Rate and equilibrium constants for Grignard reaction with alkoxysilanes and ketones

Kinetics of tetraethoxysilane reaction with n-butylmagnesium chloride, specifically solvated with dibutyl ether, diethyl ether, THF, and triethylamine, was studied in toluene. Also isopropylmagnesium chloride, isopropyltriethoxysilane, and diisopropylketone were involved in a similar investigation. The pseudo-first-order rate constants determined at a great excess of these organomagnesium compounds were used for separation of the appropriate equilibrium and rate constants. An advantage of the method consists in preclusion of non-specific solvation effects when effects of donor solvents are considered. In separate experiments, thermodynamic parameters were determined for rate and equilibrium constants, measured for the reaction of tetraethoxysilane with n-butylmagnesium chloride solvated with dibutyl ether in toluene, and also in bulk dibutyl ether. The implication of steric and solvation effects on this reaction is discussed.     

New Preparation Methodology of Functionalized Picolines

Under the organomagnesium complex n‐Bu₂CH₃MgLi conditions, picoline compounds provide a new entry to a broad range of polyfunctional picoline derivatives, after reaction with various electrophiles.     

The intramolecular tandem Michael/Mannich-type reaction of α,β-unsaturated carbonyl compounds with acyliminium ions provides access to chiral indolizidines

The intramolecular tandem Michael/Mannich-type (Michael addition/halo-Mannich-type) reaction using TiCl₄/n-Bu₄NI system between the α,β-unsaturated carbonyl compounds possessing an Evans oxazolidinone as a chiral auxiliary and N-acyliminium ion intermediates is described. The reaction was promoted in a mixed solvent of AcOEt–CH₂Cl₂ to afford indolizidine compounds with three stereogenic centers.     

Uncatalyzed synthesis of 3-amino-1,5-dihydro-2H-pyrrol-2-ones

Uncatalyzed one-pot pseudo-four-component reaction of ethyl pyruvate, anilines, and aldehydes in n-hexane as solvent, under reflux, affords a variety of 3-amino-1,5-dihydro-2H-pyrrol-2-ones in high yield. n-Hexane is an excellent driving force in preparation of the desired products. These compounds have biological and pharmacological properties and are also used in medicinal chemistry. Use of a non-toxic and inexpensive solvent, simple and efficient synthesis, clean work-up, and high yields of the products are the advantages of this method. We report the first catalyst-free method for synthesis this class of compounds.     

Oligomerization of 1-decene under the action of catalytic systems based on Al-aluminum activator-RCl and Al-RCl

Novel catalytic systems for the cationic oligomerization of 1-decene into synthetic poly(α-olefin) oils have been worked out; these systems include a highly disperse (0.1–40 μm) aluminum, an aluminum activator [I₂, Mg, (C₂H₅) _n AlCl_{3 ? n} , (CH₃)₃CCl and some other RX, HCl, benzene, and toluene], and a cocatalyst based on organic halide compounds RX (R is primary, secondary, or tertiary alkyl, allyl, or benzyl; X is Cl, Br, or I). We study the effect of various factors (characteristics of Al, nature of aluminum activator, RCl: Al molar ratio in the catalyst, concentration of Al, temperature, benzene additives, reaction duration) on the conversion of 1-decene into poly(α-olefins), the fractional composition of oligomerization products, the content of chlorine in poly(α-olefins), and the structure and physicochemical characteristics of fractions.     

A new chiral oxazoline derived from camphor and its conversion to (R)-2-methylalkanoic acids

(1S,5R,7R)-(−)-10,10-Dimethyl-3-ethyl-4-oxa-2-azatricyclo[5.2.1.0^1,5]dec-2-ene 2 was prepared in 95% yield from (1S)-1-amino-2-exo-hydroxyapocamphane 1. The chiral oxazoline could be alkylated (LDA/THF/−78°C/RX, RX=ethyl, n-propyl, n-butyl iodides or benzyl bromide) to 3 in 95% yield and >95% diastereoselectivity, and the products hydrolysed to (R)-2-methylalkanoic acids 4 (43–47% yield, 93–98% e.e.).     

