Solvolysis Products Research Articles

A novel titanosilicate with MWW structureCatalytic properties in selective epoxidation of diallyl ether with hydrogen peroxide

Abstract The catalytic activity and selectivity of Ti-MWW in the epoxidation of diallyl ether (DAE) with hydrogen peroxide to allyl glycidyl ether (AGE) and diglycidyl ether (DGE) have been studied by a comparison with those of TS-1, and the issues concerning the consecutive reaction and the selective production of AGE have been considered. Ti-MWW catalyzed the DAE epoxidation in the presence of aprotic solvents such as acetonitrile or acetone, and produced only minor levels of solvolysis products. Ti-MWW proved to be a reusable catalyst standing up to the Ti leaching and maintaining the catalytic activity and the product selectivity in the reaction–regeneration cycles. Studies with different solvents, Ti contents, reaction times, temperature, and catalyst amounts confirmed that the DAE epoxidation was a typical consecutive reaction with AGE as an intermediate product and DGE as a secondary one. The reaction rate for AGE formation was much faster than that for DGE, making the selective production of AGE possible by controlling the reaction up to a DAE conversion level of ca. 30%.

Aqueous methanolysis of an α‐D‐N‐acetylneuraminyl pyridinium zwitterion: solvolysis occurs with no intramolecular participation of the anomeric carboxylate group

AbstractThe synthesis of 3,4‐dihydro‐2H‐pyrano[3,2‐c]pyridinium α‐D‐N‐acetylneuraminoate (4), the subsequent rate constants for aqueous methanolysis and the associated reaction products are reported. When compared with the analogous 2‐deoxyglucopyranosyl 4′‐bromoisoquinolinium salt (11), the rate of solvolysis of 4 displays a reduced sensitivity towards the ionizing power of the solvent. Solvolysis product analysis showed that substitution occurs predominantly with inversion of configuration. Hence it can be concluded that the methanolysis reactions of 4 proceed via dissociative transition states with no intramolecular nucleophilic participation by the anomeric carboxylate group. Copyright © 2004 John Wiley & Sons, Ltd.

Fluorinated Heterocyclic Compounds: An Assay on the Photochemistry of Some Fluorinated 1‐Oxa‐2‐azoles: An Expedient Route to Fluorinated Heterocycles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A computational study of the role of hydrogen bonds in SN1 and E1 reactions.

The reaction between tertiary butyl chloride and water clusters was examined by applying density functional theory calculations. The carbonium ion t-Bu(+) that is normally sandwiched between the water clusters was found to be absent, such that a Cbond;O covalent bond was formed in the intermediate (Int1) after heterolysis. An (H(2)O)(4) cluster is able to bridge the front and rear of the central carbon and promotes heterolysis. A correlation between bond interchanges at the central carbon and proton relays is presented. Stereochemical scrambling in the solvolysis products is discussed in terms of this correlation. In addition, an E1 pathway for the elimination product, iso-butene, is found from Int1.

Fluorinated heterocyclic compounds: an assay on the photochemistry of some fluorinated 1-oxa-2-azoles: an expedient route to fluorinated heterocycles

Photoinduced heterocyclic rearrangements of ON bond-containing azoles have been claimed in the synthesis of target fluorinated heterocyclic compounds. In this context, the photochemical behavior of some fluorinated 1,2,4-oxadiazoles has been investigated. Irradiations of 3-amino-5-perfluoroalkyl-1,2,4-oxadiazoles at λ=313 nm in methanol gave open-chain products arising from a reaction of the nucleophilic solvent with either the first formed ring-photolytic species or with a nitrilimine moiety generated from it. Differently, irradiations in methanol with the presence of triethylamine (TEA) followed competing phototransposition pathways leading to the ring-isomers 2-amino-5-perfluoroalkyl-1,3,4-oxadiazoles (major component) and the ring degenerate isomers 5-amino-3-perfluoroalkyl-1,2,4-oxadiazoles (minor component). On the other hand, 3-amino-5-polyfluorophenyl-1,2,4-oxadiazoles underwent ring-photoisomerization into 1,3,4-oxadiazoles when irradiations were carried out at λ=254 nm. In turn, the irradiation of the 3-phenyl-5-perfluoroheptyl-1,2,4-oxadiazole at λ=254 nm in methanol gave the solvolysis product, but no ring-isomerization was observed. Some mechanistic considerations are reported, and some applications in the synthesis of target fluorinated 1,3,4-oxadiazoles are claimed.

