Alkali Metal Alkoxides Research Articles

Base-induced rearrangement of 4-amidino-3-R-furoxans into 1-substituted 3-(1-nitroalkyl)-5-R-1H-1,2,4-triazoles

A new base-induced rearrangement of furoxans, viz., a recyclization of 4-amidino-3-Rfuroxans into 1-substituted 3-(1-nitroalkyl)-5-R-1H-1,2,4-triazoles in the presence of alkali metal alkoxides and into 3-acyl-5-R-1H-1,2,4-triazoles in aqueous alkaline solutions, was found.

On the Reactivity of Silylboranes toward Lewis Bases: Heterolytic B–Si Cleavage vs. Adduct Formation

AbstractSilylboranes are important reagents in a variety of catalytic silylation and silaboration reactions. While transition‐metal‐catalyzed reactions are well established, organo‐/Lewis base‐catalyzed reactions of silylboranes have only recently emerged. For both catalytic processes the reactivity of silylboranes toward Lewis bases is of relevance. While for organo‐catalyzed reactions Lewis base activation of the silylborane has been proposed, transition‐metal‐ and especially copper‐catalyzed reactions also frequently require the presence of Lewis basic alkali metal alkoxides. In the present study we explore the reaction of K(18‐crown‐6) tert‐butoxide and the NHC 1,3‐diisopropyl‐4,5‐dimethyl‐imidazol‐2‐ylidene as exemplary Lewis bases with the two silylboranes pinB‐SiMe2Ph and pinB‐SiPh3 (pin = OCMe2CMe2O). The reaction with K(18‐crown‐6) tert‐butoxide results in activation of the boron–silicon bond. The isolated product of this activation is either the potassium silyl complex [K(18‐crown‐6)SiPh3] or [K(18‐crown‐6)(thf)2][pinB(SiMe2Ph)2], the formal Lewis acid/base adduct of [K(18‐crown‐6)SiMe2Ph] with pinB‐SiMe2Ph. Both complexes react essentially as sources of nucleophilic silyl moieties in reactions with exemplary electrophiles. In contrast, usage of the carbene leads to the formation of isolable Lewis acid/base adducts of the type (NHC)pinB‐SiR3, which do not react as sources of nucleophilic silyl moieties. The identification and characterization of these species appears of relevance for the mechanistic understanding and further development of Lewis base/organo‐ as well as transition‐metal‐catalyzed silyl transfer reactions.

Hydrophosphonylation of α‐Haloalkenals

ABSTRACTPolyfunctional β‐haloalkenyl α‐hydroxy phosphonates were synthesized chemoselectively by an economical alkali metal alkoxide catalyzed reaction of dialkyl phosphites with α‐haloenals. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:187–190, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21081

Phosphorylation of technical lignins

A method for phosphorylation of technical lignins and their derivatives by the action of thiophosphoryl chloride on air-dried sodium lignates over 5–30 min with vigorous stirring and simultaneous grinding in a solvent-free vibrating reactor at 20–80 °C followed by alkali-metal alkoxides with vigorous stirring and simultaneous grinding for 10–40 min at the same temperature and a 1:1 mole ratio of phosphorylating reagents calculated per mole of lignin OH groups was developed.

Remarkable effect of alkali metal on polymerization of cyclic esters catalyzed by samarium–alkali metal multinuclear alkoxide clusters

The remarkable effect of alkali metal on catalytic reactivity of samarium-alkali metal multinuclear alkoxide clusters is systematically studied. Three samarium-alkali metal multinuclear alkoxide clusters are synthesized in high yield by the reaction of anhydrous SmCl(3) with different molar ratios of alkali metal alkoxide and MOH (M = Na or K) in tetrahydrofuran (THF). These clusters were fully characterized by elemental analysis, IR, (1)H NMR and single-crystal structural analysis. These clusters exhibited good catalytic activity for the ring-opening polymerization of ε-caprolactone (ε-CL), L-lactide (L-LA) and trimethylene carbonate (TMC). It is interesting to note that the catalytic activity is much influenced by the alkali metals of the clusters. For the polymerization of these cyclic esters, the catalytic activities all increase with the increase of the molar ratio of alkali metal to samarium metal.

Deuterated dimethyl sulfoxide as a good NMR solvent for the characterization of alkali metal cyclopentadienides, amides, alkoxides and phenoxides

A series of alkali metal cyclopentadienides, amides, alkoxides and phenoxides was characterized using NMR spectroscopy in deuterated dimethyl sulfoxide. Deuterated dimethyl sulfoxide showed very good stability and solubility for these compounds. Very nice and well resolved spectra were obtained for most compounds tested. The low cost of the solvent makes it possible to use it for the routine characterization of these alkali salts as the ligands in organometallic synthesis.

