Reactions of t-butyl peresters—III Cuprous bromide-catalyzed reaction of peresters with ethers

Aliphatic and cyclic ethers react smoothly with t-butyl peracetate and t-butyl perbenzoate at 67–90° in the presence of cuprous bromide. The first products of this reaction are the acyloxy derivatives of the ethers, which are unstable under the chosen experimental conditions and decompose to the corresponding carboxylic acids and unsaturated ethers. Thus, 2,3-dihydrofuran was prepared from 2-benzoyloxytetrahydrofuran in a 66% yield. The unsaturated ethers add t-butyl alcohol to give the corresponding acetals, this step being catalyzed by the carboxylic acid. This reaction is general for ethers containing two adjacent methylene groups, such as n-propyl and n-butyl ethers, tetrahydrofuran, and tetrahydropyran. Diethers, such as 1,4-dioxane and 1,2-dimethoxyethane, give more stable benzoyloxy derivatives, which decompose slowly on prolonged heating to give the expected acetals in low yield.     

All ring compounds—XXIX : Thermal decomposition of t-butyl per (trans-2-substituted cyclopropyl) acetates

Three kinds of t-butyl per (trans-2-substituted cyclopropyl) acetates (RH, CH₃, C₆H₅) were synthesized from the corresponding acyl chlorides and thermally decomposed in cyclohexane to investigate the chemical stability and behaviour of the cyclopropylcarbinyl radical. Clean first-order kinetics were obtained in all of the thermal decomposition reactions. The experimental fact that the decompositoin rates and activation parameters of these three t-butyl peresters are similar to each other may indicate the absence of the ionic character in the transition state suggesting the almost complete homolytic decomposition of these peresters. Although the typical concerted decomposition might be invalid for these peresters in view of the activation parameters, it would be suggested from the product studies that the decomposition of these peresters was characterized by a considerable loss of their acyl-alky] bonds at the time of the fission of their OO bonds. The products yielded from the thermal decomposition of t-butyl per (trans-2-phenylcyclopropyl) acetate in various hydrogen donating solvents consisted of three hydrocarbons and two t-butyl ethers. The formation of these t-butyl ethers, possibly cage products, was significant.     

A facile formation of cyclic selenuranes and a cyclic selenurane oxide in the reaction of 2-methylseleno- and 2-phenylselenobenzoic acids and their derivatives with t-butyl hydroperoxide

The reaction of 2-methylselenobenzoic acid with 1,1′-carbonyldiimidazole followed by addition of t-butyl hydroperoxide gave cyclic selenuranes $\text{2a}$ and $\text{3a}$, suggesting the intramolecular insertion of the neighboring selenium atom into the OO bond of t-butyl 2-methylselenoperoxybenzoate. In the reaction of 2-phenylselenobenzoyl chloride with t-butyl hydroperoxide, cyclic selenurane $\text{2b}$ and the oxide $\text{7}$ were obtained.     

The preparation and reactions of dienol ester and dienol ester derivatives of hagemann's ester and its t-butyl analogue

The efficient conversion of Hagemann's ester and its t-butyl analogue into dienol ethers and dienol esters, and reactions of the derived dienolates with electrophiles is described.     

过氧化叔丁醇在钼催化剂下对咔唑的催化氧化研究

以油溶性过氧化叔丁醇(TBHP)为氧化剂,采用钼(Ⅵ)类催化剂,对油品中性质稳定的氮化物-咔唑进行了催化氧化研究。考察了钼催化剂及其载体对咔唑氧化的影响。结果表明,在无负载条件下,乙酰丙酮钼(MoO2(acac)2)的催化活性略高于三氧化钼(MoO3);经弱酸性树脂(D113)负载后,MoO3催化活性显著提高;三种载体(Al2O3、树脂D113和树脂D751)均能提高钼催化剂的活性,使咔唑转化率达到65%以上,其中MoO3/Al2O3催化活性最高。杂金属Ni和Co的加入导致MoO3/Al2O3催化活性降低。其次,进行了氧化反应选择性研究,实验发现在反应液中含有二苯并噻吩时,TBHP/MoO3/D113能优先氧化咔唑;而TBHP/MoO3/D751对咔唑和二苯并噻吩具有近似的氧化活性。最后根据光谱数据对咔唑系列产物的结构进行了初步推测。     

Mechanism and kinetics of the vanadium-catalyzed o-dianisidine—t-butyl hydroperoxide reaction in non-aqueous media