Kinetic and Thermodynamic Barriers to Carbon and Oxygen Alkylation of Phenol and Phenoxide Ion by the 1-(4-Methoxyphenyl)ethyl Carbocation

Rate constant ratios for addition of the three nucleophilic sites of phenol to the 1-(4-methoxyphenyl)ethyl carbocation (1+) in 50/50 (v/v) trifluoroethanol/water were determined from the relative yields of the three phenol adducts, and absolute rate constants were determined from product rate constant ratios for addition of phenol and azide ion to 1+ using k(az) = 5 x 10(9) M(-1) s(-1) for the diffusion-limited reaction of azide ion. A selectivity of 230:20:1 was determined for alkylation of phenol at oxygen, C-4 and C-2 to form 1-OPh and biphenyls 1-(4-C6H4OH) and 1-(2-C6H4OH), respectively, and of 2:2:1 for alkylation of the corresponding nucleophilic sites of phenoxide ion in diffusion-limited reactions. The Mayr nucleophilicity parameter for C-4 of phenol is N = 2.0. Encounter-limited addition of phenoxide ion to 1+ to form 1-OPh is faster than encounter-limited addition of oxygen anions that are either more or less basic than phenoxide ion. Only the products of solvolysis are observed from acid-catalyzed cleavage of 1-OPh in 50/50 (v/v) trifluoroethanol/water, but a 50% yield of biphenyls 1-(4-C6H4OH) and 1-(2-C6H4OH) are observed from spontaneous cleavage of 1-OPh, where the leaving group is phenoxide ion, because of the very low kinetic barriers to collapse of the ion pair intermediate 1+.PhO-. The 230-fold larger rate constant for O-compared to C-2-alkylation of phenol is due primarily to the larger thermodynamic driving force for oxygen addition. There are similar Marcus intrinsic barriers for these two reactions.

Physicochemical and physiological properties of 5α-cyprinol sulfate, the toxic bile salt of cyprinid fish

5alpha-Cyprinol sulfate was isolated from bile of the Asiatic carp, Cyprinus carpio. 5alpha-Cyprinol sulfate was surface active and formed micelles; its critical micellization concentration (CMC) in 0.15 M Na+ using the maximum bubble pressure device was 1.5 mM; by dye solubilization, its CMC was approximately 4 mM. At concentrations >1 mM, 5alpha-cyprinol sulfate solubilized monooleylglycerol efficiently (2.1 molecules per mol micellar bile salt). When infused intravenously into the anesthetized rat, 5alpha-cyprinol sulfate was hemolytic, cholestatic, and toxic. In the isolated rat liver, it underwent little biotransformation and was poorly transported (Tmax congruent with 0.5 micromol/min/kg) as compared with taurocholate. 5alpha-Cyprinol, its bile alcohol moiety, was oxidized to its corresponding C27 bile acid and to allocholic acid (the latter was then conjugated with taurine); these metabolites were efficiently transported. 5alpha-Cyprinol sulfate inhibited taurocholate uptake in COS-7 cells transfected with rat asbt, the apical bile salt transporter of the ileal enterocyte. 5alpha-Cyprinol had limited aqueous solubility (0.3 mM) and was poorly absorbed from the perfused rat jejunum or ileum. Sampling of carp intestinal content indicated that 5alpha-cyprinol sulfate was present at micellar concentrations, and that it did not undergo hydrolysis during intestinal transit. These studies indicate that 5alpha-cyprinol sulfate is an excellent digestive detergent and suggest that a micellar phase is present during digestion in cyprinid fish.

Carboxylation of (DPPF)-MCl 2 [DPPF=1,1′-bis(diphenylphosphino)ferrocene; M=Pt or Pd] in aqueous and non-aqueous solution : Crystal and molecular structures of [Pt(C 2O 4)(DPPF)] and of [PtCl(NO 3)(DPPF)

Treatment of the complexes [MCl 2(DPPF)] (M=Pt or Pd) {readily prepared in high yield from [MCl 2(DMSO) 2] (M=Pt ( cis-) or Pd ( trans-) and DPPF in CHCl 3} with two molar proportions of AgNO 3 in H 2O did not give the expected cation [M(DPPF)(H 2O) 2] 2+ in solution. Instead the unusual homobimetallic bridged complex [{M(μ-OH)(DPPF)} 2](NO 3) 2 was formed as an insoluble solvolysis solid product. Hence, carboxylation by addition of carboxylate anions to the solution cannot be carried out by this method. In contrast, the complex [PtCl 2(DPPF)] reacted readily with two molar proportions of AgOAc or one of Ag 2{1,1′-(OOC) 2fc} (fc=ferrocene-2H) in acetone to give the corresponding carboxylato complexes. Other carboxylato complexes were obtained from the reaction of the complexes [MCl 2(DPPF)] and the K-salts of e.g. (COOH) 2, CH 2(COOH) 2, and CH 2 CH 2 CH 2 C ( COOH) 2 in H 2O. With few exceptions, neither the K- nor the Ag-salts of the acids Me 3CCOOH and C 6H 11COOH react completely with [MCl 2(DPPF)] in aqueous or non-aqueous solutions. However, the required products were obtained by displacement of DMSO from the corresponding carboxylato complexes by DPPF in CHCl 3. All of the new carboxylato complexes and the solvolysis products were characterized physicochemically and spectroscopically. The X-ray structures of [Pt{(OOC) 2}(DPPF)] and of [PtCl(NO 3)(DPPF)] were determined, to obtain some additional information on the coordination mode of the unsymmetrical DPPF ligand in this type of complexes.