Synthesis of PEO-based block copolymers bearing cyclic hydrazide or carboxylic acid moieties and their applications as stabilizers for Fe3O4 nanoparticles

In this paper, a useful synthetic method for poly(ethylene oxide)-based block copolymers and their applications for preparation of iron oxide nanoparticles were introduced. Poly(ethylene oxide-b-N-phenylmaleimide) was first synthesized by anionic block copolymerization of ethylene oxide and N-phenylmaleimide (N-PMI) using mixed alkali metal alkoxides via the sequential monomer addition technique in a mixture of benzene dimethylsulfoxide (DMSO)/tetrahydrofuran (THF) (30/5/6∼20, v/v/v) at room temperature. Reductive deimidation of the resulting block copolymers under different reaction conditions using hydrazine monohydrate led to the formation of the corresponding water-soluble poly(ethylene oxide-b-maleic hydrazide) under acidic conditions and poly(ethylene oxideb-maleic acid) under basic conditions. Both were found to be very efficient stabilizers to prepare superparamagnetic iron oxide nanoparticles. Open image in new window

Ortho-selectivity in the nucleophilic aromatic substitution (SNAr) reactions of 3-substituted, 2,6-dichloropyridines with alkali metal alkoxides

3-Substituted, 2,6-dichloropyridines have featured in the syntheses of small molecule inhibitors of a wide variety of biological targets. Hence, the regioselective displacement of the chlorines is of significant interest. Through conducting an extensive solvent study, we have found that non-polar, aprotic solvents of low hydrogen bond basicities favour substitution of the chlorine ortho to the 3-substituent by alkali metal alkoxides. We present convincing evidence that coordination of the alkali metal counter-ion to the 3-substituent (nitro, ester, amide) is the origin of the ortho-selectivity to give a cyclic, six-membered transition state. Excellent ortho-selectivities (⩾98:2) for secondary and tertiary alkoxides were realized with the sodium counter-ion, whereas the more reactive primary alkoxides required the harder, more Lewis acidic lithium counter-ion.

ChemInform Abstract: SNAr Reactions of Nitro‐(pentafluorosulfanyl)benzenes to Generate SF5 Aryl Ethers and Sulfides.

AbstractA 3‐ to 4‐fold excess of the alkali metal alkoxides and thiolates is necessary for a high conversion.

Synthesis and Crystal Structure of Novel Biheterometal and Triheterometal Alkoxide Clusters – Highly Active Catalysts for the Polymerization of ϵ‐Caprolactone

AbstractThe effect of the alkali metal on the synthesis, crystal structure, and catalytic reactivity of lanthanide–alkali metal alkoxide clusters is reported. Anhydrous LnCl3 reacts with 6.5 equiv. of KOCH2CH2N(CH3)2 and 1.5 equiv. of KOH in tetrahydrofuran (THF) to give the corresponding lanthanide–potassium biheterometal alkoxide clusters [Ln4K20(OCH2CH2NMe2)26(OH)6] [Ln = Nd (1), Pr (2), Yb (3)] in high yield. Anhydrous YbCl3 reacts with KOCH2CH2N(CH3)2 and NaOH with different molar ratios of 1:9:3 and 1:9:4 to afford the lanthanide–potassium–sodium triheterometal alkoxide clusters [Yb2K10Na6(OCH2CH2NMe2)18(OH)4] (4) and [Yb2K8Na8(OCH2CH2NMe2)18(OH)4] (5), respectively. These clusters were fully characterized by elemental analysis, IR, 1H NMR, and single‐crystal structural analysis. The heterometal alkoxide clusters 1–5 exhibited good catalytic activity for the ring‐opening polymerization of ϵ‐caprolactone (ϵ‐CL). It is interesting to note that the catalytic activity of these heterometal alkoxide clusters increases with the increase of the molar ratio of alkali metal to lanthanide metal. For the same molar ratio of alkali metal to lanthanide metal, however, the catalytic activity of the heterometal clusters is highly dependent on the type and molar ratio of the alkali metal centers. The higher the molar ratio of potassium to sodium, the higher the catalytic activity.