The vanadium-catalyzed oxidation of o-dianisidine by t-butyl hydroperoxide is studied for the determination of trace vanadium in non-aqueous media. In acetonitrile, vanadium acts as a one-eletron mediator between the reductant and oxidant. Mechanistic studies, based on e.p.r. spectrometry and visible spectrophotometry, show that the hydroperoxide oxidizes vanadium(IV) via a radical mecahnism. The kinetics of V(IV) oxidation are investigated and a rate equation is proposed. Oxidation of o-dianisidine by the vanadium(V) formed in a one-electron step with formation of the o-dianisidine radical completes the catalytic cycle, as shown by spectroelectrochemical measurements. The radical reacts further with excess of t-butyl hydroperoxide to form the diimine, which may be used for sensitive spectrophotometric monitoring of the indicator reaction at 450 nm.     

Palladium-catalyzed allylic oxidation of olefins by t-butyl hydroperoxide and tellurium(IV) oxide

Treatment of several cyclic olefins, β-pinene, allylbenzene, and estragole with palladium(II) salt in acetic acid in the presence of t-butyl hydroperoxide and tellurium(IV) oxide afforded mainly the corresponding allylic acetates. The reaction proceeded catalytically with palladium(II) salt, t-BuOOH working as a reoxidizing agent.     

An Efficient Deprotective Method for Allylic Alcohols Protected as Methoxyethoxymethyl (MEM) And Methoxymethyl (MOM) Ethers

Methoxyethoxymethyl ethers (MEM) and methoxymethyl ethers (MOM) of allylic alcohols are readily cleaved by pyridinium paratoluenesulfonate (PPTS) in 2-butanone or t-butyl alcohol. This procedure is also efficient for deprotection of benzylic and aliphatic alcohols.     

Reaction of carboxamide with Cu2Oisonitrile complex; formation of a new chelated copper(I) complex

Reaction of carboxamides with Cu₂O in the presence of t-butyl isocyanide gave new chelated copper(I) complexes, which probably are formed by the insertion of t-butyl isocyanide into the coppernitrogen bond of copper(I) amide isonitrile complexes, which were initially produced from the carboxamides and Cu₂Ot-butyl isocyanide complex. The same chelated copper(I) complexes were prepared more readily by the reaction of the corresponding N-trimethylsilyl-carboxamides with Cu₂Ot-butyl isocyanide complex. Reactions of the copper(I) complexes thus obtained with alkylating agents, such as alkyl halides, alkyl tosylates and triethyloxonium tetrafluoroborate, also were described.     

Dielectric and raman spectroscopic studies on the rotational isomerism of t-butyl formate

Static dielectric constants, refractive indices and densities have been measured for t-butyl formate and acetate in cyclohexane at increasing concentrations and at two temperatures, 20°C and 60°C. The ΔH value for the cis-trans equilibrium of t-butyl formate and the dipole moment of the trans conformation has been calculated from the dielectric measurements taking the ΔS value calculated from the sum-over-states for the cis and trans conformations and assuming the dipole moment of the cis conformation to be equal to 1.94 D as found for t-butyl acetate, which has the cis conformation only.The relative intensities of the Raman bands corresponding to specific vibrations modes of the cis and trans conformations of t-butyl formate are measured in cyclohexane and acetonitrile at various concentrations. The enthalpy difference ΔH is also measured in the liquid state and in acetonitrile by variation of the intensity ratio of the bands with temperature.All thermodynamic quantities obtained from dielectric or Raman intensity measurements are compared with each other and with the theoretical values. The solvation energy difference between cis and trans conformations in cyclohexane and acetonitrile as well as in the liquid state are also compared with theoretical values. The large deviation of solvation energy difference between the experimental value and Onsager's model value are well described by an additional term, which considers dipole-dipole interaction.     

Nitroxydes-LXVIII : Synthese et etude cinetique de la decomposition du t-butyl isopropyl nitroxyde. Effet isotopique

Decomposition of t-butyl isopropyl nitroxide and its β²H-labelled homologue has been examined by UV and EPR. The bimolecular reaction does not show reversible formation of a dimer, but exhibits an isotope effect (k_H/k_d)_30°C?9 which shows that the rupture of the CH bond is involved in the slow step of the decomposition. The β proton coupling constant, determined by NMR, is +1.84 G.     