Solvolysis-decomposition of 2-adamantyl chloroformate: evidence for two reaction pathways.

Reaction of 2-adamantyl chloroformate under a variety of solvolytic conditions leads to 2-adamantyl chloride accompanied by solvolysis products, some with and some without retention of the CO(2) unit. For example, in 100% ethanol, only 4.8% 2-adamantyl chloride is formed with the mixed carbonate (88%) being the dominant product, and in 100% 2,2,2-trifluoroethanol, the products are both formed with loss of CO(2), 59% of the chloride and 41% of the ether. With exclusion of the specific rates in 100% and 90% ethanol and methanol, a good Grunwald-Winstein plot against Y(Cl) values (solvent ionizing power) is obtained, with a slope of 0.47 +/- 0.03. The results are compared with those reported earlier for 1-adamantyl chloroformate and isopropyl chloroformate and mechanistic conclusions are drawn.

A Highly Enantioselective 1,3-Dipolar Cycloaddition Reaction in Alcoholic Media: Ni(II)-Pybox-tipsom Catalyst.

Abstract From the viewpoint of environmentally friendly reaction conditions, catalytic asymmetric nitrone 1,3-dipolar cycloaddition (DC) reactions in protic media have been investigated. DC reaction of nitrones with alkenoyl oxazolidinone and pyrrolidinone derivatives in t -BuOH in the presence of sterically tuned bis(oxazolinyl)pyridine (pybox- tipsom 1d ) and Ni(II) complex as a chiral Lewis acid catalyst proceeded smoothly to give the corresponding cycloadducts ranging from 90:10 to >99:1 of endo / exo ratio and ranging from 90 to 98% ee for the endo adduct. The use of sterically hindered alcohols such as t -BuOH and s -BuOH as a non-halogenated solvent was shown to effect rate acceleration for the DC reaction compare to CH 2 Cl 2 at the same temperature. Furthermore, no solvolysis products of nitrones and cycloadducts were observed in these protic media despite the possible formation of Bronsted acid.

A highly enantioselective 1,3-dipolar cycloaddition reaction in alcoholic media: Ni(II)-pybox-tipsom catalyst

From the viewpoint of environmentally friendly reaction conditions, catalytic asymmetric nitrone 1,3-dipolar cycloaddition (DC) reactions in protic media have been investigated. DC reaction of nitrones with alkenoyl oxazolidinone and pyrrolidinone derivatives in t-BuOH in the presence of sterically tuned bis(oxazolinyl)pyridine (pybox-tipsom1d) and Ni(II) complex as a chiral Lewis acid catalyst proceeded smoothly to give the corresponding cycloadducts ranging from 90:10 to >99:1 of endo/exo ratio and ranging from 90 to 98% ee for the endo adduct. The use of sterically hindered alcohols such as t-BuOH and s-BuOH as a non-halogenated solvent was shown to effect rate acceleration for the DC reaction compare to CH2Cl2 at the same temperature. Furthermore, no solvolysis products of nitrones and cycloadducts were observed in these protic media despite the possible formation of Brønsted acid.

Comprehensive study of the methyl effect on the solvolysis rates of bridgehead derivatives.

The effect of a bridgehead methyl group on the hydride ion affinity in the gas phase of bicyclo[1.1.1]pent-1-yl (1+), 1-norbornyl (3+), cubyl (5+), 1-adamantyl (7+), bicyclo[2.2.2]oct-1-yl (9+),and bicyclo[3.1.1]hept-1-yl (11+) cations has been studied using density functional theory and ab initio methods. It is concluded that the methyl group always increases the stability of the substituted cations. The effect of the solvent on the stability of methyl-substituted cations in relation to the unsubstituted cations has been studied using the polarizable continuum model of the self-consistent reaction field theory. In the case of rearranging cations, the nucleophilic assistance of the solvent is determined by means of the interaction energy of the corresponding water complexes. It is concluded that the solvent causes the relative stabilization of the parent cations. As a consequence, most of the methyl-substituted bridgehead derivatives show a lower solvolysis rate than the corresponding unsubstituted compounds. A nonqualitative explanation of the methyl effect on the relative stability of bridgehead cations in both gas phase and solution is given for the first time. The ratios of solvolysis products in the case of rearranging bridgehead cations have also been computed from the relative stability of the intermediate water complexes.

