Reduction of acetophenone using supercritical 2-propanol: the substituent effect and the deuterium kinetic isotope effect

The reductions of several substituted acetophenones using supercritical 2-propanol were carried out to estimate the Hammett's reaction constant (ρ=0.33). Also, the reduction of acetophenone using supercritical deuteriated 2-propanol was carried out to determine the rate-determining step. The kinetic isotope effects were observed in the reduction using 2-deuterio-2-propanol (k_H/k_D=1.6) and O-deuterio-2-propanol (k_H/k_D=2.0). These findings suggest that the reaction proceeds via a cyclic transition state between acetophenone and 2-propanol similar to that of the Meerwein-Ponndorf-Verley reduction.     

Reactions of 2,2-bis(trifluoromethyl)oxirane with alcohols under phase transfer catalysis

It was demonstrated that the reaction of 2,2-bis(trifluoromethyl)oxirane (1) with variety of alcohols could be successfully carried out under phase transfer catalysis conditions using sodium or potassium hydroxide as a base. For example, reaction of CH₃OH, C₂H₅OCH₂CH₂OH, HOCH₂CH₂OH with one or two moles of 1 in the presence of the catalyst [(C₄H₉)₄N⁺HSO₄⁻] gives the corresponding tertiary alcohols R[OCH₂C(CF₃)₂OH]_n (n=1 or 2) in 43-53% yield, along with some O[CH₂C(CF₃)₂OH]₂. Benzyl alcohol and phenol under similar conditions are less active, producing in the reaction with 1 the corresponding adducts ArOCH₂C(CF₃)₂OH in 31-35% yield. Fluorinated alcohols, such as CF₃CH₂OH, ClCF₂CH₂OH, HCF₂CF₂CH₂OH have much higher reactivity towards 1 giving ring opening products in 82-97% yield. Even in the reaction of hindered hexafluoro-iso-propanol the corresponding adduct was isolated in 43% yield. Surprisingly, the reaction of iso-propanol and epoxide 1, results in the formation of O[CH₂C(CF₃)₂OH]₂ as a major product, isolated in 56% yield. Possible mechanism for the formation of the last product was proposed.     

Transformation of benzonitrile into benzyl alcohol and benzoate esters in supercritical alcohols

The reactions of benzonitrile in supercritical methanol, ethanol, and 2-propanol were investigated under non-catalytic conditions. In supercritical methanol, benzonitrile was converted to methyl benzoate in high yield. The esterification reaction also occurred in supercritical ethanol to afford ethyl benzoate in moderate yield. The esterification could occur via a route analogous to the Pinner reaction. On the other hand, benzonitrile in supercritical 2-propanol yielded no ester. Benzyl alcohol was the major product in supercritical 2-propanol. We investigated the reaction of the CN bond in supercritical 2-propanol. In supercritical 2-propanol, N-benzylideneaniline was transferred to the reduction product (N-benzylaniline) and hydrolysis products (benzyl alcohol and aniline). The hydrolysis reaction was restricted when the reaction was carried out in supercritical 2-propanol with a low water content. This indicates that the water in the 2-propanol acts as a reagent for the hydrolysis of the CN bond. These results suggested the following reaction process: C₆H₅CN→C₆H₅CHNH→C₆H₅CHO→C₆H₅CH₂OH.     

Allylstannation III. Synthesis of homoallylic alcohols and 4-chloro-2,6-dialkyl-3-methyltetrahydropyrans by reactions between (E/Z)-2-butenyldichloro-n-butyltin and aldehydes

2-Butenyldichloro-n-butyltin (in various cis/trans isomer ratios) reacts readily with neat RCHO (R = CH₃, C₂H₅, (CH₃)₂CH, and C₆H₅) at 25°C to give (a) linear alcohols, RCH(OH)CH₂CHCHCH₃ in the E and Z forms, (b) branched alcohols, RCH(OH)CH(CH₃)CHCH₂ in the threo and erythro forms, and (c) 2,3,4,6-tetra-substituted tetrahydropyrans (A) as a mixture of cis/trans isomers arising from the CH(CH₃)CHCl bond. The maximum yields of these tetrahydropyrans were obtained

by the use of 3–3.5 molar ratios RCHO/tin compound in the absence of solvent, whereas work-up after reactions in CH₂Cl₂ gave linear, alcohols as the main products. The formation of linear alcohols appears to be stereospecific, as the ratio of _E/_Z isomers obtained is the same as that in the organotin compound. Tetrahydropyrans are formed preferentially as the _trans isomers.     