Deuterium kinetic isotope effects in microsolvated gas-phase E2 reactions: Methanol and ethanol as solvents

The gas-phase reactions of F(-)(CH(3)OH) and F(-)(C(2)H(5)OH) with t-butyl bromide have been investigated to explore the effect of the solvent on the E2 transition state. Kinetic isotope effects (KIEs) were measured using a flowing afterglow-selected ion flow tube (FA-SIFT) mass spectrometer upon deuteration of both the alkyl halide and the alcohol. Kinetic isotope effects are significantly more pronounced than those previously observed for similar reactions of F(-)(H(2)O) with t-butyl halides. KIEs for the reaction of F(-)(CH(3)OH) with t-butyl bromide are 2.10 upon deuteration of the neutral reagent and 0.74 upon deuteration of the solvent. KIEs for the reaction of F(-)(C(2)H(5)OH) with t-butyl bromide are 3.84 upon deuteration of the neutral reagent and 0.66 upon deuteration of the solvent. The magnitude of these effects is discussed in terms of transition-state looseness. Additionally, deuteration of the neutral regent and deuteration of the solvent do not produce completely separable isotope effects, which is likely due to a crowded transition state. These results are compared to our previous work on S(N)2 and E2 solvated systems.     

Deplacements homolytiques intramoleculaires : III-decomposition du peroxyde d'allyle et de t-butyle dans les ethers et les cyclanes: expoxy-2,3 propanation de ces solvants

Product analysis of the thermolysis of allyl t-butyl peroxide in cyclohexane and tetrahydrofuran shows that an important induced decomposition of the peroxide occurs by the addition of radicals derived from the solvent, to the peroxide double bond, followed by an intramolecular homolytic displacement of the t-butoxyl group. Such a reaction is a 2,3-epoxypropanation of the solvent in which the initiator is decomposed. The reaction is shown to be general, by using other ethers and cycloalkanes as solvents.     

Reactions of siliranes with elemental sulfur and with t-butyl mercaptan. Preparation of the 2,3-dithia-1-silacyclopentane ring system

The reaction of 1,1-dimethyl-trans-2,3,-bis(2′,2′-dimethylcyclopropylidene)-1-silirane with S₈ gives a mixture of four isomeric products derived from incorporation of one sulfur atom and a cyclopropylcarbinyl-to-butenyl type rearrangement. This silirane reacts with t-butyl mercaptan to give a product of mercaptan addition in which a cyclopropylcarbinyl-to-butenyl rearrangement also has occurred. Hexamethylsilirane reacts with S₈ to give 1,1,4,4,5,5-hexamethyl-2,3-dithia-1-silacyclopentane in high yield. These reactions are discussed in terms of free radical mechanisms.     

The UV photolysis (λ = 185 nm) of liquid t-butyl methyl ether

t-Butyl methyl ether has been UV photolysed (λ = 185 nm) to a maximal conversion of less than 0·1%. A study of the products (quantum yields) has been made: methanol (0·40₅), t-butanol (0·20), isobutene (0·17₈), t-butyl neopentyl ether (0·14₂), t-butyl ethyl ether (0·13₄), 1,2-di-t-butoxyethane (0·097), methane (0·056), isobutane (0·046), isopropenyl methyl ether (0·030), hydrogen (0·020), neopentane (0·016), ethane (0·015), formaldehyde (0·012), 2-methoxy-2-methyl-4-t-butoxybutane (0·005), hexamethylethane (0·0048), 2-methoxy-2-methylbutane (0·0027), 2-methoxy-2-methyl-3-t-butoxypropane (0·002), isopropyl methyl ether (0·0015), formaldehyde t-butyl methyl acetal (0·001), formaldehyde di-t-butyl acetal (0·001), 2-methoxy-2-methyl-4,4-dimethylpentane (0-001), 2-methoxy-2-methyl-3,3-dimethylbutane (0·0003), 2,5-dimethoxy-2,5-dimethylhexane (0·0002), di-t-butyl ether (5 · 10^?5), 2,2-dimethyloxirane (?, <- 0·001). There is no decomposition of the t-BuO radical into acetone (< 5 · 10^?4) and CH₃. Cyclisation reactions leading to α,α-dimethyloxetane (< 10^?4) and 1-methoxy-1-methylcyclopropane (< 10^?4) do not occur. The material balance yields C₅H_11·97O_1·018.The main modes of fragmentation (ca 82%) are represented by the homolytic CO bond split, either into t-butyl and methoxy (ca 52%) or into t-butoxy and methyl (ca 30%), Fragmentation into methanol and isobutene (8·5%) as well as into formaldehyde and isobutane (2%) are further modes of decomposition. The break of a CC linkage (4·5%) mainly occurs by elimination of molecular methane. A CH bond split has a probability of ca 3% with the methoxy CH bond the more likely one to break.     

