Potassium Alkoxides Research Articles

立体障害の大きなアルキル及びアリールネオペンチルエーテルの効率的合成法

As a rule, the SN2 reactions of neopentyl bromide and tosylate with sodium alkoxides are extremely retarded by steric hindrance, and the yields of alkyl neopentyl ethers are poor because of side reactions such as neopentyl rearrangement, elimination, and decomposition. However, this report deals with a highly selective synthesis of alkyl and aryl neopentyl ethers. We found that the above side reactions were successfully overcome by the use of neopentyl iodide and potassium alkoxide in the mixed solvent of DMSO or DMI- alcohol (1/1-1/2) at 110-140° C. Especially, potassium benzyl oxide and triphenylmethoxide, which are stabilized by delocalization of electron, afforded the corresponding alkyl neopentyl ethers almost quantitatively under optimum conditions. On the other hand, the reactions of alkali metal aryl oxides with neopentyl iodide, tosylate, and mesylate were carried out in DMSO, DMF, and DMI. The desired aryl neopentyl ethers were readily given in substantially quantitative yields.

Reactions of β-lactones with potassium alkoxides and their complexes with 18-crown-6 in aprotic solvents

The mechanism of the reaction of β-lactones (2-oxetanones) with potassium alkoxides in aprotic solvents was investigated. Despite previous suggestions, the attack of alkoxide ion occurs on the carbonyl carbon atom of β-lactones, cleaving the acyl-oxygen bond to yield the corresponding potassium alcoholate of the respective β-hydroxycarboxylic acid ester. Next, the saturated ester is formed due to potassium hydroxide elimination. The nature of the alkoxide used and complexation of alkali metal cation by crown ether have no significant effect on the reaction course in aprotic solvents

Diastereoselective synthesis of protected syn 1,3-diols by base-catalyzed intramolecular conjugate addition of hemiacetal-derived alkoxide nucleophiles

Reaction of the illustrated unsaturated hydroxy esters (X=OMe, R 2 =H, Me) and amides (X=N(Me)OMe, R 2 =H, Me) with benzaldehyde and potassium alkoxide or amide bases is reported. The resulting benzylidene acetals are obtained in good yields (71-84%) and with hidh selectivity (>90:10). In addition to an exploration of the scope of the reaction, a mechanistic study, involving the use of deuterated benzaldehyde to ascertain the rate-determining step of the process, is described

Unprecedented route to enolates from silyl enol ethers and enol acetates: reaction with hard and soft electrophiles

Reaction of silyl enol ethers with lithium, sodium or, better, potassium alkoxides resulted in a rapid formation of enolates which were trapped with hard electrophiles and benzaldehyde. Moreover, in the aldolisation reaction, only a catalytic amount of alkali alkoxide is needed. This methodology is also applied to enol acetate. During these reactions a non-basic species, ether or ester, is produced with the enolate.

Synthesis and Some Properties of Graft Copolymers with Uniform Polyoxyethylene Side Chains

Abstract Graft copolymers with uniform polyoxyethylene (PEO) side chains were synthesized by transesterification of poly(methyl, ferf-butyl fumarate) (PMtBF) or poly(methyl, tert-butyl fumarate-co-styrene) poly-(MtBF-co-St) with potassium alkoxide of PEO monoether. The grafting efficiency increased with enhanced alkoxide reactivity, but the main factor in the ester exchange proved to be the structure of the backbone. This effect was ascribed to the thermodynamic incompatibility between fumaric polymers and PEO. The polymers were characterized by spectral methods, GPC, and DSC. In THF the graft copolymers comprising a polyfumarate backbone with PEO side chains eluted at higher elution volumes than did the backbone homopolymers. In benzene their intrinsic viscosities were lower than those of the backbones. In aqueous eluents, micelles were detected, and their aggregation number depended on the composition of the copolymer and the eluent.

Surface-mediated solid-phase reaction. Part 2. Highly selective mono- and di-C-alkylation of 1,3-dicarbonyl compounds on the surface of alumina

Highly selective mono- and di-C-alkylation of 1,3-dicarbonyl compounds with different, structurally varied alkyl halides has been achieved in high yields through a simple solvent-free reaction on the surface of alumina impregnated with sodium or potassium alkoxide.

More efficient metallation of alkylbenzenes by modified superbases from butyllithium and potassium alkoxides. Effect of alkoxide structure and concentration

Higher yields and higher reaction rates, as well as more selective metallation in the side chain of alkylbenzenes are achieved by Superbases from alkyllithium compounds and potassium alkoxides which contain an enhanced of an alkoxide with a structure more bulky than that of tert-butoxide.

What is the real mechanism of anionic polymerization of β-lactones by potassium alkoxides? A critical approach

What is the real mechanism of anionic polymerization of β-lactones by potassium alkoxides? A critical approach

Formation of organozincate ions from diorganozinc compounds and potassium alkoxides

Formation of organozincate ions from diorganozinc compounds and potassium alkoxides

Use of crown ether in the anionic polymerization of propylene oxide—2. Molecular weight and molecular weight distribution

The production of unsaturation by hydrogen abstraction from monomer (transfer reaction) during the polymerization of bulk propylene oxide catalysed by potassium alkoxide in the presence of 18-crown-6 ether was assessed by NMR spectroscopy. Chain transfer constants were measured as a function of the ratio of crown ether to potassium ion ( r − 0–4.5) over a range of temperatures ( T = 20–80°). Conditions were defined for the preparation of monofunctional poly(oxypropylene) of moderate chain length (about 200 P units, M n > 10,000 ) and narrow chain-length distribution ( M w M n ∼ 1.2 ).