Water‐Enhanced Synthesis of Higher Alcohols from CO2 Hydrogenation over a Pt/Co3O4 Catalyst under Milder Conditions

The effect of water on CO₂ hydrogenation to produce higher alcohols (C₂–C₄) was studied. Pt/Co₃O₄, which had not been used previously for this reaction, was applied as the heterogeneous catalyst. It was found that water and the catalyst had an excellent synergistic effect for promoting the reaction. High selectivity of C₂–C₄ alcohols could be achieved at 140 °C (especially with DMI (1,3‐dimethyl‐2‐imidazolidinone) as co‐solvent), which is a much lower temperature than reported previously. The catalyst could be reused at least five times without reducing the activity and selectivity. D₂O and ¹³CH₃OH labeling experiments indicated that water involved in the reaction and promoted the reaction kinetically, and ethanol was formed via CH₃OH as an intermediate.     

Optically active organoaluminum based inclusion compounds. Synthesis and characterization of (S)-(−)-α-[(C6H5)CH(CH3)N(CH3)3][Al2R6I] (R=CH3, C2H5)

The optically active quaternary ammonium salt (S)-(?)-α-[(C₆H₅)CH(CH₃)N(CH₃)₃I] reacts with AlR₃ to afford optically active organoaluminum based inclusion compounds, liquid clathrates, of the formula (S)-(?)-α-[(C₆H₅)CH(CH₃)N(CH₃)₃][Al₂R₆I] (R=CH₃, C₂H₅). Specific rotation ([α] ₂₅ ^D ) for the Al(CH₃)₃ compound was determined to be ?13.19° while that for the Al(C₂H₅)₃ analog was determined to be ?14.30°. There are 13.8 toluene molecules per anionic moiety for the trimethylaluminum based liquid clathrate while there are 15.0 toluene molecules per anion for the corresponding triethylaluminum inclusion compound.     

Allylstannation: II. A total “cis-preference” in the addition of n-Bu2ClSnCH(CH3)CHCH2 to aldehydes

1-Buten-3-yldi-n-butylchlorotin, formed by redistribution of ($\text{E}\text{Z}$)-2-butenyltri-n-butyltin and Bu₂SnCl₂, reacts readily with neat RCHO (R  C₂H₅, C₂H₅(CH₃)CH, (CH₃)₂CH, (CH₃)₃C and C₆H₅) to give high yields (80–100%) of alcohols of the type RCH(OH)CH₂CHCHCH₃ only in the Z-configuration. This appears to be the first example of total “cis-preference” in the addition of Grignard-like reagents to carbonyl compounds. The results are discussed in terms of steric requirements around the tin centre which is probably five-coordinate in the transition state.     

Bis(triphenylphosphine)platinum acetylides from functionally substituted acetylenes. A new synthesis method

A general procedure, giving high yields for the synthesis of (Ph₃P)₂Pt(CCR)₂ complexes (R = C₆H₅, C(CH₂)CH₃, (CH₂)₆CCH, CH₂OH, CH(OH)CH₃, CH(OH)C₆H₅, CH₂CH(OH)CH₃, C(OH)(CH₃)CH₃, C₆H₁₀OH, C(OH)(CH₃)CH₂CH₃, CH₂NHCH₃, CH₂NHCH₂C₆H₅, CH₂N(CH₃)₂, CH₂N(C₂H₅)₂) is reported. On the basis of the low frequency IR spectra a trans structure is proposed for all complexes. UV spectra are also reported.     