Synthesis and Chiroptical Properties of Hydroxyphenylglycine-Based Poly(m-phenyleneethynylene-p-phenyleneethynylene)s

The polymerization of 3′,5′-diiodo-4′-hydroxy-N-α-tert-butoxycarbonyl-d-phenylglycine ethyl-, hexyl-, and laurylamides 1−3 with p-diethynylbenzene was carried out to obtain optically active poly(m-phenyleneethynylene-p-phenyleneethynylene)s [poly(1)−poly(3)] with Mn’s in the range from 6100 to 7300 in 79−82% yields. The specific rotation, CD, and UV−vis spectroscopic data revealed that poly(1)−poly(3) formed helices with predominantly one-handed screw sense. The presence of intramolecular hydrogen bonding formed between amide side groups was confirmed by solution-state IR spectroscopy. The helical structures were stable to heat and alkali metal hydroxides, while responsive to H2O and alkali metal alkoxides.

Relative reactivity of hydroxyl groups in inositol derivatives: role of metal ion chelation

O-Alkylation of myo-inositol derivatives containing more than one hydroxyl group via their alkali metal alkoxides (sodium or lithium) preferentially occurs at a hydroxyl group having a vicinal cis-oxygen atom. In general the observed selectivity is relatively higher for lithium alkoxides than for the corresponding sodium alkoxide. The observed regioselectivity is also dependent on other factors such as the solvent and reaction temperature. A perusal of the results presented in this article as well as those available in the literature suggests that chelation of metal ions by inositol derivatives plays a significant role in the observed regioselectivity. Steric factors associated with the axial or equatorial disposition of the reacting hydroxyl groups do not contribute much to the outcome of these O-alkylation reactions. These results could serve as guidelines in planning synthetic strategies involving other carbohydrates and their derivatives.

Gallium alkoxides: Synthesis and properties

Compounds Ga(OR)3 (R = Me, Et, Pri, Bun, C2H4OMe) were synthesized by exchange reactions between gallium chloride and alkali metal alkoxides, the reetherefication of Ga(OPri)3 and Ga(OC2H4OMe)3 by other ROH (R = Me, Et), and anodic dissolution of metallic gallium in the presence of a electroconductive additive (LiCl, Bu4NBr). When solid GaCl3 is introduced into an alcoholic solution of NaOEt, stable soluble gallium oxoalkoxyhalides are formed. The same reaction with a GaCl3 solution in toluene or electrochemical synthesis produces nonvolatile Ga(OEt)3 samples, which have the polymer zigzag configuration [Ga(OR)4/2(OR)]∞. Mass spectrometry shows that only Ga(OPri)3 and freshly prepared X-ray amorphous Ga(OEt)3 samples (produced by reetherefication) are transferred to the gas phase. The spectra of the latter contain ions generated by penta-and hexanuclear oxoalkoxide molecules, along with fragments of orthospecies [Ga(OEt)3]2−4. IR spectra are described for all compounds synthesized.

The Multidentate Ligand (MeOMe2Si)3Si−: Unusual Coordination Modes in Alkali Metal Silanides

Chain gang: Introducing methoxy groups into (Me3Si)4Si and treatment with alkali metal alkoxides leads to hitherto unknown zwitterionic alkali metal silanides [(MeOMe2Si)3SiM] with a bicyclooctane (Li, Na) or heterocubane (K) structure. The lithium and sodium compounds form infinite chains in the solid state (see picture: green Li, blue Si, red O, gray C) and dissociate in THF solutions into zwitterionic monomers.

Controlled High-Speed Anionic Polymerization of Propylene Oxide Initiated by Onium Salts in the Presence of Triisobutylaluminum

The conventional anionic polymerization of propylene oxide (POx) proceeds at a very slow rate in low polar media and is characterized by an important transfer reaction to monomer. This only allows the formation of poly(propylene oxide) oligomers. A new polymerization strategy allowing the fast and controlled anionic polymerization of POx has been developed. It is based on the formation of complexes with both the anionic initiator and the monomer. The influences of alkali metal alkoxides (i-PrONa), ammonium salts (NBu4Cl and NOct4Br), and phosphonium salts (PBu4Cl) as initiators, in combination with triisobutylaluminum, have been investigated in terms of reactivity, molar mass control, livingness, and polymerization mechanism. PPOx with narrow polydispersities and controlled molar masses, up to 150 000 g/mol, have been obtained in hydrocarbon media, at low temperature, and in short reaction times.