Solvent Effects and Steric Course in the Solvolysis of 1,3,3-Trimethyl-2-oxocyclopentyl Mesylate in Comparison with 1,1,3,3-Tetramethyl-2-oxobutyl System

Abstract The rates of solvolysis in various solvents were determined for 1,1,3,3-tetramethyl-2-oxobutyl tosylate (1OTs) and 1,3,3-trimethyl-2-oxocyclopentyl mesylate (4OMs). The rate data for 1OTs reinforced that the linear Grunwald-Winstein (GW) relationship of 1OMs previously reported by Creary for non-aqueous solvents must also hold for aqueous organic solvents. 4OMs showed a markedly dispersed GW relationship that is, on the other hand, well correlated with an extended GW equation involving a nucleophilicity parameter. Such solvent dependence, such marked effects of added sodium azide on rates, and the 100% inversion of configuration of the solvolysis product showed that the solvolysis of 4OMs would be categorized to SN2(intermediate), whereas 1OMs and 1OTs solvolyze via limiting SN1. The negligible susceptibility of 1OTs toward nucleophilicity of solvent and azide probe indicates that the nucleofuge leaves along the C=O axis in such a manner that the back-strain (B-strain) in the ground state is efficiently relieved in the transition state. Comparison of solvolysis rates of 1OMs and 4OMs with those of the corresponding parent substrates suggests that the transition states of these substrates would not be stabilized by carbonyl π conjugation. The origin of the unexpectedly fast rates of solvolysis of 1OMs has been discussed.

Solvolyses of 2-Deoxy-alpha- and beta-D-Glucopyranosyl 4'-Bromoisoquinolinium Tetrafluoroborates.

The solvolyses of 2-deoxy-alpha- and beta-D-glucopyranosyl 4'-bromoisoquinolinium tetrafluoroborates (1 and 2) were monitored in aqueous methanol, ethanol, trifluoroethanol, and binary mixtures of ethanol and trifluoroethanol. The observed rate constants are consistent with the solvolyses of 1 and 2 proceeding via dissociative (D(N) A(N)) transition states. In comparison to the alpha-anomer, solvolysis of the beta-compound gives a greater transition state charge delocalization onto the ring oxygen atom. Analysis of the solvolysis product ratios indicates that the 2-deoxyglucosyl oxacarbenium ion is not solvent-equilibrated in the solvent mixtures studied. In the solvolysis of compound 1, the solvent trifluoroethanol facilitates diffusional separation of the leaving group and, in so doing, promotes the formation of the retained trifluoroethyl glycoside.

Isolation, structural characterization, and synthesis of a naturally occurring bisfuranopseudopterane ether: biskallolide A. Evidence for a carbocation intermediate during the facile conversion of kallolide A and isokallolide A into various solvolysis products.

The West Indian alcyonacean Pseudopterogorgia bipinnata (Verrill, 1864) is shown to contain a novel bisditerpenoid ether: biskallolide A (2). The structural assignment of 2 was mainly based on 1D and 2D NMR and MS spectral data and was further confirmed by synthesis. The 2-C-alkoxylation of furanopseudopteranes kallolide A (1) and isokallolide A (8) occurs spontaneously in some solvents and involves replacement of the C2 hydroxyl with an alkoxyl group to yield solvolysis products that display net retention of configuration. The facile solvolytic 2-C-acyloxylation of kallolide A was achieved readily under similar circumstances to afford kallolide A acetate (4) as the sole product. Mechanistic details in conversion of alcohols 1 and 8 into various solvolysis products, including dimeric ethers 2 and 9, were investigated in this study. Solvolysis of kallolide A and isokallolide A in [(18)O]-labeled solvent demonstrated that the C2 alkoxyl of the solvolysis products originated from the solvent, suggesting that these conversions may proceed through an S(N)1 mechanism with generation of a carbocation intermediate. The chemical structures of kallolide A derivatives 3-7and those of isokallolide A congeners 9-11 were established by detailed analysis of the spectral data.