Determination of the isomerization rate constant HOCH2CH2CH2CH(OO·)CH3 →HOC·HCH2CH2CH(OOH)CH3. Importance of intramolecular hydroperoxy isomerization in tropospheric chemistry

The rate constant of the title reaction is determined during thermal decomposition of di-n-pentyl peroxide C₅H₁₁O( )OC₅H₁₁ in oxygen over the temperature range 463–523 K. The pyrolysis of di-n-pentyl peroxide in O₂/N₂ mixtures is studied at atmospheric pressure in passivated quartz vessels. The reaction products are sampled through a micro-probe, collected on a liquid-nitrogen trap and solubilized in liquid acetonitrile. Analysis of the main compound, peroxide C₅H₁₀O₃, was carried out by GC/MS, GC/MS/MS [electron impact EI and NH₃ chemical ionization CI conditions]. After micro-preparative GC separation of this peroxide, the structure of two cyclic isomers (3S*,6S*)3α-hydroxy-6-methyl-1,2-dioxane and (3R*,6S*)3α-hydroxy-6-methyl-1,2-dioxane was determined from ¹H NMR spectra. The hydroperoxy-pentanal OHC( )(CH₂)₂( )CH(OOH)( )CH₃ is formed in the gas phase and is in equilibrium with these two cyclic epimers, which are predominant in the liquid phase at room temperature. This peroxide is produced by successive reactions of the n-pentoxy radical: a first one generates the CH₃C·H(CH₂)₃OH radical which reacts with O₂ to form CH₃CH(OO·)(CH₂)₃OH; this hydroxyperoxy radical isomerizes and forms the hydroperoxy HOC·H(CH₂)₂CH(OOH)CH₃ radical. This last species leads to the pentanal-hydroperoxide (also called oxo-hydroperoxide, or carbonyl-hydroperoxide, or hydroperoxypentanal), by the reaction HOC·H(CH₂)₂CH(OOH)CH₃+O₂→O()CH(CH₂)₂CH(OOH)CH₃+HO₂. The isomerization rate constant HOCH₂CH₂CH₂CH(OO·)CH₃→HOC·HCH₂CH₂CH(OOH)CH₃ (k₃) has been determined by comparison to the competing well-known reaction RO₂+NO→RO+NO₂ (k₇). By adding small amounts of NO (0–1.6×10¹⁵ molecules cm⁻³) to the di-n-pentyl peroxide/O₂/N₂ mixtures, the pentanal-hydroperoxide concentration was decreased, due to the consumption of RO₂ radicals by reaction (7). The pentanal-hydroperoxide concentration was measured vs. NO concentration at ten temperatures (463–523 K). The isomerization rate constant involving the H atoms of the CH₂( )OH group was deduced: or per H atom: The comparison of this rate constant to thermokinetics estimations leads to the conclusion that the strain energy barrier of a seven-member ring transition state is low and near that of a six-member ring. Intramolecular hydroperoxy isomerization reactions produce carbonyl-hydroperoxides which (through atmospheric decomposition) increase concentration of radicals and consequently increase atmospheric pollution, especially tropospheric ozone, during summer anticyclonic periods. Therefore, hydrocarbons used in summer should contain only short chains (<C₄) hydrocarbons or totally branched hydrocarbons, for which isomerization reactions are unlikely. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 875–887, 1998     

Stereoselective synthesis of tetrahydropyran new derivatives underlain by α-allyl ketones

Decarboxylation of α-allyl-substituted acetoacetic esters afforded α-allyl ketones that were reduced with L-selectride [LiBH(s-Bu)₃] in alcohols RCH(OH)CH₂CH₂CH=C(Me)CH₂R'. The latter reacted with methyl 4-hydroxy-3-formylbenzoate and methyl orthoformate in the presence of p-toluenesulfonic acid to provide trans-tetrahydropyrano[3,2-с][1]benzopyran. In reaction of the E-isomer of alcohol Me₂CHCH(OH) CH₂CH₂CH=C(Me)CH₂CH₂Ph with CF₃SO₃H a stereoselective cyclization occurred with the formation of 2,6-disubstituted tetrahydropyran; Prins reaction with 4-bromobenzaldehyde and salicylaldehyde in the presence of boron trifluoride etherate also proceeded stereoselectively giving a substituted tetrahydropyrano-[3,2-c][1]-benzopyran.     