Stereochimie de l'action des organomagnesiens et des organolithiens sur les dimethyl-1,2 alcoxy-1 silacyclobutanes

The reaction of organomagnesium organolithium compounds (alkyl, aryl, allyl and benzyl derivatives) with 1,2-dimethyl-1-alkoxy-l-silacyclobutanes proceeds with retention of configuration at the silicon atom. Stereochemical results are discussed in terms of the S_N2Si mechanism. The proposed configurations are supported by ¹H and ¹³C NMR data.     

MNDO method for calculations of magnesium clusters

A new set of parameters for the magnesium atom has been developed within the MNDO method. In contrast to previously published parameters, the new parameters correctly describe molecules with different chemical natures: magnesium halides, organomagnesium compounds and the recently found small magnesium clusters Mg _n (n=2-8). The average errors in the calculated heats of formation and bond lengths of magnesium compounds, including clusters are: 10.7 kcal/mol and 0.167 Å, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1384–1388, August, 1994.     

2-Ethoxy-2,3-dihydro[<Emphasis Type="Italic">d</Emphasis>][1,2]oxaphosphole 2-oxide in the synthesis of dialkyl(diaryl)(2-hydroxybenzyl)phosphine oxides

A facile method of synthesis of functionally substituted P(IV) derivatives―dialkyl(diaryl)(2-hydroxybenzyl) phosphine oxides―by the reaction of 2-ethoxy-2,3-dihydro[d][1,2]oxaphosphole 2-oxide with organomagnesium compounds, which allows wide variation of substituents on the phosphorus atom was developed.     

Generation of organo-alkaline earth metal complexes from non-polar unsaturated molecules and their synthetic applications

Organomagnesium compounds, represented by the Grignard reagents, are one of the most classical yet versatile carbanion species which have widely been utilized in synthetic chemistry. These reagents are typically prepared via oxidative addition of organic halides to magnesium metals, via halogen–magnesium exchange between halo(hetero)arenes and organomagnesium reagents or via deprotonative magnesiation of prefunctionalized (hetero)arenes. On the other hand, recent studies have demonstrated that the organo-alkaline earth metal complexes including those based on heavier alkaline earth metals such as calcium, strontium and barium could be generated from readily available non-polar unsaturated molecules such as alkenes, alkynes, 1,3-enynes and arenes through unique metallation processes. Nonetheless, the resulting organo-alkaline earth metal complexes could be further functionalized with a variety of electrophiles in various reaction modes. In particular, organocalcium, strontium and barium species have shown unprecedented reactivity in the downstream functionalization, which could not be observed in the reactivity of organomagnesium complexes. This perspective will focus on the newly emerging protocols for the generation of organo-alkaline earth metal complexes from non-polar unsaturated molecules and their applications in chemical synthesis and catalysis.

In this perspective, we highlight the recent development of metallation protocols of non-polar unsaturated molecules for the generation of organo-alkaline earth metal compounds and their applications in chemical synthesis and catalysis.     

Organomagnesium Synthesis of <Emphasis Type="Italic">sec</Emphasis>-Butyl- and <Emphasis Type="Italic">tert</Emphasis>-Alkylchlorogermanes and Their Reaction with Ethynylmagnesium Bromide

