaline-earth metal hydroxides and polyhydroxy compounds in anhydrous alcoholic media has not been reported. 

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