Catalytic hydrogen transfer over magnesia, IXa. reduction of long chain aliphatic ketones by 2-propanol

A series of symmetrical long chain aliphatic ketones of general formula CH₃−(CH₂)_n-CO-(CH₂)₂−CH₃, where n=4,5,6,7 and 8, has been used as hydrogen acceptors from 2-propanol at 573–723 K in the presence of MgO catalyst under flow conditions. The yeilds of the appropriate alcohols exceeded 50%. Above 623 K the consecutive dehydration of the alcohols formed took place with moderate yields leading to internal alkenes. The direct one-step synthesis of C₁₃ alkene from 7-tridecanone has been realized under catalytic transfer reduction (CTR) conditions with high yield (>90%) over a MgO catalyst of enhanced acidity. Part VIII: Appl. Catal. A.:General,150, 77 (1997)     

The √t law in solid-phase reactions. Analysis of the hypothesis on rate constant distribution

The reaction C₂H₅ + O₂ → C₂H₅O₂ in glassy methanol-d₄ and the H-atom abstraction by CH₃, C₂H₅, and n-C₄H₉ radicals in C₂H₅OH + C₂D₅OH and CD₃CH₂OH + C₂D₅OH glassy mixtures have been studied by electron spin resonance. The analysis of the dependence of the reaction rates on the concentration of O₂ (oxidation) and C₂H₅OH, CD₃CH₂OH (H-atom abstraction) has shown that the √t law is not conditioned by the existence of regions characterized by different rate constants.     

Excess molar enthalpies of (methanol + 1-propanol) + oxane or 1,4-dioxane mixtures at the temperature 298.15 K

Experimental excess molar enthalpies H_m^E at the temperature 298.15 K and atmospheric pressure in a flow microcalorimeter are reported for the ternary mixtures: {x₁CH₃OH+x₂C₂H₅OH+(1−x₁−x₂)C₅H₁₀O} and {x₁CH₃OH+x₂C₂H₅OH+(1−x₁−x₂)C₄H₈O₂}. The results have been correlated by means of a polynomial equation and used to construct constant excess enthalpy contours. Further, the results have been compared with those calculated from a UNIQUAC associated-solution model taking into consideration the molecular association of like alcohols, solvation between unlike alcohols and alcohols with oxane (tetrahydropyran) or 1,4-dioxane using only binary information.     

The steric and electronic effects of aliphatic fluoroalkyl groups

Ab initio calculations were performed on 18 fluorinated and unfluorinated alcohols at the B3LYP and HF levels with the 6-311G^∗∗ basis set. Molar volumes of the alcohols were computed at each level and averaged to produce a scale of relative size. From this, various isosteric replacements of potential use in drug design were suggested: ethyl by FCH₂CH₂ or HCF₂CH₂, propyl by CF₃CH₂, isopropyl by CF₃(CH₃)CH or (FCH₂)₂CH, isobutyl or t-butyl by (CF₃)₂CH, and 3-methyl-2-butyl by CF₃(CH₃)₂C. Calculation of the charge on oxygen and the Wiberg index of the CO bond allowed an electronegativity scale to be constructed for the fluoroalkyl groups. Electronegativity decreased in the order: (CF₃)₃C>(CF₃)₂CH>C₂F₅CH₂>CF₃CH₂>CH₃(CF₃)₂C>HCF₂CH₂>CF₃(CH₃)CH>(FCH₂)₂CH>FCH₂CH₂>CF₃(CH₃)₂C. This ranking agreed with literature acid dissociation data for the alcohols studied.     

Thermochemistry and kinetics of the 2-butanone-4-yl CH3C(=O)CH2CH2• + O2 reaction system

Thermochemistry and kinetic pathways on the 2-butanone-4-yl (CH₃C(=O)CH₂CH₂•) + O₂ reaction system are determined. Standard enthalpies, entropies, and heat capacities are evaluated using the G3MP2B3, G3, G3MP3, CBS-QB3 ab initio methods, and the B3LYP/6-311g(d,p) density functional calculation method. The CH₃C(=O)CH₂CH₂• radical + O₂ association reaction forms a chemically activated peroxy radical with 35 kcal mol⁻¹ excess of energy. The chemically activated adduct can undergo RO−O bond dissociation, rearrangement via intramolecular hydrogen transfer reactions to form hydroperoxide-alkyl radicals, or eliminate HO₂ and OH. The hydroperoxide-alkyl radical intermediates can undergo further reactions forming ketones, cyclic ethers, OH radicals, ketene, formaldehyde, or oxiranes. A relatively new path showing a low barrier and resulting in reactive product sets involves peroxy radical attack on a carbonyl carbon atom in a cyclic transition state structure. It is shown to be important in ketones when the cyclic transition state has five or more central atoms.     