The limits of application of organomagnesium synthesis to the substitution of chlorine atoms in tetrachlorogermane with bulky alkyl groups are established. The reaction of tetrachlorogermane with 2-butylmagnesium chloride leads to the substitution of one, two, or three chlorine atoms, yielding the corresponding alkylchlorogermanes (MeEtCH)_nGeCl_4-n . The reaction of GeCl₄ with tert-alkylmagnesium halides leads to the substitution of only one chlorine atom, yielding tert-alkyltrichlorogermanes RMe₂CGeCl₃ (R = Me, Et, Bu). tert-Butyltrichlorogermane reacts with ethylmagnesium bromide to give ethyl(tert-butyl)dichlorogermane. Isopropyltrichlorogermane reacts with tert-butylmagnesium chloride to give isopropyl(tert-butyl)dichlorogermane. This shows that the organomagnesium synthesis does allow linking of two bulky substituents to the germanium atom. The reaction of tert-alkyltrichlorogermanes and 2-butyltrichlorogermane in THF with ethynylmagnesium bromide, in which the hydrocarbon group is the most sterically accessible, allows substitution of all the three chlorine atoms, yielding the corresponding alkyl(triethynyl)germanes. The latter compounds react with the Grignard reagent and trimethylchlorosilane to give the corresponding alkyl(trimethylsilylethynyl)germanes.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 757–761.Original Russian Text Copyright © 2005 by O. Yarosh, Voronkov, Zhilitskaya, N. Yarosh, Albanov, Korotaeva.     

Studies on the intermolecular interactions of metal chelate complexesVIII: On the interactions of dithiocarbamato-copper(II) and -copper(I) complexes with haloalkanes

The interaction of Cu(II)(dtc)₂ and Cu(I)(dtc) complexes with haloalkanes were studied by the EPR method. It was found that the Cu(II)(dtc)₂ complex reacted with haloalkanes only in the presence of weak Lewis bases which formed adducts with it. The intermediate reaction product is the mixed-ligand complex Cu(II)(dtc)X_n (X = Cl, Br, n = 1 or 2); the final products being CuX₂B_n (B = Lewis bases, n = 1 or 2) and unstable resin-like residue. Cu(I)(dtc) reacted with haloalkanes without any promoters giving the mixed-ligand complex Cu(II)(dtc)X_n as product. Free radicals were detected in the reaction of Cu(I)(dtc) using the method of “radical scavenger” and were not found in the reaction of Cu(II)(dtc)₂. The reported results confirmed one of the two reaction mechanisms proposed in the previous studies. The role of the solvent on the EPR parameters of the mixed-ligand Cu(II)(dtc)X complex is also discussed.     

Novel tricyclic heterocycles (benzopyrrocolines) arising via carbanion attack on a nitrile function

A new reaction of 2-n-alkanoyl-1,2-dihydroisoquinaldonitriles 1 (isoquinoline Reissert compounds) has been discovered. As previously reported reaction of the conjugate bases of Reissert compounds with alkyl halides yields the corresponding 1-alkyl derivatives 2 . However, compounds 2 , R = n-alkyl, with only a catalytic amount of bases form the enolate ion, which attacks the neighboring nitrile functionality to produce directly in the same reaction vessel excellent yields of benzopyrrocoline derivatives 5-10 . The nmr spectrum reveals a solvent dependent tautomeric equilibrium between ketoeneamine ( a ) and ketoimine ( b ) forms. Unlike compounds 2 the double bonds of the pyridine ring of compounds 7 and 8 were readily reduced with hydrogen. Thus, n-alkanoyl Reissert compounds afford a convenient route to the corresponding benzopyrroco-lines.     

Dependence of activation parameters for phenylchlorocarbene–alkene additions on alkane solvent chain length

Activation energies, enthalpies, and entropies for the addition of phenylchlorocarbene to tetramethylethylene significantly decrease as the reaction solvent lengthens from n-pentane to n-octane to n-decane; additional decreases are minimal in n-pentadecane and n-heptadecane. Electronic structure calculations, employing a continuum solvent model, fail to reproduce the observations; instead, a qualitative model invoking solvent cage effects is proposed.     