Correlation of the rates of solvolysis of cyclopropylcarbinyl and cyclobutyl bromides using the extended Grunwald-Winstein equation

The reactions of cyclopropylcarbinyl bromide (1) and cyclobutyl bromide (2) in hydroxylic solvents proceed with both solvolysis and rearrangement. Depending on the solvent, the reactions of 1 are 10-120 times faster than those of 2, and both are faster than the previously studied allylcarbinyl bromide (3). Specific rates are reported for the reactions of 2 proceeding to solvolysis products and 3. Reactions of 1 proceed to solvolysis products and both 2 and 3; since 2 slowly undergoes further solvolysis, specific rates are obtained by a modified Guggenheim treatment. The two sets of specific rates are analyzed using the extended Grunwald-Winstein equation to give sensitivities toward changes in solvent nucleophilicity of 0.42 for 1 and 0.53 for 2 and corresponding sensitivities toward changes in solvent ionizing power of 0.75 and 0.94. A mechanism is proposed involving a rate-determining ionization with an appreciable nucleophilic solvation of the incipient carbocation.

Theoretical Study on the Reactivity of Phenyl Cation with a Propyl Group at Ortho-Position

Photosolvolysis of 2-chloropropylbenzene in trifluoroethanol (TFE) produces propylbenzene, indane, 2-trifluoroethoxypropylbenzene and other solvolysis products. Propylbenzene clearly comes from 2-propylphenyl radical intermediate while the other products suggest existence of 2-propylphenyl cation as an intermediate. Density functional theory (DFT) calculations at the B3LYP/6-31G ∗∗ level of theory were carried out to research reaction paths for the solvolysis products through the cationic intermediate. Three paths investigated in the present study well explain the products obtained in our experiments. The DFT calculations strongly suggest existence of the phenyl cation as an intermediate in the photosolvolysis of 2-chloropropylbenzene in TFE.

NMR studies of transformations of Pt(II) and Pd(II) complexes with amino acids in solution. 1. Glycine complexes

1H,13C, and195Pt NMR studies were performed for Pt(ll) and Pd(II) complexes with glycine cis- and trans-M(Gly)2, trans-Pd(GlyH)2Cl2 , cis- and trans-Pt(GlyH)2Cl2 , Na[Pd(GIy)Cl2], and K[Pt(Gly)CI2] in donor type solvents DMSO and H2O. It is shown that a cis ↔ trans equilibrium takes place in these solvents and that the equilibration rate is low for Pt(II) complexes and high for Pd(II) complexes. Therefore, the cis- and trans-complexes of Pt(II) may be recorded by NMR spectroscopy in the individual state, whereas for Pd(II) there is an equilibrium mixture of cis- and trans-isomers. Solvolysis of Cl-containing complexes in DMSO is studied. A mechanism of solvolysis involving eis ↔ trans isomerization of the dichloro complexes of Pd(II) is suggested. NMR spectral data for some solvolysis products are given.

A 19F nuclear magnetic resonance study of the conjugate Brönsted-Lewis superacid HSO3F-SbF5. Part 1

The Brönsted-Lewis superacid HSO3F-SbF5 or "magic acid" is re-investigated by modern 19F NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6]-, [SbF5(SO3F)]-, cis- and trans-[SbF4(SO3F)2]-, and mer-[SbF3(SO3F)3]- gradually decreases. Except for [Sb2F11]-, which is present in very small concentrations only, the formation of oligomers involves exclusively μ-fluorosulfato bridges. In addition to donor (SO3F)- and acceptor (SbF5) complex formation to give [SbF5(SO3F)]- and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O]+, which has previously been identified by 1H NMR and structurally characterized as [H3O][Sb2F11] by us.Key words: magic acid, conjugate superacid, fluorosulfuric acid, 19F NMR spectra.

A <sup>19</sup>F nuclear magnetic resonance study of the conjugate Brönsted-Lewis superacid HSO<sub>3</sub>F-SbF<sub>5</sub>. Part 1

The Brönsted-Lewis superacid HSO3F-SbF5 or "magic acid" is re-investigated by modern 19F NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6]-, [SbF5(SO3F)]-, cis- and trans-[SbF4(SO3F)2]-, and mer-[SbF3(SO3F)3]- gradually decreases. Except for [Sb2F11]-, which is present in very small concentrations only, the formation of oligomers involves exclusively μ-fluorosulfato bridges. In addition to donor (SO3F)- and acceptor (SbF5) complex formation to give [SbF5(SO3F)]- and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O]+, which has previously been identified by 1H NMR and structurally characterized as [H3O][Sb2F11] by us.Key words: magic acid, conjugate superacid, fluorosulfuric acid, 19F NMR spectra.