Use of crown ether in the anionic polymerization of propylene oxide—1. Rate of polymerization

The rate of anionic polymerization of bulk propylene oxide catalysed by potassium alkoxide in the presence of 18-crown-6 ether was followed dilatometrically. Rate constants were obtained at 40, 50 and 60° over a range of crown ether concentrations, so allowing calculation of activation energies for polymerization with and without added crown ether. The results were consistent with polymerization by ligand-separated and contact ion-pairs in equilibrium.

Synthesis and characterization of some heterobimetallic isopropoxides of lanthanum with zirconium

Seven heterobimetallic isopropoxide derivatives of lanthanum have been synthesized by the reaction of LaCl 3·3Pr iOH with K0 2(OPr i) 9 in different molar ratios (1:1, 1:2, 1:3) to yield hydrocarbon-soluble derivatives of the types [Cl 3- n La{Zr 2(OPr i) 9} n ] ( n = 1, 2 or 3). The reactions of the above bimetallic chloride isopropoxides with the appropriate potassium alkoxides yield derivatives of the types [(OR) 3- n La{Zr 2(OPr i) 9} n ] ( n = 1 or 2; R = Pr i and Bu t). All these have been characterized by elemental analyses and spectroscopic (IR and NMR) studies.

ChemInform Abstract: A Short Synthesis of (.+‐.)‐Muscone.

(±)-Muscone ((±)-1) has been synthesised in three steps from 2-(2′-methylprop-2′-enyl)cyclododecan-1-one (2). The synthesis involves two key transformations: a Lewis-acid-mediated intramolecular ene reaction (23) and the β-cleavage of the bicyclic potassium alkoxide 3a′ to the macrocyclic enone (Z)-11.

Interaction of alkoxides XVIII. Utilitization of the complex base from alkyllithium and potassium alkoxides in the dimetallation of phenol, thiophenol, o-, m- and p-cresol

Successful O- and ortho-ring metallation of phenol and side chain metallation in o-cresol has been achieved by use of a mixture of two molar equivalents of n-butyllithium, one molar equivalent of potassium t-butoxide, and two molar equivalents of N, N, N′, N′-tetramethylethylene diamine in hexane. Poor results were obtained with m-cresol, thiophenol and p-cresol. m-Cresol was effectively dimetallated with a mixture of two molar equivalents of tBuOK and two molar equivalents of nBuLi·TMEDA. The effectiveness of another type of complex base based on 2-ethylhexyllithium (EhexLi) and potassium alkoxides has been also investigated, especially in respect of the influence of the concentration and the structure of the alkoxide used. With a complex base from EhexLi and 3 equivalents of potassium 3-methyl-3-pentoxide phenol was successfully dimetallated even in the absence of TMEDA. Thus, the enhanced reactivity of a complex base containing a higher concentration of a more branched potasium alkoxide over that of previously used complex bases has been confirmed.

A Short Synthesis of (±)‐Muscone

Abstract(±)‐Muscone ((±)‐1) has been synthesised in three steps from 2‐(2′‐methylprop‐2′‐enyl)cyclododecan‐1‐one (2). The synthesis involves two key transformations: a Lewis‐acid‐mediated intramolecular ene reaction (2→3) and the β‐cleavage of the bicyclic potassium alkoxide 3a′ to the macrocyclic enone (Z)‐11.

ChemInform Abstract: A General Route to Five‐Coordinate Hydridosilicates.

AbstractReaction of the trialkoxysilanes (I) with the potassium alkoxides (II) yields the pentacoordinated hydridosilanes (III).

β‐Cleavage of Potassium Bicyclo[2.2.2]oct‐5‐en‐2‐olates. Stereoselective synthesis of (±)‐trichodiene

AbstractThe transformations of 12 bicyclo[2.2.2]oct‐5‐en‐2‐ols (V or VI) to 3‐(cyclohex‐3‐enyl)‐2‐alkanones (III or IV), via β‐cleavage of their potassium alkoxides in HMPA, has been investigated (cf. Table 1). As an illustration of this synthetic methodology, a stereoselective synthesis of (±)‐trichodiene ((±)‐1) is described which involves the β‐cleavage of the tricyclic potassium alkoxides 46a and 47a to cyclopentanone 4 (cf. Scheme 7).

ChemInform Abstract: β‐Cleavage of Bis(homoallylic) Potassium Alkoxides. Synthesis of γ‐Damascone.

Starting from the γ-lactone cis-1, two new syntheses of γ-damascone ((E)-4) are described. In both syntheses, the key step involves the β-cleavage of a bis(homoallylic) potassium alkoxide, viz. the transformation of 3a to 20 and (E/Z)-4, and the conversion of 21a to 23 and (E/Z)-24.

A general route to five-coordinate hydridosilicates

Five-coodinate potassium hydridosilicates, [HSi(OR) 4] − K + (R  Et, i-Pr, Ph), have been obtained in good yield from the reaction of a trialkoxy- or triarylox-silane with the corresponding potassium alkoxide or aryloxide, and characterized spectroscopically. Reaction of the hydrosilicates with an excess of Grignard reagent gives the corresponding triorganosilanes.

β‐Cleavage of Bis(homoallylic) Potassium Alkoxides. Synthesis of γ‐damascone

AbstractStarting from the γ‐lactone cis‐1, two new syntheses of γ‐damascone ((E)‐4) are described. In both syntheses, the key step involves the β‐cleavage of a bis(homoallylic) potassium alkoxide, viz. the transformation of 3a to 20 and (E/Z)‐4, and the conversion of 21a to 23 and (E/Z)‐24.