Evaluation of Initiators and Fillers in Diallyl Phthalate Resins by Differential Scanning Calorimetry

Seven organic peroxide initiators for the polymerization of diallyl-o-phthalate prepolymers were studied using differential scanning calorimetry. Included were t-butyl perbenzoate, dicumyl peroxide, α,α′-bis(t-butyl peroxy) diisopropyl-benzene, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3, di-t-butyl peroxide, and t-butyl hydroperoxide. Heats of reaction and reaction rate constants are presented for each initiator at 1, 2, 3, and 4 phr of diallyl-o-phthalate prepolymers. The differences in reaction temperature and rate are discussed. Effects of four types of commonly used fillers (asbestos floats, ground quartz, calcium silicate, and clay) on the heats of reaction of diallyl-o-phthalate prepolymers using t-butyl perbenzoate and dicumyl peroxide initiators show the large inhibiting effect of untreated kaolinite clays on this polymerization.     

The relationship between crystal structure and methyl and t-butyl group dynamics in van der Waals organic solids

We report x-ray diffractometry in a single crystal of 2-t-butyl-4-methylphenol (TMP) and low-frequency solid state nuclear magnetic resonance (NMR) proton relaxometry in a polycrystalline sample of TMP. The x-ray data show TMP to have a monoclinic, P2(1)/c, structure with eight molecules per unit cell and two crystallographically inequivalent t-butyl group (C(CH(3))(3)) sites. The proton spin-lattice relaxation rates were measured between 90 and 310 K at NMR frequencies of 8.50, 22.5, and 53.0 MHz. The relaxometry data is fitted with two models characterizing the dynamics of the t-butyl groups and their constituent methyl groups, both of which are consistent with the determined x-ray structure. In addition to presenting results for TMP, we review previously reported x-ray diffractometry and low-frequency NMR relaxometry in two other van der Waals solids which have a simpler structure. In both cases, a unique model for the reorientational dynamics was found. Finally, we review a similar previously reported analysis in a van der Waals solid with a very complex structure in which case fitting the NMR relaxometry requires very many parameters and serves mainly as a flag for a careful x-ray diffraction study.     

Effects of t-butyl substituents on valence tautomerism of 7-t-butyl-7-cyano-1,3,5-cycloheptatrienes to the norcaradiene form

Introduction of t-butyl groups to the 2-, 3-, 2,4-, or 2,5-positions of 7-t-butyl-7-cyano-1,3,5-cycloheptatriene dramatically shifts the cycloheptatriene - norcaradiene equilibrium to the norcaradiene form. The nonbonded interaction is an important factor.     

Tandem intramolecular silylformylation and silicon-assisted cross-coupling reactions. synthesis of geometrically defined alpha,beta-unsaturated aldehydes

The palladium- and copper-catalyzed cross-coupling reactions of cyclic silyl ethers with aryl iodides are reported. Silyl ethers 3 were readily prepared by intramolecular silylformylation of homopropargyl silyl ethers 2 under a carbon monoxide atmosphere. The reaction of cyclic silyl ethers 3with various aryl iodides 7 in the presence of [(allyl)PdCl](2), CuI, a hydrosilane, and KF.2H(2)O in DMF at room temperature provided the alpha,beta-unsaturated aldehyde coupling products 8 in high yields. The need for copper in this process suggested that transmetalation from silicon to copper is an important step in the mechanism. Although siloxane 3 and the product 8 are not stable under basic conditions, KF.2H(2)O provided the appropriate balance of reactivity toward silicon and reduced basicity. The addition of a hydrosilane to [(allyl)PdCl](2) was needed to reduce the palladium(II) to the active palladium(0) form.     

Iron(III) p-toluenesulfonate catalyzed synthesis of homoallyl ethers from acetals and aldehydes

Iron(III) p-toluenesulfonate, Fe(OTs)₃·6H₂O, is an inexpensive, versatile and commercially available catalyst for the allylation of acetals using allyltrimethylsilane to yield homoallyl ethers in moderate to good yields. The one-pot conversion of aldehydes to homoallyl ethers using alkoxysilanes has also been accomplished using Fe(OTs)₃·6H₂O as a catalyst. The use of mild reaction conditions and a relatively non-corrosive catalyst make this method an attractive option for the synthesis of a range of homoallyl ethers.