Controlled Anionic Homo- and Copolymerization of Ethylene Oxide and Propylene Oxide by Monomer Activation

The anionic polymerization of ethylene oxide initiated by alkali metal-based initiators suffers from low polymerization rates even in polar media. We found that the addition of triisobutylaluminum to initiators like alkali metal alkoxides or tetraalkylammonium salts strongly enhances the ethylene oxide polymerization rate, while keeping its living character. At ratio [i-Bu3Al]/[initiator] = 1.5, the controlled synthesis of poly(ethylene oxide) of relatively high molar masses is achieved in short time at room temperature in dichloromethane or toluene. Beside the formation of an aluminate 1:1 complex involving i-Bu3Al and the initiator, a second complex between the trialkylaluminum and the oxirane is formed, which strongly increases the reactivity of the epoxide monomer. Gradient di- and triblock ethylene oxide/propylene oxide copolymers of high molar mass are readily prepared with this system.

Remarkable Cocatalytic Effect of Alkali Metal Amides and Alkoxides in the Rhodium-Catalyzed Polymerization of Phenylacetylene

Polymerizations of phenylacetylene (1) with [(nbd)RhCl]2 (nbd: 2,5-norbornadiene) in the presence of alkali metal amides (2−5) in toluene at 30 °C reached completion almost instantaneously. These polymerizations are much faster than the polymerization catalyzed by the well-known conventional catalyst system, [(nbd)RhCl]2/triethylamine (Et3N) (polymer yield is 75% after 1 h under the same conditions). The molecular weights of the formed polymers (2, Mn = 270 000; 3, Mn = 297 000; 4, Mn = 310 000; 5, Mn = 396 000; after 1 h) were clearly higher than that with the [(nbd)RhCl]2/Et3N system (Mn = 118 000). KO-tBu (6) also served as cocatalyst but it was less effective than were 2−5. In the polymerization of 1 with [(nbd)RhCl]2/4−6, toluene was the optimal solvent in terms of polymer yield and molecular weight. The stoichiometric amount of cocatalyst to the Rh metal was found to be the most suitable with respect to polymer yield, beyond which there was no discernible change in the polymerization behavior. The ...

P‐Chiral Phosphinoselenoic Chlorides and Phosphinochalcogenoselenoic Acid Esters: Synthesis, Characterization, and Conformational Studies.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Activation Mechanisms of Trialkylaluminum in Alkali Metal Alkoxides or Tetraalkylammonium Salts / Propylene Oxide Controlled Anionic Polymerization

AbstractThe anionic polymerization of propylene oxide (PO) initiated by alkali metal alkoxides is in non polar solvents a very slow and non controlled reaction process. Transfer reaction to monomer is predominant, allowing only the preparation of low molar masses PPO. The influence of the addition of trialkylaluminium to either an alkali metal alkoxide or a tetraalkylammonium salt used as initiator for PO polymerization in hydrocarbon media was investigated. A strong enhancement of the polymerization rate accompanied by a drastic decrease of the transfer reactions is observed, allowing the synthesis of PPO with well controlled molar masses. At constant monomer and alkali metal alkoxide concentrations, the polymerization rate increases with increasing trialkylaluminium concentration. Results indicate that the trialkylaluminium derivative is involved in the formation of two distinct complexes, one with the alkali metal alkoxide or the tetraalkylammonium salt and another one with the PO monomer which is strongly activated towards nucleophilic active species. Significant differences between the alkali metal and tetraalkylammonium based initiators are observed. In particular much less trialkylaluminum activator is needed with the ammonium salt to get the same rate of propagation and controlled polymerization.

P-Chiral Phosphinoselenoic Chlorides and Phosphinochalcogenoselenoic Acid Esters: Synthesis, Characterization, and Conformational Studies

P-Chiral alkyl or aryl phenylphosphinoselenoic chlorides were obtained by reacting PhPCl(2) with Grignard reagents and elemental selenium. P-Chiral dialkyl chlorides were also obtained by treating PCl(3) with two different Grignard reagents and elemental selenium. The structure of the chloride was determined by X-ray molecular structure analysis. P-Chiral phosphinochalcogenoselenoic acid esters bearing a P=Se double bond were synthesized by treating the chlorides with alkali metal alkoxide and chalcogenolates, whereas those bearing a P-Se single bond were obtained by sequential treatment of the chlorides with sodium hydroxide, sulfide or selenide, and alkyl iodides. X-ray molecular structure analyses of esters showed that they adopted gauche conformations. The computational results supported the observed conformational preference. Natural bond orbital analyses of the model compounds showed that two types of nonbonding orbital interactions, n(E') -->sigma*(P=E') and n(E) --> sigma*(P-E'), are important in these compounds. Linear correlations were observed between the experimental (77)Se NMR chemical shifts or the coupling constants of P-Se bonds in the esters and the calculated P-Se bond lengths of the model compounds.