Lignin-type, α,β-unsaturated aldehydes of lignin-type in organic solvents

A 1:1 reaction of [HO(CH₂)₃]₃P with 4-hydroxy-3-methoxy-cinnamaldehyde (coniferaldehyde) or 3,5-dimethoxy-4-hydroxycinnamaldehyde (sinapaldehyde) in acetone at room temperature affords phosphonium zwitterions of the type R₃P⁺CH(4-O^?-Ar)CH₂CHO; other phosphines [R = Et, n-Bu, (CH₂)₂CN, and p-Tol] do not react under the same conditions. In alcohols R??OH(D) [R?? = CD₃, Et, (CD₃)₂CD, s-Bu, HOCH₂CH₂], the above phosphines (except the cyano-derivative) and those where R = i-Pr, Cy, Me₂Ph, MePh₂ do react within an equilibrium established between the reactants and the zwitterion-hemiacetal products R₃P⁺CH(4-O^?-Ar)CH₂CH(OH)(OR??) that are formed as a mixture of two diastereomers. The nature of the phosphine and the alcohol affects the equilibrium and the diastereomeric ratio.     

Reactions of diorganoytterbium compounds with ketones and aldehydes

Reactions of the diorganolanthanoids R₂Yb (R = PhCC or C₆F₅) with aldehydes (R′CHO) and ketones (R′₂CO) (R = Me or Ph) followed by hydrolysis generally gives the alcohols RR′CH(OH) or RR′₂COH, but, with benzophenone, reduction giving benzopinacol either competes (R = PhCC) or is predominant (R = C₆F₅).     

Direct addition of supercritical alcohols, acetone or acetonitrile to the alkenes without catalysts

The reactions of the alkenes with supercritical organic compounds under non-catalytic conditions were investigated. The H and CR₂OH, CH₂COCH₃ or CH₂CN of supercritical alcohols (CHR₂OH), acetone (CH₃COCH₃) or acetonitrile (CH₃CN) added to the CC bonds of alkenes form C-C bonds between the α-carbons of the supercritical organic compounds and the sp² carbons of the alkenes.     

Radiative Striations of Spin-Coating Films: Surface Roughness Measurement and in-situ Observation

Silica gel films were prepared by spin-coating from Si(OC₂H₅)₄-HNO₃-H₂O-ROH solutions and heated at 200°C where ROH = CH₃OH, C₂H₅OH, CH₃OC₂H₄OH and CH₃CH(OH)CH₂OH. Striations were observed with an optical microscope, and quantitatively evaluated by surface roughness measurement. A decrease in height and an increase in spacing of the striations were observed when alcohols of high boiling points were used. However, even when the boiling point of the alcohols was high, an evolution of the striations did occur on spin-coating films, which disappeared while keeping the film in the ambient atmosphere. Convections, which might be the source of the striations, were observed in sol layers placed on a stationary substrate irrespective of the boiling point of the alcohols.     

Reactivity of olefin an acetylene complexes of platinum(0) towards tetrachloro-o-benzoquinone

Tetracloro-o-benzoquinone reacts with (diphenylacetylene)bis(tirphenylphosphine)platinum(0) to give the novel platinum(II) diphenylacetylene complex, Pt(C₆Cl₄O₂)PhCCPh)(PPh₃), (I), which reacts with hydrogen halides to give the compelexes cis-PtX₂(PhCCPh((PPh₃), (X = Cl or Br). Hydrogen chloride also readily removes the tetrachloro-o-benzoquinoneligand from the adducts Ni(C₆Cl₄O₂)(Ph₂PCH₂CH₂PPh₂) and M(C₆Cl₄O₂)(PPh₃)₂, (M = Pd or Pt) but it has no reaction upon Ir(Cl)(C₆Cl₄O₂)(CO)(PPh₃)₂ at room temperature. The acetylene in (1) is susceptible to nucleophilic attact and reaction with diethylamine gives the vinyl adduct Pt(C₆Cl₄O₂)(CPhCPh)NHEt₂)(PPh₃). Other reactions of (I) have also been studied. Attemps to prepare other olefin or acetylene complexes of platinum(II) by the action of tetrachlor-o-benzoquinone on the complexes Pt(L)(PPh₃)₂, (L = PhCCH,(Et)(Me)(HO)CCCC(OH)(Me)(Et), HOCH₂OH, CF₃CCCF₃, CF₂CF₂, CF₂CH₂ or trans-PhCHCHPh) are also described.