Synthese und NMR-Spektren einiger 13C-markierter Thio- und Seleno-äther, -acetale und -orthoester

Synthesis and NMR Spectra of Some ¹³C-Labelled Thio- and Seleno-ethers, -acetals, and -orthoesters Twenty-seven different open-chain and cyclic derivatives (RX)_nCH_4-n and (RX)_nCH_3-nR′ with n = 1?3, X = S or Se, R,R′ = alkyl or aryl, 1,3,5-trithiane, and bis-(dimethylsulfonio)methane and -methanide with single or multiple ¹³C-labelling have been synthesized. The ¹³C-NMR spectra of the sulfur and selenim compounds have been measured, and the dependence of the chemical shifts (δ_c) and coupling constants [′J(C,H), ′J(Se,C)] from the substitution pattern in discussed (Fig. 1) and compared with the polyhalogeno-methanes (Fig. 2).     

The electron spin resonance spectra and structures of some aluminium derivatives of 3,6-di-t-butyl-1,2-benzoquinone

ESR spectra are reported for the aluminium derivatives of the semiquinones which are formed when the compounds Et_nAlCl_3-n (n = 0, 1, or 3) react with 3,6-di-t-butyl-1,2-benzoquinone. The conditions (solvent and other ligands about the metal) are identified under which three different types of spectra can be observed, which are assigned to monodentate non-fluxional, monodentate fluxional, and bidentate structures respectively.     

Zur chalkogenolyse von monoorganyl-germanium-trichloriden I. Halogenhaltige verbindungen

New organylgermanium sesquichlorochalcogenides (RGe)_2nY_3n−1Cl₂ (n = 3, R = t-Bu, Y=O; n = 2, R = t-Bu, Y = S; n = 2, R = t-Bu, Y=Se; n = 1, R = Mes, Y = S; n = 1, R = t-Bu, Y = Se) have been prepared by reaction of t-butyl or mesityl germanium trichloride with sodium hydroxide or sodium chalcogenides. In contrast to the sesquichalcogenides in these compounds one chalcogen atom is formally replaced by two chlorine atoms. X-ray analysis confirms that these sesquichlorochalcogenides cannot be converted into the corresponding sesquichalcogenides by replacement of the chlorine atoms owing to steric factors.     

Organolead chemistry : III. 207Pb chemical shifts in some organolead compounds

²⁰⁷Pb chemical shifts are reported for the compounds (CH₃)_4?nPb X_n, where n = 1 · 4, X = 4-FC₆H₄; n = 1, 2, 4, X = CH₃ CC; n = 1, 4, X = CH₂CH; n = 1, X = Cl, CH₃O, CH₃CO₂. A correlation between δ(²⁰⁷Pb) and δ(¹⁹F) for the 4-fluorophenyl derivatives is discussed, and solvent effects on δ(²⁰⁷Pb) for the propynyl derivatives are interpreted in terms of complex formation.     

Unexpected reactions of dichloro(ethyl)silane with DMSO in organic solvents

The effect of the solvent nature on the composition of the products formed upon the reaction between EtSi(H)Cl₂ and DMSO (molar ratio 1: 1, 0 °C) was revealed. This reaction in non-polar and low polar solvents (toluene, chloroform) gives oligoethyl(hydro)cyclo-siloxanes ((EtSi(H)O) _n , n = 3—8) as the major products in the yields up to 77%. In MeCN, oligoethyl(hydro)cyclosiloxanes are formed along with cyclic monochlorinated siloxanes ((EtSi(H)O) _n (EtSi(Cl)O), n = 2—7) in a ratio of ~7: 3 (68: 29 wt.%). In excess diethyl ether, the overall yield of oligoethyl(hydro)cyclosiloxanes does not exceed 25% and the major products are linear α,ω-diethoxyoligoethyl(hydro)siloxanes (EtO(EtSi(H)O) _n Et, n = 2—7) formed in 70—75% yields. A plausible reaction mechanism leading to the final products was suggested. Apparently, the reaction proceeds via ethyl(hydro)-and chloro(ethyl)silanones as intermediates.